explanation blue bibcodes open ADS page with paths to full text
Author name code: keenan
ADS astronomy entries on 2022-09-14
author:"Keenan, Francis P."
---------------------------------------------------------
Title: The SLED project and the dynamics of coronal flux ropes
Authors: Malherbe, Jean-Marie; Mein, Pierre; Sayède, Frédéric;
Rudawy, Pawel; Phillips, Kenneth; Keenan, Francis; Rybák, Jan
2022AdSpR..70.1562M Altcode:
Investigations of the dynamics of the hot coronal plasma are crucial
for understanding various space weather phenomena and making in-depth
analyzes of the global heating of the solar corona. We present here
numerical simulations of observations of siphon flows along loops
(simple semi-circular flux ropes) to demonstrate the capabilities of
the Solar Line Emission Dopplerometer (SLED), a new instrument under
construction for imaging spectroscopy. It is based on the Multi-channel
Subtractive Double Pass (MSDP) technique, which combines the advantages
of filters and slit spectrographs. SLED will observe coronal structures
in the forbidden lines of FeX 6374 Å and FeXIV 5303 Å, and will
measure Doppler shifts up to 150 km s<SUP>-1</SUP> at high precision
(50 m s<SUP>-1</SUP>) and cadence (1 Hz). It is optimized for studies
of the dynamics of fast evolving events such as flares or Coronal
Mass Ejections (CMEs), as well as for the detection of high-frequency
waves. Observations will be performed with the coronagraph at Lomnický
Štít Observatory (LSO), and will also occur during total solar
eclipses as SLED is a portable instrument.
---------------------------------------------------------
Title: High frequency waves in chromospheric spicules
Authors: Bate, William; Nakariakov, Valery; Jafarzadeh, Shahin; Jess,
David; Stangalini, Marco; Grant, Samuel; Keys, Peter; Christian,
Damian; Keenan, Francis
2022cosp...44.2548B Altcode:
Using high cadence observations from the Hydrogen-alpha Rapid
Dynamics camera imaging system on the Dunn Solar Telescope, we
present an investigation of the statistical properties of transverse
oscillations in spicules captured above the solar limb. At five equally
separated atmospheric heights, spanning approximately $4900-7500$~km,
we have detected a total of $15{\,}959$ individual wave events,
with a mean displacement amplitude of $151\pm 124$~km, a mean
period of $54\pm 45$~s, and a mean projected velocity amplitude
of $21\pm 13$~km{\,}s$^{-1}$. We find that both the displacement
and velocity amplitudes increase with height above the solar limb,
ranging from $132\pm 111$~km and $17.7\pm 10.6$~km{\,}s$^{-1}$ at
$\approx4900$~km, and $168\pm 125$~km and $26.3\pm 14.1$~km{\,}s$^{-1}$
at $\approx7500$~km, respectively. Following the examination of
neighboring oscillations in time and space, we find 45% of the waves
to be upwardly propagating, 49% to be downwardly propagating, and 6%
to be standing, with mean absolute phase velocities for the propagating
waves on the order of $75-150$~km{\,}s$^{-1}$. While the energy flux
of the waves propagating downwards does not appear to depend on height,
we find the energy flux of the upwardly propagating waves decreases with
atmospheric height at a rate of $-13{\,}200\pm6500$~W{\,}m$^{-2}$/Mm. As
a result, this decrease in energy flux as the waves propagate upwards
may provide significant thermal input into the local plasma.
---------------------------------------------------------
Title: High-frequency Waves in Chromospheric Spicules
Authors: Bate, W.; Jess, D. B.; Nakariakov, V. M.; Grant, S. D. T.;
Jafarzadeh, S.; Stangalini, M.; Keys, P. H.; Christian, D. J.; Keenan,
F. P.
2022ApJ...930..129B Altcode: 2022arXiv220304997B
Using high-cadence observations from the Hydrogen-alpha Rapid
Dynamics camera imaging system on the Dunn Solar Telescope, we
present an investigation of the statistical properties of transverse
oscillations in spicules captured above the solar limb. At five equally
separated atmospheric heights, spanning approximately 4900-7500 km,
we have detected a total of 15,959 individual wave events, with a
mean displacement amplitude of 151 ± 124 km, a mean period of 54
± 45 s, and a mean projected velocity amplitude of 21 ± 13 km
s<SUP>-1</SUP>. We find that both the displacement and velocity
amplitudes increase with height above the solar limb, ranging from
132 ± 111 km and 17.7 ± 10.6 km s<SUP>-1</SUP> at ≍4900 km,
and 168 ± 125 km and 26.3 ± 14.1 km s<SUP>-1</SUP> at ≍7500 km,
respectively. Following the examination of neighboring oscillations in
time and space, we find 45% of the waves to be upwardly propagating,
49% to be downwardly propagating, and 6% to be standing, with mean
absolute phase velocities for the propagating waves on the order of
75-150 km s<SUP>-1</SUP>. While the energy flux of the waves propagating
downwards does not appear to depend on height, we find the energy flux
of the upwardly propagating waves decreases with atmospheric height
at a rate of -13,200 ± 6500 W m<SUP>-2</SUP>/Mm. As a result, this
decrease in energy flux as the waves propagate upwards may provide
significant thermal input into the local plasma.
---------------------------------------------------------
Title: The Solar Line Emission Dopplerometer project
Authors: Malherbe, Jean-Marie; Mein, Pierre; Sayède, Frédéric;
Rudawy, Pawel; Phillips, Kenneth; Keenan, Francis; Rybák, Jan
2022ExA....53...83M Altcode: 2021ExA...tmp..125M; 2021arXiv211001645M
Observations of the dynamics of solar coronal structures are necessary
to investigate space weather phenomena and global heating of the
corona. The profiles of high temperature lines emitted by the hot plasma
are usually integrated by narrow band filters or recorded by classical
spectroscopy. We present in this paper details of a new transportable
instrument (under construction) for imaging spectroscopy: the Solar Line
Emission Dopplerometer (SLED). It uses the Multi-channel Subtractive
Double Pass (MSDP) technique, which combines the advantages of both
filters and narrow slit spectrographs, i.e. high temporal, spatial and
spectral resolutions. The SLED will measure at high cadence (1 Hz)
the line-of-sight velocities (Doppler shifts) of hot coronal loops,
in the forbidden lines of FeX 6374 Å and FeXIV 5303 Å. It will
follow the dynamics of fast evolving events of solar activity such
as flares or Coronal Mass Ejections (CMEs), and also study coronal
heating by short period waves. Observations will be performed with
the coronagraph at the Lomnický Štít Observatory (LSO, in Slovakia)
or during total eclipses. The SLED will also observe the dynamics of
solar prominences in Hα 6563 Å or He D3 5876 Å lines when mounted
on the Białków coronagraph (near Wrocław, Poland). It is fully
compatible with polarimetric measurements by various techniques.
---------------------------------------------------------
Title: Four Decades of Advances from MSDP to S4I and SLED Imaging
Spectrometers
Authors: Mein, P.; Malherbe, J. -M.; Sayède, F.; Rudawy, P.; Phillips,
K. J. H.; Keenan, F. P.
2021SoPh..296...30M Altcode: 2021arXiv210103918M
The Multichannel Subtractive Double Pass (MSDP) is an imaging
spectroscopy technique, which allows observations of spectral line
profiles over a 2D field of view with high spatial and temporal
resolution. It has been intensively used since 1977 on various
spectrographs (Meudon, Pic du Midi, the German Vacuum Tower Telescope,
THEMIS, Wrocław). We summarize previous developments and describe
the capabilities of a new design that has been developed at Meudon
and that has higher spectral resolution and increased channel number:
Spectral Sampling with Slicer for Solar Instrumentation (S4I), which
can be combined with a new and fast polarimetry analysis. This new
generation MSDP technique is well adapted to large telescopes. Also
presented are the goals of a derived compact version of the instrument,
the Solar Line Emission Dopplerometer (SLED), dedicated to dynamic
studies of coronal loops observed in the forbidden iron lines,
and prominences. It is designed for observing total solar eclipses,
and for deployment on the Wrocław and Lomnicky peak coronagraphs
respectively for prominence and coronal observations.
---------------------------------------------------------
Title: Improved Fe II Emission-line Models for AGNs Using New Atomic
Data Sets
Authors: Sarkar, A.; Ferland, G. J.; Chatzikos, M.; Guzmán, F.;
van Hoof, P. A. M.; Smyth, R. T.; Ramsbottom, C. A.; Keenan, F. P.;
Ballance, C. P.
2021ApJ...907...12S Altcode: 2020arXiv201109007S
Understanding the Fe II emission from active galactic nuclei
(AGNs) has been a grand challenge for many decades. The rewards
from understanding the AGN spectra would be immense, involving both
quasar classification schemes such as "Eigenvector 1" and tracing the
chemical evolution of the cosmos. Recently, three large Fe II atomic
data sets with radiative and electron collisional rates have become
available. We have incorporated these into the spectral synthesis code
CLOUDY and examined predictions using a new generation of AGN spectral
energy distribution (SED), which indicates that the ultraviolet (UV)
emission can be quite different depending on the data set utilized. The
Smyth et al. data set better reproduces the observed Fe II template
of the I ZW 1 Seyfert galaxy in the UV and optical regions, and
we adopt these data. We consider both thermal and microturbulent
clouds and show that a microturbulence of ≍100 km s<SUP>-1</SUP>
reproduces the observed shape and strength of the so-called Fe II
"UV bump." Comparing our predictions to the observed Fe II template,
we derive a typical cloud density of 10<SUP>11</SUP> cm<SUP>-3</SUP>
and photon flux of 10<SUP>20</SUP> cm<SUP>-2</SUP> s<SUP>-1</SUP>, and
show that these largely reproduce the observed Fe II emission in the UV
and optical. We calculate the I(Fe II)/I(Mg II) emission-line intensity
ratio using our best-fitting model and obtain log(I(Fe II)/I(Mg II))
∼ 0.7, suggesting many AGNs have a roughly solar Fe/Mg abundance
ratio. Finally, we vary the Eddington ratio and SED shape as a step
in understanding the Eigenvector 1 correlation.
---------------------------------------------------------
Title: Electron-impact Excitation of Fe I
Authors: Conroy, Andrew T.; Ballance, Connor P.; Ramsbottom, Catherine
A.; Keenan, Francis P.
2020ApJ...902...68C Altcode:
The Fe I spectra emitted by astrophysical sources contain information
on plasma parameters such as chemical abundances and magnetic
fields. However, to determine these parameters requires detailed plasma
modeling, which in turn needs accurate atomic data for processes such
as radiative decay and electron-impact excitation in Fe I. A lack of
fine-structure resolved collision strengths for transitions in Fe I
is addressed in this paper with the presentation of data obtained
from a Dirac R-matrix calculation. The suitability of our choice
of target description is shown, with our energies generally within
7% of literature values. Various A-values are compared with other
theoretical and experimental results, and the quality of the collision
strengths produced in this work demonstrated. A comparison of 300-
and 1000-level close-coupling expansions is made, the latter shown
to eliminate pseudoresonances in the collision strengths at electron
energies between 0.5 and 1.0 Ry. Maxwell-averaged effective collision
strengths are presented, and the convergence of our data is shown in
the temperature range 1000-100,000 K.
---------------------------------------------------------
Title: Generation of photoionized plasmas in the laboratory: Analogues
to astrophysical sources
Authors: White, S.; Irwin, R.; Warwick, R.; Sarri, G.; Gribakin,
G. F.; Keenan, F. P.; Hill, E.; Rose, S. J.; Ferland, G. J.; Wang,
F.; Zhao, G.; Han, B.; Riley, D.
2020IAUS..350..321W Altcode:
Implementation of a novel experimental approach using a bright source of
narrowband x-ray emission has enabled the production of a photoionized
argon plasma of relevance to astrophysical modelling codes such as
Cloudy. We present results showing that the photoionization parameter
ζ = 4πF/n<SUB>e</SUB> generated using the VULCAN laser was ≈ 50
erg cm s<SUP>-1</SUP>, higher than those obtained previously with more
powerful facilities. Comparison of our argon emission-line spectra
in the 4.15 - 4.25 Å range at varying initial gas pressures with
predictions from the Cloudy code and a simple time-dependent code are
also presented. Finally we briefly discuss how this proof-of-principle
experiment may be scaled to larger facilities such as ORION to produce
the closest laboratory analogue to a photoionized plasma.
---------------------------------------------------------
Title: A Search for High-Frequency Coronal Brightness Variations in
the 21 August 2017 Total Solar Eclipse
Authors: Rudawy, P.; Radziszewski, K.; Berlicki, A.; Phillips,
K. J. H.; Jess, D. B.; Keys, P. H.; Keenan, F. P.
2019SoPh..294...48R Altcode: 2019arXiv190306076R
We report on a search for short-period intensity variations in the
green-line (Fe XIV 530.3 nm) emission from the solar corona during the
21 August 2017 total eclipse viewed from Idaho in the United States. Our
experiment was performed with a much more sensitive detection system,
and with better spatial resolution, than on previous occasions (1999
and 2001 eclipses), allowing fine details of quiet coronal loops and
an active-region loop system to be seen. A guided 200-mm-aperture
Schmidt-Cassegrain telescope was used with a state-of-the-art CCD
camera having 16-bit intensity discrimination and a field-of-view
(0.43<SUP>∘</SUP>×0.43<SUP>∘</SUP>) that encompassed approximately
one third of the visible corona. The camera pixel size was 1.55
arcseconds, while the seeing during the eclipse enabled features of
≈2 arcseconds (1450 km on the Sun) to be resolved. A total of 429
images were recorded during a 122.9 second portion of the totality at
a frame rate of 3.49 s−<SUP>1</SUP>. In the analysis, we searched
particularly for short-period intensity oscillations and travelling
waves, since theory predicts fast-mode magneto-hydrodynamic (MHD) waves
with short periods may be important in quiet coronal and active-region
heating. Allowing first for various instrumental and photometric
effects, we used a wavelet technique to search for periodicities in some
404 ,000 pixels in the frequency range 0.5 -1.6 Hz (periods 2 seconds
to 0.6 seconds). We also searched for travelling waves along some 65
coronal structures. However, we found no statistically significant
evidence in either. This negative result considerably refines the
limit that we obtained from our previous analyses, and it indicates
that future searches for short-period coronal waves may be better
directed towards Doppler shifts as well as intensity oscillations.
---------------------------------------------------------
Title: Towards converged electron-impact excitation calculations of
low-lying transitions in Fe II
Authors: Smyth, R. T.; Ramsbottom, C. A.; Keenan, F. P.; Ferland,
G. J.; Ballance, C. P.
2019MNRAS.483..654S Altcode: 2018MNRAS.tmp.3048S
Absorption and emission lines of the iron-peak species Fe II are
prominent in the infrared, optical, and ultraviolet spectra of a myriad
of astrophysical sources, requiring extensive and highly reliable sets
of atomic structure and collisional data for an accurate quantitative
analysis. However, comparisons among existing calculations reveal large
discrepancies in the effective collision strengths, often up to factors
of three, highlighting the need for further steps towards new converged
calculations. Here we report a new 20 configuration, 6069 level atomic
structure model, calculated using the multiconfigurational Dirac-Fock
method. Collision strengths and effective collision strengths are
presented, for a wide range of temperatures of astrophysical relevance,
from substantial 262 level and 716 level Dirac R-matrix calculations,
plus a 716 level Breit-Pauli R-matrix calculation. Convergence of
the scattering calculations is discussed, and results are critically
compared with existing data in the literature, providing us with error
estimates for our data. As a consequence, we assign an uncertainty of
±15 per cent to relevant forbidden and allowed transitions encompassed
within a 50 level subset of the 716 level Dirac R-matrix data set. To
illustrate the implications of our new data sets for the analysis of
astronomical observations of Fe II, they are incorporated into the
CLOUDY modelling code, sample Fe II spectra are generated and compared.
---------------------------------------------------------
Title: Benchmarking Current Capabilities for the Generation of
Excitation and Photoionisation Atomic Data
Authors: Ramsbottom, Catherine; Ballance, Connor; Smyth, Ryan; Conroy,
Andrew; Fernández-Menchero, Luis; Turkington, Michael; Keenan, Francis
2018Galax...6...90R Altcode:
The spectra currently emerging from modern ground- and space-based
astronomical instruments are of exceptionally high quality and
resolution. To meaningfully analyse these spectra, researchers utilise
complex modelling codes to replicate the observations. The main inputs
to these codes are atomic data such as excitation and photoionisation
cross sections, as well as radiative transition probabilities,
energy levels, and line strengths. In this publication, the current
capabilities of the numerical methods and computer packages used in the
generation of these data are discussed. Particular emphasis is given to
Fe-peak species and the heavy systems of tungsten and molybdenum. Some
of the results presented to highlight certain issues and/or advances
have already been published in the literature, while other sections
present new recently evaluated atomic data for the first time.
---------------------------------------------------------
Title: Towards the Provision of Accurate Atomic Data for Neutral Iron
Authors: Conroy, Andrew; Ramsbottom, Catherine; Ballance, Connor;
Keenan, Francis
2018Galax...6...91C Altcode:
The rich emission and absorption line spectra of Fe I may be used to
extract crucial information on astrophysical plasmas, such as stellar
metallicities. There is currently a lack, in quality and quantity, of
accurate level-resolved effective electron-impact collision strengths
and oscillator strengths for radiative transitions. Here, we discuss the
challenges in obtaining an accurate model of the neutral iron atom and
compare our theoretical fine-structure energy levels with observation
for several increasingly large models. Radiative data is presented
for several transitions for which the atomic data is accurately known.
---------------------------------------------------------
Title: Production of photoionized plasmas in the laboratory with
x-ray line radiation
Authors: White, S.; Irwin, R.; Warwick, J. R.; Gribakin, G. F.; Sarri,
G.; Keenan, F. P.; Riley, D.; Rose, S. J.; Hill, E. G.; Ferland,
G. J.; Han, B.; Wang, F.; Zhao, G.
2018PhRvE..97f3203W Altcode: 2018arXiv180505767W
In this paper we report the experimental implementation of a
theoretically proposed technique for creating a photoionized plasma
in the laboratory using x-ray line radiation. Using a Sn laser plasma
to irradiate an Ar gas target, the photoionization parameter, ξ =4
π F /N<SUB>e</SUB> , reached values of order 50 ergcm s<SUP>-1</SUP>
, where F is the radiation flux in ergc m<SUP>-2</SUP>s<SUP>-1</SUP>
. The significance of this is that this technique allows us to mimic
effective spectral radiation temperatures in excess of 1 keV. We show
that our plasma starts to be collisionally dominated before the peak of
the x-ray drive. However, the technique is extendable to higher-energy
laser systems to create plasmas with parameters relevant to benchmarking
codes used to model astrophysical objects.
---------------------------------------------------------
Title: Photospheric Observations of Surface and Body Modes in Solar
Magnetic Pores
Authors: Keys, Peter H.; Morton, Richard J.; Jess, David B.; Verth,
Gary; Grant, Samuel D. T.; Mathioudakis, Mihalis; Mackay, Duncan H.;
Doyle, John G.; Christian, Damian J.; Keenan, Francis P.; Erdélyi,
Robertus
2018ApJ...857...28K Altcode: 2018arXiv180301859K
Over the past number of years, great strides have been made in
identifying the various low-order magnetohydrodynamic wave modes
observable in a number of magnetic structures found within the solar
atmosphere. However, one aspect of these modes that has remained
elusive, until now, is their designation as either surface or body
modes. This property has significant implications for how these modes
transfer energy from the waveguide to the surrounding plasma. Here, for
the first time to our knowledge, we present conclusive, direct evidence
of these wave characteristics in numerous pores that were observed to
support sausage modes. As well as outlining methods to detect these
modes in observations, we make estimates of the energies associated
with each mode. We find surface modes more frequently in the data,
as well as that surface modes appear to carry more energy than those
displaying signatures of body modes. We find frequencies in the range
of ∼2-12 mHz, with body modes as high as 11 mHz, but we do not find
surface modes above 10 mHz. It is expected that the techniques we have
applied will help researchers search for surface and body signatures
in other modes and in differing structures from those presented here.
---------------------------------------------------------
Title: A Si IV/O IV Electron Density Diagnostic for the Analysis of
IRIS Solar Spectra
Authors: Young, P. R.; Keenan, F. P.; Milligan, R. O.; Peter, H.
2018ApJ...857....5Y Altcode: 2018arXiv180301721Y
Solar spectra of ultraviolet bursts and flare ribbons from the Interface
Region Imaging Spectrograph (IRIS) have suggested high electron
densities of > {10}<SUP>12</SUP> cm<SUP>-3</SUP> at transition
region temperatures of 0.1 MK, based on large intensity ratios of Si
IV λ1402.77 to O IV λ1401.16. In this work, a rare observation of
the weak O IV λ1343.51 line is reported from an X-class flare that
peaked at 21:41 UT on 2014 October 24. This line is used to develop
a theoretical prediction of the Si IV λ1402.77 to O IV λ1401.16
ratio as a function of density that is recommended to be used in the
high-density regime. The method makes use of new pressure-dependent
ionization fractions that take account of the suppression of
dielectronic recombination at high densities. It is applied to two
sequences of flare kernel observations from the October 24 flare. The
first shows densities that vary between 3× {10}<SUP>12</SUP> and
3× {10}<SUP>13</SUP> cm<SUP>-3</SUP> over a seven-minute period,
while the second location shows stable density values of around 2×
{10}<SUP>12</SUP> cm<SUP>-3</SUP> over a three-minute period.
---------------------------------------------------------
Title: X-ray line coincidence photopumping in a solar flare
Authors: Keenan, F. P.; Poppenhaeger, K.; Mathioudakis, M.; Rose,
S. J.; Flowerdew, J.; Hynes, D.; Christian, D. J.; Nilsen, J.; Johnson,
W. R.
2018MNRAS.474.3782K Altcode: 2017arXiv171107761K
Line coincidence photopumping is a process where the electrons of
an atomic or molecular species are radiatively excited through the
absorption of line emission from another species at a coincident
wavelength. There are many instances of line coincidence photopumping
in astrophysical sources at optical and ultraviolet wavelengths,
with the most famous example being Bowen fluorescence (pumping of O
III 303.80 Å by He II), but none to our knowledge in X-rays. However,
here we report on a scheme where a He-like line of Ne IX at 11.000 Å
is photopumped by He-like Na X at 11.003 Å, which predicts significant
intensity enhancement in the Ne IX 82.76 Å transition under physical
conditions found in solar flare plasmas. A comparison of our theoretical
models with published X-ray observations of a solar flare obtained
during a rocket flight provides evidence for line enhancement, with the
measured degree of enhancement being consistent with that expected from
theory, a truly surprising result. Observations of this enhancement
during flares on stars other than the Sun would provide a powerful
new diagnostic tool for determining the sizes of flare loops in these
distant, spatially unresolved, astronomical sources.
---------------------------------------------------------
Title: The 2017 Release Cloudy
Authors: Ferland, G. J.; Chatzikos, M.; Guzmán, F.; Lykins, M. L.;
van Hoof, P. A. M.; Williams, R. J. R.; Abel, N. P.; Badnell, N. R.;
Keenan, F. P.; Porter, R. L.; Stancil, P. C.
2017RMxAA..53..385F Altcode: 2017arXiv170510877F
We describe the 2017 release of the spectral synthesis code Cloudy,
summarizing the many improvements to the scope and accuracy of the
physics which have been made since the previous release. Exporting the
atomic data into external data files has enabled many new large datasets
to be incorporated into the code. The use of the complete datasets is
not realistic for most calculations, so we describe the limited subset
of data used by default, which predicts significantly more lines than
the previous release of Cloudy. This version is nevertheless faster
than the previous release, as a result of code optimizations. We give
examples of the accuracy limits using small models, and the performance
requirements of large complete models. We summarize several advances
in the H- and He-like iso-electronic sequences and use our complete
collisional-radiative models to establish the densities where the
coronal and local thermodynamic equilibrium approximations work.
---------------------------------------------------------
Title: The formation of small-scale umbral brightenings in sunspot
atmospheres
Authors: Nelson, C. J.; Henriques, V. M. J.; Mathioudakis, M.; Keenan,
F. P.
2017A&A...605A..14N Altcode: 2017arXiv170505617N
Context. Sunspot atmospheres have been shown to be highly inhomogeneous
hosting both quasi-stable and transient features, such as small-scale
umbral brightenings (previously named "umbral micro-jets") and dark
fibril-like events. <BR /> Aims: We seek to understand the morphological
properties and formation mechanisms of small-scale umbral brightenings
(analogous to umbral micro-jets). In addition, we aim to understand
whether links between these events and short dynamic fibrils,
umbral flashes, and umbral dots can be established. <BR /> Methods:
A Swedish 1 m Solar Telescope (SST) filtergram time-series sampling
the Ca II H line and a CRisp Imaging Spectro-Polarimeter (SST/CRISP)
full-Stokes 15-point Ca II 8542 Å line scan dataset were used. The
spatial resolutions of these datasets are close to 0.1” and 0.18”
with cadences of 1.4 s and 29 s, respectively. These data allowed
us to construct light-curves, plot line profiles, and to perform
a weak-field approximation in order to infer the magnetic field
strength. <BR /> Results: The average lifetime and lengths of the 54
small-scale brightenings identified in the sunspot umbra are found
to be 44.2 s (σ = 20 s) and 0.56” (σ = 0.14”), respectively. The
spatial positioning and morphological evolution of these events in
Ca II H filtergrams was investigated finding no evidence of parabolic
or ballistic profiles nor a preference for co-spatial formation with
umbral flashes. Line scans in Ca II 8542 Å and the presence of Stokes
V profile reversals provided evidence that these events could form in a
similar manner to umbral flashes in the chromosphere (I.e. through the
formation of shocks either due to the steepening of localised wavefronts
or due to the impact of returning material from short dynamic fibrils,
a scenario we find evidence for). The application of the weak-field
approximation indicated that changes in the line-of-sight magnetic
field were not responsible for the modifications to the line profile
and suggested that thermodynamic effects are, in fact, the actual
cause of the increased emission. Finally, a sub-set of small-scale
brightenings were observed to form at the foot-points of short dynamic
fibrils. <BR /> Conclusions: The small-scale umbral brightenings studied
here do not appear to be jet-like in nature. Instead they appear to be
evidence of shock formation in the lower solar atmosphere. We found
no correlation between the spatial locations where these events were
observed and the occurrence of umbral dots and umbral flashes. These
events have lifetimes and spectral signatures comparable to umbral
flashes and are located at the footpoints of short dynamic fibrils,
during or at the end of the red-shifted stage. It is possible that
these features form due to the shocking of fibrilar material in the
lower atmosphere upon its return under gravity.
---------------------------------------------------------
Title: Spectroscopic Inversions of the Ca II 8542 Å Line in a
C-class Solar Flare
Authors: Kuridze, D.; Henriques, V.; Mathioudakis, M.; Koza, J.;
Zaqarashvili, T. V.; Rybák, J.; Hanslmeier, A.; Keenan, F. P.
2017ApJ...846....9K Altcode: 2017arXiv170800472K
We study the C8.4-class solar flare SOL2016-05-14T11:34 UT using
high-resolution spectral imaging in the Ca II 8542 Å line obtained
with the CRISP imaging spectropolarimeter on the Swedish 1 m Solar
Telescope. Spectroscopic inversions of the Ca II 8542 Å line using
the non-LTE code NICOLE are used to investigate the evolution of
the temperature and velocity structure in the flaring chromosphere. A
comparison of the temperature stratification in flaring and non-flaring
areas reveals strong footpoint heating during the flare peak in the
lower atmosphere. The temperature of the flaring footpoints between
{log} {τ }<SUB>500</SUB> ≈ -2.5 {and} -3.5, where τ <SUB>500</SUB>
is the continuum optical depth at 500 nm, is ∼ 5{--}6.5 {kK} close
to the flare peak, reducing gradually to ∼ 5 {kK}. The temperature in
the middle and upper chromosphere, between {log} {τ }<SUB>500</SUB>≈
-3.5 and -5.5, is estimated to be ∼6.5-20 kK, decreasing to preflare
temperatures, ∼5-10 kK, after approximately 15 minutes. However, the
temperature stratification of the non-flaring areas is unchanged. The
inverted velocity fields show that the flaring chromosphere is dominated
by weak downflowing condensations at the formation height of Ca II
8542 Å.
---------------------------------------------------------
Title: The Origin of B-type Runaway Stars: Non-LTE Abundances as
a Diagnostic
Authors: McEvoy, Catherine M.; Dufton, Philip L.; Smoker, Jonathan
V.; Lambert, David L.; Keenan, Francis P.; Schneider, Fabian R. N.;
de Wit, Willem-Jan
2017ApJ...842...32M Altcode: 2017arXiv170803527M
There are two accepted mechanisms to explain the origin of runaway
OB-type stars: the binary supernova (SN) scenario and the cluster
ejection scenario. In the former, an SN explosion within a close
binary ejects the secondary star, while in the latter close multibody
interactions in a dense cluster cause one or more of the stars to be
ejected from the region at high velocity. Both mechanisms have the
potential to affect the surface composition of the runaway star. tlusty
non-LTE model atmosphere calculations have been used to determine
the atmospheric parameters and the C, N, Mg, and Si abundances for a
sample of B-type runaways. These same analytical tools were used by
Hunter et al. for their analysis of 50 B-type open-cluster Galactic
stars (I.e., nonrunaways). Effective temperatures were deduced using
the Si-ionization balance technique, surface gravities from Balmer
line profiles, and microturbulent velocities derived using the
Si spectrum. The runaways show no obvious abundance anomalies when
compared with stars in the open clusters. The runaways do show a spread
in composition that almost certainly reflects the Galactic abundance
gradient and a range in the birthplaces of the runaways in the Galactic
disk. Since the observed Galactic abundance gradients of C, N, Mg,
and Si are of a similar magnitude, the abundance ratios (e.g., N/Mg)
are as obtained essentially uniform across the sample.
---------------------------------------------------------
Title: An assessment of Fe xx-Fe xxii emission lines in SDO/EVE
data as diagnostics for high-density solar flare plasmas using EUVE
stellar observations
Authors: Keenan, F. P.; Milligan, R. O.; Mathioudakis, M.; Christian,
D. J.
2017MNRAS.468.1117K Altcode: 2017arXiv170208714K
The Extreme Ultraviolet Variability Experiment (EVE) on the Solar
Dynamics Observatory obtains extreme-ultraviolet (EUV) spectra of
the full-disc Sun at a spectral resolution of ∼1 Å and cadence
of 10 s. Such a spectral resolution would normally be considered
to be too low for the reliable determination of electron density
(N<SUB>e</SUB>) sensitive emission line intensity ratios, due
to blending. However, previous work has shown that a limited
number of Fe xxi features in the 90-160 Å wavelength region of
EVE do provide useful N<SUB>e</SUB>-diagnostics at relatively low
flare densities (N<SUB>e</SUB> ≃ 10<SUP>11</SUP>-10<SUP>12</SUP>
cm<SUP>-3</SUP>). Here, we investigate if additional highly ionized
Fe line ratios in the EVE 90-160 Å range may be reliably employed
as N<SUB>e</SUB>-diagnostics. In particular, the potential for such
diagnostics to provide density estimates for high N<SUB>e</SUB>
(∼10<SUP>13</SUP> cm<SUP>-3</SUP>) flare plasmas is assessed. Our
study employs EVE spectra for X-class flares, combined with
observations of highly active late-type stars from the EUVE satellite
plus experimental data for well-diagnosed tokamak plasmas, both of
which are similar in wavelength coverage and spectral resolution
to those from EVE. Several ratios are identified in EVE data,
which yield consistent values of electron density, including Fe xx
113.35/121.85 and Fe xxii 114.41/135.79, with confidence in their
reliability as N<SUB>e</SUB>-diagnostics provided by the EUVE and
tokamak results. These ratios also allow the determination of density in
solar flare plasmas up to values of ∼10<SUP>13</SUP> cm<SUP>-3</SUP>.
---------------------------------------------------------
Title: Radiative Rates and Electron Impact Excitation Rates for
Transitions in He II
Authors: Aggarwal, Kanti; Igarashi, Akinori; Keenan, Francis;
Nakazaki, Shinobu
2017Atoms...5...19A Altcode: 2017arXiv170407275A
We report calculations of energy levels, radiative rates, collision
strengths, and effective collision strengths for transitions
among the lowest 25 levels of the n <= 5 configurations of
He~II. The general-purpose relativistic atomic structure package
(GRASP) and Dirac atomic R-matrix code (DARC) are adopted for the
calculations. Radiative rates, oscillator strengths, and line strengths
are reported for all electric dipole (E1), magnetic dipole (M1),
electric quadrupole (E2), and magnetic quadrupole (M2) transitions
among the 25 levels. Furthermore, collision strengths and effective
collision strengths are listed for all 300 transitions among the
above 25 levels over a wide energy (temperature) range up to 9 Ryd
(10**5.4 K). Comparisons are made with earlier available results and
the accuracy of the data is assessed.
---------------------------------------------------------
Title: Emission Line Ratios of FE III as Astrophysical Plasma
Diagnostics
Authors: Laha, Sibasish; Tyndall, Niall B.; Keenan, Francis P.;
Ballance, Connor P.; Ramsbottom, Catherine A.; Ferland, Gary J.;
Hibbert, Alan
2017ApJ...841....3L Altcode: 2017arXiv170500207L
Recent, state-of-the-art calculations of A-values and electron impact
excitation rates for Fe III are used in conjunction with the Cloudy
modeling code to derive emission-line intensity ratios for optical
transitions among the fine-structure levels of the 3d<SUP>6</SUP>
configuration. A comparison of these with high-resolution, high
signal-to-noise spectra of gaseous nebulae reveals that previous
discrepancies found between theory and observation are not fully
resolved by the latest atomic data. Blending is ruled out as a likely
cause of the discrepancies, because temperature- and density-independent
ratios (arising from lines with common upper levels) match well
with those predicted by theory. For a typical nebular plasma with
electron temperature {T}<SUB>{{e</SUB>}}=9000 K and electron density
{N}<SUB>{{e</SUB>}}={10}<SUP>4</SUP> {{cm}}<SUP>-3</SUP>, cascading
of electrons from the levels {}<SUP>3</SUP>{{{G}}}<SUB>5</SUB>,
{}<SUP>3</SUP>{{{G}}}<SUB>4</SUB> and {}<SUP>3</SUP>{{{G}}}<SUB>3</SUB>
plays an important role in determining the populations of
lower levels, such as {}<SUP>3</SUP>{{{F}}}<SUB>4</SUB>, which
provide the density diagnostic emission lines of Fe III, such as
{}<SUP>5</SUP>{{{D}}}<SUB>4</SUB> - {}<SUP>3</SUP>{{{F}}}<SUB>4</SUB>
at 4658 Å. Hence, further work on the A-values for these transitions
is recommended, ideally including measurements if possible. However,
some Fe III ratios do provide reliable {N}<SUB>{{e</SUB>}}-diagnostics,
such as 4986/4658. The Fe III cooling function, calculated with Cloudy
using the most recent atomic data, is found to be significantly greater
at T <SUB> e </SUB> ≃ 30,000 K than predicted with the existing Cloudy
model. This is due to the presence of additional emission lines with
the new data, particularly in the 1000-4000 Å wavelength region.
---------------------------------------------------------
Title: Energy levels and radiative rates for transitions in Fe V,
Co VI and Ni VII
Authors: Aggarwal, K. M.; Bogdanovich, P.; Keenan, F. P.; Kisielius, R.
2017ADNDT.114....1A Altcode: 2016arXiv160508212A
Energy levels, Landé g-factors and radiative lifetimes are reported
for the lowest 182 levels of the 3d<SUP>4</SUP>, 3d<SUP>3</SUP>4s and
3d<SUP>3</SUP>4p configurations of Fe V, Co VI and Ni VII. Additionally,
radiative rates (A-values) have been calculated for the E1, E2 and M1
transitions among these levels. The calculations have been performed
in a quasi-relativistic approach (QR) with a very large configuration
interaction (CI) wavefunction expansion, which has been found to be
necessary for these ions. Our calculated energies for all ions are
in excellent agreement with the available measurements, for most
levels. Discrepancies among various calculations for the radiative
rates of E1 transitions in Fe V are up to a factor of two for stronger
transitions (f ≥ 0.1), and larger (over an order of magnitude) for
weaker ones. The reasons for these discrepancies have been discussed
and mainly are due to the differing amount of CI and methodologies
adopted. However, there are no appreciable discrepancies in similar
data for M1 and E2 transitions, or the g-factors for the levels of Fe V,
the only ion for which comparisons are feasible.
---------------------------------------------------------
Title: Observations and Simulations of the Na I D<SUB>1</SUB> Line
Profiles in an M-class Solar Flare
Authors: Kuridze, D.; Mathioudakis, M.; Christian, D. J.; Kowalski,
A. F.; Jess, D. B.; Grant, S. D. T.; Kawate, T.; Simões, P. J. A.;
Allred, J. C.; Keenan, F. P.
2016ApJ...832..147K Altcode: 2016arXiv160908120K
We study the temporal evolution of the Na I D<SUB>1</SUB> line profiles
in the M3.9 flare SOL2014-06-11T21:03 UT, using observations at high
spectral resolution obtained with the Interferometric Bidimensional
Spectrometer instrument on the Dunn Solar Telescope combined with
radiative hydrodynamic simulations. Our results show a significant
increase in the intensities of the line core and wings during the
flare. The analysis of the line profiles from the flare ribbons
reveals that the Na I D<SUB>1</SUB> line has a central reversal
with excess emission in the blue wing (blue asymmetry). We combine
RADYN and RH simulations to synthesize Na I D<SUB>1</SUB> line
profiles of the flaring atmosphere and find good agreement with
the observations. Heating with a beam of electrons modifies the
radiation field in the flaring atmosphere and excites electrons
from the ground state 3s <SUP>2</SUP>S to the first excited state 3p
<SUP>2</SUP>P, which in turn modifies the relative population of the
two states. The change in temperature and the population density of
the energy states make the sodium line profile revert from absorption
into emission. Furthermore, the rapid changes in temperature break the
pressure balance between the different layers of the lower atmosphere,
generating upflow/downflow patterns. Analysis of the simulated spectra
reveals that the asymmetries of the Na I D<SUB>1</SUB> flare profile
are produced by the velocity gradients in the lower solar atmosphere.
---------------------------------------------------------
Title: Kelvin-Helmholtz Instability in Solar Chromospheric Jets:
Theory and Observation
Authors: Kuridze, D.; Zaqarashvili, T. V.; Henriques, V.; Mathioudakis,
M.; Keenan, F. P.; Hanslmeier, A.
2016ApJ...830..133K Altcode: 2016arXiv160801497K
Using data obtained by the high-resolution CRisp Imaging
SpectroPolarimeter instrument on the Swedish 1 m Solar Telescope,
we investigate the dynamics and stability of quiet-Sun chromospheric
jets observed at the disk center. Small-scale features, such as rapid
redshifted and blueshifted excursions, appearing as high-speed jets
in the wings of the Hα line, are characterized by short lifetimes and
rapid fading without any descending behavior. To study the theoretical
aspects of their stability without considering their formation
mechanism, we model chromospheric jets as twisted magnetic flux tubes
moving along their axis, and use the ideal linear incompressible
magnetohydrodynamic approximation to derive the governing dispersion
equation. Analytical solutions of the dispersion equation indicate
that this type of jet is unstable to Kelvin-Helmholtz instability
(KHI), with a very short (few seconds) instability growth time at
high upflow speeds. The generated vortices and unresolved turbulent
flows associated with the KHI could be observed as a broadening of
chromospheric spectral lines. Analysis of the Hα line profiles shows
that the detected structures have enhanced line widths with respect to
the background. We also investigate the stability of a larger-scale Hα
jet that was ejected along the line of sight. Vortex-like features,
rapidly developing around the jet’s boundary, are considered as
evidence of the KHI. The analysis of the energy equation in the
partially ionized plasma shows that ion-neutral collisions may lead
to fast heating of the KH vortices over timescales comparable to the
lifetime of chromospheric jets.
---------------------------------------------------------
Title: Electron impact excitation of N IV: calculations with the
DARC code and a comparison with ICFT results
Authors: Aggarwal, K. M.; Keenan, F. P.; Lawson, K. D.
2016MNRAS.461.3997A Altcode: 2016arXiv160804406A
There have been discussions in the recent literature regarding
the accuracy of the available electron impact excitation rates
(equivalently effective collision strengths Υ) for transitions
in Be-like ions. In the present paper we demonstrate, once again,
that earlier results for Υ are indeed overestimated (by up to four
orders of magnitude), for over 40 per cent of transitions and over a
wide range of temperatures. To do this we have performed two sets of
calculations for N IV, with two different model sizes consisting of
166 and 238 fine-structure energy levels. As in our previous work,
for the determination of atomic structure the GRASP (General-purpose
Relativistic Atomic Structure Package) is adopted and for the
scattering calculations (the standard and parallelised versions of)
the Dirac Atomic R-matrix Code (DARC) are employed. Calculations
for collision strengths and effective collision strengths have been
performed over a wide range of energy (up to 45 Ryd) and temperature
(up to 2.0 × 10<SUP>6</SUP> K), useful for applications in a variety
of plasmas. Corresponding results for energy levels, lifetimes and
A-values for all E1, E2, M1 and M2 transitions among 238 levels of N
IV are also reported.
---------------------------------------------------------
Title: Electron impact excitation rates for transitions in Mg V
Authors: Aggarwal, K M; Keenan, F P
2016arXiv160908351A Altcode:
Energy levels, radiative rates (A-values) and lifetimes, calculated
with the GRASP code, are reported for an astrophysically important
O-like ion Mg~V. Results are presented for transitions among the
lowest 86 levels belonging to the 2s$^2$2p$^4$, 2s2p$^5$, 2p$^6$, and
2s$^2$2p$^3$3$\ell$ configurations. There is satisfactory agreement
with earlier data for most levels/transitions, but scope remains for
improvement. Collision strengths are also calculated, with the DARC
code, and the results obtained are comparable for most transitions
(at energies above thresholds) with earlier work using the DW code. In
thresholds region, resonances have been resolved in a fine energy mesh
to determine values of effective collision strengths ($\Upsilon$)
as accurately as possible. Results are reported for all transitions
at temperatures up to 10$^6$~K, which should be sufficient for most
astrophysical applications. However, a comparison with earlier data
reveals discrepancies of up to two orders of magnitude for over 60\%
of transitions, at all temperatures. The reasons for these discrepancies
are discussed in detail.
---------------------------------------------------------
Title: Departure of High-temperature Iron Lines from the Equilibrium
State in Flaring Solar Plasmas
Authors: Kawate, T.; Keenan, F. P.; Jess, D. B.
2016ApJ...826....3K Altcode: 2016arXiv160602049K
The aim of this study is to clarify if the assumption of ionization
equilibrium and a Maxwellian electron energy distribution is valid in
flaring solar plasmas. We analyze the 2014 December 20 X1.8 flare, in
which the Fe xxi 187 Å, Fe xxii 253 Å, Fe xxiii 263 Å, and Fe xxiv
255 Å emission lines were simultaneously observed by the EUV Imaging
Spectrometer on board the Hinode satellite. Intensity ratios among these
high-temperature Fe lines are compared and departures from isothermal
conditions and ionization equilibrium examined. Temperatures derived
from intensity ratios involving these four lines show significant
discrepancies at the flare footpoints in the impulsive phase, and
at the looptop in the gradual phase. Among these, the temperature
derived from the Fe xxii/Fe xxiv intensity ratio is the lowest, which
cannot be explained if we assume a Maxwellian electron distribution
and ionization equilibrium, even in the case of a multithermal
structure. This result suggests that the assumption of ionization
equilibrium and/or a Maxwellian electron energy distribution can be
violated in evaporating solar plasma around 10 MK.
---------------------------------------------------------
Title: Ultraviolet Emission Lines of Si II in Quasars: Investigating
the "Si II Disaster"
Authors: Laha, Sibasish; Keenan, Francis P.; Ferland, Gary J.;
Ramsbottom, Catherine A.; Aggarwal, Kanti M.
2016ApJ...825...28L Altcode: 2016arXiv160407364L
The observed line intensity ratios of the Si II λ1263 and λ1307
multiplets to that of Si II λ1814 in the broad-line region (BLR) of
quasars are both an order of magnitude larger than the theoretical
values. This was first pointed out by Baldwin et al., who termed
it the “Si II disaster,” and it has remained unresolved. We
investigate the problem in the light of newly published atomic
data for Si II. Specifically, we perform BLR calculations using
several different atomic data sets within the CLOUDY modeling code
under optically thick quasar cloud conditions. In addition, we test
for selective pumping by the source photons or intrinsic galactic
reddening as possible causes for the discrepancy, and we also consider
blending with other species. However, we find that none of the options
investigated resolve the Si II disaster, with the potential exception
of microturbulent velocity broadening and line blending. We find that
a larger microturbulent velocity (∼ 500 {km} {{{s}}}<SUP>-1</SUP>)
may solve the Si II disaster through continuum pumping and other
effects. The CLOUDY models indicate strong blending of the Si II λ1307
multiplet with emission lines of O I, although the predicted degree
of blending is incompatible with the observed λ1263/λ1307 intensity
ratios. Clearly, more work is required on the quasar modeling of not
just the Si II lines but also nearby transitions (in particular those
of O I) to fully investigate whether blending may be responsible for
the Si II disaster.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Early-type stars in SMC and LMC
(Smoker+, 2015)
Authors: Smoker, J. V.; Fox, A. J.; Keenan, F. P.
2016yCat..74514346S Altcode:
FLAMES observations towards four open clusters in the LMC and SMC were
retrieved from the ESO archive and are used to study the I/HVCs towards
these galaxies and their variation on small scales. <P />(1 data file).
---------------------------------------------------------
Title: Quiet-Sun Hα Transients and Corresponding Small-scale
Transition Region and Coronal Heating
Authors: Henriques, V. M. J.; Kuridze, D.; Mathioudakis, M.; Keenan,
F. P.
2016ApJ...820..124H Altcode: 2016arXiv160204820H
Rapid blue- and redshifted excursions (RBEs and RREs) are likely to
be the on-disk counterparts of Type II spicules. Recently, heating
signatures from RBEs/RREs have been detected in IRIS slit-jaw
images dominated by transition region (TR) lines around network
patches. Additionally, signatures of Type II spicules have been observed
in Atmospheric Imaging Assembly (AIA) diagnostics. The full-disk,
ever-present nature of the AIA diagnostics should provide us with
sufficient statistics to directly determine how important RBEs and RREs
are to the heating of the TR and corona. We find, with high statistical
significance, that at least 11% of the low coronal brightenings detected
in a quiet-Sun region in He II 304 Å can be attributed to either RBEs
or RREs as observed in Hα, and a 6% match of Fe IX 171 Å detected
events to RBEs or RREs with very similar statistics for both types
of Hα features. We took a statistical approach that allows for noisy
detections in the coronal channels and provides us with a lower, but
statistical significant, bound. Further, we consider matches based on
overlapping features in both time and space, and find strong visual
indications of further correspondence between coronal events and
co-evolving but non-overlapping, RBEs and RREs.
---------------------------------------------------------
Title: Energy levels and radiative rates for transitions in Cr-like
Co IV and Ni V
Authors: Aggarwal, K. M.; Bogdanovich, P.; Karpuškienė, R.; Keenan,
F. P.; Kisielius, R.; Stancalie, V.
2016ADNDT.107..140A Altcode: 2015arXiv150907648A
We report calculations of energy levels and radiative rates (A-values)
for transitions in Cr-like Co IV and Ni V. The quasi-relativistic
Hartree-Fock (QRHF) code is adopted for calculating the data although
GRASP (general-purpose relativistic atomic structure package) and
flexible atomic code (FAC) have also been employed for comparison
purposes. No radiative rates are available in the literature to compare
with our results, but our calculated energies are in close agreement
with those compiled by NIST for a majority of the levels. However, there
are discrepancies for a few levels of up to 3%. The A-values are listed
for all significantly contributing E1, E2 and M1 transitions, and the
corresponding lifetimes reported, although unfortunately no previous
theoretical or experimental results exist to compare with our data.
---------------------------------------------------------
Title: Ultraviolet emission lines of Si II in cool star and solar
spectra
Authors: Laha, Sibasish; Keenan, Francis P.; Ferland, Gary J.;
Ramsbottom, Catherine A.; Aggarwal, Kanti M.; Ayres, Thomas R.;
Chatzikos, Marios; van Hoof, Peter A. M.; Williams, Robin J. R.
2016MNRAS.455.3405L Altcode: 2015arXiv151008755L
Recent atomic physics calculations for Si II are employed within the
CLOUDY modelling code to analyse Hubble Space Telescope (HST) STIS
ultraviolet spectra of three cool stars, β Geminorum, α Centauri A
and B, as well as previously published HST/GHRS observations of α
Tau, plus solar quiet Sun data from the High Resolution Telescope
and Spectrograph. Discrepancies found previously between theory and
observation for line intensity ratios involving the 3s<SUP>2</SUP>3p
<SUP>2</SUP>P<SUB>J</SUB>-3s3p<SUP>2</SUP> <SUP>4</SUP>P_{J^' }}
intercombination multiplet of Si II at ∼ 2335 Å are significantly
reduced, as are those for ratios containing the 3s<SUP>2</SUP>3p
<SUP>2</SUP>P<SUB>J</SUB>-3s3p<SUP>2</SUP> <SUP>2</SUP>D_{J^' }}
transitions at ∼1816 Å. This is primarily due to the effect of
the new Si II transition probabilities. However, these atomic data
are not only very different from previous calculations, but also show
large disagreements with measurements, specifically those of Calamai
et al. for the intercombination lines. New measurements of transition
probabilities for Si II are hence urgently required to confirm (or
otherwise) the accuracy of the recently calculated values. If the new
calculations are confirmed, then a long-standing discrepancy between
theory and observation will have finally been resolved. However,
if the older measurements are found to be correct, then the agreement
between theory and observation is simply a coincidence and the existing
discrepancies remain.
---------------------------------------------------------
Title: Hα Line Profile Asymmetries and the Chromospheric Flare
Velocity Field
Authors: Kuridze, D.; Mathioudakis, M.; Simões, P. J. A.; Rouppe van
der Voort, L.; Carlsson, M.; Jafarzadeh, S.; Allred, J. C.; Kowalski,
A. F.; Kennedy, M.; Fletcher, L.; Graham, D.; Keenan, F. P.
2015ApJ...813..125K Altcode: 2015arXiv151001877K
The asymmetries observed in the line profiles of solar flares can
provide important diagnostics of the properties and dynamics of the
flaring atmosphere. In this paper the evolution of the Hα and Ca ii
λ8542 lines are studied using high spatial, temporal, and spectral
resolution ground-based observations of an M1.1 flare obtained with
the Swedish 1 m Solar Telescope. The temporal evolution of the Hα
line profiles from the flare kernel shows excess emission in the red
wing (red asymmetry) before flare maximum and excess in the blue wing
(blue asymmetry) after maximum. However, the Ca ii λ8542 line does
not follow the same pattern, showing only a weak red asymmetry during
the flare. RADYN simulations are used to synthesize spectral line
profiles for the flaring atmosphere, and good agreement is found
with the observations. We show that the red asymmetry observed in
Hα is not necessarily associated with plasma downflows, and the blue
asymmetry may not be related to plasma upflows. Indeed, we conclude
that the steep velocity gradients in the flaring chromosphere modify
the wavelength of the central reversal in the Hα line profile. The
shift in the wavelength of maximum opacity to shorter and longer
wavelengths generates the red and blue asymmetries, respectively.
---------------------------------------------------------
Title: The large- and small-scale Ca II K structure of the Milky
Way from observations of Galactic and Magellanic sightlines⋆
Authors: Smoker, J. V.; Keenan, F. P.; Fox, A. J.
2015A&A...582A..59S Altcode: 2015arXiv151100470S
<BR /> Aims: The large and small-scale (pc) structure of the Galactic
interstellar medium can be investigated by utilising spectra of
early-type stellar probes of known distances in the same region of the
sky. This paper determines the variation in line strength of Ca ii at
3933.661 Å as a function of probe separation for a large sample of
stars, including a number of sightlines in the Magellanic Clouds. <BR />
Methods: FLAMES-GIRAFFE data taken with the Very Large Telescope towards
early-type stars in 3 Galactic and 4 Magellanic open clusters in Ca ii
are used to obtain the velocity, equivalent width, column density, and
line width of interstellar Galactic calcium for a total of 657 stars,
of which 443 are Magellanic Cloud sightlines. In each cluster there
are between 43 and 111 stars observed. Additionally, FEROS and UVES Ca
ii K and Na i D spectra of 21 Galactic and 154 Magellanic early-type
stars are presented and combined with data from the literature to
study the calcium column density - parallax relationship. <BR />
Results: For the four Magellanic clusters studied with FLAMES,
the strength of the Galactic interstellar Ca ii K equivalent width
on transverse scales from ~0.05-9 pc is found to vary by factors of
~1.8-3.0, corresponding to column density variations of ~0.3-0.5 dex
in the optically-thin approximation. Using FLAMES, FEROS, and UVES
archive spectra, the minimum and maximum reduced equivalent widths for
Milky Way gas are found to lie in the range ~35-125 mÅ and ~30-160
mÅ for Ca ii K and Na i D, respectively. The range is consistent
with a previously published simple model of the interstellar medium
consisting of spherical cloudlets of filling factor ~0.3, although other
geometries are not ruled out. Finally, the derived functional form for
parallax (π) and Ca ii column density (N<SUB>CaII</SUB>) is found
to be π(mas) = 1 / (2.39 × 10<SUP>-13</SUP> × N<SUB>CaII</SUB>
(cm<SUP>-2</SUP>) + 0.11). Our derived parallax is ~25 per cent
lower than predicted by Megier et al. (2009, A&A, 507, 833)
at a distance of ~100 pc and ~15 percent lower at a distance of
~200 pc, reflecting inhomogeneity in the Ca ii distribution in
the different sightlines studied. <P />Reduced spectra and Tables
A.1-A.17 are only available at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/582/A59">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/582/A59</A>Figures
A.1-A.37 are available in electronic form at <A
href="http://www.aanda.org/10.1051/0004-6361/201425190/olm">http://www.aanda.org</A>
---------------------------------------------------------
Title: Large- and small-scale structure of the intermediate- and
high-velocity clouds towards the LMC and SMC
Authors: Smoker, J. V.; Fox, A. J.; Keenan, F. P.
2015MNRAS.451.4346S Altcode: 2015arXiv151100843S
We employ Ca II K and Na I D interstellar absorption-line spectroscopy
of early-type stars in the Large and Small Magellanic Clouds
(LMC, SMC) to investigate the large- and small-scale structure in
foreground intermediate- and high-velocity clouds (I/HVCs). Data
include FLAMES-GIRAFFE Ca II K observations of 403 stars in four open
clusters, plus FEROS or UVES spectra of 156 stars in the LMC and
SMC. The FLAMES observations are amongst the most extensive probes
to date of Ca II structures on ∼20 arcsec scales in Magellanic
I/HVCs. From the FLAMES data within a 0.5° field of view, the Ca
II K equivalent width in the I/HVC components towards three clusters
varies by factors of ≥10. There are no detections of molecular gas
in absorption at intermediate or high velocities, although molecular
absorption is present at LMC and Galactic velocities towards some
sightlines. The FEROS/UVES data show Ca II K I/HVC absorption in ∼60
per cent of sightlines. The range in the Ca II/Na I ratio in I/HVCs is
from -0.45 to +1.5 dex, similar to previous measurements for I/HVCs. In
10 sightlines we find Ca II/O I ratios in I/HVC gas ranging from 0.2
to 1.5 dex below the solar value, indicating either dust or ionization
effects. In nine sightlines I/HVC gas is detected in both H I and Ca
II at similar velocities, implying that the two elements form part of
the same structure.
---------------------------------------------------------
Title: Early-type stars observed in the ESO UVES Paranal Observatory
Project - V. Time-variable interstellar absorption
Authors: McEvoy, Catherine M.; Smoker, Jonathan V.; Dufton, Philip L.;
Smith, Keith T.; Kennedy, Michael B.; Keenan, Francis P.; Lambert,
David L.; Welty, Daniel E.; Lauroesch, James T.
2015MNRAS.451.1396M Altcode: 2015arXiv150601348M
The structure and properties of the diffuse interstellar medium (ISM)
on small scales, sub-au to 1 pc, are poorly understood. We compare
interstellar absorption lines, observed towards a selection of O-
and B-type stars at two or more epochs, to search for variations over
time caused by the transverse motion of each star combined with changes
in the structure in the foreground ISM. Two sets of data were used: 83
VLT/UVES spectra with approximately 6 yr between epochs and 21 McDonald
observatory 2.7-m telescope echelle spectra with 6-20 yr between
epochs, over a range of scales from ∼0-360 au. The interstellar
absorption lines observed at the two epochs were subtracted and searched
for any residuals due to changes in the foreground ISM. Of the 104
sightlines investigated with typically five or more components in Na
I D, possible temporal variation was identified in five UVES spectra
(six components), in Ca II, Ca I and/or Na I absorption lines. The
variations detected range from 7 per cent to a factor of 3.6 in column
density. No variation was found in any other interstellar species. Most
sightlines show no variation, with 3σ upper limits to changes of the
order 0.1-0.3 dex in Ca II and Na I. These variations observed imply
that fine-scale structure is present in the ISM, but at the resolution
available in this study, is not very common at visible wavelengths. A
determination of the electron densities and lower limits to the total
number density of a sample of the sightlines implies that there is
no striking difference between these parameters in sightlines with,
and sightlines without, varying components.
---------------------------------------------------------
Title: Electron impact excitation of Astrophysically Important C
III Ion
Authors: Aggarwal, Kanti M.; KEENAN, FRANCIS P.
2015IAUGA..2253165A Altcode:
Emission lines of many Be-like ions, including C~III, have been
observed in the solar and stellar plasmas and are useful for density
and temperature diagnostics. C~III is also important for studies of
fusion plasmas. For modelling and diagnostics, atomic data for energy
levels, radiative rates (A-values) and excitation rates (equivalently
effective collision strengths) are required. Therefore, we have
adopted the GRASP code to calculate energy levels, A-values (for E1,
E2, M1 and M2 transitions) and lifetimes among 166 levels of the n
<= 5 configurations. Energy levels are assessed to be accurate
to better than 1% for most levels, and A-values to better than 20%
for most transitions. For A-values and lifetimes there are no large
discrepancies between theory and measurement. For collision strengths
DARC is adopted, resonances are resolved in a fine energy mesh and are
averaged over a Maxwellian velocity distribution to determine effective
collision strengths up to a temperature of 800,000 K. Unfortunately, a
comparison with the similar R-matrix calculations of Fernandez-Menchero
et al [A&A 566 (2014) A104] shows differences up to over an order
of magnitude for about 20% transitions (among the lowest 78 levels)
over the complete temperature range of the results. In most cases
their results are larger, up to a factor of 20, and the differences
are similar and comparable to those already noted for other Be-like
ions, namely Al~X, Cl~XIV, K~XVI, Ti~XIX and Ge~XXIX - see Aggarwal
& Keenan [MNRAS 447 (2015) 3849]. Based on several comparisons
and considering the wide range of partial waves included (up to 40.5)
and the energy range adopted for collision strengths (up to 21 Ryd),
our results are estimated to be accurate to better than 20% for a
majority of transitions, allowed and forbidden. Detailed comparisons
for all parameters for C~III and possible reasons for discrepancies
will be presented during the conference and will also be soon available
in MNRAS.
---------------------------------------------------------
Title: VizieR Online Data Catalog: CaIIK spectra of 7 Galactic and
MC open clusters (Smoker+, 2015)
Authors: Smoker, J.; Keenan, F. P.; Fox, A. J.
2015yCat..35820059S Altcode:
The data on which the current paper is based were extracted from the
ESO archive and are FLAMES-GIRAFFE observations towards three open
clusters located in the Milky Way, and two in each of the Large and
Small Magellanic Clouds, plus FEROS and UVES observations towards stars
located in the Magellanic system and Milky Way. <P />(18 data files).
---------------------------------------------------------
Title: Stout: Cloudy's Atomic and Molecular Database
Authors: Lykins, M. L.; Ferland, G. J.; Kisielius, R.; Chatzikos,
M.; Porter, R. L.; van Hoof, P. A. M.; Williams, R. J. R.; Keenan,
F. P.; Stancil, P. C.
2015ApJ...807..118L Altcode: 2015arXiv150601741L
We describe a new atomic and molecular database we developed for use in
the spectral synthesis code Cloudy. The design of Stout is driven by the
data needs of Cloudy, which simulates molecular, atomic, and ionized
gas with kinetic temperatures 2.8 {{K}}\lt T\lt {10}<SUP>10</SUP>
{{K}} and densities spanning the low-to high-density limits. The
radiation field between photon energies 10<SUP>-8</SUP> Ry and 100
MeV is considered, along with all atoms and ions of the lightest 30
elements, and ∼10<SUP>2</SUP> molecules. For ease of maintenance, the
data are stored in a format as close as possible to the original data
sources. Few data sources include the full range of data we need. We
describe how we fill in the gaps in the data or extrapolate rates
beyond their tabulated range. We tabulate data sources both for the
atomic spectroscopic parameters and for collision data for the next
release of Cloudy. This is not intended as a review of the current
status of atomic data, but rather a description of the features of
the database which we will build upon.
---------------------------------------------------------
Title: Radiative hydrodynamic modelling and observations of the
X-class solar flare on 2011 March 9
Authors: Kennedy, Michael B.; Milligan, Ryan O.; Allred, Joel C.;
Mathioudakis, Mihalis; Keenan, Francis P.
2015A&A...578A..72K Altcode: 2015arXiv150407541K
<BR /> Aims: We investigated the response of the solar atmosphere to
non-thermal electron beam heating using the radiative transfer and
hydrodynamics modelling code RADYN. The temporal evolution of the
parameters that describe the non-thermal electron energy distribution
were derived from hard X-ray observations of a particular flare, and
we compared the modelled and observed parameters. <BR /> Methods:
The evolution of the non-thermal electron beam parameters during
the X1.5 solar flare on 2011 March 9 were obtained from analysis of
RHESSI X-ray spectra. The RADYN flare model was allowed to evolve for
110 s, after which the electron beam heating was ended, and was then
allowed to continue evolving for a further 300 s. The modelled flare
parameters were compared to the observed parameters determined from
extreme-ultraviolet spectroscopy. <BR /> Results: The model produced
a hotter and denser flare loop than that observed and also cooled more
rapidly, suggesting that additional energy input in the decay phase of
the flare is required. In the explosive evaporation phase a region of
high-density cool material propagated upward through the corona. This
material underwent a rapid increase in temperature as it was unable to
radiate away all of the energy deposited across it by the non-thermal
electron beam and via thermal conduction. A narrow and high-density
(n<SUB>e</SUB> ≤ 10<SUP>15</SUP> cm<SUP>-3</SUP>) region at the
base of the flare transition region was the source of optical line
emission in the model atmosphere. The collision-stopping depth of
electrons was calculated throughout the evolution of the flare, and
it was found that the compression of the lower atmosphere may permit
electrons to penetrate farther into a flaring atmosphere compared to
a quiet Sun atmosphere.
---------------------------------------------------------
Title: Energy levels, radiative rates and electron impact excitation
rates for transitions in C III
Authors: Aggarwal, Kanti M.; Keenan, Francis P.
2015MNRAS.450.1151A Altcode: 2015arXiv150307673A
We report energy levels, radiative rates (A-values) and lifetimes for
the astrophysically important Be-like ion C III. For the calculations,
166 levels belonging to the n ≤ 5 configurations are considered and
the GRASP (General-purpose Relativistic Atomic Structure Package) is
adopted. Einstein A-coefficients are provided for all E1, E2, M1 and M2
transitions, while lifetimes are compared with available measurements
as well as theoretical results, and no large discrepancies noted. Our
energy levels are assessed to be accurate to better than 1 per cent
for a majority of levels, and A-values to better than 20 per cent for
most transitions. Collision strengths are also calculated, for which
the Dirac Atomic R-matrix Code (DARC) is used. A wide energy range,
up to 21 Ryd, is considered and resonances resolved in a fine energy
mesh in the thresholds region. The collision strengths are subsequently
averaged over a Maxwellian velocity distribution to determine effective
collision strengths up to a temperature of 8.0 × 10<SUP>5</SUP> K,
sufficient for most astrophysical applications. Our data are compared
with the recent R-matrix calculations of Fernández-Menchero et al., and
significant differences (up to over an order of magnitude) are noted for
several transitions over the complete temperature range of the results.
---------------------------------------------------------
Title: The Radiated Energy Budget Of Chromospheric Plasma In A Major
Solar Flare Deduced From Multi-Wavelength Observations
Authors: Milligan, Ryan; Kerr, Graham Stewart; Dennis, Brian; Hudson,
Hugh; Fletcher, Lyndsay; Allred, Joel; Chamberlin, Phillip; Ireland,
Jack; Mathioudakis, Mihalis; Keenan, Francis
2015TESS....130209M Altcode:
The response of the lower solar atmosphere is an important diagnostic
tool for understanding energy transport during solar flares. The 15
February 2011 X-class flare was fortuitously observed by a host of
space-based instruments that sampled the chromospheric response over
a range of lines and continua at <20s cadence. These include the
free-bound EUV continua of H I (Lyman), He I, and He II, plus the
emission lines of He II at 304Å and H I (Lyα) at 1216Å by SDO/EVE,
the UV continua at 1600Å and 1700Å by SDO/AIA, and the white light
continuum at 4504Å, 5550Å, and 6684Å, along with the Ca II H line
at 3968Å using Hinode/SOT. RHESSI also observed the entire event at
energies up to ~100keV, making it possible to determine the properties
of the nonthermal electrons deemed to be responsible for driving the
enhanced chromospheric emission under the assumption of thick-target
collisions. Integrating over the duration of the impulsive phase,
the total energy contained in the nonthermal electrons was found to be
>2×10<SUP>31</SUP> erg. By comparison, the summed energy detected by
instruments onboard SDO and Hinode amounted to ~3×10<SUP>30</SUP> erg;
about 15% of the total nonthermal energy. The Lyα line was found to
dominate the measured radiative losses in contrast to the predictions
of numerical simulations. Parameters of both the driving electron
distribution and the resulting chromospheric response are presented
in detail to encourage the numerical modeling of flare heating for
this event to determine the depth of the solar atmosphere at which
these line and continuum processes originate, and the mechanism(s)
responsible for their generation.
---------------------------------------------------------
Title: Electron impact excitation of Be-like ions: a comparison of
DARC and ICFT results
Authors: Aggarwal, Kanti M.; Keenan, Francis P.
2015MNRAS.447.3849A Altcode: 2015arXiv150100808A
Emission lines of Be-like ions are frequently observed in
astrophysical plasmas, and many are useful for density and temperature
diagnostics. However, accurate atomic data for energy levels, radiative
rates (A-values) and effective electron excitation collision strengths
(Υ) are required for reliable plasma modelling. In general, it is
reasonably straightforward to calculate energy levels and A-values to
a high level of accuracy. By contrast, considerable effort is required
to calculate Υ, and hence it is not always possible to assess the
accuracy of available data. Recently, two independent calculations
(adopting the R-matrix method) but with different approaches (DARC and
ICFT) have appeared for a range of Be-like ions. Therefore, in this
work we compare the two sets of Υ, highlight the large discrepancies
for a significant number of transitions and suggest possible reasons
for these.
---------------------------------------------------------
Title: The Dynamics of Rapid Redshifted and Blueshifted Excursions
in the Solar Hα Line
Authors: Kuridze, D.; Henriques, V.; Mathioudakis, M.; Erdélyi, R.;
Zaqarashvili, T. V.; Shelyag, S.; Keys, P. H.; Keenan, F. P.
2015ApJ...802...26K Altcode: 2015arXiv150106205K
We analyze high temporal and spatial resolution time-series of spectral
scans of the Hα line obtained with the CRisp Imaging SpectroPolarimeter
instrument mounted on the Swedish Solar Telescope. The data reveal
highly dynamic, dark, short-lived structures known as Rapid Redshifted
and Blueshifted Excursions (RREs, RBEs) that are on-disk absorption
features observed in the red and blue wings of spectral lines formed
in the chromosphere. We study the dynamics of RREs and RBEs by tracking
their evolution in space and time, measuring the speed of the apparent
motion, line of sight (LOS) Doppler velocity, and transverse velocity
of individual structures. A statistical study of their measured
properties shows that RREs and RBEs have similar occurrence rates,
lifetimes, lengths, and widths. They also display non-periodic,
nonlinear transverse motions perpendicular to their axes at speeds of
4-31 km s<SUP>-1</SUP>. Furthermore, both types of structures either
appear as high speed jets and blobs that are directed outwardly from
a magnetic bright point with speeds of 50-150 km s<SUP>-1</SUP>,
or emerge within a few seconds. A study of the different velocity
components suggests that the transverse motions along the LOS of
the chromospheric flux tubes are responsible for the formation and
appearance of these redshifted/blueshifted structures. The short
lifetime and fast disappearance of the RREs/RBEs suggests that, similar
to type II spicules, they are rapidly heated to transition region
or even coronal temperatures. We speculate that the Kelvin-Helmholtz
instability triggered by observed transverse motions of these structures
may be a viable mechanism for their heating.
---------------------------------------------------------
Title: Stable umbral chromospheric structures
Authors: Henriques, V. M. J.; Scullion, E.; Mathioudakis, M.; Kiselman,
D.; Gallagher, P. T.; Keenan, F. P.
2015A&A...574A.131H Altcode: 2014arXiv1412.6100H
<BR /> Aims: We seek to understand the morphology of the chromosphere in
sunspot umbra. We investigate if the horizontal structures observed
in the spectral core of the Ca II H line are ephemeral visuals
caused by the shock dynamics of more stable structures, and examine
their relationship with observables in the H-alpha line. <BR />
Methods: Filtergrams in the core of the Ca II H and H-alpha lines
as observed with the Swedish 1-m Solar Telescope are employed. We
utilise a technique that creates composite images and tracks the
flash propagation horizontally. <BR /> Results: We find 0.̋15 wide
horizontal structures, in all of the three target sunspots, for every
flash where the seeing is moderate to good. Discrete dark structures
are identified that are stable for at least two umbral flashes, as well
as systems of structures that live for up to 24 min. We find cases of
extremely extended structures with similar stability, with one such
structure showing an extent of 5”. Some of these structures have a
correspondence in H-alpha, but we were unable to find a one-to-one
correspondence for every occurrence. If the dark streaks are formed at
the same heights as umbral flashes, there are systems of structures
with strong departures from the vertical for all three analysed
sunspots. <BR /> Conclusions: Long-lived Ca II H filamentary horizontal
structures are a common and likely ever-present feature in the umbra
of sunspots. If the magnetic field in the chromosphere of the umbra
is indeed aligned with the structures, then the present theoretical
understanding of the typical umbra needs to be revisited. <P />Movies
associated to Figs. 3 and 4 are available in electronic form at <A
href="http://www.aanda.org/10.1051/0004-6361/201424664/olm">http://www.aanda.org</A>
---------------------------------------------------------
Title: Energy levels, radiative rates and electron impact excitation
rates for transitions in Fe XIV
Authors: Aggarwal, Kanti M.; Keenan, Francis P.
2014MNRAS.445.2015A Altcode: 2014arXiv1409.4214A
Energies and lifetimes are reported for the lowest 136 levels of Fe
XIV, belonging to the (1s<SUP>2</SUP>2s<SUP>2</SUP>2p<SUP>6</SUP>)
3s<SUP>2</SUP>3p, 3s3p<SUP>2</SUP>, 3s<SUP>2</SUP>3d, 3p<SUP>3</SUP>,
3s3p3d, 3p<SUP>2</SUP>3d, 3s3d<SUP>2</SUP>, 3p3d<SUP>2</SUP> and
3s<SUP>2</SUP>4ℓ configurations. Additionally, radiative rates,
oscillator strengths and line strengths are calculated for all electric
dipole (E1), magnetic dipole (M1), electric quadrupole (E2) and magnetic
quadrupole (M2) transitions. Theoretical lifetimes determined from
these radiative rates for most levels show satisfactory agreement
with earlier calculations, as well as with measurements. Electron
impact excitation collision strengths are also calculated with the
Dirac atomic R-matrix code (DARC) over a wide energy range up to 260
Ryd. Furthermore, resonances have been resolved in a fine energy
mesh to determine effective collision strengths, obtained after
integrating the collision strengths over a Maxwellian distribution
of electron velocities. Results are listed for all 9180 transitions
among the 136 levels over a wide range of electron temperatures, up
to 10<SUP>7.1</SUP> K. Comparisons are made with available results in
the literature, and the accuracy of the present data is assessed.
---------------------------------------------------------
Title: Energy levels, radiative rates and electron impact excitation
rates for transitions in Be-like Cl XIV, K XVI and Ge XXIX
Authors: Aggarwal, Kanti M.; Keenan, Francis P.
2014PhyS...89l5401A Altcode: 2014arXiv1409.3745A
Results for energy levels, radiative rates and electron impact
excitation (effective) collision strengths for transitions in Be-like
Cl XIV, K XVI and Ge XXIX are reported. For the calculations of energy
levels and radiative rates the general-purpose relativistic atomic
structure package is adopted, while for determining the collision
strengths and subsequently the excitation rates, the Dirac atomic
R-matrix code is used. Oscillator strengths, radiative rates and line
strengths are listed for all E1, E2, M1 and M2 transitions among the
lowest 98 levels of the n≤slant 4 configurations. Furthermore,
lifetimes are provided for all levels and comparisons made with
available theoretical and experimental results. Resonances in the
collision strengths are resolved in a fine energy mesh and averaged over
a Maxwellian velocity distribution to obtain the effective collision
strengths. Results obtained are listed over a wide temperature range
up to 10<SUP>7.8</SUP> K, depending on the ion.
---------------------------------------------------------
Title: The Radiated Energy Budget of Chromospheric Plasma in a Major
Solar Flare Deduced from Multi-wavelength Observations
Authors: Milligan, Ryan O.; Kerr, Graham S.; Dennis, Brian R.; Hudson,
Hugh S.; Fletcher, Lyndsay; Allred, Joel C.; Chamberlin, Phillip C.;
Ireland, Jack; Mathioudakis, Mihalis; Keenan, Francis P.
2014ApJ...793...70M Altcode: 2014arXiv1406.7657M
This paper presents measurements of the energy radiated by the lower
solar atmosphere, at optical, UV, and EUV wavelengths, during an
X-class solar flare (SOL2011-02-15T01:56) in response to an injection
of energy assumed to be in the form of nonthermal electrons. Hard
X-ray observations from RHESSI were used to track the evolution of
the parameters of the nonthermal electron distribution to reveal the
total power contained in flare accelerated electrons. By integrating
over the duration of the impulsive phase, the total energy contained
in the nonthermal electrons was found to be >2 × 10<SUP>31</SUP>
erg. The response of the lower solar atmosphere was measured in
the free-bound EUV continua of H I (Lyman), He I, and He II, plus
the emission lines of He II at 304 Å and H I (Lyα) at 1216 Å by
SDO/EVE, the UV continua at 1600 Å and 1700 Å by SDO/AIA, and the
white light continuum at 4504 Å, 5550 Å, and 6684 Å, along with the
Ca II H line at 3968 Å using Hinode/SOT. The summed energy detected
by these instruments amounted to ~3 × 10<SUP>30</SUP> erg about 15%
of the total nonthermal energy. The Lyα line was found to dominate
the measured radiative losses. Parameters of both the driving electron
distribution and the resulting chromospheric response are presented
in detail to encourage the numerical modeling of flare heating for
this event, to determine the depth of the solar atmosphere at which
these line and continuum processes originate, and the mechanism(s)
responsible for their generation.
---------------------------------------------------------
Title: Energy levels, radiative rates and electron impact excitation
rates for transitions in Si II
Authors: Aggarwal, Kanti M.; Keenan, Francis P.
2014MNRAS.442..388A Altcode: 2014arXiv1405.0184A
Energies for the lowest 56 levels, belonging to the 3s<SUP>2</SUP>
3p, 3s 3p<SUP>2</SUP>, 3p<SUP>3</SUP>, 3s<SUP>2</SUP> 3d, 3s 3p 3d,
3s<SUP>2</SUP> 4ℓ and 3s<SUP>2</SUP> 5ℓ configurations of Si
II, are calculated using the General-purpose Relativistic Atomic
Structure Package (GRASP) code. Analogous calculations have also
been performed (for up to 175 levels) using the Flexible Atomic Code
(FAC). Furthermore, radiative rates are calculated for all E1, E2,
M1 and M2 transitions. Extensive comparisons are made with available
theoretical and experimental energy levels, and the accuracy of the
present results is assessed to be better than 0.1 Ryd. Similarly,
the accuracy for radiative rates (and subsequently lifetimes) is
estimated to be better than 20 per cent for most of the (strong)
transitions. Electron impact excitation collision strengths are
also calculated, with the Dirac Atomic R-matrix Code (DARC), over
a wide energy range up to 13 Ryd. Finally, to determine effective
collision strengths, resonances are resolved in a fine energy mesh in
the thresholds region. These collision strengths are averaged over a
Maxwellian velocity distribution and results listed over a wide range
of temperatures, up to 10<SUP>5.5</SUP> K. Our data are compared with
earlier R-matrix calculations and differences noted, up to a factor of
2, for several transitions. Although scope remains for improvement,
the accuracy for our results of collision strengths and effective
collision strengths is assessed to be about 20 per cent for a majority
of transitions.
---------------------------------------------------------
Title: Dynamic properties of bright points in an active region
Authors: Keys, P. H.; Mathioudakis, M.; Jess, D. B.; Mackay, D. H.;
Keenan, F. P.
2014A&A...566A..99K Altcode: 2014arXiv1405.3923K
Context. Bright points (BPs) are small-scale, magnetic features
ubiquitous across the solar surface. Previously, we have observed and
noted their properties for quiet Sun regions. Here, we determine the
dynamic properties of BPs using simultaneous quiet Sun and active region
data. <BR /> Aims: The aim of this paper is to compare the properties
of BPs in both active and quiet Sun regions and to determine any
difference in the dynamics and general properties of BPs as a result of
the varying magnetic activity within these two regions. <BR /> Methods:
High spatial and temporal resolution G-band observations of active
region AR11372 were obtained with the Rapid Oscillations in the Solar
Atmosphere instrument at the Dunn Solar Telescope. Three subfields of
varying polarity and magnetic flux density were selected with the aid of
magnetograms obtained from the Helioseismic and Magnetic Imager on board
the Solar Dynamics Observatory. Bright points within these subfields
were subsequently tracked and analysed. <BR /> Results: It is found that
BPs within active regions display attenuated velocity distributions
with an average horizontal velocity of ~0.6 km s<SUP>-1</SUP>,
compared to the quiet region which had an average velocity of 0.9 km
s<SUP>-1</SUP>. Active region BPs are also ~21% larger than quiet
region BPs and have longer average lifetimes (~132 s) than their
quiet region counterparts (88 s). No preferential flow directions are
observed within the active region subfields. The diffusion index (γ) is
estimated at ~1.2 for the three regions. <BR /> Conclusions: We confirm
that the dynamic properties of BPs arise predominately from convective
motions. The presence of stronger field strengths within active regions
is the likely reason behind the varying properties observed. We believe
that larger amounts of magnetic flux will attenuate BP velocities by a
combination of restricting motion within the intergranular lanes and
by increasing the number of stagnation points produced by inhibited
convection. Larger BPs are found in regions of higher magnetic flux
density and we believe that lifetimes increase in active regions as
the magnetic flux stabilises the BPs.
---------------------------------------------------------
Title: Plasma properties and Stokes profiles during the lifetime of
a photospheric magnetic bright point
Authors: Hewitt, R. L.; Shelyag, S.; Mathioudakis, M.; Keenan, F. P.
2014A&A...565A..84H Altcode: 2014arXiv1404.0132H
<BR /> Aims: In this paper we aim to investigate the evolution of plasma
properties and Stokes parameters in photospheric magnetic bright points
using 3D magneto-hydrodynamical simulations and radiative diagnostics of
solar granulation. <BR /> Methods: Simulated time-dependent radiation
parameters and plasma properties were investigated throughout the
evolution of a bright point. Synthetic Stokes profiles for the FeI
630.25 nm line were calculated, which also allowed the evolution of the
Stokes-I line strength and Stokes-V area and amplitude asymmetries
to be investigated. <BR /> Results: Our results are consistent
with theoretical predictions and published observations describing
convective collapse, and confirm this as the bright point formation
process. Through degradation of the simulated data to match the spatial
resolution of SOT, we show that high spatial resolution is crucial for
the detection of changing spectro-polarimetric signatures throughout
a magnetic bright point's lifetime. We also show that the signature
downflow associated with the convective collapse process tends towards
zero as the radiation intensity in the bright point peaks, because
of the magnetic forces present restricting the flow of material in
the flux tube. <P />Appendix A is available in electronic form at <A
href="http://www.aanda.org/10.1051/0004-6361/201322882/olm">http://www.aanda.org</A>
---------------------------------------------------------
Title: Intensity Enhancement of O VI Ultraviolet Emission Lines in
Solar Spectra due to Opacity
Authors: Keenan, F. P.; Doyle, J. G.; Madjarska, M. S.; Rose, S. J.;
Bowler, L. A.; Britton, J.; McCrink, L.; Mathioudakis, M.
2014ApJ...784L..39K Altcode: 2014arXiv1403.1470K
Opacity is a property of many plasmas. It is normally expected that if
an emission line in a plasma becomes optically thick, then its intensity
ratio to that of another transition that remains optically thin
should decrease. However, radiative transfer calculations undertaken
both by ourselves and others predict that under certain conditions the
intensity ratio of an optically thick to an optically thin line can show
an increase over the optically thin value, indicating an enhancement
in the former. These conditions include the geometry of the emitting
plasma and its orientation to the observer. A similar effect can
take place between lines of differing optical depths. While previous
observational studies have focused on stellar point sources, here we
investigate the spatially resolved solar atmosphere using measurements
of the I(1032 Å)/I(1038 Å) intensity ratio of O VI in several regions
obtained with the Solar Ultraviolet Measurements of Emitted Radiation
instrument on board the Solar and Heliospheric Observatory satellite. We
find several I(1032 Å)/I(1038 Å) ratios observed on the disk to be
significantly larger than the optically thin value of 2.0, providing
the first detection (to our knowledge) of intensity enhancement in
the ratio arising from opacity effects in the solar atmosphere. The
agreement between observation and theory is excellent and confirms
that the O VI emission originates from a slab-like geometry in the
solar atmosphere, rather than from cylindrical structures.
---------------------------------------------------------
Title: Early-type stars observed in the ESO UVES Paranal Observatory
Project - IV. Studies of CN, CH<SUP>+</SUP> and CH in the interstellar
medium
Authors: Smoker, J.; Ledoux, C.; Jehin, E.; Keenan, F. P.; Kennedy,
M.; Cabanac, R.; Melo, C.
2014MNRAS.438.1127S Altcode: 2013MNRAS.tmp.2928S
High spectral resolution (∼80 000) and signal-to-noise observations
from the Ultraviolet and Visual Echelle Spectrograph Paranal Observatory
Project (UVES-POP) are used to study the interstellar molecular lines CN
(3874 Å), CH<SUP>+</SUP> (3957, 4232 Å) and CH (3886, 4300 Å) towards
74 O- and B-type stellar sightlines. Additionally, archive data are
presented for 140 ELODIE early-type stellar sightlines at R = 42 000,
plus 25 FEROS at R = 48 000 and 3 UVES at R > 50 000, mainly in the
CH<SUP>+</SUP> (4232 Å) and CH (3886, 4300 Å) transitions. Detection
rates are ∼45 per cent for CN and ∼67 per cent for the other lines
in the POP sample, and ∼10-15 per cent for CH<SUP>+</SUP> and CH lines
in the additional sample. CH and CH<SUP>+</SUP> are well correlated
between log[N(CH) cm<SUP>-2</SUP>]∼12-14, implying that these clouds
are CH<SUP>+</SUP>-like CH and not CN-like CH. CH is also very well
correlated with Na I D in the range log[N(Na I cm<SUP>-2</SUP>])
∼12.2-14.2. A few sightlines show tentative velocity shifts of ∼2
km s<SUP>-1</SUP> between CH and CH<SUP>+</SUP>, which appear to be
caused by differences in component strength in blends, and hence do
not provide firm evidence for shocks. Finally, we describe a search
for <SUP>13</SUP>CH<SUP>+</SUP> in a sightline towards HD 76341. No
<SUP>13</SUP>CH<SUP>+</SUP> is detected, placing a limit on the
<SUP>13</SUP>CH<SUP>+</SUP> to <SUP>12</SUP>CH<SUP>+</SUP> ratio of
∼0.01. If a formal fit is attempted, the equivalent width ratio in
the two isotopes is a factor ∼90 but with large errors.
---------------------------------------------------------
Title: Energy levels, radiative rates and electron impact excitation
rates for transitions in Al X
Authors: Aggarwal, Kanti M.; Keenan, Francis P.
2014MNRAS.438.1223A Altcode: 2013MNRAS.tmp.2966A; 2013arXiv1311.5516A
Energy levels, radiative rates and lifetimes are calculated among the
lowest 98 levels of the n ≤ 4 configurations of Be-like Al X. The
GRASP (General-purpose Relativistic Atomic Structure Package) is adopted
and data are provided for all E1, E2, M1 and M2 transitions. Similar
data are also obtained with the FAC (Flexible Atomic Code) to
assess the accuracy of the calculations. Based on comparisons between
calculations with the two codes as well as with available measurements,
our listed energy levels are assessed to be accurate to better than
0.3 per cent. However, the accuracy for radiative rates and lifetimes
is estimated to be about 20 per cent. Collision strengths are also
calculated for which the DARC (Dirac Atomic R-matrix Code) is used. A
wide energy range (up to 380 Ryd) is considered and resonances resolved
in a fine energy mesh in the thresholds region. The collision strengths
are subsequently averaged over a Maxwellian velocity distribution to
determine effective collision strengths up to a temperature of 1.6 ×
10<SUP>7</SUP> K. Our results are compared with the previous (limited)
atomic data and significant differences (up to a factor of 4) are noted
for several transitions, particularly those which are not allowed in
jj coupling.
---------------------------------------------------------
Title: Electron-impact Excitation Collision Strengths and Theoretical
Line Intensities for Transitions in S III
Authors: Grieve, M. F. R.; Ramsbottom, C. A.; Hudson, C. E.; Keenan,
F. P.
2014ApJ...780..110G Altcode: 2013arXiv1308.0241G
We present Maxwellian-averaged effective collision strengths for the
electron-impact excitation of S III over a wide range of electron
temperatures of astrophysical importance, log T<SUB>e</SUB> (K)
= 3.0-6.0. The calculation incorporates 53 fine-structure levels
arising from the six configurations—3s <SUP>2</SUP>3p <SUP>2</SUP>,
3s3p <SUP>3</SUP>, 3s <SUP>2</SUP>3p3d, 3s <SUP>2</SUP>3p4s, 3s
<SUP>2</SUP>3p4p, and 3s <SUP>2</SUP>3p4d—giving rise to 1378
individual lines and is undertaken using the recently developed RMATRX
II plus FINE95 suite of codes. A detailed comparison is made with a
previous R-matrix calculation and significant differences are found
for some transitions. The atomic data are subsequently incorporated
into the modeling code CLOUDY to generate line intensities for a
range of plasma parameters, with emphasis on allowed ultraviolet
extreme-ultraviolet emission lines detected from the Io plasma
torus. Electron density-sensitive line ratios are calculated with
the present atomic data and compared with those from CHIANTI v7.1,
as well as with Io plasma torus spectra obtained by Far-Ultraviolet
Spectroscopic Explorer and Extreme-Ultraviolet Explorer. The present
line intensities are found to agree well with the observational results
and provide a noticeable improvement on the values predicted by CHIANTI.
---------------------------------------------------------
Title: Characteristics of Transverse Waves in Chromospheric Mottles
Authors: Kuridze, D.; Verth, G.; Mathioudakis, M.; Erdélyi, R.;
Jess, D. B.; Morton, R. J.; Christian, D. J.; Keenan, F. P.
2013ApJ...779...82K Altcode: 2013arXiv1310.3628K
Using data obtained by the high temporal and spatial resolution
Rapid Oscillations in the Solar Atmosphere instrument on the Dunn
Solar Telescope, we investigate at an unprecedented level of detail
transverse oscillations in chromospheric fine structures near the solar
disk center. The oscillations are interpreted in terms of propagating
and standing magnetohydrodynamic kink waves. Wave characteristics
including the maximum transverse velocity amplitude and the phase
speed are measured as a function of distance along the structure's
length. Solar magnetoseismology is applied to these measured parameters
to obtain diagnostic information on key plasma parameters (e.g.,
magnetic field, density, temperature, flow speed) of these localized
waveguides. The magnetic field strength of the mottle along the ~2 Mm
length is found to decrease by a factor of 12, while the local plasma
density scale height is ~280 ± 80 km.
---------------------------------------------------------
Title: Solar Flare Impulsive Phase Emission Observed with SDO/EVE
Authors: Kennedy, Michael B.; Milligan, Ryan O.; Mathioudakis, Mihalis;
Keenan, Francis P.
2013ApJ...779...84K Altcode: 2013arXiv1310.4649K
Differential emission measures (DEMs) during the impulsive phase
of solar flares were constructed using observations from the
EUV Variability Experiment (EVE) and the Markov-Chain Monte Carlo
method. Emission lines from ions formed over the temperature range log
T<SUB>e</SUB> = 5.8-7.2 allow the evolution of the DEM to be studied
over a wide temperature range at 10 s cadence. The technique was applied
to several M- and X-class flares, where impulsive phase EUV emission
is observable in the disk-integrated EVE spectra from emission lines
formed up to 3-4 MK and we use spatially unresolved EVE observations
to infer the thermal structure of the emitting region. For the nine
events studied, the DEMs exhibited a two-component distribution during
the impulsive phase, a low-temperature component with peak temperature
of 1-2 MK, and a broad high-temperature component from 7 to 30 MK. A
bimodal high-temperature component is also found for several events,
with peaks at 8 and 25 MK during the impulsive phase. The origin of the
emission was verified using Atmospheric Imaging Assembly images to be
the flare ribbons and footpoints, indicating that the constructed DEMs
represent the spatially average thermal structure of the chromospheric
flare emission during the impulsive phase.
---------------------------------------------------------
Title: Energy levels and radiative rates for transitions in Ti VII
Authors: Aggarwal, Kanti M.; Keenan, Francis P.
2013PhyS...88f5304A Altcode: 2013arXiv1311.0650A
We report calculations of energy levels, radiative rates, oscillator
strengths and line strengths for transitions among the lowest 231 levels
of Ti VII. The general-purpose relativistic atomic structure package and
flexible atomic code are adopted for the calculations. Radiative rates,
oscillator strengths and line strengths are provided for all electric
dipole (E1), magnetic dipole (M1), electric quadrupole (E2) and magnetic
quadrupole (M2) transitions among the 231 levels, although calculations
have been performed for a much larger number of levels (159 162). In
addition, lifetimes for all 231 levels are listed. Comparisons are
made with existing results and the accuracy of the data is assessed. In
particular, the most recent calculations reported by Singh et al (2012
Can. J. Phys. 90 833) are found to be unreliable, with discrepancies
for energy levels of up to 1 Ryd and for radiative rates of up to five
orders of magnitude for several transitions, particularly the weaker
ones. Based on several comparisons among a variety of calculations
with two independent codes, as well as with the earlier results, our
listed energy levels are estimated to be accurate to better than 1%
(within 0.1 Ryd), whereas results for radiative rates and other related
parameters should be accurate to better than 20%.
---------------------------------------------------------
Title: Electron impact excitation of Mg VIII . Collision strengths,
transition probabilities and theoretical EUV and soft X-ray line
intensities for Mg VIII
Authors: Grieve, M. F. R.; Ramsbottom, C. A.; Keenan, F. P.
2013A&A...556A..24G Altcode:
Context. Mg viii emission lines are observed in a range of astronomical
objects such as the Sun, other cool stars and in the coronal line
region of Seyfert galaxies. Under coronal conditions Mg viii emits
strongly in the extreme ultraviolet (EUV) and soft X-ray spectral
regions which makes it an ideal ion for plasma diagnostics. <BR
/> Aims: Two theoretical atomic models, consisting of 125 fine
structure levels, are developed for the Mg viii ion. The 125 levels
arise from the 2s<SUP>2</SUP>2p, 2s2p<SUP>2</SUP>, 2p<SUP>3</SUP>,
2s<SUP>2</SUP>3s, 2s<SUP>2</SUP>3p, 2s<SUP>2</SUP>3d, 2s2p3s, 2s2p3p,
2s2p3d, 2p<SUP>2</SUP>3s, 2p<SUP>2</SUP>3p and 2p<SUP>2</SUP>3d
configurations. Electron impact excitation collision strengths and
radiative transition probabilities are calculated for both Mg viii
models, compared with existing data, and the best model selected to
generate a set of theoretical emission line intensities. The EUV lines,
covering 312-790 Å, are compared with existing solar spectra (SERTS-89
and SUMER), while the soft X-ray transitions (69-97 Å) are examined
for potential density diagnostic line ratios and also compared with
the limited available solar and stellar observational data. <BR />
Methods: The R-matrix codes Breit-Pauli RMATRXI and RMATRXII are
utilised, along with the PSTGF code, to calculate the collision
strengths for two Mg viii models. Collision strengths are averaged
over a Maxwellian distribution to produce the corresponding effective
collision strengths for use in astrophysical applications. Transition
probabilities are also calculated using the CIV3 atomic structure
code. The best data are then incorporated into the modelling code CLOUDY
and line intensities generated for a range of electron temperatures
and densities appropriate to solar and stellar coronal plasmas. <BR />
Results: The present effective collision strengths are compared with two
previous calculations. Good levels of agreement are found with the most
recent, but there are large differences with the other for forbidden
transitions. The resulting line intensities compare favourably with
the observed values from the SERTS-89 and SUMER spectra. Theoretical
soft X-ray emission lines are presented and several density diagnostic
line ratios examined, which are in reasonable agreement with the
limited observational data available. <P />The effective collision
strength data are only available at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/556/A24">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/556/A24</A>
---------------------------------------------------------
Title: Expanded Iron UTA Spectra—Probing the Thermal Stability
Limits in AGN Clouds
Authors: Ferland, G. J.; Kisielius, R.; Keenan, F. P.; van Hoof,
P. A. M.; Jonauskas, V.; Lykins, M. L.; Porter, R. L.; Williams,
R. J. R.
2013ApJ...767..123F Altcode: 2013arXiv1303.0316F
The Fe unresolved transition arrays (UTAs) produce prominent features in
the ~15-17 Å wavelength range in the spectra of active galactic nuclei
(AGNs). Here, we present new calculations of the energies and oscillator
strengths of inner-shell lines from Fe XIV, Fe XV, and Fe XVI. These
are crucial ions since they are dominant at inflection points in the gas
thermal stability curve, and UTA excitation followed by autoionization
is an important ionization mechanism for these species. We incorporate
these, and data reported in previous papers, into the plasma simulation
code Cloudy. This updated physics is subsequently employed to reconsider
the thermally stable phases in absorbing media in AGNs. We show how
the absorption profile of the Fe XIV UTA depends on density, due to
the changing populations of levels within the ground configuration.
---------------------------------------------------------
Title: Transit timing variations in WASP-10b induced by stellar
activity
Authors: Barros, S. C. C.; Boué, G.; Gibson, N. P.; Pollacco, D. L.;
Santerne, A.; Keenan, F. P.; Skillen, I.; Street, R. A.
2013MNRAS.430.3032B Altcode: 2013arXiv1301.3760B; 2013MNRAS.tmp..760B
The hot-Jupiter WASP-10b was reported by Maciejewski et al. to
show transit timing variations (TTVs) with an amplitude of ∼3.5
min. These authors proposed that the observed TTVs were caused by
a 0.1M<SUB>Jup</SUB> perturbing companion with an orbital period of
∼5.23 d, and hence, close to the outer 5:3 mean-motion resonance
with WASP-10b. To test this scenario, we present eight new transit
light curves of WASP-10b obtained with the Faulkes Telescope North
and the Liverpool Telescope. The new light curves, together with 22
previously published ones, were modelled with a Markov Chain Monte Carlo
transit fitting code. Transit depth differences reported for WASP-10b
are thought to be due to starspot-induced brightness modulation of the
host star. Assuming the star is brighter at the activity minimum, we
favour a small planetary radius. We find R_p =1.039^{+0.043}_{-0.049}
{R_Jup} in agreement with Johnson et al. and Maciejewski et al. Recent
studies find no evidence for a significant eccentricity in this
system. We present consistent system parameters for a circular orbit
and refine the orbital ephemeris of WASP-10b. Our homogeneously derived
transit times do not support the previous claimed TTV signal, which
was strongly dependent on two previously published transits that have
been incorrectly normalized. Nevertheless, a linear ephemeris is not
a statistically good fit to the transit times of WASP-10b. We show
that the observed transit time variations are due to spot occultation
features or systematics. We discuss and exemplify the effects of
occultation spot features in the measured transit times and show that
despite spot occultation during egress and ingress being difficult
to distinguish in the transit light curves, they have a significant
effect in the measured transit times. We conclude that if we account
for spot features, the transit times of WASP-10b are consistent with a
linear ephemeris with the exception of one transit (epoch 143) which
is a partial transit. Therefore, there is currently no evidence for
the existence of a companion to WASP-10b. Our results support the lack
of TTVs of hot-Jupiters reported for the Kepler sample.
---------------------------------------------------------
Title: Failed filament eruption inside a coronal mass ejection in
active region 11121
Authors: Kuridze, D.; Mathioudakis, M.; Kowalski, A. F.; Keys, P. H.;
Jess, D. B.; Balasubramaniam, K. S.; Keenan, F. P.
2013A&A...552A..55K Altcode: 2013arXiv1302.5931K
<BR /> Aims: We study the formation and evolution of a failed filament
eruption observed in NOAA active region 11121 near the southeast limb on
November 6, 2010. <BR /> Methods: We used a time series of SDO/AIA 304,
171, 131, 193, 335, and 94 Å images, SDO/HMI magnetograms, as well as
ROSA and ISOON Hα images to study the erupting active region. <BR />
Results: We identify coronal loop arcades associated with a quadrupolar
magnetic configuration, and show that the expansion and cancellation
of the central loop arcade system over the filament is followed by
the eruption of the filament. The erupting filament reveals a clear
helical twist and develops the same sign of writhe in the form of
inverse γ-shape. <BR /> Conclusions: The observations support the
"magnetic breakout" process in which the eruption is triggered by
quadrupolar reconnection in the corona. We propose that the formation
mechanism of the inverse γ-shape flux rope is the magnetohydrodynamic
helical kink instability. The eruption has failed because of the
large-scale, closed, overlying magnetic loop arcade that encloses
the active region. <P />Movies are available in electronic form at
<A href="http://www.aanda.org">http://www.aanda.org</A>
---------------------------------------------------------
Title: Tracking magnetic bright point motions through the solar
atmosphere
Authors: Keys, P. H.; Mathioudakis, M.; Jess, D. B.; Shelyag, S.;
Christian, D. J.; Keenan, F. P.
2013MNRAS.428.3220K Altcode: 2012MNRAS.tmp..182K; 2012arXiv1210.5904K
High-cadence, multiwavelength observations and simulations are
employed for the analysis of solar photospheric magnetic bright
points (MBPs) in the quiet Sun. The observations were obtained with
the Rapid Oscillations in the Solar Atmosphere (ROSA) imager and
the Interferometric Bidimensional Spectrometer at the Dunn Solar
Telescope. Our analysis reveals that photospheric MBPs have an average
transverse velocity of approximately 1 km s<SUP>-1</SUP>, whereas their
chromospheric counterparts have a slightly higher average velocity of
1.4 km s<SUP>-1</SUP>. Additionally, chromospheric MBPs were found to be
around 63 per cent larger than the equivalent photospheric MBPs. These
velocity values were compared with the output of numerical simulations
generated using the muram code. The simulated results were similar,
but slightly elevated, when compared to the observed data. An average
velocity of 1.3 km s<SUP>-1</SUP> was found in the simulated G-band
images and an average of 1.8 km s<SUP>-1</SUP> seen in the velocity
domain at a height of 500 km above the continuum formation layer. Delays
in the change of velocities were also analysed. Average delays of ∼4
s between layers of the simulated data set were established and values
of ∼29 s observed between G-band and Ca ii K ROSA observations. The
delays in the simulations are likely to be the result of oblique
granular shock waves, whereas those found in the observations are
possibly the result of a semi-rigid flux tube.
---------------------------------------------------------
Title: Vortices in the Solar Photosphere
Authors: Shelyag, S.; Fedun, V.; Erdélyi, R.; Keenan, F. P.;
Mathioudakis, M.
2012ASPC..463..107S Altcode: 2012arXiv1202.1966S
Using numerical simulations of the magnetized solar photosphere
and radiative diagnostics of the simulated photospheric models,
we further analyse the physical nature of magnetic photospheric
intergranular vortices. We confirm the magnetic nature of the vortices
and find that most MHD Umov-Poynting flux is produced by horizontal
vortex motions in the magnetised intergranular lanes. In addition,
we consider possible ways to directly observe photospheric magnetic
vortices using spectropolarimetry. Although horizontal plasma motions
cannot be detected in the spectropolarimetric observations of solar disk
center, we find an observational signature of photospheric vortices in
simulated observations of Stokes-V amplitude asymmetry close to the
solar limb. Potential ways to find the vortices in the observations
are discussed.
---------------------------------------------------------
Title: The Source of 3 Minute Magnetoacoustic Oscillations in
Coronal Fans
Authors: Jess, D. B.; De Moortel, I.; Mathioudakis, M.; Christian,
D. J.; Reardon, K. P.; Keys, P. H.; Keenan, F. P.
2012ApJ...757..160J Altcode: 2012arXiv1208.3194J
We use images of high spatial, spectral, and temporal resolution,
obtained using both ground- and space-based instrumentation, to
investigate the coupling between wave phenomena observed at numerous
heights in the solar atmosphere. Analysis of 4170 Å continuum images
reveals small-scale umbral intensity enhancements, with diameters
~0farcs6, lasting in excess of 30 minutes. Intensity oscillations
of ≈3 minutes are observed to encompass these photospheric
structures, with power at least three orders of magnitude higher
than the surrounding umbra. Simultaneous chromospheric velocity and
intensity time series reveal an 87° ± 8° out-of-phase behavior,
implying the presence of standing modes created as a result of
partial wave reflection at the transition region boundary. We find a
maximum waveguide inclination angle of ≈40° between photospheric
and chromospheric heights, combined with a radial expansion factor
of <76%. An average blueshifted Doppler velocity of ≈1.5 km
s<SUP>-1</SUP>, in addition to a time lag between photospheric and
chromospheric oscillatory phenomena, confirms the presence of upwardly
propagating slow-mode waves in the lower solar atmosphere. Propagating
oscillations in EUV intensity are detected in simultaneous coronal
fan structures, with a periodicity of 172 ± 17 s and a propagation
velocity of 45 ± 7 km s<SUP>-1</SUP>. Numerical simulations reveal that
the damping of the magnetoacoustic wave trains is dominated by thermal
conduction. The coronal fans are seen to anchor into the photosphere
in locations where large-amplitude umbral dot (UD) oscillations
manifest. Derived kinetic temperature and emission measure time series
display prominent out-of-phase characteristics, and when combined with
the previously established sub-sonic wave speeds, we conclude that
the observed EUV waves are the coronal counterparts of the upwardly
propagating magnetoacoustic slow modes detected in the lower solar
atmosphere. Thus, for the first time, we reveal how the propagation
of 3 minute magnetoacoustic waves in solar coronal structures is a
direct result of amplitude enhancements occurring in photospheric UDs.
---------------------------------------------------------
Title: Time-dependent Density Diagnostics of Solar Flare Plasmas
Using SDO/EVE
Authors: Milligan, Ryan O.; Kennedy, Michael B.; Mathioudakis, Mihalis;
Keenan, Francis P.
2012ApJ...755L..16M Altcode: 2012arXiv1207.1990M
Temporally resolved electron density measurements of solar flare plasmas
are presented using data from the EUV Variability Experiment (EVE) on
board the Solar Dynamics Observatory. The EVE spectral range contains
emission lines formed between 10<SUP>4</SUP> and 10<SUP>7</SUP> K,
including transitions from highly ionized iron (gsim10 MK). Using
three density-sensitive Fe XXI ratios, peak electron densities of
10<SUP>11.2</SUP>-10<SUP>12.1</SUP> cm<SUP>-3</SUP> were found during
four X-class flares. While previous measurements of densities at such
high temperatures were made at only one point during a flaring event,
EVE now allows the temporal evolution of these high-temperature
densities to be determined at 10 s cadence. A comparison with GOES
data revealed that the peak of the density time profiles for each line
ratio correlated well with that of the emission measure time profile
for each of the events studied.
---------------------------------------------------------
Title: Mechanisms for MHD Poynting Flux Generation in Simulations
of Solar Photospheric Magnetoconvection
Authors: Shelyag, S.; Mathioudakis, M.; Keenan, F. P.
2012ApJ...753L..22S Altcode: 2012arXiv1206.0030S
We investigate the generation mechanisms of MHD Poynting flux in the
magnetized solar photosphere. Using radiative MHD modeling of the
solar photosphere with initial magnetic configurations that differ
in their field strength and geometry, we show the presence of two
different mechanisms for MHD Poynting flux generation in simulations
of solar photospheric magnetoconvection. The weaker mechanism is
connected to vertical transport of weak horizontal magnetic fields in
the convectively stable layers of the upper photosphere, while the
stronger is the production of Poynting flux in strongly magnetized
intergranular lanes experiencing horizontal vortex motions. These
mechanisms may be responsible for the energy transport from the solar
convection zone to the higher layers of the solar atmosphere.
---------------------------------------------------------
Title: Solar Flare Observations of the EUV Continua
Authors: Milligan, Ryan O.; Chamberlin, P.; Hudson, H.; Woods, T.;
Mathioudakis, M.; Fletcher, L.; Kowalski, A.; Keenan, F.
2012AAS...22052105M Altcode:
Recent solar flare simulations suggest that the energy deposited in the
chromosphere by nonthermal electrons during a flare's impulsive phase
is re-emitted in the form of recombination (free-bound) continua, in
particular, the Lyman, Balmer, and Paschen continua of hydrogen, and
the He I and He II continua (Allred et al. 2005). However, definitive
observations of free-bound emission during solar flares have been scarce
in recent years as many modern, space-based instruments do not have
the required sensitivity, wavelength coverage, or duty cycle. With
the launch of SDO, these observations are now routinely available
thanks to the EUV Variability Experiment (EVE) instrument. Here we
present unambiguous, spectrally and temporally resolved detections of
enhanced free-free and free-bound continua during the first X-class
solar flare of Solar Cycle 24. While we find that the flare energy
in the EVE spectral range amounts to at most a few percent of the
total flare energy, these findings highlight the capability of EVE
in giving us the first comprehensive look at these diagnostically
important continuum components.
---------------------------------------------------------
Title: Electron Impact Excitation Of Ti XIX
Authors: Aggarwal, Kanti M.; Keenan, F. P.
2012AAS...22020801A Altcode:
Emission lines of Ti XIX are important for the modeling and diagnostics
of lasing, fusion and astrophysical plasmas, for which atomic data
are required for a variety of parameters, such as energy levels,
radiative rates (A- values), and excitation rates or equivalently
the effective collision strengths (Υ), which are obtained from the
electron impact collision strengths (Ω). Experimentally, energy levels
are available for Ti XIX on the NIST website, but there is paucity for
accurate collisional atomic data. Therefore, here we report a complete
set of results (namely energy levels, radiative rates, and effective
collision strengths) for all transitions among the lowest 98 levels
of Ti XIX. These levels belong to the (1s2) 2s2, 2s2p, 2p2, 2s3l,
2p3l, 2s4l, and 2p4l configurations. Finally, we also report the A-
values for four types of transitions, namely electric dipole (E1),
electric quadrupole (E2), magnetic dipole (M1), and magnetic quadrupole
(M2), because these are also required for plasma modeling. For our
calculations of wavefunctions, we have adopted the fully relativistic
GRASP code, and for the calculations of Ω, the Dirac atomic R-matrix
code (DARC) of PH Norrington and IP Grant. Additionally, parallel
calculations have also been performed with the Flexible Atomic Code
(FAC) of Gu, so that all atomic parameters can be rigorously assessed
for accuracy.
---------------------------------------------------------
Title: Transverse Oscillations in Chromospheric Mottles
Authors: Kuridze, D.; Morton, R. J.; Erdélyi, R.; Dorrian, G. D.;
Mathioudakis, M.; Jess, D. B.; Keenan, F. P.
2012ApJ...750...51K Altcode: 2012arXiv1202.5697K
A number of recent investigations have revealed that transverse
waves are ubiquitous in the solar chromosphere. The vast majority
of these have been reported in limb spicules and active region
fibrils. We investigate long-lived, quiet-Sun, on-disk features such as
chromospheric mottles (jet-like features located at the boundaries of
supergranular cells) and their transverse motions. The observations
were obtained with the Rapid Oscillations in the Solar Atmosphere
instrument at the Dunn Solar Telescope. The data set is comprised
of simultaneous imaging in the Hα core, Ca II K, and G band of an
on-disk quiet-Sun region. Time-distance techniques are used to study
the characteristics of the transverse oscillations. We detect over
40 transverse oscillations in both bright and dark mottles, with
periods ranging from 70 to 280 s, with the most frequent occurrence
at ~165 s. The velocity amplitudes and transverse displacements
exhibit characteristics similar to limb spicules. Neighboring mottles
oscillating in-phase are also observed. The transverse oscillations
of individual mottles are interpreted in terms of magnetohydrodynamic
kink waves. Their estimated periods and damping times are consistent
with phase mixing and resonant mode conversion.
---------------------------------------------------------
Title: Observations of Enhanced Extreme Ultraviolet Continua during
an X-Class Solar Flare Using SDO/EVE
Authors: Milligan, Ryan O.; Chamberlin, Phillip C.; Hudson, Hugh S.;
Woods, Thomas N.; Mathioudakis, Mihalis; Fletcher, Lyndsay; Kowalski,
Adam F.; Keenan, Francis P.
2012ApJ...748L..14M Altcode: 2012arXiv1202.1731M
Observations of extreme ultraviolet (EUV) emission from an X-class solar
flare that occurred on 2011 February 15 at 01:44 UT are presented,
obtained using the EUV Variability Experiment (EVE) on board the
Solar Dynamics Observatory. The complete EVE spectral range covers
the free-bound continua of H I (Lyman continuum), He I, and He II,
with recombination edges at 91.2, 50.4, and 22.8 nm, respectively. By
fitting the wavelength ranges blueward of each recombination edge
with an exponential function, light curves of each of the integrated
continua were generated over the course of the flare, as was emission
from the free-free continuum (6.5-37 nm). The He II 30.4 nm and Lyα
121.6 nm lines, and soft X-ray (SXR; 0.1-0.8 nm) emission from GOES are
also included for comparison. Each free-bound continuum was found to
have a rapid rise phase at the flare onset similar to that seen in the
25-50 keV light curves from RHESSI, suggesting that they were formed
by recombination with free electrons in the chromosphere. However,
the free-free emission exhibited a slower rise phase seen also in the
SXR emission from GOES, implying a predominantly coronal origin. By
integrating over the entire flare the total energy emitted via
each process was determined. We find that the flare energy in the
EVE spectral range amounts to at most a few percent of the total
flare energy, but EVE gives us a first comprehensive look at these
diagnostically important continuum components.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Intermediate high-velocity clouds
distances (Smoker+, 2011)
Authors: Smoker, J. V.; Fox, A. J.; Keenan, F. P.
2012yCat..74151105S Altcode:
We use a combination of new observations and data from various
astronomical archives. The FEROS observations were taken on the nights
of 2006 December 8 and 9. <P />(1 data file).
---------------------------------------------------------
Title: Propagating Wave Phenomena Detected in Observations and
Simulations of the Lower Solar Atmosphere
Authors: Jess, D. B.; Shelyag, S.; Mathioudakis, M.; Keys, P. H.;
Christian, D. J.; Keenan, F. P.
2012ApJ...746..183J Altcode: 2012arXiv1201.1981J
We present high-cadence observations and simulations of the solar
photosphere, obtained using the Rapid Oscillations in the Solar
Atmosphere imaging system and the MuRAM magnetohydrodynamic (MHD) code,
respectively. Each data set demonstrates a wealth of magnetoacoustic
oscillatory behavior, visible as periodic intensity fluctuations
with periods in the range 110-600 s. Almost no propagating waves with
periods less than 140 s and 110 s are detected in the observational
and simulated data sets, respectively. High concentrations of power
are found in highly magnetized regions, such as magnetic bright points
and intergranular lanes. Radiative diagnostics of the photospheric
simulations replicate our observational results, confirming that the
current breed of MHD simulations are able to accurately represent the
lower solar atmosphere. All observed oscillations are generated as
a result of naturally occurring magnetoconvective processes, with no
specific input driver present. Using contribution functions extracted
from our numerical simulations, we estimate minimum G-band and 4170 Å
continuum formation heights of 100 km and 25 km, respectively. Detected
magnetoacoustic oscillations exhibit a dominant phase delay of -8°
between the G-band and 4170 Å continuum observations, suggesting
the presence of upwardly propagating waves. More than 73% of MBPs
(73% from observations and 96% from simulations) display upwardly
propagating wave phenomena, suggesting the abundant nature of
oscillatory behavior detected higher in the solar atmosphere may be
traced back to magnetoconvective processes occurring in the upper
layers of the Sun's convection zone.
---------------------------------------------------------
Title: The Origin of Type I Spicule Oscillations
Authors: Jess, D. B.; Pascoe, D. J.; Christian, D. J.; Mathioudakis,
M.; Keys, P. H.; Keenan, F. P.
2012ApJ...744L...5J Altcode: 2011arXiv1111.5464J
We use images of high spatial and temporal resolution, obtained with
the Rapid Oscillations in the Solar Atmosphere instrument at the Dunn
Solar Telescope, to reveal how the generation of transverse waves
in Type I spicules is a direct result of longitudinal oscillations
occurring in the photosphere. Here we show how pressure oscillations,
with periodicities in the range of 130-440 s, manifest in small-scale
photospheric magnetic bright points, and generate kink waves in
the Sun's outer atmosphere with transverse velocities approaching
the local sound speed. Through comparison of our observations with
advanced two-dimensional magnetohydrodynamic simulations, we provide
evidence for how magnetoacoustic oscillations, generated at the
solar surface, funnel upward along Type I spicule structures, before
undergoing longitudinal-to-transverse mode conversion into waves at
twice the initial driving frequency. The resulting kink modes are
visible in chromospheric plasma, with periodicities of 65-220 s, and
amplitudes often exceeding 400 km. A sausage mode oscillation also
arises as a consequence of the photospheric driver, which is visible
in both simulated and observational time series. We conclude that the
mode conversion and period modification is a direct consequence of
the 90° phase shift encompassing opposite sides of the photospheric
driver. The chromospheric energy flux of these waves are estimated to
be ≈3 × 10<SUP>5</SUP> W m<SUP>-2</SUP>, which indicates that they
are sufficiently energetic to accelerate the solar wind and heat the
localized corona to its multi-million degree temperatures.
---------------------------------------------------------
Title: High-precision transit observations of the exoplanet WASP-13b
with the RISE instrument
Authors: Barros, S. C. C.; Pollacco, D. L.; Gibson, N. P.; Keenan,
F. P.; Skillen, I.; Steele, I. A.
2012MNRAS.419.1248B Altcode: 2011arXiv1108.3996B; 2011MNRAS.tmp.1769B
WASP-13b is a sub-Jupiter mass exoplanet orbiting a G1V type star with
a period of 4.35 d. The current uncertainty in its impact parameter
(0 < b < 0.46) results in poorly defined stellar and planetary
radii. To better constrain the impact parameter, we have obtained
high-precision transit observations with the rapid imager to search for
exoplanets (RISE) instrument mounted on 2.0-m Liverpool Telescope. We
present four new transits which are fitted with a Markov chain Monte
Carlo routine to derive accurate system parameters. We found an
orbital inclination of 85?2 ± 0?3 resulting in stellar and planetary
radii of 1.56 ± 0.04 R<SUB>⊙</SUB> and 1.39 ± 0.05R<SUB>Jup</SUB>,
respectively. This suggests that the host star has evolved off the main
sequence and is in the hydrogen-shell-burning phase. We also discuss how
the limb darkening affects the derived system parameters. With a density
of 0.17ρ<SUB>J</SUB>, WASP-13b joins the group of low-density planets
whose radii are too large to be explained by standard irradiation
models. We derive a new ephemeris for the system, T<SUB>0</SUB>= 245
5575.5136 ± 0.0016 (HJD) and P= 4.353 011 ± 0.000 013 d. The planet
equilibrium temperature (T<SUB>equ</SUB>= 1500 K) and the bright host
star (V= 10.4 mag) make it a good candidate for follow-up atmospheric
studies.
---------------------------------------------------------
Title: New transiting exoplanets from the SuperWASP-North survey
Authors: Faedi, Francesca; Barros, Susana C. C.; Pollacco, Don;
Simpson, Elaine K.; McCormac, James; Moulds, Victoria; Watson, Chris;
Todd, Ian; Keenan, F.; Fitzsimmons, Alan; Chew, Yilen Gómez Maqueo
2011IAUS..276..143F Altcode:
The Wide Angle Search for Planet (WASP) project is one of the leading
projects in the discovery of transiting exoplanets. We present 1)
the current status of the WASP-North survey, 2) our recent exoplanet
discoveries, and 3) we exemplify how these results fit into our
understanding of transiting exoplanet properties and how they can help
to understand exoplanet diversity.
---------------------------------------------------------
Title: The Velocity Distribution of Solar Photospheric Magnetic
Bright Points
Authors: Keys, P. H.; Mathioudakis, M.; Jess, D. B.; Shelyag, S.;
Crockett, P. J.; Christian, D. J.; Keenan, F. P.
2011ApJ...740L..40K Altcode: 2011arXiv1109.3565K
We use high spatial resolution observations and numerical simulations to
study the velocity distribution of solar photospheric magnetic bright
points. The observations were obtained with the Rapid Oscillations in
the Solar Atmosphere instrument at the Dunn Solar Telescope, while the
numerical simulations were undertaken with the MURaM code for average
magnetic fields of 200 G and 400 G. We implemented an automated bright
point detection and tracking algorithm on the data set and studied
the subsequent velocity characteristics of over 6000 structures,
finding an average velocity of approximately 1 km s<SUP>-1</SUP>, with
maximum values of 7 km s<SUP>-1</SUP>. Furthermore, merging magnetic
bright points were found to have considerably higher velocities,
and significantly longer lifetimes, than isolated structures. By
implementing a new and novel technique, we were able to estimate the
background magnetic flux of our observational data, which is consistent
with a field strength of 400 G.
---------------------------------------------------------
Title: A search for line intensity enhancements in the far-UV spectra
of active late-type stars arising from opacity
Authors: Keenan, F. P.; Christian, D. J.; Rose, S. J.; Mathioudakis, M.
2011A&A...534A..71K Altcode: 2011arXiv1109.0513K
Context. Radiative transfer calculations have predicted intensity
enhancements for optically thick emission lines, as opposed to the
normal intensity reductions, for astrophysical plasmas under certain
conditions. In particular, the results are predicted to be dependent
both on the geometry of the emitting plasma and the orientation of the
observer. Hence in principle the detection of intensity enhancement
may provide a way of determining the geometry of an unresolved
astronomical source. <BR /> Aims: To investigate such enhancements
we have analysed a sample of active late-type stars observed in the
far ultraviolet spectral region. <BR /> Methods: Emission lines of O
vi in the FUSE satellite spectra of ɛ Eri, II Peg and Prox Cen were
searched for intensity enhancements due to opacity. <BR /> Results:
We have found strong evidence for line intensity enhancements due to
opacity during active or flare-like activity for all three stars. The
O vi 1032/1038 line intensity ratios, predicted to have a value of
2.0 in the optically thin case, are found to be up to ~30% larger
during several orbital phases. <BR /> Conclusions: Our measurements,
combined with radiative transfer models, allow us to constrain both
the geometry of the O vi emitting regions in our stellar sources and
the orientation of the observer. A spherical emitting plasma can be
ruled out, as this would lead to no intensity enhancement. In addition,
the theory tells us that the line-of-sight to the plasma must be close
to perpendicular to its surface, as observations at small angles to
the surface lead to either no intensity enhancement or the usual line
intensity decrease over the optically thin value. For the future, we
outline a laboratory experiment, that could be undertaken with current
facilities, which would provide an unequivocal test of predictions of
line intensity enhancement due to opacity, in particular the dependence
on plasma geometry.
---------------------------------------------------------
Title: A lower mass for the exoplanet WASP-21b
Authors: Barros, S. C. C.; Pollacco, D. L.; Gibson, N. P.; Howarth,
I. D.; Keenan, F. P.; Simpson, E. K.; Skillen, I.; Steele, I. A.
2011MNRAS.416.2593B Altcode: 2011MNRAS.tmp.1200B; 2011arXiv1106.2118B
We present high-precision transit observations of the exoplanet
WASP-21b, obtained with the Rapid Imager to Search for Exoplanets
instrument mounted on the 2.0-m Liverpool Telescope. A transit model
is fitted, coupled with a Markov chain Monte Carlo routine, to derive
accurate system parameters. The two new high-precision transits allow
us to estimate the stellar density directly from the light curve. Our
analysis suggests that WASP-21 is evolving off the main sequence which
led to a previous overestimation of the stellar density. Using isochrone
interpolation, we find a stellar mass of 0.86 ± 0.04 M<SUB>⊙</SUB>,
which is significantly lower than previously reported (1.01 ± 0.03
M<SUB>⊙</SUB>). Consequently, we find a lower planetary mass of 0.27
± 0.01 M<SUB>Jup</SUB>. A lower inclination (87?4 ± 0?3) is also found
for the system than previously reported, resulting in a slightly larger
stellar (R<SUB>*</SUB>= 1.10 ± 0.03 R<SUB>⊙</SUB>) and planetary
radius (R<SUB>p</SUB>= 1.14 ± 0.04 R<SUB>Jup</SUB>). The planet radius
suggests a hydrogen/helium composition with no core which strengthens
the correlation between planetary density and host star metallicity. A
new ephemeris is determined for the system, i.e. T<SUB>0</SUB>= 245
5084.519 74 ± 0.000 20 (HJD) and P= 4.322 5060 ± 0.000 0031 d. We
found no transit timing variations in WASP-21b.
---------------------------------------------------------
Title: Small-scale Hα jets in the solar chromosphere
Authors: Kuridze, D.; Mathioudakis, M.; Jess, D. B.; Shelyag, S.;
Christian, D. J.; Keenan, F. P.; Balasubramaniam, K. S.
2011A&A...533A..76K Altcode: 2011arXiv1108.1043K
<BR /> Aims: High temporal and spatial resolution observations from
the Rapid Oscillations in the Solar Atmosphere (ROSA) multiwavelength
imager on the Dunn Solar Telescope are used to study the velocities
of small-scale Hα jets in an emerging solar active region. <BR
/> Methods: The dataset comprises simultaneous imaging in the Hα
core, Ca ii K, and G band, together with photospheric line-of-sight
magnetograms. Time-distance techniques are employed to determine
projected plane-of-sky velocities. <BR /> Results: The Hα images
are highly dynamic in nature, with estimated jet velocities as high
as 45 km s<SUP>-1</SUP>. These jets are one-directional, with their
origin seemingly linked to underlying Ca ii K brightenings and G-band
magnetic bright points. <BR /> Conclusions: It is suggested that the
siphon flow model of cool coronal loops is suitable for interpreting our
observations. The jets are associated with small-scale explosive events,
and may provide a mass outflow from the photosphere to the corona.
---------------------------------------------------------
Title: Distance limits to intermediate- and high-velocity clouds
Authors: Smoker, J. V.; Fox, A. J.; Keenan, F. P.
2011MNRAS.415.1105S Altcode: 2011MNRAS.tmp..967S
We present optical spectra of 403 stars and quasi-stellar objects in
order to obtain distance limits towards intermediate- and high-velocity
clouds (IHVCs), including new Fibre-fed Extended Range Optical
Spectrograph (FEROS) observations plus archival ELODIE, FEROS,
High Resolution Echelle Spectrometer (HIRES) and Ultraviolet and
Visual Echelle Spectrograph (UVES) data. The non-detection of Ca
II K interstellar (IS) absorption at a velocity of -130 to -60 km
s<SUP>-1</SUP> towards HDE 248894 (d∼ 3 kpc) and HDE 256725 (d∼
8 kpc) in data at signal-to-noise ratio (S/N) > 450 provides a
new firm lower distance limit of 8 kpc for the anti-centre shell
HVC. Similarly, the non-detection of Ca II K IS absorption towards
HD 86248 at S/N ∼ 500 places a lower distance limit of 7.6 kpc for
Complex EP, unsurprising since this feature is probably related to the
Magellanic System. The lack of detection of Na I D at S/N = 35 towards
Mrk 595 puts an improved upper limit for the Na I column density of log
(N<SUB>NaD</SUB> <) 10.95 cm<SUP>-2</SUP> towards this part of the
Cohen Stream where Ca II was detected by Wakker et al. Absorption at
∼-40 km s<SUP>-1</SUP> is detected in Na I D towards the Galactic
star PG 0039+049 at S/N = 75, placing a firm upper distance limit of 1
kpc for the intermediate-velocity cloud south (IVS), where a tentative
detection had previously been obtained by Centurión et al. Ca II K and
Na I D absorption is detected at -53 km s<SUP>-1</SUP> towards HD 93521,
which confirms the upper distance limit of 2.4 kpc for part of the IV
arch complex obtained using the International Ultraviolet Explorer
(IUE) data by Danly. Towards HD 216411 in Complex H a non-detection
in Na D towards gas with log(?) = 20.69 cm<SUP>-2</SUP> puts a lower
distance limit of 6.6 kpc towards this HVC complex. Additionally, Na
I D absorption is detected at -43.7 km s<SUP>-1</SUP> in the star HD
218915 at a distance of 5.0 kpc in gas in the same region of the sky as
Complex H. Finally, the Na I/Ca II and Ca II/H I ratios of the current
sample are found to lie in the range observed for previous studies
of IHVCs. Based on European Southern Observatory (ESO) programme IDs
078.C-0493(A) and 171.D-0237(B).
---------------------------------------------------------
Title: The spin-orbit angles of the transiting exoplanets WASP-1b,
WASP-24b, WASP-38b and HAT-P-8b from Rossiter-McLaughlin observations
Authors: Simpson, E. K.; Pollacco, D.; Cameron, A. Collier; Hébrard,
G.; Anderson, D. R.; Barros, S. C. C.; Boisse, I.; Bouchy, F.; Faedi,
F.; Gillon, M.; Hebb, L.; Keenan, F. P.; Miller, G. R. M.; Moutou,
C.; Queloz, D.; Skillen, I.; Sorensen, P.; Stempels, H. C.; Triaud,
A.; Watson, C. A.; Wilson, P. A.
2011MNRAS.414.3023S Altcode: 2010arXiv1011.5664S; 2011MNRAS.tmp..600S
We present observations of the Rossiter-McLaughlin effect for the
transiting exoplanets WASP-1b, WASP-24b, WASP-38b and HAT-P-8b,
and deduce the orientations of the planetary orbits with respect
to the host stars' rotation axes. The planets WASP-24b, WASP-38b
and HAT-P-8b appear to move in prograde orbits and be well aligned,
having sky-projected spin-orbit angles consistent with zero: λ=-4?7
± 4?0, 15°<SUP>+33</SUP><SUB>-43</SUB> and ?, respectively. The host
stars have T<SUB>eff</SUB> < 6250 K and conform with the trend of
cooler stars having low obliquities. WASP-38b is a massive planet
on a moderately long period, eccentric orbit so may be expected to
have a misaligned orbit given the high obliquities measured in similar
systems. However, we find no evidence for a large spin-orbit angle. By
contrast, WASP-1b joins the growing number of misaligned systems
and has an almost polar orbit, λ=?. It is neither very massive,
eccentric nor orbiting a hot host star, and therefore does not share
the properties of many other misaligned systems. This work is based
on observations collected with the SOPHIE spectrograph on the 1.93-m
telescope at Observatoire de Haute-Provence (CNRS), France, by the
SOPHIE Consortium; the Nordic Optical Telescope, operated on the island
of La Palma jointly by Denmark, Finland, Iceland, Norway and Sweden,
in the Spanish Observatorio del Roque de los Muchachos of the Instituto
de Astrofisica de Canarias and the HARPS spectrograph mounted on the
European Southern Observatory (ESO) 3.6-m telescope at the La Silla
Observatory in Chile under proposal 084.C-0185.
---------------------------------------------------------
Title: WASP-39b: a highly inflated Saturn-mass planet orbiting a
late G-type star
Authors: Faedi, F.; Barros, S. C. C.; Anderson, D. R.; Brown, D. J. A.;
Collier Cameron, A.; Pollacco, D.; Boisse, I.; Hébrard, G.; Lendl,
M.; Lister, T. A.; Smalley, B.; Street, R. A.; Triaud, A. H. M. J.;
Bento, J.; Bouchy, F.; Butters, O. W.; Enoch, B.; Haswell, C. A.;
Hellier, C.; Keenan, F. P.; Miller, G. R. M.; Moulds, V.; Moutou, C.;
Norton, A. J.; Queloz, D.; Santerne, A.; Simpson, E. K.; Skillen, I.;
Smith, A. M. S.; Udry, S.; Watson, C. A.; West, R. G.; Wheatley, P. J.
2011A&A...531A..40F Altcode: 2011arXiv1102.1375F
We present the discovery of WASP-39b, a highly inflated transiting
Saturn-mass planet orbiting a late G-type dwarf star with a period of
4.055259 ± 0.000008 d, Transit Epoch T<SUB>0</SUB> = 2 455 342.9688
± 0.0002 (HJD), of duration 0.1168 ± 0.0008 d. A combined analysis
of the WASP photometry, high-precision follow-up transit photometry,
and radial velocities yield a planetary mass of M<SUB>pl</SUB> =
0.28 ± 0.03 M<SUB>J</SUB> and a radius of R<SUB>pl</SUB> = 1.27
± 0.04 R<SUB>J</SUB>, resulting in a mean density of 0.14 ± 0.02
ρ<SUB>J</SUB>. The stellar parameters are mass M<SUB>⋆</SUB>
= 0.93 ± 0.03 M<SUB>⊙</SUB>, radius R<SUB>⋆</SUB> = 0.895 ±
0.23 R<SUB>⊙</SUB>, and age 9<SUP>+3</SUP><SUB>-4</SUB> Gyr. Only
WASP-17b and WASP-31b have lower densities than WASP-39b, although
they are slightly more massive and highly irradiated planets. From
our spectral analysis, the metallicity of WASP-39 is measured to
be [Fe/H] = -0.12 ± 0.1 dex, and we find the planet to have an
equilibrium temperature of 1116<SUP>+33</SUP><SUB>-32</SUB> K. Both
values strengthen the observed empirical correlation between these
parameters and the planetary radius for the known transiting Saturn-mass
planets. <P />Spectroscopic and photometric data are only available
at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)
or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/531/A40
---------------------------------------------------------
Title: Early-type stars observed in the ESO UVES Paranal Observatory
Project - III. Sub-parsec and au-scale structure in the interstellar
medium*
Authors: Smoker, J. V.; Bagnulo, S.; Cabanac, R.; Keenan, F. P.;
Fossati, L.; Ledoux, C.; Jehin, E.; Melo, C.
2011MNRAS.414...59S Altcode: 2011MNRAS.tmp..681S
UVES interstellar observations from the Paranal Observatory Project
are presented for early-type stars located in the line of sight to
the nearby open clusters IC 2391 (Omni Vel) and NGC 6475 (M7), with
spectroscopic resolution R∼ 80 000 and signal-to-noise ratios in the
Ti ii (3383 Å), Ca ii K, CH<SUP>+</SUP> (4232 Å), Na i D and K i
(7698 Å) lines of several hundred. The sightlines are a mixture of
cluster and non-cluster objects. A total of 22 early-type stars (A and
B type) are present in our sample towards IC 2391, with 21 towards NGC
6475/M7, and enable us to probe for differences in column density on
scales from ∼0.07 to 7.3 and ∼0.05 to 4.9 pc in the respective
clusters. Additionally, towards Praesepe the Na i D interstellar
variation only is probed towards 13 sightlines and transverse scales
of ∼0.16-10.7 pc at R= 70 000. Towards IC 2391 variations are found
in Ti ii, Ca ii K and Na i D column density in different sightlines
of up to 0.7, 1.0 and 1.8 dex (excluding one star), respectively. This
kind of variability correlates well with the Hipparcos parallax of the
objects, and probes structure within the Local Bubble. For cluster-only
objects the variations are 0.3, 0.3 and 0.5 dex, respectively. For the
field of view towards NGC 6475 the corresponding maximum variations
are somewhat smaller, being 0.5, 0.3, 0.8 and 1.0 dex for Ti ii,
Ca ii K, Na i and K i, respectively, for all objects and 0.4, 0.2,
0.6 and 0.7 dex for the cluster-only objects. These are uncorrelated
with parallax, and again demonstrate that Ca ii K tends to be more
smoothly distributed than Na i D. A few likely cluster sightlines show
evidence for CH<SUP>+</SUP> and variations in this molecular species of
a factor of 10 in equivalent width over sub-pc scales. Towards Praesepe
variation in interstellar Na i D is small, being a maximum of only
∼0.4 dex (including measurement errors), but with fewer sightlines
studied. Overall, the scatter in the data is similar for the singly
ionized species Ti ii and Ca ii, lending more support to the hypothesis
that these two species sample similar parts of the interstellar medium
(ISM). This also appears to be the case for the neutral species Na i D
and K i in the one cluster studied. Finally, multiple-epoch observations
from a variety of archive sources are used to search for astronomical
unit (au) scale structure in the ISM towards 46 sightlines. There are
tentative indications of structure on scales of tens to thousands of
au for three sightlines. Future observations will confirm the veracity
or otherwise of the time-variable components and others presented.
---------------------------------------------------------
Title: Independent Discovery of the Transiting Exoplanet HAT-P-14b
Authors: Simpson, E. K.; Barros, S. C. C.; Brown, D. J. A.; Collier
Cameron, A.; Pollacco, D.; Skillen, I.; Stempels, H. C.; Boisse, I.;
Faedi, F.; Hébrard, G.; McCormac, J.; Sorensen, P.; Street, R. A.;
Anderson, D.; Bento, J.; Bouchy, F.; Butters, O. W.; Enoch, B.;
Haswell, C. A.; Hebb, L.; Hellier, C.; Holmes, S.; Horne, K.; Keenan,
F. P.; Lister, T. A.; Maxted, P. F. L.; Miller, G. R. M.; Moulds,
V.; Moutou, C.; Norton, A. J.; Parley, N.; Santerne, A.; Smalley, B.;
Smith, A. M. S.; Todd, I.; Watson, C. A.; West, R. G.; Wheatley, P. J.
2011AJ....141..161S Altcode: 2010arXiv1009.3470S
We present SuperWASP observations of HAT-P-14b, a hot Jupiter discovered
by Torres et al. The planet was found independently by the SuperWASP
team and named WASP-27b after follow-up observations had secured the
discovery, but prior to the publication by Torres et al. Our analysis of
HAT-P-14/WASP-27 is in good agreement with the values found by Torres
et al. and we provide additional evidence against astronomical false
positives. Due to the brightness of the host star, V <SUB>mag</SUB> =
10, HAT-P-14b is an attractive candidate for further characterization
observations. The planet has a high impact parameter and the primary
transit is close to grazing. This could readily reveal small deviations
in the orbital parameters indicating the presence of a third body in
the system, which may be causing the small but significant orbital
eccentricity. Our results suggest that the planet may undergo a grazing
secondary eclipse. However, even a non-detection would tightly constrain
the system parameters.
---------------------------------------------------------
Title: ROSA: A High-cadence, Synchronized Multi-camera Solar Imaging
System
Authors: Christian, Damian Joseph; Jess, D. B.; Mahtioudakis, M.;
Keenan, F. P.
2011SPD....42.1507C Altcode: 2011BAAS..43S.1507C
The Rapid Oscillations in the Solar Atmosphere (ROSA) instrument
is a synchronized, six-camera high-cadence solar imaging instrument
developed by Queen's University Belfast and recently commissioned at
the Dunn Solar Telescope at the National Solar Observatory in Sunspot,
New Mexico, USA, as a common-user instrument. Consisting of six 1k x 1k
Peltier-cooled frame-transfer CCD cameras with very low noise (0.02 -
15 e/pixel/s), each ROSA camera is capable of full-chip readout speeds
in excess of 30 Hz, and up to 200 Hz when the CCD is windowed. ROSA
will allow for multi-wavelength studies of the solar atmosphere at
a high temporal resolution. We will present the current instrument
set-up and parameters, observing modes, and future plans, including a
new high QE camera allowing 15 Hz for Halpha. Interested parties should
see https://habu.pst.qub.ac.uk/groups/arcresearch/wiki/de502/ROSA.html
---------------------------------------------------------
Title: Chromospheric velocities of a C-class flare
Authors: Keys, P. H.; Jess, D. B.; Mathioudakis, M.; Keenan, F. P.
2011A&A...529A.127K Altcode: 2011arXiv1103.4252K
<BR /> Aims: We use high spatial and temporal resolution observations
from the Swedish Solar Telescope to study the chromospheric velocities
of a C-class flare originating from active region NOAA 10969. <BR />
Methods: A time-distance analysis is employed to estimate directional
velocity components in Hα and Ca ii K image sequences. Also, imaging
spectroscopy has allowed us to determine flare-induced line-of-sight
velocities. A wavelet analysis is used to analyse the periodic nature
of associated flare bursts. <BR /> Results: Time-distance analysis
reveals velocities as high as 64 km s<SUP>-1</SUP> along the flare
ribbon and 15 km s<SUP>-1</SUP> perpendicular to it. The velocities are
very similar in both the Hα and Ca ii K time series. Line-of-sight Hα
velocities are red-shifted with values up to 17 km s<SUP>-1</SUP>. The
high spatial and temporal resolution of the observations have allowed
us to detect velocities significantly higher than those found in
earlier studies. Flare bursts with a periodicity of ≈60 s are also
detected. These bursts are similar to the quasi-periodic oscillations
observed at hard X-ray and radio wavelength data. <BR /> Conclusions:
Some of the highest velocities detected in the solar atmosphere are
presented. Line-of-sight velocity maps show considerable mixing of
both the magnitude and direction of velocities along the flare path. A
change in direction of the velocities at the flare kernel has also been
detected which may be a signature of chromospheric evaporation. <P
/>Movies associated to Fig. 5 are only available in electronic form
at <A href="http://www.aanda.org">http://www.aanda.org</A>
---------------------------------------------------------
Title: Vorticity in the solar photosphere
Authors: Shelyag, S.; Keys, P.; Mathioudakis, M.; Keenan, F. P.
2011A&A...526A...5S Altcode: 2010arXiv1010.5604S
<BR /> Aims: We use magnetic and non-magnetic 3D numerical simulations
of solar granulation and G-band radiative diagnostics from the resulting
models to analyse the generation of small-scale vortex motions in
the solar photosphere. <BR /> Methods: Radiative MHD simulations of
magnetoconvection are used to produce photospheric models. Our starting
point is a non-magnetic model of solar convection, where we introduce
a uniform magnetic field and follow the evolution of the field in the
simulated photosphere. We find two different types of photospheric
vortices, and provide a link between the vorticity generation and the
presence of the intergranular magnetic field. A detailed analysis of
the vorticity equation, combined with the G-band radiative diagnostics,
allows us to identify the sources and observational signatures of
photospheric vorticity in the simulated photosphere. <BR /> Results: Two
different types of photospheric vorticity, magnetic and non-magnetic,
are generated in the domain. Non-magnetic vortices are generated by the
baroclinic motions of the plasma in the photosphere, while magnetic
vortices are produced by the magnetic tension in the intergranular
magnetic flux concentrations. The two types of vortices have different
shapes. We find that the vorticity is generated more efficiently in
the magnetised model. Simulated G-band images show a direct connection
between magnetic vortices and rotary motions of photospheric bright
points, and suggest that there may be a connection between the magnetic
bright point rotation and small-scale swirl motions observed higher
in the atmosphere.
---------------------------------------------------------
Title: New exoplanets from the SuperWASP-North survey
Authors: Faedi, F.; Barros, S. C. C.; Pollacco, D.; Simpson,
E. K.; McCormac, J.; Moulds, V.; Watson, C.; Todd, I.; Keenan, F.;
Fitzsimmons, A.
2011EPJWC..1101003F Altcode:
We present the current status of the WASP search for transiting
exoplanets, focusing on recent planet discoveries from SuperWASP-North
and the joint equatorial region (-20≤Dec≤+20) observed by both WASP
telescopes. We report the results of monitoring of WASP planets, and
discuss how these contribute to our understanding of planet properties
and their diversity.
---------------------------------------------------------
Title: WASP-37b: A 1.8 M <SUB>J</SUB> Exoplanet Transiting a
Metal-poor Star
Authors: Simpson, E. K.; Faedi, F.; Barros, S. C. C.; Brown, D. J. A.;
Collier Cameron, A.; Hebb, L.; Pollacco, D.; Smalley, B.; Todd, I.;
Butters, O. W.; Hébrard, G.; McCormac, J.; Miller, G. R. M.; Santerne,
A.; Street, R. A.; Skillen, I.; Triaud, A. H. M. J.; Anderson, D. R.;
Bento, J.; Boisse, I.; Bouchy, F.; Enoch, B.; Haswell, C. A.; Hellier,
C.; Holmes, S.; Horne, K.; Keenan, F. P.; Lister, T. A.; Maxted,
P. F. L.; Moulds, V.; Moutou, C.; Norton, A. J.; Parley, N.; Pepe,
F.; Queloz, D.; Segransan, D.; Smith, A. M. S.; Stempels, H. C.;
Udry, S.; Watson, C. A.; West, R. G.; Wheatley, P. J.
2011AJ....141....8S Altcode: 2010arXiv1008.3096S
We report on the discovery of WASP-37b, a transiting hot Jupiter
orbiting an m <SUB>v</SUB> = 12.7 G2-type dwarf, with a period of
3.577469 ± 0.000011 d, transit epoch T <SUB>0</SUB> = 2455338.6188
± 0.0006 (HJD; dates throughout the paper are given in Coordinated
Universal Time (UTC)), and a transit duration 0.1304<SUP>+0.0018</SUP>
<SUB>-0.0017</SUB> d. The planetary companion has a mass M
<SUB>p</SUB> = 1.80 ± 0.17 M <SUB>J</SUB> and radius R <SUB>p</SUB> =
1.16<SUP>+0.07</SUP> <SUB>-0.06</SUB> R <SUB>J</SUB>, yielding a mean
density of 1.15<SUP>+0.12</SUP> <SUB>-0.15</SUB> ρ<SUB>J</SUB>. From a
spectral analysis, we find that the host star has M <SUB>sstarf</SUB>
= 0.925 ± 0.120 M <SUB>sun</SUB>, R <SUB>sstarf</SUB> = 1.003 ±
0.053 R <SUB>sun</SUB>, T <SUB>eff</SUB> = 5800 ± 150 K, and [Fe/H]
= -0.40 ± 0.12. WASP-37 is therefore one of the lowest metallicity
stars to host a transiting planet.
---------------------------------------------------------
Title: WASP-38b: a transiting exoplanet in an eccentric, 6.87d
period orbit
Authors: Barros, S. C. C.; Faedi, F.; Collier Cameron, A.; Lister,
T. A.; McCormac, J.; Pollacco, D.; Simpson, E. K.; Smalley, B.; Street,
R. A.; Todd, I.; Triaud, A. H. M. J.; Boisse, I.; Bouchy, F.; Hébrard,
G.; Moutou, C.; Pepe, F.; Queloz, D.; Santerne, A.; Segransan, D.;
Udry, S.; Bento, J.; Butters, O. W.; Enoch, B.; Haswell, C. A.;
Hellier, C.; Keenan, F. P.; Miller, G. R. M.; Moulds, V.; Norton,
A. J.; Parley, N.; Skillen, I.; Watson, C. A.; West, R. G.; Wheatley,
P. J.
2011A&A...525A..54B Altcode: 2010arXiv1010.0849B
<BR /> Aims: We report the discovery of WASP-38b, a long period
transiting planet in an eccentric 6.871815 day orbit. The transit
epoch is 2 455 335.92050 ± 0.00074 (HJD) and the transit duration
is 4.663 h. <BR /> Methods: WASP-38b's discovery was enabled
due to an upgrade to the SuperWASP-North cameras. We performed a
spectral analysis of the host star HD 146389/BD+10 2980 that yielded
T<SUB>eff</SUB> = 6150 ± 80 K, log g = 4.3 ± 0.1, v sin i = 8.6
± 0.4 km s<SUP>-1</SUP>, M_* = 1.16 ± 0.04 M<SUB>⊙</SUB> and R_*
= 1.33 ± 0.03 R<SUB>⊙</SUB>, consistent with a dwarf of spectral
type F8. Assuming a main-sequence mass-radius relation for the star,
we fitted simultaneously the radial velocity variations and the transit
light curves to estimate the orbital and planetary parameters. <BR
/> Results: The planet has a mass of 2.69 ± 0.06 M<SUB>Jup</SUB>
and a radius of 1.09 ± 0.03 R<SUB>Jup</SUB> giving a density,
ρ<SUB>p</SUB> = 2.1 ± 0.1 ρ<SUB>J</SUB>. The high precision of
the eccentricity e = 0.0314 ± 0.0044 is due to the relative transit
timing from the light curves and the RV shape. The planet equilibrium
temperature is estimated at 1292 ± 33 K. WASP-38b is the longest
period planet found by SuperWASP-North and with a bright host star (V
= 9.4 mag), is a good candidate for followup atmospheric studies. <P
/>Photometry and RV data are only available in electronic form at the
CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/525/A54">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/525/A54</A>
---------------------------------------------------------
Title: VizieR Online Data Catalog: WASP-39b: a highly inflated
Saturn-mass planet orbiting a late G-type star.
Authors: Faedi, F.; Barros, S. C. C.; Anderson, D. R.; Brown, D. J. A.;
Collier, Cameron A.; Pollacco, D.; Boisse, I.; Hebrard, G.; Lendl,
M.; Lister, T. A.; Smalley, B.; Street, R. A.; Triaud, A. H. M. J.;
Bento, J.; Butters, O. W.; Enoch, B.; Bouchy, F.; Haswell, C. A.;
Hellier, C.; Keenan, F. P.; Miller, G. R. M.; Moulds, V.; Moutou, C.;
Norton, A. J.; Queloz, D.; Santerne, A.; Simpson, E. K.; Skillen, I.;
Smith, A. M. S.; Udry, S.; Watson, C. A.; West, R. G.; Wheatley, P. J.
2011yCat..35310040F Altcode: 2011yCat..35319040F
We report the discovery WASP-39b a highly inflated transiting extrasolar
planet. We performed a simultaneous fit to transit photometry and
radial velocity measurements and obtained a planetary density of
0.141+/-0.02rho<SUB>J</SUB> (where rho<SUB>J</SUB> is the density of
Jupiter). Thus, WASP-39b is the third least dense planet identified
by a ground-based transit survey. <P />(4 data files).
---------------------------------------------------------
Title: Search for Rapid Changes in the Visible-Light Corona during
the 21 June 2001 Total Solar Eclipse
Authors: Rudawy, P.; Phillips, K. J. H.; Buczylko, A.; Williams,
D. R.; Keenan, F. P.
2010SoPh..267..305R Altcode: 2010arXiv1009.5205R; 2010SoPh..tmp..183R
Some 8000 images obtained with the Solar Eclipse Coronal Imaging System
(SECIS) fast-frame CCD camera instrument located at Lusaka, Zambia,
during the total eclipse of 21 June 2001 have been analysed to search
for short-period oscillations in intensity that could be a signature of
solar coronal heating mechanisms by MHD wave dissipation. Images were
taken in white-light and Fe XIV green-line (5303 Å) channels over 205
seconds (frame rate 39 s<SUP>−1</SUP>), approximately the length of
eclipse totality at this location, with a pixel size of four arcseconds
square. The data are of considerably better quality than those that
we obtained during the 11 August 1999 total eclipse (Rudawy et al.:
Astron. Astrophys. 416, 1179, 2004), in that the images are much better
exposed and enhancements in the drive system of the heliostat used
gave a much improved image stability. Classical Fourier and wavelet
techniques have been used to analyse the emission at 29 518 locations,
of which 10 714 had emission at reasonably high levels, searching
for periodic fluctuations with periods in the range 0.1 - 17 seconds
(frequencies 0.06 - 10 Hz). While a number of possible periodicities
were apparent in the wavelet analysis, none of the spatially and
time-limited periodicities in the local brightness curves was found
to be physically important. This implies that the pervasive Alfvén
wave-like phenomena (Tomczyk et al.: Science317, 1192, 2007) using
polarimetric observations with the Coronal Multi-Channel Polarimeter
(CoMP) instrument do not give rise to significant oscillatory intensity
fluctuations.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Transits of WASP-38b (Barros+,
2011)
Authors: Barros, S. C. C.; Faedi, F.; Collier, Cameron A.; Lister,
T. A.; McCormac, J.; Pollacco, D.; Simpson, E. K.; Smalley, B.; Street,
R. A.; Todd, I.; Triaud, A. H. M. J.; Boisse, I.; Bouchy, F.; Hebrard,
G.; Moutou, C.; Pepe, F.; Queloz, D.; Santerne, A.; Segransan, D.;
Udry, S.; Bento, J.; Butters, O. W.; Enoch, B.; Haswell, C. A.;
Hellier, C.; Keenan, F. P.; Miller, G. R. M.; Moulds, V.; Norton,
A. J.; Parley, N.; Skillen, I.; Watson, C. A.; West, R. G.; Wheatleys,
P. J.
2010yCat..35250054B Altcode: 2010yCat..35259054B
WASP-38b's discovery was enabled due to an upgrade to the
SuperWASP-North cameras. We performed a spectral analysis of the host
star HD 146389/BD+10 2980. <P />(6 data files).
---------------------------------------------------------
Title: The Area Distribution of Solar Magnetic Bright Points
Authors: Crockett, P. J.; Mathioudakis, M.; Jess, D. B.; Shelyag,
S.; Keenan, F. P.; Christian, D. J.
2010ApJ...722L.188C Altcode: 2010arXiv1009.2410C
Magnetic bright points (MBPs) are among the smallest observable objects
on the solar photosphere. A combination of G-band observations and
numerical simulations is used to determine their area distribution. An
automatic detection algorithm, employing one-dimensional intensity
profiling, is utilized to identify these structures in the observed and
simulated data sets. Both distributions peak at an area of ≈45,000
km<SUP>2</SUP>, with a sharp decrease toward smaller areas. The
distributions conform with log-normal statistics, which suggests
that flux fragmentation dominates over flux convergence. Radiative
magneto-convection simulations indicate an independence in the MBP
area distribution for differing magnetic flux densities. The most
commonly occurring bright point size corresponds to the typical width
of inter-granular lanes.
---------------------------------------------------------
Title: A Study of Magnetic Bright Points in the Na I D<SUB>1</SUB>
Line
Authors: Jess, D. B.; Mathioudakis, M.; Christian, D. J.; Crockett,
P. J.; Keenan, F. P.
2010ApJ...719L.134J Altcode: 2010arXiv1007.2515J
High-cadence, multiwavelength, optical observations of solar magnetic
bright points (MBPs), captured at the disk center using the ROSA and
IBIS imaging systems on the Dunn Solar Telescope, are presented. MBPs
manifesting in the Na I D<SUB>1</SUB> core are found to preferentially
exist in regions containing strong downflows, in addition to cospatial
underlying photospheric magnetic field concentrations. Downdrafts
within Na I D<SUB>1</SUB> bright points exhibit speeds of up
to 7 km s<SUP>-1</SUP>, with preferred structural symmetry in
intensity, magnetic field, and velocity profiles about the bright
point center. Excess intensities associated with G-band and Ca II K
observations of MBPs reveal a power-law trend when plotted as a function
of the magnetic flux density. However, Na I D<SUB>1</SUB> observations
of the same magnetic features indicate an intensity plateau at weak
magnetic field strengths below ≈150 G, suggesting the presence of a
two-component heating process: one which is primarily acoustic and the
other predominantly magnetic. We suggest that this finding is related to
the physical expansion of magnetic flux tubes, with weak field strengths
(≈50 G) expanding by ~76%, compared to a ~44% expansion when higher
field strengths (≈150 G) are present. These observations provide the
first experimental evidence of rapid downdrafts in Na I D<SUB>1</SUB>
MBPs and reveal the nature of a previously unresolved intensity plateau
associated with these structures.
---------------------------------------------------------
Title: Highly Ionized sodium X-ray line emission from the solar
corona and the abundance of sodium
Authors: Phillips, K. J. H.; Aggarwal, K. M.; Landi, E.; Keenan, F. P.
2010A&A...518A..41P Altcode: 2010arXiv1005.4375P
Context. The Na X X-ray lines between 10.9 and 11.2 Å have attracted
little attention but are of interest since they enable an estimate
of the coronal abundance of Na to be made. This is of great interest
in the continuing debate on the nature of the FIP (first ionization
potential) effect. <BR /> Aims: Observations of the Na X lines with
the Solar Maximum Mission Flat Crystal Spectrometer and a rocket-borne
X-ray spectrometer are used to measure the Na/Ne abundance ratio,
i.e. the ratio of an element with very low FIP to one with high
FIP. <BR /> Methods: New atomic data are used to generate synthetic
spectra which are compared with the observations, with temperature
and the Na/Ne abundance ratio as free parameters. <BR /> Results:
Temperature estimates from the observations indicate that the line
emission is principally from non-flaring active regions, and that the
Na/Ne abundance ratio is 0.07 ± 50%. <BR /> Conclusions: The Na/Ne
abundance ratio is close to a coronal value for which the abundances
of low-FIP elements (FIP < 10 eV) are enhanced by a factor of 3 to 4
over those found in the photosphere. For low-temperature (T<SUB>e</SUB>
≤slant 1.5 MK) spectra, the presence of Fe XVII lines requires that
either a higher-temperature component is present or a revision of
ionization or recombination rates is needed.
---------------------------------------------------------
Title: Aristarchos RISE2: A Wide-Field Fast Imager for Exoplanet
Transit Timing
Authors: Boumis, P.; Pollacco, D.; Steele, I.; Meaburn, J.; Xilouris,
E. M.; Katsiyannis, A. C.; Bode, M.; Bates, S. D.; Goudis, C. D.;
Keenan, F. P.; Watson, C.
2010ASPC..424..426B Altcode:
The detection of exoplanets is currently of great topical interest in
astronomy. The Rapid Imager for Surveys of Exoplanets 2 (RISE2) camera
will be built for exoplanet studies and in particular for detection
of transit timing variations (TTV) induced by the presence of a third
body in the system. It will be identical to RISE which has been running
successfully on the 2m Liverpool Telescope since 2008 but modified for
the 2.3m ARISTARCHOS telescope. For TTV work the RISE/LT combination
is regularly producing timings with accuracy <10 seconds making it
the best suited instrument for this work. Furthermore, RISE2/AT has the
added benefit of being located at a significantly different longitude
to the LT/RISE on La Palma, hence extending the transit coverage.
---------------------------------------------------------
Title: The spin-orbit alignment of the transiting exoplanet WASP-3b
from Rossiter-McLaughlin observations
Authors: Simpson, E. K.; Pollacco, D.; Hébrard, G.; Gibson, N. P.;
Barros, S. C. C.; Boisse, I.; Bouchy, F.; Collier Cameron, A.; Miller,
G. R. M.; Watson, C. A.; Keenan, F. P.
2010MNRAS.405.1867S Altcode: 2010MNRAS.tmp..548S; 2009arXiv0912.3643S
We present an observation of the Rossiter-McLaughlin effect for
the planetary system WASP-3. Radial velocity measurements were
made during transit using the SOPHIE spectrograph at the 1.93-m
telescope at Haute-Provence Observatory. The shape of the effect
shows that the sky-projected angle between the stellar rotation
axis and planetary orbital axis (λ) is small and consistent
with zero within . WASP-3b joins the ~two-thirds of planets with
measured spin-orbit angles that are well aligned and are thought
to have undergone a dynamically gentle migration process such as
planet-disc interactions. We find a systematic effect which leads to
an anomalously high determination of the projected stellar rotational
velocity (vsini = 19.6<SUP>+2.2</SUP><SUB>-2.1</SUB>kms<SUP>-1</SUP>)
compared to the value found from spectroscopic line broadening
(vsini = 13.4 +/- 1.5kms<SUP>-1</SUP>). This is thought to be
caused by a discrepancy in the assumptions made in the extraction
and modelling of the data. Using a model developed by Hirano et
al. designed to address this issue, we find vsini to be consistent
with the value obtained from spectroscopic broadening measurements
(vsini = 15.7<SUP>+1.4</SUP><SUB>-1.3</SUB>kms<SUP>-1</SUP>). <P
/>Based on observations collected with the SOPHIE spectrograph
on the 1.93-m telescope at Observatoire de Haute-Provence (CNRS),
France, by the SOPHIE Consortium (program 08B.PNP.SIMP). <P />E-mail:
esimpson05@qub.ac.uk
---------------------------------------------------------
Title: A photospheric bright point model
Authors: Shelyag, S.; Mathioudakis, M.; Keenan, F. P.; Jess, D. B.
2010A&A...515A.107S Altcode: 2010arXiv1003.1653S
<BR /> Aims: A magneto-hydrostatic model is constructed with
spectropolarimetric properties close to those of solar photospheric
magnetic bright points. <BR /> Methods: Results of solar radiative
magneto-convection simulations are used to produce the spatial
structure of the vertical component of the magnetic field. The
horizontal component of magnetic field is reconstructed using the
self-similarity condition, while the magneto-hydrostatic equilibrium
condition is applied to the standard photospheric model with the
magnetic field embedded. Partial ionisation processes are found to be
necessary for reconstructing the correct temperature structure of the
model. <BR /> Results: The structures obtained are in good agreement
with observational data. By combining the realistic structure of
the magnetic field with the temperature structure of the quiet solar
photosphere, the continuum formation level above the equipartition
layer can be found. Preliminary results are shown of wave propagation
through this magnetic structure. The observational consequences of the
oscillations are examined in continuum intensity and in the Fe I 6302
Å magnetically sensitive line.
---------------------------------------------------------
Title: Emission lines of FeXI in the 257-407Å wavelength region
observed in solar spectra from EIS/Hinode and SERTS
Authors: Keenan, F. P.; Milligan, R. O.; Jess, D. B.; Aggarwal, K. M.;
Mathioudakis, M.; Thomas, R. J.; Brosius, J. W.; Davila, J. M.
2010MNRAS.404.1617K Altcode: 2010MNRAS.tmp..299K; 2010arXiv1001.3627K
Theoretical emission-line ratios involving FeXI transitions in the
257-407Å wavelength range are derived using fully relativistic
calculations of radiative rates and electron impact excitation
cross-sections. These are subsequently compared with both long
wavelength channel Extreme-Ultraviolet Imaging Spectrometer (EIS)
spectra from the Hinode satellite (covering 245-291Å) and first-order
observations (~235-449Å) obtained by the Solar Extreme-ultraviolet
Research Telescope and Spectrograph (SERTS). The 266.39, 266.60 and
276.36Å lines of FeXI are detected in two EIS spectra, confirming
earlier identifications of these features, and 276.36Å is found to
provide an electron density (N<SUB>e</SUB>) diagnostic when ratioed
against the 257.55Å transition. Agreement between theory and
observation is found to be generally good for the SERTS data sets,
with discrepancies normally being due to known line blends, while the
257.55Å feature is detected for the first time in SERTS spectra. The
most useful FeXI electron density diagnostic is found to be the
308.54/352.67 intensity ratio, which varies by a factor of 8.4 between
N<SUB>e</SUB> = 10<SUP>8</SUP> and 10<SUP>11</SUP>cm<SUP>-3</SUP>,
while showing little temperature sensitivity. However, the
349.04/352.67 ratio potentially provides a superior diagnostic,
as it involves lines which are closer in wavelength, and varies
by a factor of 14.7 between N<SUB>e</SUB> = 10<SUP>8</SUP> and
10<SUP>11</SUP>cm<SUP>-3</SUP>. Unfortunately, the 349.04Å line is
relatively weak, and also blended with the second-order FeX 174.52Å
feature, unless the first-order instrument response is enhanced.
---------------------------------------------------------
Title: Microflare Activity Driven by Forced Magnetic Reconnection
Authors: Jess, D. B.; Mathioudakis, M.; Browning, P. K.; Crockett,
P. J.; Keenan, F. P.
2010ApJ...712L.111J Altcode: 2010arXiv1002.3792J
High cadence, multiwavelength, optical observations of a solar active
region, obtained with the Swedish Solar Telescope, are presented. Two
magnetic bright points are seen to separate in opposite directions
at a constant velocity of 2.8 km s<SUP>-1</SUP>. After a separation
distance of ≈4400 km is reached, multiple Ellerman bombs are
observed in both Hα and Ca-K images. As a result of the Ellerman
bombs, periodic velocity perturbations in the vicinity of the magnetic
neutral line, derived from simultaneous Michelson Doppler Imager data,
are generated with amplitude ±6 km s<SUP>-1</SUP> and wavelength
≈1000 km. The velocity oscillations are followed by an impulsive
brightening visible in Hα and Ca-K, with a peak intensity enhancement
of 63%. We interpret these velocity perturbations as the magnetic field
deformation necessary to trigger forced reconnection. A time delay of
≈3 minutes between the Hα-wing and Ca-K observations indicates that
the observed magnetic reconnection occurs at a height of ~200 km above
the solar surface. These observations are consistent with theoretical
predictions and provide the first observational evidence of microflare
activity driven by forced magnetic reconnection.
---------------------------------------------------------
Title: ROSA: A High-cadence, Synchronized Multi-camera Solar Imaging
System
Authors: Jess, D. B.; Mathioudakis, M.; Christian, D. J.; Keenan,
F. P.; Ryans, R. S. I.; Crockett, P. J.
2010SoPh..261..363J Altcode: 2009arXiv0912.4118J; 2010SoPh..tmp...12J
The Rapid Oscillations in the Solar Atmosphere (ROSA) instrument
is a synchronized, six-camera high-cadence solar imaging instrument
developed by Queen's University Belfast. The system is available on
the Dunn Solar Telescope at the National Solar Observatory in Sunspot,
New Mexico, USA, as a common-user instrument. Consisting of six 1k
× 1k Peltier-cooled frame-transfer CCD cameras with very low noise
(0.02 - 15 e s<SUP>−1</SUP> pixel<SUP>−1</SUP>), each ROSA camera
is capable of full-chip readout speeds in excess of 30 Hz, or 200 Hz
when the CCD is windowed. Combining multiple cameras and fast readout
rates, ROSA will accumulate approximately 12 TB of data per 8 hours
observing. Following successful commissioning during August 2008,
ROSA will allow for multi-wavelength studies of the solar atmosphere
at a high temporal resolution.
---------------------------------------------------------
Title: A transit timing analysis of seven RISE light curves of the
exoplanet system HAT-P-3
Authors: Gibson, N. P.; Pollacco, D. L.; Barros, S.; Benn, C.;
Christian, D.; Hrudková, M.; Joshi, Y. C.; Keenan, F. P.; Simpson,
E. K.; Skillen, I.; Steele, I. A.; Todd, I.
2010MNRAS.401.1917G Altcode: 2009MNRAS.tmp.1666G; 2009MNRAS.tmp.1684G; 2009arXiv0909.4170G
We present seven light curves of the exoplanet system HAT-P-3, taken
as part of a transit timing programme using the rapid imager to
search for exoplanets instrument on the Liverpool Telescope. The
light curves are analysed using a Markov chain Monte Carlo
algorithm to update the parameters of the system. The inclination
is found to be i = 86.75<SUP>+0.22</SUP><SUB>-0.21</SUB>°, the
planet-star radius ratio to be R<SUB>p</SUB>/R<SUB>*</SUB>
= 0.1098<SUP>+0.0010</SUP><SUB>-0.0012</SUB>
and the stellar radius to be R<SUB>*</SUB> =
0.834<SUP>+0.018</SUP><SUB>-0.026</SUB>R<SUB>solar</SUB>, consistent
with previous results but with a significant improvement in the
precision. Central transit times and uncertainties for each light curve
are also determined, and a residual permutation algorithm is used as
an independent check on the errors. The transit times are found to be
consistent with a linear ephemeris, and a new ephemeris is calculated as
T<SUB>c</SUB>(0) = 2454856.70118 +/- 0.00018 HJD and P = 2.899738 +/-
0.000007 d. Model timing residuals are fitted to the measured timing
residuals to place upper mass limits for a hypothetical perturbing
planet as a function of the period ratio. These show that we have
probed for planets with masses as low as 0.33 and 1.81 M<SUB>⊕</SUB>
in the interior and exterior 2:1 resonances, respectively, assuming
the planets are initially in circular orbits.
---------------------------------------------------------
Title: Radiative rates and electron impact excitation rates for
transitions in Cr VIII
Authors: Aggarwal, K. M.; Kato, T.; Keenan, F. P.; Murakami, I.
2009A&A...506.1501A Altcode:
Aims: In this paper we report on calculations of energy levels,
radiative rates, oscillator strengths, line strengths, and effective
collision strengths for transitions among the lowest 362 levels
of the (1s^22s^22p^6) 3s^23p^5, 3s3p^6, 3s^23p^43d, 3s3p^53d,
3s^23p^33d^2, 3s3p^43d^2, 3p^63d, and 3s^23p^44ℓ configurations
of Cr viii. <BR />Methods: The general-purpose relativistic atomic
structure package (grasp) and flexible atomic code (fac) are adopted
for the calculations. <BR />Results: Radiative rates, oscillator
strengths, and line strengths are reported for all electric dipole
(E1), magnetic dipole (M1), electric quadrupole (E2), and magnetic
quadrupole (M2) transitions among the 362 levels. Comparisons are
made with earlier available results and the accuracy of the data
is assessed. Additionally, lifetimes for all 362 levels are listed,
although comparisons with other theoretical results are limited to only
a few levels. Our energy levels are estimated to be accurate to better
than 3% (within 0.4 Ryd), whereas results for other parameters are
probably accurate to better than 20%. Finally, electron impact collision
strengths and excitation rates are computed for all transitions over a
wide energy (temperature) range. For these calculations, FAC is adopted
and results in the form of effective collision strengths are reported
over a wide temperature range of 10<SUP>5.0</SUP>-10<SUP>6.6</SUP>
K. <P />Full Tables [see full textsee full text], [see full textsee
full text], and Table 6 are only available in electronic form at the
CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via
http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/506/1501
---------------------------------------------------------
Title: SN 2008S: an electron-capture SN from a super-AGB progenitor?
Authors: Botticella, M. T.; Pastorello, A.; Smartt, S. J.; Meikle,
W. P. S.; Benetti, S.; Kotak, R.; Cappellaro, E.; Crockett,
R. M.; Mattila, S.; Sereno, M.; Patat, F.; Tsvetkov, D.; van Loon,
J. Th.; Abraham, D.; Agnoletto, I.; Arbour, R.; Benn, C.; di Rico,
G.; Elias-Rosa, N.; Gorshanov, D. L.; Harutyunyan, A.; Hunter, D.;
Lorenzi, V.; Keenan, F. P.; Maguire, K.; Mendez, J.; Mobberley, M.;
Navasardyan, H.; Ries, C.; Stanishev, V.; Taubenberger, S.; Trundle,
C.; Turatto, M.; Volkov, I. M.
2009MNRAS.398.1041B Altcode: 2009arXiv0903.1286B
We present comprehensive photometric and spectroscopic observations
of the faint transient SN 2008S discovered in the nearby galaxy NGC
6946. SN 2008S exhibited slow photometric evolution and almost no
spectral variability during the first nine months, implying a long
photon diffusion time and a high-density circumstellar medium. Its
bolometric luminosity (~=10<SUP>41</SUP>ergs<SUP>-1</SUP> at peak) is
low with respect to most core-collapse supernovae but is comparable
to the faintest Type II-P events. Our quasi-bolometric light curve
extends to 300 d and shows a tail phase decay rate consistent
with that of <SUP>56</SUP>Co. We propose that this is evidence
for an explosion and formation of <SUP>56</SUP>Ni (0.0014 +/-
0.0003M<SUB>solar</SUB>). Spectra of SN 2008S show intense emission
lines of Hα, [CaII] doublet and CaII near-infrared (NIR) triplet,
all without obvious P-Cygni absorption troughs. The large mid-infrared
(MIR) flux detected shortly after explosion can be explained by a light
echo from pre-existing dust. The late NIR flux excess is plausibly
due to a combination of warm newly formed ejecta dust together with
shock-heated dust in the circumstellar environment. We reassess the
progenitor object detected previously in Spitzer archive images,
supplementing this discussion with a model of the MIR spectral energy
distribution. This supports the idea of a dusty, optically thick shell
around SN 2008S with an inner radius of nearly 90AU and outer radius of
450AU, and an inferred heating source of 3000K. The luminosity of the
central star is L ~= 10<SUP>4.6</SUP>L<SUB>solar</SUB>. All the nearby
progenitor dust was likely evaporated in the explosion leaving only the
much older dust lying further out in the circumstellar environment. The
combination of our long-term multiwavelength monitoring data and the
evidence from the progenitor analysis leads us to support the scenario
of a weak electron-capture supernova explosion in a super-asymptotic
giant branch progenitor star (of initial mass 6-8M<SUB>solar</SUB>)
embedded within a thick circumstellar gaseous envelope. We suggest
that all of main properties of the electron-capture SN phenomenon are
observed in SN 2008S and future observations may allow a definitive
answer.
---------------------------------------------------------
Title: Possible evidence of asymmetry in SN 2007rt, a type IIn
supernova
Authors: Trundle, C.; Pastorello, A.; Benetti, S.; Kotak, R.; Valenti,
S.; Agnoletto, I.; Bufano, F.; Dolci, M.; Elias-Rosa, N.; Greiner, T.;
Hunter, D.; Keenan, F. P.; Lorenzi, V.; Maguire, K.; Taubenberger, S.
2009A&A...504..945T Altcode: 2009arXiv0904.0119T
An optical photometric and spectroscopic analysis of the slowly-evolving
type IIn SN 2007rt is presented, covering a duration of 481 days after
discovery. Its earliest spectrum, taken approximately 100 days after the
explosion epoch, indicates the presence of a dense circumstellar medium,
with which the supernova ejecta is interacting. This is supported by
the slowly-evolving light curve. A notable feature in the spectrum of SN
2007rt is the presence of a broad He i 5875 line, not usually detected
in type IIn supernovae. This may imply that the progenitor star has a
high He/H ratio, having shed a significant portion of its hydrogen shell
via mass-loss. An intermediate resolution spectrum reveals a narrow Hα
P-Cygni profile, the absorption component of which has a width of 128 km
s<SUP>-1</SUP>. This slow velocity suggests that the progenitor of SN
2007rt recently underwent mass-loss with wind speeds comparable to the
lower limits of those detected in luminous blue variables. Asymmetries
in the line profiles of H and He at early phases bears some resemblance
to double-peaked features observed in a number of Ib/c spectra. These
asymmetries may be indicative of an asymmetric or bipolar outflow or
alternatively dust formation in the fast expanding ejecta. In addition,
the late time spectrum, at over 240 days post-explosion, shows clear
evidence for the presence of newly formed dust. <P />Appendix B is
only available in electronic from at http://www.aanda.org
---------------------------------------------------------
Title: VizieR Online Data Catalog: Cr VIII radiative and excitation
rates (Aggarwal+, 2009)
Authors: Aggarwal, K. M.; Kato, T.; Keenan, F. P.; Murakami, I.
2009yCat..35061501A Altcode:
The General purpose relativistic atomic structure package (GRASP) and
flexible atomic code (FAC) have been adopted for the calculations. <P
/>(5 data files).
---------------------------------------------------------
Title: A Transit Timing Analysis of Nine Rise Light Curves of the
Exoplanet System TrES-3
Authors: Gibson, N. P.; Pollacco, D.; Simpson, E. K.; Barros,
S.; Joshi, Y. C.; Todd, I.; Keenan, F. P.; Skillen, I.; Benn, C.;
Christian, D.; Hrudková, M.; Steele, I. A.
2009ApJ...700.1078G Altcode: 2009arXiv0905.4680G
We present nine newly observed transits of TrES-3, taken as part of
a transit timing program using the RISE instrument on the Liverpool
Telescope. A Markov-Chain Monte Carlo analysis was used to determine the
planet-star radius ratio and inclination of the system, which were found
to be R<SUB>p</SUB> /R <SUB>sstarf</SUB> = 0.1664<SUP>+0.0011</SUP>
<SUB>-0.0018</SUB> and i = 81.73<SUP>+0.13</SUP> <SUB>-0.04</SUB>,
respectively, consistent with previous results. The central
transit times and uncertainties were also calculated, using
a residual-permutation algorithm as an independent check on the
errors. A re-analysis of eight previously published TrES-3 light curves
was conducted to determine the transit times and uncertainties using
consistent techniques. Whilst the transit times were not found to be in
agreement with a linear ephemeris, giving χ<SUP>2</SUP> = 35.07 for 15
degrees of freedom, we interpret this to be the result of systematics
in the light curves rather than a real transit timing variation. This
is because the light curves that show the largest deviation from a
constant period either have relatively little out-of-transit coverage
or have clear systematics. A new ephemeris was calculated using the
transit times and was found to be T<SUB>c</SUB> (0) = 2454632.62610
± 0.00006 HJD and P = 1.3061864 ± 0.0000005 days. The transit times
were then used to place upper mass limits as a function of the period
ratio of a potential perturbing planet, showing that our data are
sufficiently sensitive to have probed sub-Earth mass planets in both
interior and exterior 2:1 resonances, assuming that the additional
planet is in an initially circular orbit.
---------------------------------------------------------
Title: Automated detection and tracking of solar magnetic bright
points
Authors: Crockett, P. J.; Jess, D. B.; Mathioudakis, M.; Keenan, F. P.
2009MNRAS.397.1852C Altcode: 2009MNRAS.tmp..999C; 2009arXiv0905.3138C
Magnetic bright points (MBPs) in the internetwork are among the
smallest objects in the solar photosphere and appear bright against the
ambient environment. An algorithm is presented that can be used for the
automated detection of the MBPs in the spatial and temporal domains. The
algorithm works by mapping the lanes through intensity thresholding. A
compass search, combined with a study of the intensity gradient across
the detected objects, allows the disentanglement of MBPs from bright
pixels within the granules. Object growing is implemented to account
for any pixels that might have been removed when mapping the lanes. The
images are stabilized by locating long-lived objects that may have
been missed due to variable light levels and seeing quality. Tests of
the algorithm, employing data taken with the Swedish Solar Telescope,
reveal that ~90 per cent of MBPs within a 75 × 75 arcsec<SUP>2</SUP>
field of view are detected.
---------------------------------------------------------
Title: Electron-impact excitation of OII fine-structure levels
Authors: Kisielius, R.; Storey, P. J.; Ferland, G. J.; Keenan, F. P.
2009MNRAS.397..903K Altcode: 2009MNRAS.tmp..870K; 2009arXiv0907.4209K
Effective collision strengths for forbidden transitions among the five
energetically lowest fine-structure levels of OII are calculated in
the Breit-Pauli approximation using the R-matrix method. Results are
presented for the electron temperature range 100-100000 K. The accuracy
of the calculations is evaluated via the use of different types of
radial orbital sets and a different configuration expansion basis for
the target wavefunctions. A detailed assessment of previous available
data is given, and erroneous results are highlighted. Our results
reconfirm the validity of the original Seaton and Osterbrock scaling for
the optical OII ratio, a matter of some recent controversy. Finally, we
present plasma diagnostic diagrams using the best collision strengths
and transition probabilities. <P />This paper is dedicated to the
memory of Don Osterbrock (1924-2007) and Mike Seaton (1923-2007),
who first calibrated the OII density indicator, and did so much to
advance the study of nebulae. <P />E-mail: R.Kisielius@itpa.lt
---------------------------------------------------------
Title: The 0.5M<SUB>J</SUB> transiting exoplanet WASP-13b
Authors: Skillen, I.; Pollacco, D.; Collier Cameron, A.; Hebb, L.;
Simpson, E.; Bouchy, F.; Christian, D. J.; Gibson, N. P.; Hébrard,
G.; Joshi, Y. C.; Loeillet, B.; Smalley, B.; Stempels, H. C.; Street,
R. A.; Udry, S.; West, R. G.; Anderson, D. R.; Barros, S. C. C.;
Enoch, B.; Haswell, C. A.; Hellier, C.; Horne, K.; Irwin, J.; Keenan,
F. P.; Lister, T. A.; Maxted, P.; Mayor, M.; Moutou, C.; Norton,
A. J.; Parley, N.; Queloz, D.; Ryans, R.; Todd, I.; Wheatley, P. J.;
Wilson, D. M.
2009A&A...502..391S Altcode: 2009arXiv0905.3115S
We report the discovery of WASP-13b, a low-mass M<SUB>p</SUB> = 0.46
<SUP>+ 0.06 </SUP><SUB>- 0.05</SUB> M<SUB>J</SUB> transiting exoplanet
with an orbital period of 4.35298 ± 0.00004 days. The transit has a
depth of 9 mmag, and although our follow-up photometry does not allow
us to constrain the impact parameter well (0 < b < 0.46), with
radius in the range R<SUB>p</SUB> 1.06-1.21 R<SUB>J</SUB> the location
of WASP-13b in the mass-radius plane is nevertheless consistent with
H/He-dominated, irradiated, low core mass and core-free theoretical
models. The G1V host star is similar to the Sun in mass (M<SUB>*</SUB>
= 1.03<SUP>+0.11</SUP>_ {- 0.09} M<SUB>⊙</SUB>) and metallicity
([M/H] = 0.0±0.2), but is possibly older (8.5<SUP>+ 5.5 </SUP>_-4.9
Gyr). <P />The SuperWASP and JGT differential photometry, and SOPHIE
radial velocities of WASP-13 are only available in electronic form
at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)
or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/502/391
---------------------------------------------------------
Title: Possible Connection Between Umbral and Bright Point
Oscillations
Authors: Andic, Aleksandra; Jess, D. B.; Mathioudakis, M.; Keenan,
F. P.; Bloomfield, D. S.
2009SPD....40.0909A Altcode:
Active region NOAA 10794 was observed using the Rapid Dual Imager
(RDI) instrument on the Dunn Solar Telescope at the National Solar
Observatory, Sacramento Peak. G-band and H-alpha filters were employed
for the observations, and the resulting data were subjected to both
speckle reconstruction and wavelet analyses. <P />Intensity oscillations
in the period range 8--584 s were detected. Those with frequencies
near the Nyquist value of 125 mHz had a similar behavior to other
oscillations detected in the period range of 8 - 60 s. <P />However,
oscillations in the range around 180s observed above bright points
show a temporal coincidence in the light curve shape and the number
of the emitted frequencies in an umbral flash, indicating a possible
connection.
---------------------------------------------------------
Title: VizieR Online Data Catalog: WASP-13b photometry and radial
velocities (Skillen+, 2009)
Authors: Skillen, I.; Pollacco, D.; Collier Cameron, A.; Hebb, L.;
Simpson, E.; Bouchy, F.; Christian, D. J.; Gibson, N. P.; Hebrard,
G.; Joshi, Y. C.; Loeillet, B.; Smalley, B.; Stempels, H. C.; Street,
R. A.; Udry, S.; West, R. G.; Anderson, D. R.; Barros, S. C. C.;
Enoch, B.; Haswell, C. A.; Hellier, C.; Horne, K.; Irwin, J.; Keenan,
F. P.; Lister, T. A.; Maxted, P.; Mayor, M.; Moutou, C.; Norton,
A. J.; Parley, N.; Queloz, D.; Ryans, R.; Todd, I.; Wheatley, P. J.;
Wilson, D. M.
2009yCat..35020391S Altcode:
WASP-13 was monitored with the SuperWASP-N Camera (La Palma) from 2006
November 27 to 2007 April 1. <P />(3 data files).
---------------------------------------------------------
Title: Alfvén Waves in the Lower Solar Atmosphere
Authors: Jess, David B.; Mathioudakis, Mihalis; Erdélyi, Robert;
Crockett, Philip J.; Keenan, Francis P.; Christian, Damian J.
2009Sci...323.1582J Altcode: 2009arXiv0903.3546J
The flow of energy through the solar atmosphere and the heating of the
Sun’s outer regions are still not understood. Here, we report the
detection of oscillatory phenomena associated with a large bright-point
group that is 430,000 square kilometers in area and located near the
solar disk center. Wavelet analysis reveals full-width half-maximum
oscillations with periodicities ranging from 126 to 700 seconds
originating above the bright point and significance levels exceeding
99%. These oscillations, 2.6 kilometers per second in amplitude,
are coupled with chromospheric line-of-sight Doppler velocities
with an average blue shift of 23 kilometers per second. A lack of
cospatial intensity oscillations and transversal displacements rules
out the presence of magneto-acoustic wave modes. The oscillations
are a signature of Alfvén waves produced by a torsional twist of
±22 degrees. A phase shift of 180 degrees across the diameter of the
bright point suggests that these torsional Alfvén oscillations are
induced globally throughout the entire brightening. The energy flux
associated with this wave mode is sufficient to heat the solar corona.
---------------------------------------------------------
Title: Ultraviolet and extreme-ultraviolet line ratio diagnostics
for O IV
Authors: Keenan, F. P.; Crockett, P. J.; Aggarwal, K. M.; Jess, D. B.;
Mathioudakis, M.
2009A&A...495..359K Altcode: 2009arXiv0901.2222K
Aims: We generate theoretical ultraviolet and extreme-ultraviolet
emission line ratios for O IV and show their strong versatility
as electron temperature and density diagnostics for astrophysical
plasmas. <BR />Methods: Recent fully relativistic calculations of
radiative rates and electron impact excitation cross sections for O
IV, supplemented with earlier data for A-values and proton excitation
rates, are used to derive theoretical O IV line intensity ratios for
a wide range of electron temperatures and densities. <BR />Results:
Diagnostic line ratios involving ultraviolet or extreme-ultraviolet
transitions in O IV are presented, that are applicable to a wide variety
of astrophysical plasmas ranging from low density gaseous nebulae to the
densest solar and stellar flares. Comparisons with observational data,
where available, show good agreement between theory and experiment,
providing support for the accuracy of the diagnostics. However,
diagnostics are also presented involving lines that are blended in
existing astronomical spectra, in the hope this might encourage further
observational studies at higher spectral resolution.
---------------------------------------------------------
Title: WASP-10b: a 3M<SUB>J</SUB>, gas-giant planet transiting a
late-type K star
Authors: Christian, D. J.; Gibson, N. P.; Simpson, E. K.; Street,
R. A.; Skillen, I.; Pollacco, D.; Collier Cameron, A.; Joshi, Y. C.;
Keenan, F. P.; Stempels, H. C.; Haswell, C. A.; Horne, K.; Anderson,
D. R.; Bentley, S.; Bouchy, F.; Clarkson, W. I.; Enoch, B.; Hebb,
L.; Hébrard, G.; Hellier, C.; Irwin, J.; Kane, S. R.; Lister, T. A.;
Loeillet, B.; Maxted, P.; Mayor, M.; McDonald, I.; Moutou, C.; Norton,
A. J.; Parley, N.; Pont, F.; Queloz, D.; Ryans, R.; Smalley, B.;
Smith, A. M. S.; Todd, I.; Udry, S.; West, R. G.; Wheatley, P. J.;
Wilson, D. M.
2009MNRAS.392.1585C Altcode: 2008arXiv0806.1482C
We report the discovery of WASP-10b, a new transiting extrasolar
planet (ESP) discovered by the Wide Angle Search for Planets (WASP)
Consortium and confirmed using Nordic Optical Telescope FIbre-fed
Echelle Spectrograph and SOPHIE radial velocity data. A 3.09-d period,
29 mmag transit depth and 2.36 h duration are derived for WASP-10b
using WASP and high-precision photometric observations. Simultaneous
fitting to the photometric and radial velocity data using a
Markov Chain Monte Carlo procedure leads to a planet radius of
1.28R<SUB>J</SUB>, a mass of 2.96M<SUB>J</SUB> and eccentricity of
~0.06. WASP-10b is one of the more massive transiting ESPs, and we
compare its characteristics to the current sample of transiting ESP,
where there is currently little information for masses greater than
~2M<SUB>J</SUB> and non-zero eccentricities. WASP-10's host star,
GSC 2752-00114 (USNO-B1.01214-0586164) is among the fainter stars in
the WASP sample, with V = 12.7 and a spectral type of K5. This result
shows promise for future late-type dwarf star surveys.
---------------------------------------------------------
Title: WASP-14b: 7.3 M<SUB>J</SUB> transiting planet in an eccentric
orbit
Authors: Joshi, Y. C.; Pollacco, D.; Collier Cameron, A.; Skillen, I.;
Simpson, E.; Steele, I.; Street, R. A.; Stempels, H. C.; Christian,
D. J.; Hebb, L.; Bouchy, F.; Gibson, N. P.; Hébrard, G.; Keenan,
F. P.; Loeillet, B.; Meaburn, J.; Moutou, C.; Smalley, B.; Todd,
I.; West, R. G.; Anderson, D. R.; Bentley, S.; Enoch, B.; Haswell,
C. A.; Hellier, C.; Horne, K.; Irwin, J.; Lister, T. A.; McDonald,
I.; Maxted, P.; Mayor, M.; Norton, A. J.; Parley, N.; Perrier, C.;
Pont, F.; Queloz, D.; Ryans, R.; Smith, A. M. S.; Udry, S.; Wheatley,
P. J.; Wilson, D. M.
2009MNRAS.392.1532J Altcode: 2008arXiv0806.1478J
We report the discovery of a 7.3 M<SUB>J</SUB> exoplanet WASP-14b,
one of the most massive transiting exoplanets observed to date. The
planet orbits the 10th-magnitude F5V star USNO-B111118-0262485 with a
period of 2.243752 d and orbital eccentricity e = 0.09. A simultaneous
fit of the transit light curve and radial velocity measurements yields
a planetary mass of 7.3 +/- 0.5 M<SUB>J</SUB> and a radius of 1.28
+/- 0.08 R<SUB>J</SUB>. This leads to a mean density of about 4.6
gcm<SUP>-3</SUP> making it the densest transiting exoplanets yet found
at an orbital period less than 3 d. We estimate this system to be at a
distance of 160 +/- 20 pc. Spectral analysis of the host star reveals
a temperature of 6475 +/- 100 K, logg = 4.07 cms<SUP>-2</SUP> and v
sini = 4.9 +/- 1.0 kms<SUP>-1</SUP>, and also a high lithium abundance,
logN(Li) = 2.84 +/- 0.05. The stellar density, effective temperature
and rotation rate suggest an age for the system of about 0.5-1.0 Gyr.
---------------------------------------------------------
Title: Updated parameters for the transiting exoplanet WASP-3b using
RISE, a new fast camera for the Liverpool Telescope
Authors: Gibson, N. P.; Pollacco, D.; Simpson, E. K.; Joshi, Y. C.;
Todd, I.; Benn, C.; Christian, D.; Hrudková, M.; Keenan, F. P.;
Meaburn, J.; Skillen, I.; Steele, I. A.
2008A&A...492..603G Altcode: 2008arXiv0810.3526G
Some of the first results are reported from RISE - a new fast camera
mounted on the Liverpool Telescope primarily designed to obtain high
time-resolution light curves of transiting extrasolar planets for the
purpose of transit timing. A full and partial transit of WASP-3 are
presented, and a Markov-Chain Monte Carlo analysis is used to update
the parameters from the discovery paper. This results in a planetary
radius of 1.29^+0.05<SUB>-0.12</SUB> R<SUB>J</SUB> and therefore a
density of 0.82<SUP>+0.14</SUP><SUB>-0.09</SUB>~ρ_J, consistent with
previous results. The inclination is 85.06^+0.16<SUB>-0.15</SUB> deg,
in agreement (but with a significant improvement in the precision) with
the previously determined value. Central transit times are found to be
consistent with the ephemeris given in the discovery paper; however,
a new ephemeris calculated using the longer baseline results in T_c(0)
= 2 454 605.55915 ± 0.00023 HJD and P = 1.846835 ± 0.000002 days.
---------------------------------------------------------
Title: Do All Flares Have White-Light Emission?
Authors: Jess, D. B.; Mathioudakis, M.; Crockett, P. J.; Keenan, F. P.
2008ApJ...688L.119J Altcode: 2008arXiv0810.1443J
High-cadence, multiwavelength optical observations of a solar active
region (NOAA AR 10969), obtained with the Swedish Solar Telescope,
are presented. Difference imaging of white light continuum data
reveals a white-light brightening, 2 minutes in duration, linked to a
cotemporal and cospatial C2.0 flare event. The flare kernel observed
in the white-light images has a diameter of 300 km, thus rendering it
below the resolution limit of most space-based telescopes. Continuum
emission is present only during the impulsive stage of the flare,
with the effects of chromospheric emission subsequently delayed
by ≈2 minutes. The localized flare emission peaks at 300% above
the quiescent flux. This large, yet tightly confined, increase in
emission is only resolvable due to the high spatial resolution of
the Swedish Solar Telescope. An investigation of the line-of-sight
magnetic field derived from simultaneous MDI data shows that the
continuum brightening is located very close to a magnetic polarity
inversion line. In addition, an Hα flare ribbon is directed along
a region of rapid magnetic energy change, with the footpoints of the
ribbon remaining cospatial with the observed white-light brightening
throughout the duration of the flare. The observed flare parameters
are compared with current observations and theoretical models for M-
and X-class events and we determine the observed white-light emission
is caused by radiative back-warming. We suggest that the creation of
white-light emission is a common feature of all solar flares.
---------------------------------------------------------
Title: VizieR Online Data Catalog: SuperWASP-North extrasolar planet
candidates (Clarkson+, 2007)
Authors: Clarkson, W. I.; Enoch, B.; Haswell, C. A.; Norton, A. J.;
Christian, D. J.; Collier Cameron, A.; Kane, S. R.; Horne, K. D.;
Lister, T. A.; Street, R. A.; West, R. G.; Wilson, D. M.; Evans, N.;
Fitzsimmons, A.; Hellier, C.; Hodgkin, S. T.; Irwin, J.; Keenan,
F. P.; Osborne, J. P.; Parley, N. R.; Pollacco, D. L.; Ryans, R.;
Skillen, I.; Wheatley, P. J.
2008yCat..73810851C Altcode:
The Wide Angle Search for Planets (WASP) photometrically surveys a
large number of nearby stars to uncover candidate extrasolar planet
systems by virtue of small-amplitude light curve dips on a <=5d
time-scale typical of the 'Hot-Jupiters'. Observations with the
SuperWASP-North instrument between 2004 April and September produced a
rich photometric data set of some 1.3x10<SUP>9</SUP> data points from
6.7 million stars. Our custom-built data acquisition and processing
system produces ~0.02mag photometric precision at V=13. <P />We
present the transit candidates in the 03h-06h RA range. Out of 141895
light curves with sufficient sampling to provide adequate coverage,
2688 show statistically significant transit-like periodicities. Out
of these, 44 pass a visual inspection of the light curve, of which
24 are removed through a set of cuts on the statistical significance
of artefacts. All but four of the remaining 20 objects are removed
when prior information at higher spatial resolution from existing
catalogues is taken into account. Of the four candidates remaining,
one is considered a good candidate for follow-up observations with
three further second-priority targets. We provide detailed information
on these candidates, as well as a selection of the false-positives and
astrophysical false-alarms that were eliminated, and discuss briefly
the impact of sampling on our results. <P />(1 data file).
---------------------------------------------------------
Title: Energy levels, radiative rates, and electron impact excitation
rates for transitions in O VII
Authors: Aggarwal, K. M.; Keenan, F. P.
2008A&A...489.1377A Altcode:
Aims: In this paper we report calculations for energy levels,
radiative rates, and electron impact excitation rates for transitions
in O vii. <BR />Methods: The grasp (general-purpose relativistic
atomic structure package) is adopted for calculating energy levels
and radiative rates. For determining the collision strengths and
subsequently the excitation rates, the Dirac atomic R-matrix code
(darc) and the flexible atomic code (fac) are used. <BR />Results:
Oscillator strengths, radiative rates, and line strengths are
reported for all E1, E2, M1, and M2 transitions among the lowest
49 levels of O vii. Collision strengths have been averaged over
a Maxwellian velocity distribution, and the resulting effective
collision strengths are reported over a wide temperature range below
2×10<SUP>6</SUP> K. Additionally, lifetimes are also listed for all
levels. <P />Tables 2 and 6 are only available in electronic form
at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)
or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/489/1377
---------------------------------------------------------
Title: Effective collision strengths for transitions in Ni XIX
Authors: Aggarwal, K. M.; Keenan, F. P.
2008A&A...488..365A Altcode:
Aims: In this paper we report electron impact collision strengths
and excitation rates for transitions among the lowest 89 levels
of Ni xix. <BR />Methods: The Dirac atomic R-matrix code (darc)
is adopted for the calculations of collision strengths and
subsequently the effective collision strengths. <BR />Results:
Collision strengths for resonance transitions among 89 levels arising
from the (1s^2) 2s^22p^6, 2s^22p^53ℓ, 2s2p^63ℓ, 2s^22p^54ℓ,
and 2s2p^64ℓ configurations of Ni xix are reported over a wide
energy range below 250 Ryd. Additionally, effective collision
strengths for all 3916 transitions among the 89 levels are listed
over a wide temperature range below 10<SUP>7</SUP> K. Comparisons
are made among different calculations and the accuracy of the
data is assessed. Finally, comparisons between theoretical and
experimental intensity ratios of some prominent lines of Ni xix are
discussed. <P />Table 3 is only available in electronic form at the
CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via
http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/488/365
---------------------------------------------------------
Title: Emission lines of FeX in active region spectra obtained with
the Solar Extreme-ultraviolet Research Telescope and Spectrograph
Authors: Keenan, F. P.; Jess, D. B.; Aggarwal, K. M.; Thomas, R. J.;
Brosius, J. W.; Davila, J. M.
2008MNRAS.389..939K Altcode: 2008MNRAS.tmp..860K; 2008arXiv0806.3354K
Fully relativistic calculations of radiative rates and electron
impact excitation cross-sections for FeX are used to derive
theoretical emission-line ratios involving transitions in
the 174-366Å wavelength range. A comparison of these with
solar active region observations obtained during the 1989
and 1995 flights of the Solar Extreme-ultraviolet Research
Telescope and Spectrograph (SERTS) reveals generally very good
agreement between theory and experiment. Several FeX emission
features are detected for the first time in SERTS spectra, while the
3s<SUP>2</SUP>3p<SUP>5</SUP><SUP>2</SUP>P<SUB>3/2</SUB>-3s<SUP>2</SUP>3p<SUP>4</SUP>(<SUP>1</SUP>S)3d
<SUP>2</SUP>D<SUB>3/2</SUB> transition at 195.32Å is identified for
the first time (to our knowledge) in an astronomical source. The most
useful FeX electron density (N<SUB>e</SUB>) diagnostic line ratios are
assessed to be 175.27/174.53 and 175.27/177.24, which both involve lines
close in wavelength and free from blends, vary by factors of 13 between
N<SUB>e</SUB> = 10<SUP>8</SUP> and 10<SUP>11</SUP>cm<SUP>-3</SUP>,
and yet show little temperature sensitivity. Should these lines
not be available, then the 257.25/345.74 ratio may be employed
to determine N<SUB>e</SUB>, although this requires an accurate
evaluation of the instrument intensity calibration over a relatively
large wavelength range. However, if the weak 324.73Å line of FeX
is reliably detected, the use of 324.73/345.74 or 257.25/324.73
is recommended over 257.25/345.74. Electron densities deduced from
175.27/174.53 and 175.27/177.24 for the stars Procyon and α Cen,
using observations from the Extreme-Ultraviolet Explorer (EUVE)
satellite, are found to be consistent and in agreement with the values
of N<SUB>e</SUB> determined from other diagnostic ratios in the EUVE
spectra. A comparison of several theoretical extreme-ultraviolet
FeX line ratios with experimental values for a θ-pinch, for which
the plasma parameters have been independently determined, reveals
reasonable agreement between theory and observation, providing some
independent support for the accuracy of the adopted atomic data.
---------------------------------------------------------
Title: Transition Region Velocity Oscillations Observed by EUNIS-06
Authors: Jess, D. B.; Rabin, D. M.; Thomas, R. J.; Brosius, J. W.;
Mathioudakis, M.; Keenan, F. P.
2008ApJ...682.1363J Altcode: 2008arXiv0804.1629J
Spectroscopic measurements of NOAA AR 10871, obtained with the Extreme
Ultraviolet Normal Incidence Spectrograph (EUNIS) sounding rocket
instrument on 2006 April 12, reveal velocity oscillations in the He
II 303.8 Å emission line formed at T ≈ 5 × 10<SUP>4</SUP> K. The
oscillations appear to arise in a bright active region loop arcade
about 25<SUP>”</SUP> wide which crosses the EUNIS slit. The period
of these transition region oscillations is 26 +/- 4 s, coupled with
a velocity amplitude of ±10 km s<SUP>-1</SUP>, detected over four
complete cycles. Similar oscillations are observed in lines formed at
temperatures up to T ≈ 4 × 10<SUP>5</SUP> K, but we find no evidence
for the coupling of these velocity oscillations with corresponding
phenomena in the corona. We interpret the detected oscillations as
originating from an almost purely adiabatic plasma, and infer that
they are generated by the resonant transmission of MHD waves through
the lower active region atmospheres. Through the use of seismological
techniques, we establish that the observed velocity oscillations display
wave properties most characteristic of fast body global sausage modes.
---------------------------------------------------------
Title: Energy levels, radiative rates, and excitation rates for
transitions in O IV
Authors: Aggarwal, K. M.; Keenan, F. P.
2008A&A...486.1053A Altcode:
Aims: In this paper we report calculations for energy levels, radiative
rates, and excitation rates for transitions in O IV. <BR />Methods:
The grasp (general-purpose relativistic atomic structure package)
and fac (flexible atomic code) were adopted for calculating energy
levels and radiative rates, and the Dirac atomic R-matrix code
(darc) used to determine the excitation rates. <BR />Results:
Oscillator strengths and radiative rates are reported for all
E1, E2, M1, and M2 transitions among the lowest 75 levels of
O iv. Additionally, lifetimes are reported for all levels and
comparisons made with those available in the literature. Finally,
effective collision strengths are reported for all transitions over a
wide temperature range below 10<SUP>6</SUP> K. Comparisons are made
with earlier results and the accuracy of the data is assessed. <P
/>Tables 3, 5 and 6 are only available in electronic form at the
CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via
http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/486/1053
---------------------------------------------------------
Title: Radiative rates and electron impact excitation rates for
H-like Ar XVIII
Authors: Aggarwal, K. M.; Hamada, K.; Igarashi, A.; Jonauskas, V.;
Keenan, F. P.; Nakazaki, S.
2008A&A...487..383A Altcode:
Aims: In this paper we report on calculations for energy levels,
radiative rates, collision strengths, and effective collision
strengths for transitions among the lowest 25 levels of the
n ≤ 5 configurations of H-like Ar xviii. <BR />Methods: The
general-purpose relativistic atomic structure package (grasp) and
Dirac atomic R-matrix code (darc) are adopted for the calculations. <BR
/>Results: Radiative rates, oscillator strengths, and line strengths
are reported for all electric dipole (E1), magnetic dipole (M1),
electric quadrupole (E2), and magnetic quadrupole (M2) transitions
among the 25 levels. Furthermore, collision strengths and effective
collision strengths are listed for all 300 transitions among the
above 25 levels over a wide energy (temperature) range up to 800 Ryd
(10<SUP>7.4</SUP> K). <P />Tables 2-4 are only available in electronic
form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)
or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/487/383
---------------------------------------------------------
Title: VizieR Online Data Catalog: OVII radiative and excitation rates
(Aggarwal+, 2008)
Authors: Aggarwal, K. M.; Keenan, F. P.
2008yCat..34891377A Altcode:
In this paper we report calculations for energy levels, radiative
rates, and electron impact excitation rates for transitions in OVII. <P
/>The GRASP (general-purpose relativistic atomic structure package)
is adopted for calculating energy levels and radiative rates. For
determining the collision strengths and subsequently the excitation
rates, the Dirac atomic R-matrix code (DARC) and the flexible atomic
code (FAC) are used. <P />Oscillator strengths, radiative rates, and
line strengths are reported for all E1, E2, M1, and M2 transitions among
the lowest 49 levels of OVII. Collision strengths have been averaged
over a Maxwellian velocity distribution, and the resulting effective
collision strengths are reported over a wide temperature range below
2x10<SUP>6</SUP>K. Additionally, lifetimes are also listed for all
levels. <P />(3 data files).
---------------------------------------------------------
Title: RISE: a fast-readout imager for exoplanet transit timing
Authors: Steele, I. A.; Bates, S. D.; Gibson, N.; Keenan, F.; Meaburn,
J.; Mottram, C. J.; Pollacco, D.; Todd, I.
2008SPIE.7014E..6JS Altcode: 2008SPIE.7014E.217S; 2008arXiv0809.3351S
By the precise timing of the low amplitude (0.005 - 0.02 magnitude)
transits of exoplanets around their parent star it should be possible
to infer the presence of other planetary bodies in the system down to
Earth-like masses. We describe the design and construction of RISE, a
fast-readout frame transfer camera for the Liverpool Telescope designed
to carry out this experiment. The results of our commissioning tests
are described as well as the data reduction procedure necessary. We
present light curves of two objects, showing that the desired timing
and photometric accuracy can be obtained providing that autoguiding
is used to keep the target on the same detector pixel for the entire
(typically 4 hour) observing run.
---------------------------------------------------------
Title: Radiative rates and electron impact excitation rates for
H-like Fe XXVI
Authors: Aggarwal, K. M.; Hamada, K.; Igarashi, A.; Jonauskas, V.;
Keenan, F. P.; Nakazaki, S.
2008A&A...484..879A Altcode:
Aims: In this paper we report on calculations for energy levels,
radiative rates, collision strengths, and effective collision strengths
for transitions among the lowest 25 levels of the n ≤ 5 configurations
of H-like Fe XXVI. <BR />Methods: The general-purpose relativistic
atomic structure package (GRASP) and Dirac atomic R-matrix code
(DARC) are adopted for the calculations. <BR />Results: Radiative
rates, oscillator strengths, and line strengths are reported for all
electric dipole (E1), magnetic dipole (M1), electric quadrupole
(E2), and magnetic quadrupole (M2) transitions among the 25
levels. Furthermore, collision strengths and effective collision
strengths are reported for all the 300 transitions among the above
25 levels over a wide energy (temperature) range up to 1500 Ryd
(10<SUP>7.7</SUP> K). Comparisons are made with earlier available
results and the accuracy of the data is assessed. <P />Table 1 is
also available and Tables 2-5 are only available in electronic form
at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)
or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/484/879
---------------------------------------------------------
Title: Discovery of Spatial Periodicities in a Coronal Loop Using
Automated Edge-Tracking Algorithms
Authors: Jess, D. B.; Mathioudakis, M.; Erdélyi, R.; Verth, G.;
McAteer, R. T. J.; Keenan, F. P.
2008ApJ...680.1523J Altcode: 2008arXiv0802.1971J
A new method for automated coronal loop tracking, in both spatial
and temporal domains, is presented. Applying this technique to TRACE
data, obtained using the 171 Å filter on 1998 July 14, we detect a
coronal loop undergoing a 270 s kink-mode oscillation, as previously
found by Aschwanden et al. However, we also detect flare-induced,
and previously unnoticed, spatial periodicities on a scale of 3500 km,
which occur along the coronal loop edge. Furthermore, we establish a
reduction in oscillatory power for these spatial periodicities of 45%
over a 222 s interval. We relate the reduction in detected oscillatory
power to the physical damping of these loop-top oscillations.
---------------------------------------------------------
Title: Line intensity enhancements in stellar coronal X-ray spectra
due to opacity effects
Authors: Rose, S. J.; Matranga, M.; Mathioudakis, M.; Keenan, F. P.;
Wark, J. S.
2008A&A...483..887R Altcode: 2008arXiv0803.3184R
Context: The I(15.01 Å)/I(16.78 Å) emission line intensity ratio
in Fe xvii has been reported to deviate from its theoretical value
in solar and stellar X-ray spectra. This is attributed to opacity in
the 15.01 Å line, leading to a reduction in its intensity, and was
interpreted in terms of a geometry in which the emitters and absorbers
are spatially distinct. <BR />Aims: We study the I(15.01 Å)/I(16.78
Å) intensity ratio for the active cool dwarf EV Lac, in both flare and
quiescent spectra. <BR />Methods: The observations were obtained with
the Reflection Grating Spectrometer on the XMM-Newton satellite. The
emission measure distribution versus temperature reconstruction
technique is used for our analysis. <BR />Results: We find that the
15.01 Å line exhibits a significant enhancement in intensity over the
optically thin value. To our knowledge, this is the first time that such
an enhancement has been detected on such a sound statistical basis. We
interpret this enhancement in terms of a geometry in which the emitters
and absorbers are not spatially distinct, and where the geometry is such
that resonant pumping of the upper level has a greater effect on the
observed line intensity than resonant absorption in the line-of-sight.
---------------------------------------------------------
Title: VizieR Online Data Catalog: SuperWASP-North extrasolar planet
candidates (Kane+, 2008)
Authors: Kane, S. R.; Clarkson, W. I.; West, R. G.; Wilson, D. M.;
Christian, D. J.; Collier Cameron, A.; Enoch, B.; Lister, T. A.;
Street, R. A.; Evans, A.; Fitzsimmons, A.; Haswell, C. A.; Hellier, C.;
Hodgkin, S. T.; Horne, K.; Irwin, J.; Keenan, F. P.; Norton, A. J.;
Osborne, J.; Parley, N. R.; Pollacco, D. L.; Ryans, R.; Skillen, I.;
Wheatley, P. J.
2008yCat..73841097K Altcode:
The SuperWASP-N instrument is a robotic observatory designed to provide
precision photometry for large areas of sky. First light was achieved
in 2003 November and observations have continued until the present
time. <P />(3 data files).
---------------------------------------------------------
Title: VizieR Online Data Catalog: NiXIX effective collision strengths
(Aggarwal+, 2008)
Authors: Aggarwal, K. M.; Keenan, F. P.
2008yCat..34880365A Altcode:
In this paper we report electron impact collision strengths and
excitation rates for transitions among the lowest 89 levels of
NiXIX. <P />The Dirac atomic R-matrix code (DARC) is adopted for the
calculations of collision strengths and subsequently the effective
collision strengths. <P />Collision strengths for resonance
transitions among 89 levels arising from the (1s<SUP>2</SUP>)
2s<SUP>2</SUP>2p<SUP>6</SUP>, 2s<SUP>2</SUP>2p<SUP>5</SUP>3l,
2s2p<SUP>6</SUP>3l, 2s<SUP>2</SUP>2p<SUP>5</SUP>4l, and
2s2p<SUP>6</SUP>4l configurations of NiXIX are reported over a
wide energy range below 250Ryd. Additionally, effective collision
strengths for all 3916 transitions among the 89 levels are listed
over a wide temperature range below 10<SUP>7</SUP>K. Comparisons are
made among different calculations and the accuracy of the data is
assessed. Finally, comparisons between theoretical and experimental
intensity ratios of some prominent lines of NiXIX are discussed. <P
/>(3 data files).
---------------------------------------------------------
Title: Metallicity and Physical Conditions in the Magellanic Bridge
Authors: Lehner, N.; Howk, J. C.; Keenan, F. P.; Smoker, J. V.
2008ApJ...678..219L Altcode: 2008arXiv0801.2534L
We present a new analysis of the diffuse gas in the Magellanic Bridge
(R.A. gtrsim 3<SUP>h</SUP>) based on HST STIS E140M and FUSE spectra
of two early-type stars lying within the Bridge and a QSO behind it. We
derive the column densities of the H I (from Lyα), N I, O I, Ar I, Si
II, S II, and Fe II of the gas in the Bridge. Using the atomic species,
we determine the first gas-phase metallicity of the Magellanic Bridge,
[Z/H] = - 1.02 +/- 0.07 toward one sight line and -1.7 < [Z/H] < -
0.9 toward the other, a factor of 2 or more smaller than the present-day
SMC metallicity. Using the metallicity and N(H I), we show that the
Bridge gas along our three lines of sight is ~70%-90% ionized, despite
high H I columns, log N(H I) simeq 19.6 - 20.1. Possible sources for
the ongoing ionization are certainly the hot stars within the Bridge,
hot gas (revealed by O VI absorption), and leaking photons from the SMC
and LMC. From the analysis of C II*, we deduce that the overall density
of the Bridge must be low (<0.03-0.1 cm<SUP>-3</SUP>). We argue
that our findings combined with other recent observational results
should motivate new models of the evolution of the SMC-LMC-Galaxy
system. <P />Based on observations made with the NASA-CNES-CSA Far
Ultraviolet Spectroscopic Explorer. FUSE is operated for NASA by The
Johns Hopkins University under NASA contract NAS5-32985. Based on
observations made with the NASA/ESA Hubble Space Telescope, obtained
at the Space Telescope Science Institute, which is operated by the
Association of Universities for Research in Astronomy, Inc., under
NASA contract NAS5-26555.
---------------------------------------------------------
Title: High frequency oscillations in the solar chromosphere and
their connection with heating
Authors: Andic, Aleksandra; Mathioudakis, M.; Keenan, F. P.; Jess,
D. B.; Bloomfield, D. S.
2008IAUS..247..312A Altcode: 2007IAUS..247..312A
High frequency acoustic waves have been suggested as a source of
mechanical heating in the quiet solar chromosphere. To investigate
this, we have observed intensity oscillations of several lines in the
frequency interval 1.64-70mHz using data from the VTT Tenerife and the
Dunn Solar Telescope at the National Solar Observatory. Our analysis
of Fe i 543.45 nm, Fe i 543.29 nm and the G-band, indicate that the
majority of oscillations are connected with the magnetic fields and
do not provide sufficient mechanical flux for the heating of the
chromosphere. This correlation is also observed in quiet Sun areas.
---------------------------------------------------------
Title: Solar feature tracking in both spatial and temporal domains
Authors: Jess, D. B.; Mathioudakis, M.; Erdélyi, R.; Verth, G.;
McAteer, R. T. J.; Keenan, F. P.
2008IAUS..247..288J Altcode: 2007IAUS..247..288J
A new method for automated coronal loop tracking, in both spatial and
temporal domains, is presented. The reliability of this technique
was tested with TRACE 171 Å observations. The application of this
technique to a flare-induced kink-mode oscillation, revealed a 3500
km spatial periodicity which occur along the loop edge. We establish
a reduction in oscillatory power, for these spatial periodicities,
of 45% over a 322 s interval. We relate the reduction in oscillatory
power to the physical damping of these loop-top oscillations.
---------------------------------------------------------
Title: VizieR Online Data Catalog: On IV radiative and excitation
rates (Aggarwal+, 2008)
Authors: Aggarwal, K. M.; Keenan, F. P.
2008yCat..34861053A Altcode:
In this paper we report calculations for energy levels, radiative
rates, and excitation rates for transitions in O IV. <P />The GRASP
(general-purpose relativistic atomic structure package) and FAC
(flexible atomic code) we adopted for calculating energy levels and
radiative rates, and the Dirac atomic R-matrix code (DARC) used
to determine the excitation rates. <P />Oscillator strengths and
radiative rates are reported for all E1, E2, M1, and M2 transitions
among the lowest 75 levels of O IV. Additionally, lifetimes are
reported for all levels and comparisons made with those available
in the literature. Finally, effective collision strengths are
reported for all transitions over a wide temperature range below
10<SUP>6</SUP>K. Comparisons are made with earlier results and the
accuracy of the data is assessed. <P />(7 data files).
---------------------------------------------------------
Title: Twisting flux tubes as a cause of micro-flaring activity
Authors: Jess, D. B.; McAteer, R. T. J.; Mathioudakis, M.; Keenan,
F. P.; Andic, A.; Bloomfield, D. S.
2008IAUS..247..360J Altcode: 2007IAUS..247..360J
High-cadence optical observations of an H-α blue-wing bright point
near solar AR NOAA 10794 are presented. The data were obtained with the
Dunn Solar Telescope at the National Solar Observatory/Sacramento Peak
using a newly developed camera system, the rapid dual imager. Wavelet
analysis is undertaken to search for intensity-related oscillatory
signatures, and periodicities ranging from 15 to 370 s are found with
significance levels exceeding 95%. During two separate microflaring
events, oscillation sites surrounding the bright point are observed to
twist. We relate the twisting of the oscillation sites to the twisting
of physical flux tubes, thus giving rise to reconnection phenomena. We
derive an average twist velocity of 8.1 km/s and detect a peak in the
emitted flux between twist angles of 180° and 230°.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Fe XXVI radiative and excitation
rates (Aggarwal+, 2008)
Authors: Aggarwal, K. M.; Hamada, K.; Igarashi, A.; Jonauskas, V.;
Keenan, F. P.; Nakazaki, S.
2008yCat..34840879A Altcode:
In this paper we report on calculations for energy levels, radiative
rates, collision strengths, and effective collision strengths for
transitions among the lowest 25 levels of the n<=5 configurations of
H-like Fe XXVI. <P />The General purpose relativistic atomic structure
package (GRASP) and Dirac atomic R-matrix code (DARC) have been adopted
for the calculations. <P />(5 data files).
---------------------------------------------------------
Title: WASP-3b: a strongly irradiated transiting gas-giant planet
Authors: Pollacco, D.; Skillen, I.; Collier Cameron, A.; Loeillet,
B.; Stempels, H. C.; Bouchy, F.; Gibson, N. P.; Hebb, L.; Hébrard,
G.; Joshi, Y. C.; McDonald, I.; Smalley, B.; Smith, A. M. S.; Street,
R. A.; Udry, S.; West, R. G.; Wilson, D. M.; Wheatley, P. J.; Aigrain,
S.; Alsubai, K.; Benn, C. R.; Bruce, V. A.; Christian, D. J.; Clarkson,
W. I.; Enoch, B.; Evans, A.; Fitzsimmons, A.; Haswell, C. A.; Hellier,
C.; Hickey, S.; Hodgkin, S. T.; Horne, K.; Hrudková, M.; Irwin,
J.; Kane, S. R.; Keenan, F. P.; Lister, T. A.; Maxted, P.; Mayor,
M.; Moutou, C.; Norton, A. J.; Osborne, J. P.; Parley, N.; Pont, F.;
Queloz, D.; Ryans, R.; Simpson, E.
2008MNRAS.385.1576P Altcode: 2008MNRAS.tmp..320P; 2007arXiv0711.0126P
We report the discovery of WASP-3b, the third transiting exoplanet to
be discovered by the WASP and SOPHIE collaboration. WASP-3b transits
its host star USNO-B1.01256-0285133 every 1.846834 +/- 0.000002 d. Our
high-precision radial velocity measurements present a variation with
amplitude characteristic of a planetary-mass companion and in phase
with the light curve. Adaptive optics imaging shows no evidence for
nearby stellar companions, and line-bisector analysis excludes faint,
unresolved binarity and stellar activity as the cause of the radial
velocity variations. We make a preliminary spectroscopic analysis of
the host star and find it to have T<SUB>eff</SUB> = 6400 +/- 100K and
log g = 4.25 +/- 0.05 which suggests it is most likely an unevolved
main-sequence star of spectral type F7-8V. Our simultaneous modelling
of the transit photometry and reflex motion of the host leads us to
derive a mass of 1.76<SUP>+0.08</SUP><SUB>-0.14</SUB> M<SUB>J</SUB>
and radius 1.31<SUP>+0.07</SUP><SUB>-0.14</SUB> R<SUB>J</SUB> for
WASP-3b. The proximity and relative temperature of the host star
suggests that WASP-3b is one of the hottest exoplanets known, and
thus has the potential to place stringent constraints on exoplanet
atmospheric models.
---------------------------------------------------------
Title: SuperWASP-N extrasolar planet candidates from fields
06<SUP>h</SUP> < RA < 16<SUP>h</SUP>
Authors: Kane, S. R.; Clarkson, W. I.; West, R. G.; Wilson, D. M.;
Christian, D. J.; Collier Cameron, A.; Enoch, B.; Lister, T. A.;
Street, R. A.; Evans, A.; Fitzsimmons, A.; Haswell, C. A.; Hellier, C.;
Hodgkin, S. T.; Horne, K.; Irwin, J.; Keenan, F. P.; Norton, A. J.;
Osborne, J.; Parley, N. R.; Pollacco, D. L.; Ryans, R.; Skillen, I.;
Wheatley, P. J.
2008MNRAS.384.1097K Altcode: 2007arXiv0711.2581K; 2008MNRAS.tmp...80K
The Wide Angle Search for Planets (WASP) survey currently operates two
installations, designated SuperWASP-N and SuperWASP-S, located in the
Northern and Southern hemispheres, respectively. These installations
are designed to provide high time-resolution photometry for the
purpose of detecting transiting extrasolar planets, asteroids, and
transient events. Here, we present results from a transit-hunting
observing campaign using SuperWASP-N covering a right ascension
(RA) range of 06<SUP>h</SUP> < RA < 16<SUP>h</SUP>. This paper
represents the fifth and final in the series of transit candidates
released from the 2004 observing season. In total, 729335 stars from
33 fields were monitored with 130566 having sufficient precision to
be scanned for transit signatures. Using a robust transit detection
algorithm and selection criteria, six stars were found to have events
consistent with the signature of a transiting extrasolar planet based
on the photometry, including the known transiting planet XO-1b. These
transit candidates are presented here along with discussion of follow-up
observations and the expected number of candidates in relation to the
overall observing strategy.
---------------------------------------------------------
Title: Effective collision strengths for allowed transitions among
the n ≤ 5 degenerate levels of Al XIII
Authors: Aggarwal, K. M.; Igarashi, A.; Keenan, F. P.; Nakazaki, S.
2008A&A...479..585A Altcode:
Aims:In this paper we report on calculations of collision strengths
and effective collision strengths for allowed transitions among the n
≤ 5 degenerate levels of Al xiii. <BR />Methods: The Dirac atomic
R-matrix code (darc) has been adopted for these calculations. <BR
/>Results: Collision strengths are reported over a wide energy range
below 300 Ryd, and effective collision strengths are provided for
electron temperatures of 4.4 ≤ log T<SUB>e</SUB> ≤ 6.8 K.
---------------------------------------------------------
Title: Iron abundances from optical FeIII absorption lines in B-type
stellar spectra
Authors: Thompson, H. M. A.; Keenan, F. P.; Dufton, P. L.; Trundle,
C.; Ryans, R. S. I.; Crowther, P. A.
2008MNRAS.383..729T Altcode: 2007MNRAS.tmp.1131T; 2007arXiv0710.3252T
The role of optical FeIII absorption lines in B-type stars as iron
abundance diagnostics is considered. To date, ultraviolet Fe lines have
been widely used in B-type stars, although line blending can severely
hinder their diagnostic power. Using optical spectra, covering a
wavelength range ~3560-9200Å, a sample of Galactic B-type main-sequence
and supergiant stars of spectral types B0.5 to B7 are investigated. A
comparison of the observed FeIII spectra of supergiants, and those
predicted from the model atmosphere codes TLUSTY [plane-parallel,
non-local thermodynamic equilibrium (LTE)], with spectra generated
using SYNSPEC (LTE), and CMFGEN (spherical, non-LTE), reveal that
non-LTE effects appear small. In addition, a sample of main-sequence and
supergiant objects, observed with the Fiber-fed Extended Range Optical
Spectrograph (FEROS), reveal LTE abundance estimates consistent with
the Galactic environment and previous optical studies. Based on the
present study, we list a number of FeIII transitions which we recommend
for estimating the iron abundance from early B-type stellar spectra.
---------------------------------------------------------
Title: VizieR Online Data Catalog: SuperWASP-North extrasolar planet
candidates (Street+, 2007)
Authors: Street, R. A.; Christian, D. J.; Clarkson, W. I.; Collier
Cameron, A.; Enoch, B.; Kane, S. R.; Lister, T. A.; West, R. G.;
Wilson, D. M.; Evans, A.; Fitzsimmons, A.; Haswell, C. A.; Hellier,
C.; Hodgkin, S. T.; Horne, K.; Irwin, J.; Keenan, F. P.; Norton, A. J.;
Osborne, J.; Pollacco, D. L.; Ryans, R.; Skillen, I.; Wheatley, P. J.;
Barnes, J.
2008yCat..83790816S Altcode:
The SuperWASP-I (Wide Angle Search for Planets-I) instrument observed
6.7 million stars between 8 and 15mag from La Palma during the 2004
May-September season. Our transit-hunting algorithm selected 11626
objects from the 184442 stars within the RA (right ascension) range
18-21h. We describe our thorough selection procedure whereby catalogue
information is exploited along with careful study of the SuperWASP data
to filter out, as far as possible, transit mimics. We have identified
35 candidates which we recommend for follow-up observations. <P />(2
data files).
---------------------------------------------------------
Title: Twisting flux tubes as a cause of micro-flaring activity
Authors: Jess, D. B.; McAteer, R. T. J.; Mathioudakis, M.; Keenan,
F. P.; Andic, A.; Bloomfield, D. S.
2007A&A...476..971J Altcode: 2007arXiv0709.2268J
High-cadence optical observations of an H-α blue-wing bright point
near solar AR NOAA 10794 are presented. The data were obtained with the
Dunn Solar Telescope at the National Solar Observatory/Sacramento Peak
using a newly developed camera system, the rapid dual imager. Wavelet
analysis is undertaken to search for intensity-related oscillatory
signatures, and periodicities ranging from 15 to 370 s are found with
significance levels exceeding 95%. During two separate microflaring
events, oscillation sites surrounding the bright point are observed to
twist. We relate the twisting of the oscillation sites to the twisting
of physical flux tubes, thus giving rise to reconnection phenomena. We
derive an average twist velocity of 8.1 km s<SUP>-1</SUP> and detect
a peak in the emitted flux between twist angles of 180° and 230°. <P
/>Figure 4 is available as a movie at http://www.aanda.org
---------------------------------------------------------
Title: Energy levels, radiative rates and excitation rates for
transitions in Ni XI
Authors: Aggarwal, K. M.; Keenan, F. P.
2007A&A...475..393A Altcode:
Aims:In this paper we report calculations for energy levels, radiative
rates and excitation rates for transitions in Ni xi. <BR />Methods:
The grasp (General-purpose Relativistic Atomic Structure Package)
and fac (Flexible Atomic Code) have been adopted for calculating
energy levels and radiative rates, and the Dirac Atomic R-matrix
Code (darc) has been used to determine the excitation rates. <BR
/>Results: Oscillator strengths, radiative rates and line strengths
are reported for all E1, E2, M1 and M2 transitions among the lowest
250 levels of Ni xi. Additionally, lifetimes are also reported for
all levels. However, results for excitation rates are presented
only for transitions among the lowest 17 levels. <P />Tables
1, 3, 4 and 7 are only available in electronic form at the CDS
via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via
http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/475/393
---------------------------------------------------------
Title: An investigation of FeXVI emission lines in solar and stellar
extreme-ultraviolet and soft X-ray spectra
Authors: Keenan, F. P.; Drake, J. J.; Aggarwal, K. M.
2007MNRAS.381.1727K Altcode: 2007arXiv0708.2640K; 2007MNRAS.tmp..918K
New fully relativistic calculations of radiative rates and electron
impact excitation cross-sections for FeXVI are used to determine
theoretical emission-line ratios applicable to the 251-361 and
32-77Å portions of the extreme-ultraviolet (EUV) and soft X-ray
spectral regions, respectively. A comparison of the EUV results with
observations from the Solar Extreme-Ultraviolet Research Telescope
and Spectrograph (SERTS) reveals excellent agreement between theory
and experiment. However, for emission lines in the 32-49Å portion of
the soft X-ray spectral region, there are large discrepancies between
theory and measurement for both a solar flare spectrum obtained with the
X-Ray Spectrometer/Spectrograph Telescope (XSST) and for observations
of Capella from the Low-Energy Transmission Grating Spectrometer (LETGS)
on the Chandra X-ray Observatory. These are probably due to blending in
the solar flare and Capella data from both first-order lines and from
shorter wavelength transitions detected in second and third order. By
contrast, there is very good agreement between our theoretical results
and the XSST and LETGS observations in the 50-77Å wavelength range,
contrary to previous results. In particular, there is no evidence
that the FeXVI emission from the XSST flare arises from plasma at a
much higher temperature than that expected for FeXVI in ionization
equilibrium, as suggested by earlier work.
---------------------------------------------------------
Title: VizieR Online Data Catalog: SuperWASP-North extrasolar planet
candidates (Lister+, 2007)
Authors: Lister, T. A.; West, R. G.; Wilson, D. M.; Collier
Cameron, A.; Clarkson, W. I.; Street, R. A.; Enoch, B.; Parley,
N. R.; Christian, D. J.; Kane, S. R.; Evans, A.; Fitzsimmons, A.;
Haswell, C. A.; Hellier, C.; Hodgkin, S. T.; Horne, K.; Irwin, J.;
Keenan, F. P.; Norton, A. J.; Osborne, J.; Pollacco, D. L.; Ryans,
R.; Skillen, I.; Wheatley, P. J.; Barnes, J. R.
2007yCat..83790647L Altcode:
The photometric data were obtained with the SuperWASP-North (SW-N)
instrument at the Observatorio del Roque de los Muchachos, La Palma,
Canary Islands, during 2004 May to September. Follow-up spectroscopic
observations of a small number of transit candidates were obtained by
one of us (JRB) as part of another observing program using the 3.6-m
CanadaFranceHawaii Telescope (CFHT) and ESPaDOnS echelle spectrograph
on Mauna Kea, Hawaii, on the nights of 2005 September 23-24. <P />(2
data files).
---------------------------------------------------------
Title: Line intensity enhancements in both stellar and laser-plasma
coronal X-ray spectra due to opacity effects
Authors: Wark, Justin; Rose, Steven; Keenan, Francis; Mathioudakis,
Michail; Matranga, Marco
2007APS..DPPUO4009W Altcode:
The intensity of optically thin transitions increase linearly with
optical depth. As one might expect an optically thick line to increase
less quickly than linearly, the thick to thin ratio is normally thought
to decrease with increasing optical depth. However, for systems in
coronal equilibrium, this is not necessarily the case, and this ratio
can have enhancements that are a function of plasma geometry and viewing
angle. Here we consider the X-ray spectra for a number of late-type
active stars, obtained with the Reflection Grating Spectrometer on the
XMM-Newton satellite. Both flare and quiescent spectra are considered,
and intensity ratios studied which involve the Fe XVII 15.01 å and
16.78 å transitions. We consider a large dataset for a number of
stars, and in particular the case of EV Lac, where the 15.01 å line
exhibits an enhancement in intensity over the optically thin value,
which we interpret in terms of a geometry consistent with a largely
planar feature on the surface of the star being observed at an angle of
order 45 degrees. We show that such enhancements due to opacity should
also be observable in laser-produced plasmas of specific geometry.
---------------------------------------------------------
Title: Energy levels and radiative rates for transitions in Co XI
Authors: Aggarwal, K. M.; Keenan, F. P.; Msezane, A. Z.
2007A&A...473..995A Altcode:
Aims: In this paper we report calculations for energy levels and
radiative rates for transitions in Co xi. <BR />Methods: The
General purpose Relativistic Atomic Structure Package (grasp)
and the Flexible Atomic Code (fac) have been adopted for the
calculations of energy levels and radiative rates. <BR />Results:
Energies for the lowest 287 levels of Co xi, including those among the
(1s^22s^22p^6) 3s^23p^5, 3s3p^6, 3s^23p^43d, 3s3p^53d, 3s^23p^33d^2,
and 3s^23p^44s configurations, are reported. Additionally, radiative
rates and oscillator strengths are reported for all electric dipole
(E1) transitions with f ≥ 10<SUP>-5</SUP> among these levels,
and similar results for magnetic dipole (M1), electric quadrupole
(E2), and magnetic quadrupole (M2) transitions are reported only
for those with f≥10<SUP>-8</SUP>. Comparisons are made with the
available results in the literature, and the accuracy of the present
data is assessed. Finally, lifetimes for all excited levels are also
listed, although measurements are presently available for only one of
these. <P />Tables 1 and 3-6 are only available in electronic form
at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)
or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/473/995
---------------------------------------------------------
Title: High-frequency oscillations in a solar active region observed
with the RAPID DUAL IMAGER
Authors: Jess, D. B.; Andić, A.; Mathioudakis, M.; Bloomfield, D. S.;
Keenan, F. P.
2007A&A...473..943J Altcode: 2007arXiv0707.2716J
High-cadence, synchronized, multiwavelength optical observations
of a solar active region (NOAA 10794) are presented. The data
were obtained with the Dunn Solar Telescope at the National Solar
Observatory/Sacramento Peak using a newly developed camera system:
the rapid dual imager. Wavelet analysis is undertaken to search
for intensity related oscillatory signatures, and periodicities
ranging from 20 to 370 s are found with significance levels exceeding
95%. Observations in the H-α blue wing show more penumbral oscillatory
phenomena when compared to simultaneous G-band observations. The H-α
oscillations are interpreted as the signatures of plasma motions with
a mean velocity of 20 km s<SUP>-1</SUP>. The strong oscillatory power
over H-α blue-wing and G-band penumbral bright grains is an indication
of the Evershed flow with frequencies higher than previously reported.
---------------------------------------------------------
Title: SuperWASP-North extrasolar planet candidates between
3<SUP>h</SUP> < RA < 6<SUP>h</SUP>
Authors: Clarkson, W. I.; Enoch, B.; Haswell, C. A.; Norton, A. J.;
Christian, D. J.; Collier Cameron, A.; Kane, S. R.; Horne, K. D.;
Lister, T. A.; Street, R. A.; West, R. G.; Wilson, D. M.; Evans, N.;
Fitzsimmons, A.; Hellier, C.; Hodgkin, S. T.; Irwin, J.; Keenan,
F. P.; Osborne, J. P.; Parley, N. R.; Pollacco, D. L.; Ryans, R.;
Skillen, I.; Wheatley, P. J.
2007MNRAS.381..851C Altcode: 2007arXiv0708.0785C; 2007MNRAS.tmp..824C
The Wide Angle Search for Planets (WASP) photometrically surveys a large
number of nearby stars to uncover candidate extrasolar planet systems
by virtue of small-amplitude light curve dips on a <~5-d time-scale
typical of the `Hot-Jupiters'. Observations with the SuperWASP-North
instrument between 2004 April and September produced a rich photometric
data set of some 1.3 × 10<SUP>9</SUP> data points from 6.7 million
stars. Our custom-built data acquisition and processing system produces
~0.02 mag photometric precision at V = 13. <P />We present the transit
candidates in the 03<SUP>h</SUP>-06<SUP>h</SUP> RA range. Out of 141895
light curves with sufficient sampling to provide adequate coverage,
2688 show statistically significant transit-like periodicities. Out
of these, 44 pass a visual inspection of the light curve, of which
24 are removed through a set of cuts on the statistical significance
of artefacts. All but four of the remaining 20 objects are removed
when prior information at higher spatial resolution from existing
catalogues is taken into account. Of the four candidates remaining,
one is considered a good candidate for follow-up observations with
three further second-priority targets. We provide detailed information
on these candidates, as well as a selection of the false-positives and
astrophysical false-alarms that were eliminated, and discuss briefly
the impact of sampling on our results.
---------------------------------------------------------
Title: VizieR Online Data Catalog: NiXI radiative and excitation rates
(Aggarwal+, 2007)
Authors: Aggarwal, M.; Keenan, F. P.
2007yCat..34750393A Altcode:
In this paper we report calculations for energy levels, radiative rates
and excitation rates for transitions in NiXI. The GRASP (General-purpose
Relativistic Atomic Structure Package) and FAC (Flexible Atomic Code)
have been adopted for calculating energy levels and radiative rates,
and the Dirac Atomic R-matrix Code (DARC) has been used to determine
the excitation rates. Oscillator strengths, radiative rates and line
strengths are reported for all E1, E2, M1 and M2 transitions among the
lowest 250 levels of NiXI. Additionally, lifetimes are also reported
for all levels. However, results for excitation rates are presented
only for transitions among the lowest 17 levels. <P />(5 data files).
---------------------------------------------------------
Title: SuperWASP-North extrasolar planet candidates: candidates from
fields 17h<RA<18h
Authors: Lister, T. A.; West, R. G.; Wilson, D. M.; Collier Cameron,
A.; Clarkson, W. I.; Street, R. A.; Enoch, B.; Parley, N. R.;
Christian, D. J.; Kane, S. R.; Evans, A.; Fitzsimmons, A.; Haswell,
C. A.; Hellier, C.; Hodgkin, S. T.; Horne, Keith; Irwin, J.; Keenan,
F. P.; Norton, A. J.; Osborne, J.; Pollacco, D. L.; Ryans, R.; Skillen,
I.; Wheatley, P. J.; Barnes, J. R.
2007MNRAS.379..647L Altcode: 2007MNRAS.tmp..555L; 2007arXiv0705.2603L
We have performed photometric observations of nearly seven million
stars with 8 < V < 15 with the SuperWASP-North instrument from
La Palma between 2004 May to September. Fields in the right ascension
range 17-18h, yielding over 185000 stars with sufficient quality data,
have been searched for transits using a modified box least-squares (BLS)
algorithm. We find a total of 58 initial transiting candidates which
have high signal-to-noise ratio in the BLS, show multiple transit-like
dips and have passed visual inspection. Analysis of the blending and
the inferred planetary radii for these candidates leave, a total of
seven transiting planet candidates which pass all the tests plus four
which pass the majority. We discuss the derived parameters for these
candidates and their properties and comment on the implications for
future transit searches.
---------------------------------------------------------
Title: SuperWASP-N extrasolar planet candidates between 18 <
RA < 21h
Authors: Street, R. A.; Christian, D. J.; Clarkson, W. I.; Collier
Cameron, A.; Enoch, B.; Kane, S. R.; Lister, T. A.; West, R. G.;
Wilson, D. M.; Evans, A.; Fitzsimmons, A.; Haswell, C. A.; Hellier,
C.; Hodgkin, S. T.; Horne, K.; Irwin, J.; Keenan, F. P.; Norton, A. J.;
Osborne, J.; Pollacco, D. L.; Ryans, R.; Skillen, I.; Wheatley, P. J.;
Barnes, J.
2007MNRAS.379..816S Altcode: 2007MNRAS.tmp..572S; 2007arXiv0705.2598S
The SuperWASP-I (Wide Angle Search for Planets-I) instrument observed
6.7 million stars between 8 and 15mag from La Palma during the 2004
May-September season. Our transit-hunting algorithm selected 11626
objects from the 184442 stars within the RA (right ascension) range
18-21h. We describe our thorough selection procedure whereby catalogue
information is exploited along with careful study of the SuperWASP data
to filter out, as far as possible, transit mimics. We have identified
35 candidates which we recommend for follow-up observations.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Energy levels and radiative rates
in Co XI (Aggarwal+, 2007)
Authors: Aggarwal, K. M.; Keenan, F. P.; Msezane, A. Z.
2007yCat..34730995A Altcode:
In this paper we report calculations for energy levels and radiative
rates for transitions in Co XI. The General purpose Relativistic
Atomic Structure Package GRASP and the Flexible Atomic Code FAC have
been adopted for the calculations of energy levels and radiative
rates. <P />Energies for the lowest 287 levels of Co XI, including
those among the (1s<SUP>2</SUP>2s<SUP>2</SUP>2p<SUP>6</SUP>)
3s<SUP>2</SUP>3p<SUP>5</SUP>, 3s3p<SUP>6</SUP>,
3s<SUP>2</SUP>3p<SUP>4</SUP>3d, 3s3p<SUP>5</SUP>3d,
3s<SUP>2</SUP>3p<SUP>3</SUP>3d<SUP>2</SUP>, and
3s<SUP>2</SUP>3p<SUP>4</SUP>4s configurations, are
reported. Additionally, radiative rates and oscillator strengths
are reported for all electric dipole (E1) transitions with
f>=10<SUP>-5</SUP> among these levels, and similar results
for magnetic dipole (M1), electric quadrupole (E2), and magnetic
quadrupole (M2) transitions are reported only for those with
f>=10<SUP>-8</SUP>. Comparisons are made with the available
results in the literature, and the accuracy of the present data is
assessed. Finally, lifetimes for all excited levels are also listed,
although measurements are presently available for only one of these. <P
/>(5 data files).
---------------------------------------------------------
Title: Small Scale Structure in the ISM towards IC 2391 and NGC 6475
Authors: Smoker, J. V.; Hunter, I.; Keenan, F. P.; Ledoux, C.; Jehin,
E.; Melo, C.; Bagnulo, S.; Cabanac, R.
2007ASPC..365...82S Altcode:
We describe UVES spectroscopic observations towards early-type stars
located in the nearby open clusters IC 2391 (D=175 pc) and NGC 6475/M
7 (D=301 pc), with resolution ∼80,000 and S/N ratio per pixel of
∼140 to ∼360. The aim is to investigate the small-scale structure
variations within parts of the local ISM and determine how they are
dependent on element and ionisation stage observed, thus providing
information on cloud parameters such as structure and sizes. The data
used are taken from on-line versions of the Paranal Observatory Project
(POP: http://www.eso.org/uvespop). A total of 25 early-type stars (A
and B-type) are present in our sample towards IC 2391 with 23 towards
NGC 6475/M 7, and enable us to probe differences in column densities
on scales from ∼0.07--7.3-pc and ∼0.05---4.9-pc (in the respective
clusters) for the optical transitions detected (Ti II (3383Å), Ca II
(3933Å), Na I (5889, 5895Å) and K I (7698Å)). Towards NGC 6475 the
Ca II column density is found to be constant to ∼0.15 dex over scales
of ∼0.4--4-pc. A much greater scatter in the measurements for Na
I D is observed with differences of up to ∼0.45 dex in sightlines
separated by ∼4 pc. In the future work we will perform the same
analysis for Ti II and K I towards both clusters.
---------------------------------------------------------
Title: Iron abundances of B-type post-asymptotic giant branch stars
in globular clusters: Barnard29 in M13 and ROA5701 in ωCen
Authors: Thompson, H. M. A.; Keenan, F. P.; Dufton, P. L.; Ryans,
R. S. I.; Smoker, J. V.; Lambert, D. L.; Zijlstra, A. A.
2007MNRAS.378.1619T Altcode: 2007MNRAS.tmp..506T; 2007arXiv0705.2196T
High-resolution optical and ultraviolet (UV) spectra of two B-type
post-asymptotic giant branch (post-AGB) stars in globular clusters,
Barnard29 in M13 and ROA5701 in ωCen, have been analysed using model
atmosphere techniques. The optical spectra have been obtained with
FEROS on the ESO 2.2-m telescope and the 2d-Coudé spectrograph on
the 2.7-m McDonald telescope, while the UV observations are from the
Goddard high-resolution spectrograph on the Hubble Space Telescope
(HST). Abundances of light elements (C, N, O, Mg, Al and S) plus Fe have
been determined from the optical spectra, while the UV data provide
additional Fe abundance estimates from FeIII absorption lines in the
1875-1900 Å wavelength region. A general metal underabundance relative
to young B-type stars is found for both Barnard29 and ROA5701. These
results are consistent with the metallicities of the respective
clusters, as well as with previous studies of the objects. The derived
abundance patterns suggest that the stars have not undergone a gas-dust
separation, contrary to previous suggestions, although they may have
evolved from the AGB before the onset of the third dredge-up. However,
the Fe abundances derived from the HST spectra are lower than those
expected from the metallicities of the respective clusters, by 0.5
dex for Barnard29 and 0.8 dex for ROA5701. A similar systematic
underabundance is also found for other B-type stars in environments
of known metallicity, such as the Magellanic Clouds. These results
indicate that the FeIII UV lines may yield abundance values which are
systematically too low by typically 0.6 dex and hence such estimates
should be treated with caution. <P />This paper includes data taken
at the McDonald Observatory of the University of Texas at Austin,
and on the ESO 2.2-m La Silla, programme 0077.D-025(A). <P />E-mail:
h.thompson@qub.ac.uk
---------------------------------------------------------
Title: Observations towards early-type stars in the ESO-POP Survey -
II. Searches for intermediate- and high-velocity clouds
Authors: Smoker, J. V.; Hunter, I.; Kalberla, P. M. W.; Keenan,
F. P.; Morras, R.; Hanuschik, R.; Thompson, H. M. A.; Silva, D.;
Bajaja, E.; Poppel, W. G. L.; Arnal, M.
2007MNRAS.378..947S Altcode: 2007arXiv0704.1315S; 2007MNRAS.tmp..469S
We present Ca II K and Ti II optical spectra of early-type stars taken
mainly from the ultraviolet and visual echelle spectrograph (UVES)
Paranal Observatory Project, plus H I 21-cm spectra, from the Vila-Elisa
and Leiden-Dwingeloo Surveys, which are employed to obtain distances
to intermediate- and high-velocity clouds (IHVCs). H I emission at a
velocity of -117 km s<SUP>-1</SUP> towards the sightline HD 30677 ([
image ]) with column density ~1.7 × 10<SUP>19</SUP> cm<SUP>-2</SUP> has
no corresponding Ca II K absorption in the UVES spectrum, which has a
signal-to-noise ratio (S/N) of 610 per resolution element. The star has
a spectroscopically determined distance of 2.7 kpc, and hence sets this
as a firm lower distance limit towards Anti-Centre cloud ACII. Towards
another sightline (HD 46185 with [ image ]), H I at a velocity of
+122 km s<SUP>-1</SUP> and column density of 1.2 × 10<SUP>19</SUP>
cm<SUP>-2</SUP> is seen. The corresponding Ca II K spectrum has a S/N
of 780, although no absorption is observed at the cloud velocity. This
similarly places a firm lower distance limit of 2.9 kpc towards this
parcel of gas that may be an intermediate-velocity (IV) cloud. The
lack of IV Ca II absorption towards HD 196426 ([ image ]) at a S/N
of 500 reinforces a lower distance limit of ~700 pc towards this part
of complex gp, where the H I column density is 1.1 × 10<SUP>19</SUP>
cm<SUP>-2</SUP> and velocity is +78 km s<SUP>-1</SUP>. Additionally,
no IV Ca II is seen in absorption in the spectrum of HD 19445,
which is strong in H I with a column density of 8 × 10<SUP>19</SUP>
cm<SUP>-2</SUP> at a velocity of ~-42 km s<SUP>-1</SUP>, placing a firm
although uninteresting lower distance limit of 39 pc to this part of
IV South. Finally, no high-velocity Ca II K absorption is seen towards
HD 115363 ([ image ]) at a S/N of 410, placing a lower distance of
~3.2 kpc towards the HVC gas at velocity of ~+224 km s<SUP>-1</SUP>
and H I column density of 5.2 × 10<SUP>19</SUP> cm<SUP>-2</SUP>. This
gas is in the same region of the sky as complex WE (Wakker 2001), but
at higher velocities. The non-detection of Ca II K absorption sets a
lower distance of ~3.2 kpc towards the HVC, which is unsurprising if
this feature is indeed related to the Magellanic System.
---------------------------------------------------------
Title: A giant outburst two years before the core-collapse of a
massive star
Authors: Pastorello, A.; Smartt, S. J.; Mattila, S.; Eldridge, J. J.;
Young, D.; Itagaki, K.; Yamaoka, H.; Navasardyan, H.; Valenti, S.;
Patat, F.; Agnoletto, I.; Augusteijn, T.; Benetti, S.; Cappellaro,
E.; Boles, T.; Bonnet-Bidaud, J. -M.; Botticella, M. T.; Bufano, F.;
Cao, C.; Deng, J.; Dennefeld, M.; Elias-Rosa, N.; Harutyunyan, A.;
Keenan, F. P.; Iijima, T.; Lorenzi, V.; Mazzali, P. A.; Meng, X.;
Nakano, S.; Nielsen, T. B.; Smoker, J. V.; Stanishev, V.; Turatto,
M.; Xu, D.; Zampieri, L.
2007Natur.447..829P Altcode: 2007astro.ph..3663P
The death of massive stars produces a variety of supernovae,
which are linked to the structure of the exploding stars. The
detection of several precursor stars of type II supernovae has been
reported (see, for example, ref. 3), but we do not yet have direct
information on the progenitors of the hydrogen-deficient type Ib and Ic
supernovae. Here we report that the peculiar type Ib supernova SN 2006jc
is spatially coincident with a bright optical transient that occurred
in 2004. Spectroscopic and photometric monitoring of the supernova
leads us to suggest that the progenitor was a carbon-oxygen Wolf-Rayet
star embedded within a helium-rich circumstellar medium. There are
different possible explanations for this pre-explosion transient. It
appears similar to the giant outbursts of luminous blue variable stars
(LBVs) of 60-100 solar masses, but the progenitor of SN 2006jc was
helium- and hydrogen-deficient (unlike LBVs). An LBV-like outburst
of a Wolf-Rayet star could be invoked, but this would be the first
observational evidence of such a phenomenon. Alternatively, a massive
binary system composed of an LBV that erupted in 2004, and a Wolf-Rayet
star exploding as SN 2006jc, could explain the observations.
---------------------------------------------------------
Title: VizieR Online Data Catalog: SuperWASP exoplanetary transit
survey (Christian+, 2006)
Authors: Christian, D. J.; Pollacco, D. L.; Skillen, I.; Street,
R. A.; Keenan, F. P.; Clarkson, W. I.; Collier Cameron, A.; Kane,
S. R.; Lister, T. A.; West, R. G.; Enoch, B.; Evans, A.; Fitzsimmons,
A.; Haswell, C. A.; Hellier, C.; Hodgkin, S. T.; Horne, K.; Irwin, J.;
Norton, A. J.; Osborne, J.; Ryans, R.; Wheatley, P. J.; Wilson, D. M.
2007yCat..73721117C Altcode:
The SW telescopes were designed to cover a large area of sky and achieve
photometric accuracy of a few mmag and improve on the success of the
prototype WASP0 instrument <P />(1 data file).
---------------------------------------------------------
Title: VizieR Online Data Catalog: SuperWASP exoplanetary transit
survey (Christian+, 2006)
Authors: Christian, D. J.; Pollacco, D. L.; Skillen, I.; Street,
R. A.; Keenan, F. P.; Clarkson, W. I.; Collier Cameron, A.; Kane,
S. R.; Lister, T. A.; West, R. G.; Enoch, B.; Evans, A.; Fitzsimmons,
A.; Haswell, C. A.; Hellier, C.; Hodgkin, S. T.; Horne, K.; Irwin, J.;
Norton, A. J.; Osborne, J.; Ryans, R.; Wheatley, P. J.; Wilson, D. M.
2007yCat..83721117C Altcode:
The SW telescopes were designed to cover a large area of sky and achieve
photometric accuracy of a few mmag and improve on the success of the
prototype WASP0 instrument <P />(1 data file).
---------------------------------------------------------
Title: Erratum: The Super WASP wide-field exoplanetary transit survey:
candidates from fields 23 h < RA < 03 h
Authors: Christian, D. J.; Pollacco, D. L.; Skillen, I.; Street,
R. A.; Keenan, F. P.; Clarkson, W. I.; Collier Cameron, A.; Kane,
S. R.; Lister, T. A.; West, R. G.; Enoch, B.; Evans, A.; Fitzsimmons,
A.; Haswell, C. A.; Hellier, C.; Hodgkin, S. T.; Horne, K.; Irwin, J.;
Norton, A. J.; Osborne, J.; Ryans, R.; Wheatley, P. J.; Wilson, D. M.
2007MNRAS.376.1424C Altcode: 2006astro.ph..8142C; 2007MNRAS.tmp..172C
Photometric transit surveys promise to complement the currently known
sample of extra-solar planets by providing additional information on
the planets and especially their radii. Here we present extra-solar
planet (ESP) candidates from one such survey called, the Wide Angle
Search for Planets (WASP) obtained with the SuperWASP wide-field
imaging system. Observations were taken with SuperWASP-North located
in La Palma during the April to October 2004 observing season. The
data cover fields between 23hr and 03hr in RA at declinations above
+12. This amounts to over $\approx$400,000 stars with V magnitudes
8 to 13.5. For the stars brighter than 12.5, we achieve better than
1 percent photometric precision. Here we present 41 sources with low
amplitude variability between $\approx$ 1 and 10 mmag, from which we
select 12 with periods between 1.2 and 4.4 days as the most promising
extrasolar planet candidates. We discuss the properties of these ESP
candidates, the expected fraction of transits recovered for our sample,
and implications for the frequency and detection of hot-Jupiters.
---------------------------------------------------------
Title: Fe XIII emission lines in active region spectra obtained with
the Solar Extreme-Ultraviolet Research Telescope and Spectrograph
Authors: Keenan, F. P.; Jess, D. B.; Aggarwal, K. M.; Thomas, R. J.;
Brosius, J. W.; Davila, J. M.
2007MNRAS.376..205K Altcode: 2006astro.ph.12493K; 2007MNRAS.tmp...38K
Recent fully relativistic calculations of radiative
rates and electron impact excitation cross-sections
for Fe XIII are used to generate emission-line ratios
involving 3s<SUP>2</SUP>3p<SUP>2</SUP>-3s3p<SUP>3</SUP> and
3s<SUP>2</SUP>3p<SUP>2</SUP>-3s<SUP>2</SUP>3p3d transitions in
the 170-225 and 235-450 Å wavelength ranges covered by the Solar
Extreme-Ultraviolet Research Telescope and Spectrograph (SERTS). A
comparison of these line ratios with SERTS active region observations
from rocket flights in 1989 and 1995 reveals generally very good
agreement between theory and experiment. Several new Fe XIII emission
features are identified, at wavelengths of 203.79, 259.94, 288.56 and
290.81 Å. However, major discrepancies between theory and observation
remain for several Fe XIII transitions, as previously found by Landi
and others, which cannot be explained by blending. Errors in the adopted
atomic data appear to be the most likely explanation, in particular for
transitions which have 3s<SUP>2</SUP>3p3d <SUP>1</SUP>D<SUB>2</SUB>
as their upper level. The most useful Fe XIII electron-density
diagnostics in the SERTS spectral regions are assessed, in terms of
the line pairs involved being (i) apparently free of atomic physics
problems and blends, (ii) close in wavelength to reduce the effects
of possible errors in the instrumental intensity calibration, and
(iii) very sensitive to changes in N<SUB>e</SUB> over the range
10<SUP>8</SUP>-10<SUP>11</SUP> cm<SUP>-3</SUP>. It is concluded that
the ratios which best satisfy these conditions are 200.03/202.04 and
203.17/202.04 for the 170-225 Å wavelength region, and 348.18/320.80,
348.18/368.16, 359.64/348.18 and 359.83/368.16 for 235-450 Å.
---------------------------------------------------------
Title: WASP-1b and WASP-2b: two new transiting exoplanets detected
with SuperWASP and SOPHIE
Authors: Collier Cameron, A.; Bouchy, F.; Hébrard, G.; Maxted, P.;
Pollacco, D.; Pont, F.; Skillen, I.; Smalley, B.; Street, R. A.;
West, R. G.; Wilson, D. M.; Aigrain, S.; Christian, D. J.; Clarkson,
W. I.; Enoch, B.; Evans, A.; Fitzsimmons, A.; Fleenor, M.; Gillon,
M.; Haswell, C. A.; Hebb, L.; Hellier, C.; Hodgkin, S. T.; Horne, K.;
Irwin, J.; Kane, S. R.; Keenan, F. P.; Loeillet, B.; Lister, T. A.;
Mayor, M.; Moutou, C.; Norton, A. J.; Osborne, J.; Parley, N.; Queloz,
D.; Ryans, R.; Triaud, A. H. M. J.; Udry, S.; Wheatley, P. J.
2007MNRAS.375..951C Altcode: 2006astro.ph..9688C; 2007MNRAS.tmp.1491C
We have detected low-amplitude radial-velocity variations in two
stars, USNO-B1.0 1219-0005465 (GSC 02265-00107 = WASP-1) and USNO-B1.0
0964-0543604 (GSC 00522-01199 = WASP-2). Both stars were identified as
being likely host stars of transiting exoplanets in the 2004 SuperWASP
wide-field transit survey. Using the newly commissioned radial-velocity
spectrograph SOPHIE at the Observatoire de Haute-Provence, we found that
both objects exhibit reflex orbital radial-velocity variations with
amplitudes characteristic of planetary-mass companions and in-phase
with the photometric orbits. Line-bisector studies rule out faint
blended binaries as the cause of either the radial-velocity variations
or the transits. We perform preliminary spectral analyses of the host
stars, which together with their radial-velocity variations and fits to
the transit light curves yield estimates of the planetary masses and
radii. WASP-1b and WASP-2b have orbital periods of 2.52 and 2.15 d,
respectively. Given mass estimates for their F7V and K1V primaries,
we derive planet masses 0.80-0.98 and 0.81-0.95 times that of Jupiter,
respectively. WASP-1b appears to have an inflated radius of at least
1.33 R<SUB>Jup</SUB>, whereas WASP-2b has a radius in the range
0.65-1.26 R<SUB>Jup</SUB>.
---------------------------------------------------------
Title: Energy levels and radiative rates for inner shell transitions
of Fe XVI
Authors: Aggarwal, K. M.; Keenan, F. P.
2007A&A...463..399A Altcode:
Aims:In this paper we report calculations for energy levels and
radiative rates for transitions in Fe xvi. <BR />Methods: The
General purpose Relativistic Atomic Structure Package (grasp) has
been adopted for the calculations of energy levels and radiative
rates. <BR />Results: Energies for the lowest 134 levels among the
(1s^22s^2) 2p^63ℓ, 2p^53s^2, 2p^53s3p, 2p^53s3d, 2p^53p3d, and
2p^53p<SUP>2</SUP> configurations of Fe xvi are reported. Additionally,
radiative rates, oscillator strengths, and line strengths are
reported for all electric dipole (E1), magnetic dipole (M1), electric
quadrupole (E2), magnetic quadrupole (M2), and electric octupole (E3)
transitions among these levels. Comparisons are made with the available
results in the literature, and the accuracy of the present results is
assessed. Finally, lifetimes for all excited levels are also listed,
although no measurements are presently available with which to compare
these. <P />Tables 2, 3 and 5 are only available in electronic form
at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)
or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/463/399
---------------------------------------------------------
Title: A fast hybrid algorithm for exoplanetary transit searches
Authors: Collier Cameron, A.; Pollacco, D.; Street, R. A.; Lister,
T. A.; West, R. G.; Wilson, D. M.; Pont, F.; Christian, D. J.;
Clarkson, W. I.; Enoch, B.; Evans, A.; Fitzsimmons, A.; Haswell, C. A.;
Hellier, C.; Hodgkin, S. T.; Horne, K.; Irwin, J.; Kane, S. R.; Keenan,
F. P.; Norton, A. J.; Parley, N. R.; Osborne, J.; Ryans, R.; Skillen,
I.; Wheatley, P. J.
2006MNRAS.373..799C Altcode: 2006MNRAS.tmp.1227C; 2006astro.ph..9418C
We present a fast and efficient hybrid algorithm for selecting
exoplanetary candidates from wide-field transit surveys. Our method
is based on the widely used SysRem and Box Least-Squares (BLS)
algorithms. Patterns of systematic error that are common to all stars
on the frame are mapped and eliminated using the SysRem algorithm. The
remaining systematic errors caused by spatially localized flat-fielding
and other errors are quantified using a boxcar-smoothing method. We
show that the dimensions of the search-parameter space can be reduced
greatly by carrying out an initial BLS search on a coarse grid of
reduced dimensions, followed by Newton-Raphson refinement of the
transit parameters in the vicinity of the most significant solutions. We
illustrate the method's operation by applying it to data from one field
of the SuperWASP survey, comprising 2300 observations of 7840 stars
brighter than V = 13.0. We identify 11 likely transit candidates. We
reject stars that exhibit significant ellipsoidal variations caused
indicative of a stellar-mass companion. We use colours and proper
motions from the Two Micron All Sky Survey and USNO-B1.0 surveys to
estimate the stellar parameters and the companion radius. We find that
two stars showing unambiguous transit signals pass all these tests,
and so qualify for detailed high-resolution spectroscopic follow-up.
---------------------------------------------------------
Title: Looking towards the detection of exoearths with SuperWASP
Authors: Street, R. A.; Christian, D. J.; Clarkson, W. I.; Collier
Cameron, A.; Enoch, B.; Evans, A.; Fitzsimmons, A.; Haswell, C. A.;
Hellier, C.; Hodgkin, S. T.; Horne, Keith; Irwin, J.; Keenan, F. P.;
Kane, S. R.; Lister, T. A.; Norton, A. J.; Osborne, J.; Pollacco,
D.; Ryans, R.; Skillen, I.; West, R. G.; Wheatley, P. J.; Wilson, D.
2006IJAsB...5..183S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Energy levels and radiative rates for transitions in Fe IX
Authors: Aggarwal, K. M.; Keenan, F. P.; Kato, T.; Murakami, I.
2006A&A...460..331A Altcode:
Aims.In this paper we report calculations for energy levels and
radiative rates for transitions in Fe IX.<BR /> Methods: .The General
purpose Relativistic Atomic Structure Package (grasp) has been adopted
for the calculation of energy levels and radiative rates.<BR />
Results: .Energies for the lowest 360 levels, including those from
the (1s^22s^22p^6) 3s^23p^6, 3s^23p^53d, 3s3p^63d, 3s^23p^43d^2, and
3s^23p^54ℓ configurations of Fe IX, are reported. Additionally,
radiative rates, oscillator strengths, and line strengths are
reported for all electric dipole (E1), magnetic dipole (M1), electric
quadrupole (E2), and magnetic quadrupole (M2) transitions among
these levels. Comparisons are made with the available results in the
literature, and the accuracy of the present data is assessed. Finally,
lifetimes for all excited levels are listed, and comparisons made with
earlier available measurements and theoretical results.<BR />
---------------------------------------------------------
Title: Energy levels and radiative rates for transitions in Ni XIX
Authors: Aggarwal, K. M.; Keenan, F. P.
2006A&A...460..959A Altcode:
Aims.In this paper we report calculations for energy levels and
radiative rates for transitions in Ni XIX.<BR /> Methods: .The General
purpose Relativistic Atomic Structure Package (grasp) has been adopted
for the calculation of energy levels and radiative rates.<BR />
Results: .Energies for the lowest 89 levels from the (1s^2) 2s^22p^6,
2s^22p^53ℓ, 2s2p^63ℓ, 2s^22p^54ℓ and 2s2p^64ℓ configurations
of Ni XIX, are reported. Additionally, radiative rates, oscillator
strengths, and line strengths are reported for all electric dipole (E1),
magnetic dipole (M1), electric quadrupole (E2), and magnetic quadrupole
(M2) transitions among these levels. Comparisons are made with the
available results in the literature, and the accuracy of the present
data is assessed. Finally, lifetimes for all excited levels are listed,
and comparisons made with earlier available theoretical results.<BR />
---------------------------------------------------------
Title: The SuperWASP wide-field exoplanetary transit survey:
candidates from fields 23 h < RA < 03 h
Authors: Christian, D. J.; Pollacco, D. L.; Skillen, I.; Street,
R. A.; Keenan, F. P.; Clarkson, W. I.; Collier Cameron, A.; Kane,
S. R.; Lister, T. A.; West, R. G.; Enoch, B.; Evans, A.; Fitzsimmons,
A.; Haswell, C. A.; Hellier, C.; Hodgkin, S. T.; Horne, K.; Irwin, J.;
Norton, A. J.; Osborne, J.; Ryans, R.; Wheatley, P. J.; Wilson, D. M.
2006MNRAS.372.1117C Altcode: 2006MNRAS.tmp.1118C
Photometric transit surveys promise to complement the currently
known sample of extra-solar planets (ESPs) by providing additional
information on the planets and especially their radii. Here, we
present ESP candidates from one such survey called, the Wide Angle
Search for Planets (WASP) obtained with the SuperWASP wide-field imaging
system. Observations were taken with SuperWASP North located in La Palma
during the 2004 April to October observing season. The data cover fields
between 23 and 03 h in RA at declinations above +12. This amounts to
over ~400000 stars with V magnitudes 8-13.5. For the stars brighter than
12.5, we achieve better than 1 per cent photometric precision. Here,
we present 41 sources with low-amplitude variability between ~1 and
10 mmag, from which we select 12 with periods between 1.2 and 4.4 d as
the most promising ESP candidates. We discuss the properties of these
ESP candidates, the expected fraction of transits recovered for our
sample and implications for the frequency and detection of hot-Jupiters.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Fe XVI radiative rates (Aggarwal+,
2007)
Authors: Aggarwal, K. M.; Keenan, F. P.
2006yCat..34630399A Altcode:
In this paper we report calculations for energy levels and radiative
rates for transitions in Fe XVI. The General purpose Relativistic
Atomic Structure Package GRASP has been adopted for the calculations
of energy levels and radiative rates. <P />Energies for the lowest
134 levels among the (1s<SUP>2</SUP>2s<SUP>2</SUP>) 2p<SUP>6</SUP>3l,
2p<SUP>5</SUP>3s<SUP>2</SUP>, 2p<SUP>5</SUP>3s3p, 2p<SUP>5</SUP>3s3d,
2p<SUP>5</SUP>3p3d, and 2p<SUP>5</SUP>3p<SUP>2</SUP> configurations
of Fe XVI are reported. Additionally, radiative rates, oscillator
strengths, and line strengths are reported for all electric dipole
(E1), magnetic dipole (M1), electric quadrupole (E2), magnetic
quadrupole (M2), and electric octupole (E3) transitions among
these levels. Comparisons are made with the available results
in the literature, and the accuracy of the present results is
assessed. Finally, lifetimes for all excited levels are also listed,
although no measurements are presently available with which to compare
these. <P />(4 data files).
---------------------------------------------------------
Title: The Influence of Magnetic Field on Oscillations in the Solar
Chromosphere
Authors: Bloomfield, D. Shaun; McAteer, R. T. James; Mathioudakis,
Mihalis; Keenan, Francis P.
2006ApJ...652..812B Altcode: 2006astro.ph..8314B
Two sequences of solar images obtained by the Transition Region and
Coronal Explorer in three UV passbands are studied using wavelet
and Fourier analysis and compared to the photospheric magnetic
flux measured by the Michelson Doppler Interferometer on the Solar
Heliospheric Observatory to study wave behavior in differing magnetic
environments. Wavelet periods show deviations from the theoretical
cutoff value and are interpreted in terms of inclined fields. The
variation of wave speeds indicates that a transition from dominant
fast-magnetoacoustic waves to slow modes is observed when moving from
network into plages and umbrae. This implies preferential transmission
of slow modes into the upper atmosphere, where they may lead to heating
or be detected in coronal loops and plumes.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Interstellar NaI, TiII &
CaIIK obs. (Hunter+, 2006)
Authors: Hunter, I.; Smoker, J. V.; Keenan, F. P.; Ledoux, C.; Jehin,
E.; Cabanac, R.; Melo, C.; Bagnulo, S.
2006yCat..73671478H Altcode:
We have extracted spectra for three interstellar species, namely the
NaI UV doublet, TiII and CaII K along the sightlines to 74 O- and B-type
field stars from An Atlas of High-Resolution Spectra of Stars across the
Hertzsprung-Russell Diagram, available from the Ultraviolet and Visual
Echelle Spectrograph Paranal Observatory Project. <P />The spectra
presented in this paper are the merged versions of the POP survey
available online at http://www.eso.org/uvespop . <P />(3 data files).
---------------------------------------------------------
Title: The WASP Project and the SuperWASP Cameras
Authors: Pollacco, D. L.; Skillen, I.; Collier Cameron, A.; Christian,
D. J.; Hellier, C.; Irwin, J.; Lister, T. A.; Street, R. A.; West,
R. G.; Anderson, D. R.; Clarkson, W. I.; Deeg, H.; Enoch, B.; Evans,
A.; Fitzsimmons, A.; Haswell, C. A.; Hodgkin, S.; Horne, K.; Kane,
S. R.; Keenan, F. P.; Maxted, P. F. L.; Norton, A. J.; Osborne, J.;
Parley, N. R.; Ryans, R. S. I.; Smalley, B.; Wheatley, P. J.; Wilson,
D. M.
2006PASP..118.1407P Altcode: 2006astro.ph..8454P
The SuperWASP cameras are wide-field imaging systems at the
Observatorio del Roque de los Muchachos on the island of La Palma in
the Canary Islands, and at the Sutherland Station of the South African
Astronomical Observatory. Each instrument has a field of view of some
482 deg<SUP>2</SUP> with an angular scale of 13.7" pixel<SUP>-1</SUP>,
and is capable of delivering photometry with accuracy better than 1% for
objects having V~7.0-11.5. Lower quality data for objects brighter than
V~15.0 are stored in the project archive. The systems, while designed to
monitor fields with high cadence, are capable of surveying the entire
visible sky every 40 minutes. Depending on the observational strategy,
the data rate can be up to 100 Gbytes per night. We have produced
a robust, largely automatic reduction pipeline and advanced archive,
which are used to serve the data products to the consortium members. The
main science aim of these systems is to search for bright transiting
exoplanet systems suitable for spectroscopic follow-up observations. The
first 6 month season of SuperWASP-North observations produced light
curves of ~6.7 million objects with 12.9 billion data points.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Fe IX radiative and excitation
rates (Aggarwal+, 2006)
Authors: Aggarwal, K. M.; Keenan, F. P.; Kato, T.; Murakami, I.
2006yCat..34600331A Altcode:
In this paper we report calculations for energy levels and radiative
rates for transitions in Fe IX. The General purpose Relativistic Atomic
Structure Package (GRASP) has been adopted for the calculation of
energy levels and radiative rates. Energies for the lowest 360 levels,
including those from the (1s<SUP>2</SUP>2s<SUP>2</SUP>2p<SUP>6</SUP>)
3s<SUP>2</SUP>3p<SUP>6</SUP>, 3s<SUP>2</SUP>3p<SUP>5</SUP>3d,
3s3p<SUP>6</SUP>3d, 3s<SUP>2</SUP>3p<SUP>4</SUP>3d<SUP>2</SUP>,
and 3s<SUP>2</SUP>3p<SUP>5</SUP>4l configurations of Fe IX, are
reported. Additionally, radiative rates, oscillator strengths, and
line strengths are reported for all electric dipole (E1), magnetic
dipole (M1), electric quadrupole (E2), and magnetic quadrupole (M2)
transitions among these levels. Comparisons are made with the available
results in the literature, and the accuracy of the present data is
assessed. <P />(4 data files).
---------------------------------------------------------
Title: The WASP project in the era of robotic telescope networks
Authors: Christian, D. J.; Pollacco, D. L.; Skillen, I.; Irwin, J.;
Clarkson, W. I.; Collier Cameron, A.; Evans, N.; Fitzsimmons, A.;
Haswell, C. A.; Hellier, C.; Hodgkin, S. T.; Horne, K.; Kane, S. R.;
Keenan, F. P.; Lister, T. A.; Norton, A. J.; Osborne, J.; Ryans, R.;
Street, R. A.; West, R. G.; Wheatley, P. J.
2006AN....327..800C Altcode:
We present the current status of the WASP project, a pair of wide angle
photometric telescopes, individually called SuperWASP. SuperWASP-I
is located in La Palma, and SuperWASP-II at Sutherland in South
Africa. SW-I began operations in April 2004. SW-II is expected to
be operational in early 2006. Each SuperWASP instrument consists of
up to 8 individual cameras using ultra-wide field lenses backed by
high-quality passively cooled CCDs. Each camera covers 7.8×7.8 sq
degrees of sky, for nearly 500 sq degrees of total sky coverage. One
of the current aims of the WASP project is the search for extra-solar
planet transits with a focus on brighter stars in the magnitude range
∼8 to 13. Additionally, WASP will search for optical transients,
track Near-Earth Objects, and study many types of variable stars and
extragalactic objects. The collaboration has developed a custom-built
reduction pipeline that achieves better than 1 percent photometric
precision. We discuss future goals, which include: nightly on-mountain
reductions that could be used to automatically drive alerts via a small
robotic telescope network, and possible roles of the WASP telescopes
as providers in such a network. Additional technical details of the
telescopes, data reduction, and consortium members and institutions
can be found on the web site at: http://www.superwasp.org/.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Ni XIX radiative and excitation
rates (Aggarwal+, 2006)
Authors: Aggarwal, K. M.; Keenan, F. P.
2006yCat..34600959A Altcode:
In this paper we report calculations for energy levels and radiative
rates for transitions in Ni XIX. The General purpose Relativistic
Atomic Structure Package (GRASP) has been adopted for the calculation
of energy levels and radiative rates. Energies for the lowest 89
levels from the (1s<SUP>2</SUP>) 2s<SUP>2</SUP>2p<SUP>6</SUP>,
2s<SUP>2</SUP>2p<SUP>5</SUP>3l, 2s2p<SUP>6</SUP>3l,
2s<SUP>2</SUP>2p<SUP>5</SUP>4l and 2s2p<SUP>6</SUP>4l configurations
of Ni XIX, are reported. Additionally, radiative rates, oscillator
strengths, and line strengths are reported for all electric dipole
(E1), magnetic dipole (M1), electric quadrupole (E2), and magnetic
quadrupole (M2) transitions among these levels. <P />(5 data files).
---------------------------------------------------------
Title: Energy levels and transition probabilities for boron-like
Fe XXII
Authors: Jonauskas, V.; Bogdanovich, P.; Keenan, F. P.; Kisielius, R.;
Foord, M. E.; Heeter, R. F.; Rose, S. J.; Ferland, G. J.; Norrington,
P. H.
2006A&A...455.1157J Altcode:
The Multiconfiguration Dirac-Fock method is used to calculate the
energies of the 407 lowest levels in Fe XXII. These results are
cross-checked using a suite of codes which employ the configuration
interaction method on the basis set of transformed radial orbitals with
variable parameters, and takes into account relativistic corrections
in the Breit-Pauli approximation. Transition probabilities, oscillator
and line strengths are presented for electric dipole (E1), electric
quadrupole (E2) and magnetic dipole (M1) transitions among these
levels. The total radiative transition probabilities, as well as the
five largest values from each level be it of E1, M1, E2, M2, or E3
type, are also provided. Finally, the results are compared with data
compiled by NIST.
---------------------------------------------------------
Title: The WASP Project and SuperWASP Camera
Authors: Pollacco, D.; Skillen, I.; Collier Cameron, A.; Christian,
D.; Irwin, J.; Lister, T.; Street, R.; West, R.; Clarkson, W.; Evans,
N.; Fitzsimmons, A.; Haswell, C.; Hellier, C.; Hodgkin, S.; Horne,
K.; Jones, B.; Kane, S.; Keenan, F.; Norton, A.; Osborne, J.; Ryans,
R.; Wheatley, P.
2006Ap&SS.304..253P Altcode: 2006Ap&SS.tmp..107P
The WASP project and infrastructure supporting the SuperWASP Facility
are described. As the instrument, reduction pipeline and archive system
are now fully operative we expect the system to have a major impact in
the discovery of bright exo-planet candidates as well in more general
variable star projects.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Boron-like Fe XXII transition
probabilities (Jonauskas+, 2006)
Authors: Jonauskas, V.; Bogdanovich, P.; Keenan, F. P.; Kisielius, R.;
Foord, M. E.; Heeter, R. F.; Rose, S. J.; Ferland, G. J.; Norrington,
P. H.
2006yCat..34551157J Altcode:
Energy levels and the corresponding transition probabilities as
well as oscillator strengths and line strengths for allowed (E1)
and forbidden (E2, M1) transitions among the lowest 407 levels of
boron-like Fe XXII are presented. Calculations were performed using
the multiconfigurational Dirac-Fock GRASP code. <P />(4 data files).
---------------------------------------------------------
Title: Opacity in the upper atmospheres of active stars. II. AD Leonis
Authors: Christian, D. J.; Mathioudakis, M.; Bloomfield, D. S.;
Dupuis, J.; Keenan, F. P.; Pollacco, D. L.; Malina, R. F.
2006A&A...454..889C Altcode: 2006astro.ph..2447C
We present FUV and UV spectroscopic observations of AD Leonis, with
the aim of investigating opacity effects in the transition regions
of late-type stars. The C III lines in FUSE spectra show significant
opacity during both the quiescent and flaring states of AD Leonis, with
up to 30% of the expected flux being lost during the latter. Other FUSE
emission lines tested for opacity include those of O VI, while C IV, Si
IV and N V transitions observed with stis are also investigated. These
lines only reveal modest amounts of opacity with losses during flaring
of up to 20%. Optical depths have been calculated for homogeneous
and inhomogeneous geometries, giving path lengths of ≈20-60 km and
≈10-30 km, respectively, under quiescent conditions. However path
lengths derived during flaring are ≈2-3 times larger. These values
are in excellent agreement with both estimates of the small-scale
structure observed in the solar transition region, and path lengths
derived previously for several other active late-type stars.
---------------------------------------------------------
Title: First results from SECIS observations of the 2001 total
Solar eclipse
Authors: Katsiyannis, A. C.; Williams, D. R.; Murtagh, F.; McAteer,
R. T. J.; Keenan, F. P.
2006AIPC..848...95K Altcode:
SECIS observations of the June 2001 total solar eclipse were taken
using an Fe XIV 5303 Å filter. Existing software was modified and new
code was developed for the reduction and analysis of these data. The
observations, data reduction, study of the atmospheric and instrumental
effects, together with some preliminary results are discussed. Emphasis
is given to the techniques used for the automated alignment of the
8000 images, the software developed for the automated detection of
intensity oscillations using wavelet analysis and the application of the
Monte Carlo randomisation test as a means of checking the reliability
of those detections. In line with findings from the 1999 SECIS total
eclipse observations, intensity oscillations with periods in the range
of 7-8 s, lying outside coronal loops were also detected.
---------------------------------------------------------
Title: CaII K interstellar observations towards early-type disc
and halo stars, abundances and distances of intermediate- and
high-velocity clouds
Authors: Smoker, J. V.; Lynn, B. B.; Christian, D. J.; Keenan, F. P.
2006MNRAS.370..151S Altcode: 2006MNRAS.tmp..635S
We present CaII K (λ<SUB>air</SUB> = 3933.661Å) interstellar
observations towards 20 early-type stars, to place lower distance limits
to intermediate- and high-velocity clouds (IHVCs) in their lines of
sight. The spectra are also employed to estimate the Ca abundance
in the low-velocity gas towards these objects, when combined with
Leiden-Dwingeloo 21-cm HI survey data of spatial resolution . Nine of
the stars, which lie towards IHVC complexes H, K and gp, were observed
with the intermediate dispersion spectrograph on the Isaac Newton
Telescope at a resolution R = λ/Δλ of 9000 (~33kms<SUP>-1</SUP>)
and signal-to-noise ratio (S/N) per pixel of 75-140. A further
nine objects were observed with the Utrecht Echelle Spectrograph on
the William Herschel Telescope at R = 40000 (~7.5kms<SUP>-1</SUP>)
and S/N per pixel of 10-25. Finally, two objects were observed in
both CaII K and NaI D lines using the 2D COUDÉ spectrograph on the
McDonald 2.7-m telescope at R = 35000 (~8.5 kms<SUP>-1</SUP>). The
abundance of CaII K {log<SUB>10</SUB>(A) = log<SUB>10</SUB>[N(CaII
K)]-log<SUB>10</SUB>[N(HI)]} plotted against HI column density for the
objects in the current sample with heights above the Galactic plane
(z) exceeding 1000pc is found to obey the Wakker & Mathis (2000)
relation. Also, the reduced column density of CaII K as function
of z is consistent with the larger sample taken from Smoker et
al. (2003). Higher S/N observations than those previously taken towards
HVC complex H stars HD13256 and HILT 190 reinforce the assertion that
this lies at a distance exceeding 4000pc. No obvious absorption is
detected in observations of ALS10407 and HD357657 towards IVC complex
gp. The latter star has a spectroscopically estimated distance of
~2040pc, although this was derived assuming the star lies on the main
sequence and without any reddening correction being applied. Finally,
no CaII K absorption is detected towards two stars along the line
of sight to complex K, namely PG1610+529 and PG1710+490. The latter
is at a distance of ~700pc, hence placing a lower distance limit to
this complex, where previously only an upper distance limit of 6800pc
was available.
---------------------------------------------------------
Title: Observational Evidence of Gentle and Explosive Chromospheric
Evaporation
Authors: Milligan, R. O.; Gallagher, P. T.; Mathioudakis, M.; Keenan,
F. P.
2006ESASP.617E.138M Altcode: 2006soho...17E.138M
No abstract at ADS
---------------------------------------------------------
Title: Soft X-Ray Emission Lines of Fe XV in Solar Flare Observations
and the Chandra Spectrum of Capella
Authors: Keenan, F. P.; Drake, J. J.; Chung, S.; Brickhouse, N. S.;
Aggarwal, K. M.; Msezane, A. Z.; Ryans, R. S. I.; Bloomfield, D. S.
2006ApJ...645..597K Altcode: 2006astro.ph..1591K
Recent calculations of atomic data for Fe XV have been used to generate
theoretical line ratios involving n=3-4 transitions in the soft X-ray
spectral region (~52-83 Å), for a wide range of electron temperatures
and densities applicable to solar and stellar coronal plasmas. A
comparison of these with solar flare observations from a rocket-borne
spectrograph (X-Ray Spectrometer/Spectrograph Telescope [XSST]) reveals
generally good agreement between theory and experiment. In particular,
the 82.76 Å emission line in the XSST spectrum is identified, for
the first time to our knowledge in an astrophysical source, as the
3s3d<SUP>3</SUP>D<SUB>3</SUB>-3s4p<SUP>3</SUP>P<SUB>2</SUB> transition
of Fe XV. Most of the Fe XV transitions that are blended have had
the species responsible clearly identified, although there remain
a few instances in which this has not been possible. The line ratio
calculations are also compared with a co-added spectrum of Capella
obtained with the Chandra satellite, which is probably the highest
signal-to-noise ratio observation achieved for a stellar source in the
~25-175 Å soft X-ray region. Good agreement is found between theory
and experiment, indicating that the Fe XV lines are reliably detected
in Chandra spectra and hence may be employed as diagnostics to determine
the temperature and/or density of the emitting plasma. However, the line
blending in the Chandra data is such that individual emission lines
are difficult to measure accurately, and fluxes may only be reliably
determined via detailed profile fitting of the observations. The
co-added Capella spectrum is made available to hopefully encourage
further exploration of the soft X-ray region in astronomical sources.
---------------------------------------------------------
Title: Observational Evidence of Chromospheric Evaporation
Authors: Milligan, Ryan O.; Gallagher, P. T.; Mathioudakis, M.;
Keenan, F. P.
2006SPD....37.0828M Altcode: 2006BAAS...38R.662M
Observational evidence for chromospheric evaporation during the
impulsive phase of two solar flares is presented using data from the
Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) and the
Coronal Diagnostic Spectrometer (CDS) on board SOHO. For the first
time, co-spatial imaging and spectroscopy have been used to observe
both gentle and explosive evaporation processes within HXR emitting
regions. For a GOES C9.1 flare, a low flux of non-thermal electrons
was found to produce low-velocity upflows in the cool He I and O V
emission lines and moderate upflows in the 8 MK Fe XIX line indicative
of gentle evaporation. An M2.2 flare, on the other hand, showed
low-velocity downflows in the He I and O V lines and high-velocity
upflows in the Fe XIX line, for an electron flux value which was an
order of magnitude higher, indicative of an explosive process. These
findings confirm that the dynamic response of the solar atmosphere is
sensitively dependent on the flux of incident electrons as predicted
by current hydrodynamical simulations.
---------------------------------------------------------
Title: A non-LTE abundance analysis of the post-AGB star ROA5701
Authors: Thompson, H. M. A.; Keenan, F. P.; Dufton, P. L.; Ryans,
R. S. I.; Smoker, J. V.
2006MNRAS.368.1749T Altcode: 2006astro.ph..5223T; 2006MNRAS.tmp..396T
An analysis of high-resolution Anglo-Australian Telescope
(AAT)/University College London Échelle Spectrograph (UCLÉS) optical
spectra for the ultraviolet (UV)-bright star ROA5701 in the globular
cluster ω Cen (NGC5139) is performed, using non-local thermodynamic
equilibrium (non-LTE) model atmospheres to estimate stellar atmospheric
parameters and chemical composition. Abundances are derived for C, N,
O, Mg, Si and S, and compared with those found previously by Moehler
et al. We find a general metal underabundance relative to young B-type
stars, consistent with the average metallicity of the cluster. Our
results indicate that ROA5701 has not undergone a gas-dust separation
scenario as previously suggested. However, its abundance pattern does
imply that ROA5701 has evolved off the asymptotic giant branch (AGB)
prior to the onset of the third dredge-up.
---------------------------------------------------------
Title: The effect of dust obscuration in RR Telescopii on optical
and IR long-term photometry and Fe II emission lines
Authors: Kotnik-Karuza, D.; Friedjung, M.; Whitelock, P. A.; Marang,
F.; Exter, K.; Keenan, F. P.; Pollacco, D. L.
2006A&A...452..503K Altcode: 2006astro.ph..3155K
Aims.Infrared and optical photometric and spectroscopic observations of
the symbiotic nova RR Tel are used to study the effects and properties
of dust in symbiotic binaries containing a cool Mira component, as
well as showing "obscuration events" of increased absorption, which
are typical for such Miras.<BR /> Methods: .A set of photometric
observations of the symbiotic nova <ASTROBJ>RR Tel</ASTROBJ> in
different wavelength bands - visual from 1949 to 2002 and near-infrared
({JHKL}) from 1975 to 2002 - are presented. The variability due to the
normal Mira pulsation was removed from the JHKL data, which were then
compared with the American Association of Variable Star Observers'
({AAVSO}) visual light curve. The changes of the Fe II emission
line fluxes during the 1996-2000 obscuration episode were studied in
the optical spectra taken with the Anglo-Australian telescope. <BR
/> Results: .We discuss the three periods during which the Mira
component was heavily obscured by dust as observed in the different
wavelength bands. A change in the correlations of J with other infrared
magnitudes was observed with the colour becoming redder after JD 2 446
600. Generally, J-K was comparable, while K-L was larger than typical
values for single Miras. A distance estimate of 2.5 kpc, based on the
IR data, is given. A larger flux decrease for the permitted than for
the forbidden Fe II lines, during the obscuration episode studied,
has been found. There is no evidence for other correlations with line
properties, in particular with wavelength, which suggests obscuration
due to separate optically thick clouds in the outer layers.<BR />
---------------------------------------------------------
Title: Opacity in the transition region of cool dwarfs: A powerful
diagnostic
Authors: Mathioudakis, M.; Christian, D. J.; Bloomfield, D. S.;
Keenan, F. P.; Linsky, J. L.; Dupuis, J.
2006ASPC..348..159M Altcode:
A detailed study of the C III 1176Å multiplet in active cool stars
has shown significant deviations of the line flux from the optically
thin approximation. These deviations become more pronounced during
flares. Opacity can be used as a powerful diagnostic to estimate path
lengths in the transition region. Our analysis reveals that stellar
transition regions have very small spatial characteristics typically
in the range of 10 - 100 km. These path lengths are in agreement with
the small scale structure seen in the solar transition region.
---------------------------------------------------------
Title: Study of X-ray photoionized Fe plasma and comparisons with
astrophysical modeling codes
Authors: Foord, M. E.; Heeter, R. F.; Chung, H. -K.; van Hoof,
P. A. M.; Bailey, J. E.; Cuneo, M. E.; Liedahl, D. A.; Fournier,
K. B.; Jonauskas, V.; Kisielius, R.; Ramsbottom, C.; Springer, P. T.;
Keenan, F. P.; Rose, S. J.; Goldstein, W. H.
2006JQSRT..99..712F Altcode:
The charge state distributions of Fe, Na and F are determined
in a photoionized laboratory plasma using high-resolution X-ray
spectroscopy. Independent measurements of the density and radiation
flux indicate the ionization parameter ξ in the plasma reaches values
ξ=20 25ergcms<SUP></SUP> under near steady-state conditions. A
curve-of-growth analysis, which includes the effects of velocity
gradients in a one-dimensional expanding plasma, fits the observed
line opacities. Absorption lines are tabulated in the wavelength
region 8 17Å. Initial comparisons with a number of astrophysical
X-ray photoionization models show reasonable agreement.
---------------------------------------------------------
Title: Observational Evidence of Gentle Chromospheric Evaporation
during the Impulsive Phase of a Solar Flare
Authors: Milligan, Ryan O.; Gallagher, Peter T.; Mathioudakis, Mihalis;
Keenan, Francis P.
2006ApJ...642L.169M Altcode: 2006astro.ph..3652M
Observational evidence of gentle chromospheric evaporation during
the impulsive phase of a C9.1 solar flare is presented using data
from the Reuven Ramaty High-Energy Solar Spectroscopic Imager and the
Coronal Diagnostic Spectrometer on board the Solar and Heliospheric
Observatory. Until now, evidence of gentle evaporation has often
been reported during the decay phase of solar flares, where thermal
conduction is thought to be the driving mechanism. Here we show that
the chromospheric response to a low flux of nonthermal electrons
(>=5×10<SUP>9</SUP> ergs cm<SUP>-2</SUP> s<SUP>-1</SUP>) results
in plasma upflows of 13+/-16, 16+/-18, and 110+/-58 km s<SUP>-1</SUP>
in the cool He I and O V emission lines and the 8 MK Fe XIX line,
respectively. These findings, in conjunction with other recently
reported work, now confirm that the dynamic response of the solar
atmosphere is sensitively dependent on the flux of incident electrons.
---------------------------------------------------------
Title: Electron impact excitation of Fe XVI: radiative and excitation
rates
Authors: Aggarwal, K. M.; Keenan, F. P.
2006A&A...450.1249A Altcode:
Aims.In this paper we report calculations for energy levels, radiative
rates, collision strengths, and effective collision strengths for
transitions in Fe XVI.<BR /> Methods: . For energy levels and radiative
rates we have used the General purpose Relativistic Atomic Structure
Package (grasp), and for the compuations of collision strengths the
Dirac Atomic R-matrix Code (darc) has been adopted.<BR /> Results:
. Energies for the lowest 39 levels among the n ≤ 7 (ℓ ≤ 4)
configurations of Fe XVI are reported. Additionally, radiative rates,
oscillator strengths, and line strengths are reported for all electric
dipole (E1), magnetic dipole (M1), electric quadrupole (E2), and
magnetic quadrupole (M2) transitions among these levels. Electron
impact excitation collision strengths have also been calculated for
all 741 transitions among the above 39 levels over a wide energy
range up to 220 Ryd. Resonances have been resolved in the threshold
region, and effective collision strengths have been obtained over a
wide temperature range up to 10<SUP>7</SUP> K. Comparisons are made
with the available results in the literature, and the accuracy of the
present results is assessed.<BR />
---------------------------------------------------------
Title: Sensitive HI Spectra Through the Arms of the SMC
Authors: Muller, Erik; Smoker, Jonathan; Keenan, Francis
2006atnf.prop..152M Altcode:
We request two complete 12 hour synthesis cycles of (total of ~24 hours)
on the ATCA be allocated to obtaining high spatial resolution and
sensitive measurements of the HI in the Magellanic Bridge, towards two
continuum objects. These resulting data will be of sufficient spatial
and velocity resolution to combine with proposed UVES spectroscopic
measurements to enable accurate and precise measurements of the
relative Ca II K/HI abundance levels in three different parts of the
SMC: through two unrelated locations in the 'transverse' arm of the
SMC, and one sight line through the 'radial' arm. We will therefore be
probing, for the first time, the abundance levels of the kinematically
distinct and tidally-generated arms of the SMC.
---------------------------------------------------------
Title: Early-type stars observed in the ESO UVES Paranal
Observatory Project - I. Interstellar NaI UV, TiII and CaII K
observations<SUP>*</SUP>
Authors: Hunter, I.; Smoker, J. V.; Keenan, F. P.; Ledoux, C.; Jehin,
E.; Cabanac, R.; Melo, C.; Bagnulo, S.
2006MNRAS.367.1478H Altcode: 2006astro.ph..1363H; 2006MNRAS.tmp..277H
We present an analysis of interstellar NaI (λ<SUB>air</SUB>=
3302.37 and 3302.98 Å), TiII(λ<SUB>air</SUB>= 3383.76 Å) and CaII K
(λ<SUB>air</SUB>= 3933.66 Å) absorption features for 74 sightlines
towards O- and B-type stars in the Galactic disc. The data were
obtained from the Ultraviolet and Visual Echelle Spectrograph Paranal
Observatory Project, at a spectral resolution of 3.75 km s<SUP>-1</SUP>
and with mean signal-to-noise ratios per pixel of 260, 300 and 430
for the NaI, TiII and CaII observations, respectively. Interstellar
features were detected in all but one of the TiII sightlines and all
of the CaII sightlines. The dependence of the column density of these
three species with distance, height relative to the Galactic plane,
HI column density, reddening and depletion relative to the solar
abundance has been investigated. We also examine the accuracy of using
the NaI column density as an indicator of that for HI. In general,
we find similar strong correlations for both Ti and Ca, and weaker
correlations for Na. Our results confirm the general belief that Ti
and Ca occur in the same regions of the interstellar medium (ISM) and
also that the TiII/CaII ratio is constant over all parameters. We hence
conclude that the absorption properties of Ti and Ca are essentially
constant under the general ISM conditions of the Galactic disc.
---------------------------------------------------------
Title: An investigation of Fe XV emission lines in solar flare spectra
Authors: Keenan, F. P.; Aggarwal, K. M.; Bloomfield, D. S.; Msezane,
A. Z.; Widing, K. G.
2006A&A...449.1203K Altcode: 2005astro.ph.12571K
Previously, large discrepancies have been found between theory
and observation for Fe XV emission line ratios in solar flare
spectra covering the 224-327 Å wavelength range, obtained by the
Naval Research Laboratory's S082A instrument on board Skylab. These
discrepancies have been attributed to either errors in the adopted
atomic data or the presence of additional atomic processes not
included in the modelling, such as fluorescence. However our analysis
of these plus other S082A flare observations (the latter containing
Fe XV transitions between 321-482 Å), performed using the most
recent Fe XV atomic physics calculations in conjunction with a
chianti synthetic flare spectrum, indicate that blending of the
lines is primarily responsible for the discrepancies. As a result,
most Fe XV lines cannot be employed as electron density diagnostics
for solar flares, at least at the spectral resolution of S082A and
similar instruments (i.e. 0.1 Å). An exception is the intensity
ratio I(3s3p <SUP>3</SUP>P{2}-3p<SUP>2</SUP> <SUP>3</SUP>P{1})/I(3s3p
<SUP>3</SUP>P{2}-3p<SUP>2</SUP> <SUP>1</SUP>D{2}) = I(321.8 Å)/I(327.0
Å), which appears to provide good estimates of the electron density
at this spectral resolution.
---------------------------------------------------------
Title: VizieR Online Data Catalog: RR Tel JHKL photometry 1975-2002
(Kotnik-Karuza+, 2006)
Authors: Kotnik-Karuza, D.; Friedjung, M.; Whitelock, P. A.; Marang,
F.; Exter, K.; Keenan, F. P.; Pollacco, D. L.
2006yCat..34520503K Altcode:
The file table1.dat contains a list of JHKL magnitudes monitored from
the South African Astronomical Observatory (SAAO) from 1975 to 2002. The
JHKL magnitudes are accurate to better than 0.03mag in JHK and 0.05mag
at L. Some of the early data, which had been published in Feast et
al. (1983MNRAS.202..951F), were subsequently slightly corrected to
the SAAO system as defined by Carter (1990MNRAS.242....1C). <P />(1
data file).
---------------------------------------------------------
Title: RHESSI and SOHO CDS Observations of Explosive Chromospheric
Evaporation
Authors: Milligan, Ryan O.; Gallagher, Peter T.; Mathioudakis, Mihalis;
Bloomfield, D. Shaun; Keenan, Francis P.; Schwartz, Richard A.
2006ApJ...638L.117M Altcode: 2005astro.ph..9664M
Simultaneous observations of explosive chromospheric evaporation
are presented using data from the Reuven Ramaty High-Energy Solar
Spectroscopic Imager (RHESSI) and the Coronal Diagnostic Spectrometer
(CDS) on board the Solar and Heliospheric Observatory. For the first
time, cospatial imaging and spectroscopy have been used to observe
explosive evaporation within a hard X-ray emitting region. RHESSI
X-ray images and spectra were used to determine the flux of nonthermal
electrons accelerated during the impulsive phase of an M2.2 flare. When
we assumed a thick-target model, the injected electron spectrum was
found to have a spectral index of ~7.3, a low-energy cutoff of ~20 keV,
and a resulting flux of >=4×10<SUP>10</SUP> ergs cm<SUP>-2</SUP>
s<SUP>-1</SUP>. The dynamic response of the atmosphere was determined
using CDS spectra; we found a mean upflow velocity of 230+/-38 km
s<SUP>-1</SUP> in Fe XIX (592.23 Å) and associated downflows of
36+/-16 and 43+/-22 km s<SUP>-1</SUP> at chromospheric and transition
region temperatures, respectively, relative to an averaged quiet-Sun
spectra. The errors represent a 1 σ dispersion. The properties of
the accelerated electron spectrum and the corresponding evaporative
velocities were found to be consistent with the predictions of theory.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Fe XVI radiative and excitation
rates (Aggarwal+, 2006)
Authors: Aggarwal, K. M.; Keenan, F. P.
2006yCat..34501249A Altcode:
In this paper we report calculations for energy levels, radiative
rates, collision strengths, and effective collision strengths for
transitions in Fe XVI. <P />For energy levels and radiative rates we
have used the General purpose Relativistic Atomic Structure Package
(GRASP), and for the computations of collision strengths the Dirac
Atomic R-matrix Code (DARC) has been adopted. <P />Energies for the
lowest 39 levels among the n<=7 (l<=4) configurations of Fe XVI
are reported. Additionally, radiative rates, oscillator strengths,
and line strengths are reported for all electric dipole (E1), magnetic
dipole (M1), electric quadrupole (E2), and magnetic quadrupole (M2)
transitions among these levels. Electron impact excitation collision
strengths have also been calculated for all 741 transitions among the
above 39 levels over a wide energy range up to 220 Ryd. Resonances
have been resolved in the threshold region, and effective collision
strengths have been obtained over a wide temperature range up to
10<SUP>7</SUP>K. Comparisons are made with the available results in
the literature, and the accuracy of the present results is assessed. <P
/>(5 data files).
---------------------------------------------------------
Title: Serendipitous Asteroid Lightcurve Survey Using SuperWASP
Authors: Parley, N. R.; McBride, N.; Green, S. F.; Haswell, C. A.;
Clarkson, W. I.; Christian, D. J.; Collier-Cameron, A.; Evans, N. A.;
Fitzsimmons, A.; Hellier, C.; Hodgkin, S. T.; Horne, K.; Irwin, J.;
Kane, S. R.; Keenan, F. P.; Lister, T. A.; Norton, A. J.; Osborne,
J. P.; Pollacco, D.; Ryans, R.; Skillen, I.; Street, R. A.; West,
R. G.; Wheatley, P. J.
2005EM&P...97..261P Altcode:
The SuperWASP project is an ultra-wide angle search for extra solar
planetary transits. However, it can also serendipitously detect
solar system objects, such as asteroids and comets. Each SuperWASP
instrument consists of up to eight cameras, combined with high-quality
peltier-cooled CCDs, which photometrically survey large numbers of
stars in the magnitude range 7 15. Each camera covers a 7.8 × 7.8
degree field of view. Located on La Palma, the SuperWASP-I instrument
has been observing the Northern Hemisphere with five cameras since its
inauguration in April 2004. The ultra-wide angle field of view gives
SuperWASP the possibility of discovering new fast moving (near to Earth)
asteroids that could have been missed by other instruments. However,
it provides an excellent opportunity to produce a magnitude-limited
lightcurve survey of known main belt asteroids. As slow moving asteroids
stay within a single SuperWASP field for several weeks, and may be
seen in many fields, a survey of all objects brighter than magnitude
15 is possible. This will provide a significant increase in the total
number of lightcurves available for statistical studies without the
inherent bias against longer periods present in the current data
sets. We present the methodology used in the automated collection
of asteroid data from SuperWASP and some of the first examples of
lightcurves from numbered asteroids.
---------------------------------------------------------
Title: Preliminary Results from Secis Observations of the 2001 Total
Solar Eclipse
Authors: Katsiyannis, A. C.; Williams, D. R.; Murtagh, F.; McAteer,
R. T. J.; Keenan, F. P.
2005ESASP.600E..86K Altcode: 2005ESPM...11...86K; 2005dysu.confE..86K
No abstract at ADS
---------------------------------------------------------
Title: First Results from Secis Observations of the 2001 Total
Solar Eclipse
Authors: Katsiyannis, A. C.; Williams, D. R.; Murtagh, F.; McAteer,
R. T. J.; Keenan, F. P.
2005ESASP.596E..45K Altcode: 2005ccmf.confE..45K
No abstract at ADS
---------------------------------------------------------
Title: Ca II K observations of QSOs in the line-of-sight to the
Magellanic Bridge
Authors: Smoker, J. V.; Keenan, F. P.; Thompson, H. M. A.; Brüns,
C.; Muller, E.; Lehner, N.; Lee, J. -K.; Hunter, I.
2005A&A...443..525S Altcode: 2005astro.ph.10507S
We describe medium-resolution spectroscopic observations taken
with the ESO Multi-Mode Instrument (emmi) in the Ca ii K line
(λ_air=3933.661 Å) towards 7 QSOs located in the line-of-sight
to the Magellanic Bridge. At a spectral resolution R = λ/Δλ =
6000, five of the sightlines have a signal-to-noise (S/N) ratio
of 20 or higher. Definite Ca absorption due to Bridge material is
detected towards 3 objects, with probable detection towards two
other sightlines. Gas-phase Ca ii K Bridge and Milky Way abundances
or lower limits for the all sightlines are estimated by the use of
Parkes 21-cm H i emission line data. These data only have a spatial
resolution of 14 arcmin compared with the optical observations which
have milli-arcsecond resolution. With this caveat, for the three objects
with sound Ca ii K detections, we find that the ionic abundance of Ca
ii K relative to H i, A=log(N(Ca K)/N(H i)) for low-velocity Galactic
gas ranges from -8.3 to -8.8 dex, with H i column densities varying
from 3-6×10<SUP>20</SUP> cm<SUP>-2</SUP>. For Magellanic Bridge gas,
the values of A are 0.5 dex higher, ranging from -7.8 to -8.2 dex,
with N(H i) = 1{-}5×10<SUP>20</SUP> cm<SUP>-2</SUP>. Higher values
of A correspond to lower values of N(H i), although numbers are
small. For the sightline towards B 0251-675, the Bridge gas has two
different velocities, and in only one of these is Ca ii tentatively
detected, perhaps indicating gas of a different origin or present-day
characteristics (such as dust content), although this conclusion is
uncertain and there is the possibility that one of the components could
be related to the Magellanic Stream. Higher signal-to-noise Ca ii K
data and higher resolution H i data are required to determine whether
A changes with N(H i) over the Bridge and if the implied difference in
the metalicity of the two Bridge components towards B 0251-675 is real.
---------------------------------------------------------
Title: High-resolution spectroscopic observations of post-asymptotic
giant branch candidates from the Edinburgh-Cape Survey
Authors: Lynn, B. B.; Keenan, F. P.; Dufton, P. L.; Rolleston,
W. R. J.; Smoker, J. V.; Ryans, R. S. I.; Kilkenny, D.; O'Donoghue,
D.; Hambly, N.; McGillivray, H. T.
2005MNRAS.363..911L Altcode: 2005MNRAS.tmp..846L
High spectral resolution (R~ 40000) and signal-to-noise optical
spectra, obtained at the Very Large Telescope (VLT), are presented for
three post-asymptotic giant branch (AGB) candidates selected from the
Edinburgh-Cape (EC) Faint Blue Object Survey. The stellar atmospheric
parameters and chemical compositions, derived using sophisticated
non-local thermodynamic equilibrium calculations, reveal that EC
14102-1337 and EC 20068-7324 are both in an evolved post-horizontal
branch (HB) evolutionary state. However, EC 11507-2253 is most likely
a post-AGB star.
---------------------------------------------------------
Title: Plasma diagnostics of active-region evolution and implications
for coronal heating
Authors: Milligan, R. O.; Gallagher, P. T.; Mathioudakis, M.; Keenan,
F. P.; Bloomfield, D. S.
2005MNRAS.363..259M Altcode: 2005MNRAS.tmp..764M; 2005astro.ph..9219M
A detailed study is presented of the decaying solar-active region NOAA
10103 observed with the Coronal Diagnostic Spectrometer (CDS), the
Michelson Doppler Imager (MDI) and the Extreme-ultraviolet Imaging
Telescope (EIT) onboard the Solar and Heliospheric Observatory
(SOHO). Electron-density maps formed using SiX (356.03 Å/347.41 Å)
show that the density varies from ~10<SUP>10</SUP>cm<SUP>-3</SUP>
in the active-region core to ~7 × 10<SUP>8</SUP>cm<SUP>-3</SUP>
at the region boundaries. Over the 5d of observations, the average
electron density fell by ~30 per cent. Temperature maps formed using
FeXVI (335.41 Å)/FeXIV (334.18 Å) show electron temperatures of
~2.34 × 10<SUP>6</SUP> K in the active-region core and ~2.10 ×
10<SUP>6</SUP> K at the region boundaries. Similarly to the electron
density, there was a small decrease in the average electron temperature
over the 5-d period. The radiative, conductive and mass-flow losses
were calculated and used to determine the resultant heating rate
(P<SUB>H</SUB>). Radiative losses were found to dominate the
active-region cooling process. As the region decayed, the heating
rate decreased by almost a factor of 5 between the first and last
day of observations. The heating rate was then compared to the
total unsigned magnetic flux , yielding a power law of the form
P<SUB>H</SUB>~Φ<SUP>0.81+/-0.32</SUP><SUB>tot</SUB>. This result
suggests that waves rather than nanoflares may be the dominant heating
mechanism in this active region.
---------------------------------------------------------
Title: Electron impact excitation of Ar XVII
Authors: Aggarwal, K. M.; Keenan, F. P.
2005A&A...441..831A Altcode:
Energies for the lowest 49 levels among the 1s<SUP>2</SUP> and
1snℓ (n = 2-5) configurations of Ar XVII have been calculated
using the grasp code of Dyall et al. (1989, Comput. Phys. Comm.,
55, 424). Additionally, radiative rates, oscillator strengths, and
line strengths are calculated for all electric dipole (E1), magnetic
dipole (M1), electric quadrupole (E2), and magnetic quadrupole (M2)
transitions among these levels. Furthermore, collision strengths have
also been calculated for all the 1176 transitions among the above 49
levels using the Dirac Atomic R-matrix Code (DARC) of Norrington &
Grant (2005, Comput. Phys. Commun., in preparation), over a wide energy
range up to 580 Ryd. Resonances have been resolved in the threshold
region, and effective collision strengths have been obtained over a
wide temperature range up to log T<SUB>e</SUB> = 7.2 K. Comparisons
are made with the limited results available in the literature, and the
accuracy of the data is assessed. Our energy levels are estimated to
be accurate to better than 0.1%, whereas results for other parameters
are probably accurate to better than 20%.
---------------------------------------------------------
Title: Fe II emission lines of RR Tel during an obscuration event
Authors: Kotnik-Karuza, D.; Friedjung, M.; Exter, K.; Keenan, F. P.;
Pollacco, D. L.
2005AIPC..797..577K Altcode:
A study of the behaviour of the permitted Fe II and forbidden [Fe II]
emission lines during a dust obscuration episode, suggests a larger
flux decrease for the permitted than for the forbidden lines. No
other correlation with line properties have been found. Possible
interpretations are discussed.
---------------------------------------------------------
Title: Effective collision strengths for transitions in Fe X
Authors: Aggarwal, K. M.; Keenan, F. P.
2005A&A...439.1215A Altcode:
Collision strengths for 4005 transitions among the lowest 90 levels
of the (1s^22s^22p^6) 3s^23p^5, 3s3p^6, 3s^23p^43d, 3s3p^53d and
3s^23p^33d<SUP>2</SUP> configurations of Fe X have been calculated
using the Dirac Atomic R-matrix Code (DARC) of Norrington & Grant
(2005, Comput. Phys. Commun., in preparation), over a wide energy
range up to 210 Ryd. Resonances have been resolved in the threshold
region, and effective collision strengths have been obtained over a
wide temperature range up to 10<SUP>7</SUP> K. The present calculations
should represent a significant improvement (in both range and accuracy)
over the earlier available results of Bhatia & Doschek (1995,
At. Data Nucl. Data Tables, 60, 97), Tayal (2001, ApJS, 132, 117)
and Pelan & Berrington (2001, A&A, 365, 258). Based on several
comparisons, the accuracy of our data is assessed to be better than 20%,
for a majority of transitions.
---------------------------------------------------------
Title: An Analytic Geometry-variant Approach to Line Ratio Enhancement
above the Optically Thin Limit
Authors: Kerr, F. M.; Rose, S. J.; Wark, J. S.; Keenan, F. P.
2005ApJ...629.1091K Altcode:
We describe a simple theoretical model to investigate the anomalous
effects of opacity on spectral line ratios, as previously studied in
elements such as Fe XV and Fe XVII. The model developed is general: it
is not specific to a particular atomic system, thus giving applicability
to a number of coronal and chromospheric plasmas; furthermore, it may
be applied to a variety of astrophysically relevant geometries. The
analysis is underpinned by geometrical arguments, and we outline a
technique for it to be used as a tool for the explicit diagnosis of
plasma geometry in distant astrophysical objects.
---------------------------------------------------------
Title: Modeling X-Ray Photoionized Plasmas Produced at the Sandia
Z-Facility
Authors: van Hoof, P. A. M.; Foord, M. E.; Heeter, R. F.; Bailey,
J. E.; Chung, H. -K.; Cuneo, M. E.; Goldstein, W. H.; Jonauskas, V.;
Keenan, F. P.; Kisielius, R.; Liedahl, D. A.; Ramsbottom, C.; Rose,
S. J.; Springer, P. T.; Thoe, R. S.
2005Ap&SS.298..147V Altcode: 2005Ap&SS.298..147H
In experiments at the high-power Z-facility at Sandia National
Laboratory in Albuquerque, New Mexico, we have been able to produce a
low density photoionized laboratory plasma of Fe mixed with NaF. The
conditions in the experiment allow a meaningful comparison with X-ray
emission from astrophysical sources. The charge state distributions of
Fe, Na and F are determined in this plasma using high resolution X-ray
spectroscopy. Independent measurements of the density and radiation
flux indicate unprecedented values for the ionization parameter ξ =
20 25 erg cm s<SUP>-1</SUP> under nearly steady-state conditions. First
comparisons of the measured charge state distributions with X-ray
photoionization models show reasonable agreement, although many
questions remain.
---------------------------------------------------------
Title: Soft X-ray emission lines of Fe XV in spectra of the Sun
and Capella
Authors: Drake, J. J.; Keenan, F. P.; Chung, S.; Brickhouse, N. S.;
Aggarwal, K. M.; Msezane, A. Z.; Ryans, R. S. I.; Bloomfield, D. S.
2005AIPC..774..349D Altcode:
Recent calculations of atomic data for Fe XV have been used to generate
theoretical line ratios involving n = 3-4 transitions in the soft X-ray
spectral region (~52-83 Å) for a wide range of electron temperatures
and densities applicable to solar and stellar coronal plasmas. The
line ratio calculations are compared with solar flare observations
from a rocket-borne spectrograph (XSST) and with a co-added spectra
of Capella obtained with the Chandra LETGS, representing the highest
signal-to-noise observation achieved for a stellar source in the
30-80 Å soft X-ray region. Results are promising for use of Fe XV
as astrophysical plasma diagnostics: Agreement between theory and
observation is generally good, after particular account is taken of line
blending. The 82.76 Å emission line in the XSST spectrum is identified,
for the first time to our knowledge in an astrophysical source, as
the 3s3d <SUP>3</SUP>D3-3s4p <SUP>3</SUP>P2 transition of Fe XV.
---------------------------------------------------------
Title: Energy levels and radiative rates for transitions in Ar XIII,
Ar XIV and Ar XV
Authors: Aggarwal, K. M.; Keenan, F. P.; Nakazaki, S.
2005A&A...436.1141A Altcode:
Energies for 524 levels of Ar XIII, 460 levels of Ar XIV and 156
levels of Ar XV have been calculated using the grasp code of Dyall et
al. (1989). Additionally, radiative rates, oscillator strengths, and
line strengths are calculated for all electric dipole (E1), magnetic
dipole (M1), electric quadrupole (E2), and magnetic quadrupole (M2)
transitions among these levels. Comparisons are made with the limited
results available in the literature, and the accuracy of the data is
assessed. Our energy levels are estimated to be accurate to better
than 1%, whereas results for other parameters are probably accurate
to better than 20%. Additionally, the level lifetimes derived from
our radiative rates are in excellent agreement with measured values.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Electron impact excitation of Ar
XVII (Aggarwal+, 2005)
Authors: Aggarwal, K. M.; Keenan, F. P.
2005yCat..34410831A Altcode:
Energies for the lowest 49 levels among the 1s^2 and 1snl (n=2-5)
configurations of Ar XVII have been calculated using the GRASP code of
Dyall et al. (1989, Comput. Phys. Commun., 55, 424). Additionally,
radiative rates, oscillator strengths, and line strengths are
calculated for all electric dipole (E1), magnetic dipole (M1),
electric quadrupole (E2), and magnetic quadrupole (M2) transitions
among these levels. Furthermore, collision strengths have also been
calculated for all the 1176 transitions among the above 49 levels
using the Dirac Atomic R-matrix Code (DARC) of Norrington & Grant
(2005, Comput. Phys. Commun., in prep.), over a wide energy range up
to 580Ryd. Resonances have been resolved in the threshold region,
and effective collision strengths have been obtained over a wide
temperature range up to log T<SUB>e</SUB>=7.2K. Comparisons are made
with the limited results available in the literature, and the accuracy
of the data is assessed. Our energy levels are estimated to be accurate
to better than 0.1%, whereas results for other parameters are probably
accurate to better than 20%. <P />(8 data files).
---------------------------------------------------------
Title: Fe XI Emission Lines in a High-Resolution Extreme-Ultraviolet
Active Region Spectrum Obtained by the Solar Extreme Ultraviolet
Research Telescope and Spectrograph
Authors: Keenan, F. P.; Aggarwal, K. M.; Ryans, R. S. I.; Milligan,
R. O.; Bloomfield, D. S.; Brosius, J. W.; Davila, J. M.; Thomas, R. J.
2005ApJ...624..428K Altcode: 2005astro.ph..4106K
New calculations of radiative rates and electron impact excitation cross
sections for Fe XI are used to derive emission-line intensity ratios
involving 3s<SUP>2</SUP>3p<SUP>4</SUP>-3s<SUP>2</SUP>3p<SUP>3</SUP>3d
transitions in the 180-223 Å wavelength range. These ratios are
subsequently compared with observations of a solar active region
obtained during the 1995 flight of the Solar Extreme Ultraviolet
Research Telescope and Spectrograph (SERTS). The version of SERTS flown
in 1995 incorporated a multilayer grating that enhanced the instrumental
sensitivity for features in the ~170-225 Å wavelength range, observed
in second order between 340 and 450 Å. This enhancement led to the
detection of many emission lines not seen on previous SERTS flights,
which were measured with the highest spectral resolution (0.03 Å)
ever achieved for spatially resolved active region spectra in this
wavelength range. However, even at this high spectral resolution,
several of the Fe XI lines are found to be blended, although the sources
of the blends are identified in the majority of cases. The most useful
Fe XI electron density diagnostic line intensity ratio is I(184.80
Å)/I(188.21 Å). This ratio involves lines close in wavelength
and free from blends, and it varies by a factor of 11.7 between
N<SUB>e</SUB>=10<SUP>9</SUP> and 10<SUP>11</SUP> cm<SUP>-3</SUP>
yet shows little temperature sensitivity. An unknown line in the
SERTS spectrum at 189.00 Å is found to be due to Fe XI, the first
time (to our knowledge) this feature has been identified in the solar
spectrum. Similarly, there are new identifications of the Fe XI 192.88,
198.56, and 202.42 Å features, although the latter two are blended
with S VIII/Fe XII and Fe XIII, respectively.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Effective collision strengths
for Fe X trans. (Aggarwal+, 2005)
Authors: Aggarwal, K. M.; Keenan, F. P.
2005yCat..34391215A Altcode:
Collision strengths for 4005 transitions among the lowest 90
levels of the (1s<SUP>2</SUP>2s<SUP>2</SUP>2p<SUP>6</SUP>)
3s<SUP>2</SUP>3p<SUP>5</SUP>, 3s3p<SUP>6</SUP>,
3s<SUP>2</SUP>3p<SUP>4</SUP>3d, 3s3p<SUP>5</SUP>3d and
3s<SUP>2</SUP>3p<SUP>3</SUP>3d<SUP>2</SUP> configurations of Fe X
have been calculated using the Dirac Atomic R-matrix Code (DARC) of
Norrington & Grant (2005, Comput. Phys. Commun. , in prep.), over
a wide energy range up to 210Ryd. Resonances have been resolved in the
threshold region, and effective collision strengths have been obtained
over a wide temperature range up to 10<SUP>7</SUP>K. The present
calculations should represent a significant improvement (in both range
and accuracy) over the earlier available results of Bhatia & Doschek
(1995, At. Data Nucl. Data Tables, 60, 97), Tayal (2001ApJS..132..117T)
and Pelan & Berrington (2001A&A...365..258P). Based on several
comparisons, the accuracy of our data is assessed to be better than 20%,
for a majority of transitions. <P />(4 data files).
---------------------------------------------------------
Title: Chromospheric Response to Non-Thermal Electrons During Flares
Using RHESSI and SOHO/CDS
Authors: Milligan, R. O.; Gallagher, P. T.; Mathioudakis, M.; Keenan,
F. P.
2005AGUSMSP52A..04M Altcode:
Many current solar flare models predict a relationship between the
amount of energy deposited in the chromospheric and transition region
layers of the solar atmosphere by non-thermal electrons, and the
velocity at which this superheated material rises. For the first time,
we present findings from simultaneous observations of loop footpoints
using RHESSI and SOHO/CDS. RHESSI HXR images and spectra are used to
determine the flux of non-thermal electrons using the thick-target
bremsstrahlung model, while upflow velocities in the Fe XIX emission
line are observed using CDS.
---------------------------------------------------------
Title: The Application Of À Trous Wave Filtering And Monte Carlo
Analysis On Secis 2001 Solar Eclipse Observations
Authors: Katsiyannis, A. C.; Murtagh, F.; Keenan, F. P.
2005SoPh..228..323K Altcode: 2005astro.ph..4181K
Eight thousand images of the solar corona were captured during the
June 2001 total solar eclipse. New software for the alignment of the
images and an automated technique for detecting intensity oscillations
using multi-scale wavelet analysis were developed. Large areas of
the images covered by the Moon and the upper corona were scanned
for oscillations and the statistical properties of the atmospheric
effects were determined. The à Trous wavelet transform was used for
noise reduction and Monte Carlo analysis as a significance test of
the detections. The effectiveness of those techniques is discussed
in detail.
---------------------------------------------------------
Title: Energy levels and transition probabilities for nitrogen-like
Fe xx
Authors: Jonauskas, V.; Bogdanovich, P.; Keenan, F. P.; Foord, M. E.;
Heeter, R. F.; Rose, S. J.; Ferland, G. J.; Kisielius, R.; van Hoof,
P. A. M.; Norrington, P. H.
2005A&A...433..745J Altcode:
Energies of the 700 lowest levels in ion{Fe}{xx} have been obtained
using the multiconfiguration Dirac-Fock method. Configuration
interaction method on the basis set of transformed radial orbitals
with variable parameters taking into account relativistic corrections
in the Breit-Pauli approximation was used to crosscheck our presented
results. Transition probabilities, oscillator and line strengths
are presented for electric dipole (E1), electric quadrupole (E2) and
magnetic dipole (M1) transitions among these levels. The total radiative
transition probabilities from each level are also provided. Results
are compared with data compiled by NIST and with other theoretical
work. <P />Tables 8 to 10 are only available in electronic form at
the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or
via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/433/745 Tables 1-7
are only available in electronic form at http://www.edpsciences.org
---------------------------------------------------------
Title: AB Dor: Evidence for stellar coronal opacity in Fe XVII
Authors: Matranga, M.; Mathioudakis, M.; Kay, H. R. M.; Keenan, F. P.
2005ESASP.560..807M Altcode: 2005csss...13..807M
No abstract at ADS
---------------------------------------------------------
Title: Variables in the Pleiades and Hyades from SuperWASP-I
commissioning data
Authors: Lister, T. A.; Collier Cameron, A.; Christian, D. J.;
Clarkson, W. I.; Evans, N.; Fitzsimmons, A.; Haswell, C. A.; Hellier,
C.; Hodgkin, S. T.; Horne, K.; Kane, S. R.; Keenan, F. P.; Norton,
A. J.; Pollacco, D. L.; Ryans, R.; Skillen, I.; Street, R. A.; West,
R. G.; Wheatley, P. J.
2005ESASP.560..763L Altcode: 2005csss...13..763L
No abstract at ADS
---------------------------------------------------------
Title: Current status of the SuperWASP project
Authors: Christian, D. J.; Pollacco, D. L.; Clarkson, W. I.; Collier
Cameron, A.; Evans, N.; Fitzsimmons, A.; Haswell, C. A.; Hellier,
C.; Hodgkin, S. T.; Horne, K.; Kane, S. R.; Keenan, F. P.; Lister,
T. A.; Norton, A. J.; Ryans, R.; Skillen, I.; Street, R. A.; West,
R. G.; Wheatley, P. J.
2005ESASP.560..475C Altcode: 2004astro.ph.11019C; 2005csss...13..475C
We present the current status of the SuperWASP project, a Wide Angle
Search for Planets. SuperWASP consists of up to 8 individual cameras
using ultra-wide field lenses backed by high-quality passively cooled
CCDs. Each camera covers 7.8 x 7.8 sq degrees of sky, for nearly 500 sq
degrees of sky coverage. SuperWASP I, located in LaPalma, is currently
operational with 5 cameras and is conducting a photometric survey
of a large numbers of stars in the magnitude range ~7 to 15. The
collaboration has developed a custom-built reduction pipeline and
aims to achieve better than 1 percent photometric precision. The
pipeline will also produce well sampled light curves for all the
stars in each field which will be used to detect: planetary transits,
optical transients, and track Near-Earth Objects. Status of current
observations, and expected rates of extrasolar planetary detections
will be presented. The consortium members, institutions, and further
details can be found on the web site at: http://www.superwasp.org.
---------------------------------------------------------
Title: Magnetohydrodynamic mode coupling in the quiet-Sun network
Authors: Bloomfield, D. S.; McAteer, R. T. J.; Mathioudakis, M.;
Williams, D. R.; Keenan, F. P.
2005ESASP.560..449B Altcode: 2005csss...13..449B
No abstract at ADS
---------------------------------------------------------
Title: Flare X-Ray Observations of AB Doradus: Evidence of Stellar
Coronal Opacity
Authors: Matranga, M.; Mathioudakis, M.; Kay, H. R. M.; Keenan, F. P.
2005ApJ...621L.125M Altcode: 2005astro.ph..2063M
X-ray spectra of the late-type star AB Dor obtained with the
XMM-Newton satellite are analyzed. AB Dor was particularly active
during the observations. An emission measure reconstruction technique
is employed to analyze flare and quiescent spectra, with emphasis on
the Fe XVII 15-17 Å wavelength region. The Fe XVII 16.78 Å/15.01 Å
line ratio increases significantly in the hotter flare plasma. This
change in the ratio is opposite to the theoretical predictions
and is attributed to the scattering of 15.01 Å line photons from
the line of sight. The escape probability technique indicates an
optical depth of ~0.4 for the 15.01 Å line. During the flare, the
electron density is 4.4<SUP>+2.7</SUP><SUB>-1.6</SUB>×10<SUP>10</SUP>
cm<SUP>-3</SUP>, and the fractional Fe abundance is 0.5+/-0.1 of the
solar photospheric value. Using these parameters, a path length of
~8000 km is derived. There is no evidence of opacity in the quiescent
X-ray spectrum of the star.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Radiative rates in Ar XIII,
Ar XIV & Ar XV (Aggarwal+, 2005)
Authors: Aggarwal, K. M.; Keenan, F. P.; Nakazaki, S.
2005yCat..34361141A Altcode:
Energies for 524 levels of Ar XIII, 460 levels of Ar XIV and 156
levels of Ar X V have been calculated using the GRAS code of Dyall
et al. (1989, Comput. Phys. Commun, 55, 424). Additionally, radiative
rates, oscillator strengths, and line strengths are calculated for all
electric dipole (E1), magnetic dipole (M1), electric quadrupole (E2),
and magnetic quadrupole (M2) transitions among these levels. Comparisons
are made with the limited results available in the literature, and the
accuracy of the data is assessed. Our energy levels are estimated to
be accurate to better than 1%, whereas results for other parameters
are probably accurate to better than 20%. Additionally, the level
lifetimes derived from our radiative rates are in excellent agreement
with measured values. <P />(12 data files).
---------------------------------------------------------
Title: Electron impact excitation of Al XIII: A relativistic approach
Authors: Aggarwal, K. M.; Keenan, F. P.; Rose, S. J.
2005A&A...432.1151A Altcode:
Energy levels, radiative rates, collision strengths, and effective
collision strengths for all transitions up to and including the n =
5 levels of Al XIII have been computed in the jj coupling scheme
including relativistic effects. All partial waves with angular
momentum J ≤ 60 have been included, and resonances have been
resolved in a fine energy grid in the threshold region. Collision
strengths are tabulated at energies above thresholds in the range
170.0 ≤ E ≤ 300.0 Ryd, and results for effective collision
strengths, obtained after integrating the collision strengths over a
Maxwellian distribution of electron velocities, are tabulated over a
wide temperature range of 4.4 ≤ log T<SUB>e</SUB> ≤ 6.8 K. The
importance of including relativistic effects in a calculation is
discussed in comparison with the earlier available non-relativistic
results. <P />Tables 2 4 are available only in electronic form at
the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or
via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/432/1151
---------------------------------------------------------
Title: VizieR Online Data Catalog: FeXX energy levels + transition
probabilities (Jonauskas+, 2005)
Authors: Jonauskas, V.; Bogdanovich, P.; Keenan, F. P.; Foord, E. M.;
Heeter, R. F.; Rose, S. J.; Ferland, G. J.; Kisielius, R.; van Hoof,
P. A. M.; Norrington, P. H.
2005yCat..34330745J Altcode:
Energy levels and the corresponding transition probabilities as
well as oscillator strengths and line strengths for allowed (E1)
and forbidden (E2, M1) transitions among the lowest 700 levels of
nitrogen-like Fe XX are presented. Calculations were performed using
the multiconfigurational Dirac-Fock GRASP code. <P />(4 data files).
---------------------------------------------------------
Title: Observations of Hα Intensity Oscillations in a Flare Ribbon
Authors: McAteer, R. T. James; Gallagher, Peter T.; Brown, Daniel S.;
Bloomfield, D. Shaun; Moore, Ruth; Williams, David R.; Mathioudakis,
Mihalis; Katsiyannis, A.; Keenan, Francis P.
2005ApJ...620.1101M Altcode:
High-cadence Hα blue wing observations of a C9.6 solar flare
obtained at Big Bear Solar Observatory using the Rapid Dual Imager
are presented. Wavelet and time-distance methods were used to study
oscillatory power along the ribbon, finding periods of 40-80 s during
the impulsive phase of the flare. A parametric study found statistically
significant intensity oscillations with amplitudes of 3% of the peak
flare amplitude, periods of 69 s (14.5 mHz) and oscillation decay times
of 500 s. These measured properties are consistent with the existence
of flare-induced acoustic waves within the overlying loops.
---------------------------------------------------------
Title: Emission lines of FeXV in spectra obtained with the Solar
Extreme-Ultraviolet Research Telescope and Spectrograph
Authors: Keenan, F. P.; Aggarwal, K. M.; Milligan, R. O.; Ryans,
R. S. I.; Bloomfield, D. S.; Srigengan, V.; O'Mullane, M. G.; Lawson,
K. D.; Msezane, A. Z.; Brosius, J. W.; Davila, J. M.; Thomas, R. J.
2005MNRAS.356.1592K Altcode: 2004MNRAS.tmp..752K
Recent R-matrix calculations of electron impact excitation rates
in Mg-like FeXV are used to derive theoretical emission-line ratios
involving transitions in the 243-418 Åwavelength range. A comparison
of these with a data set of solar active region, subflare and off-limb
spectra, obtained during rocket flights by the Solar Extreme-Ultraviolet
Research Telescope and Spectrograph (SERTS), reveals generally
very good agreement between theory and observation, indicating that
most of the FeXV emission lines may be employed with confidence as
electron density diagnostics. In particular, the 312.55-Åline of
FeXV is not significantly blended with a CoXVII transition in active
region spectra, as suggested previously, although the latter does
make a major contribution in the subflare observations. Most of the
FeXV transitions which are blended have had the species responsible
clearly identified, although there remain a few instances where
this has not been possible. We briefly address the long-standing
discrepancy between theory and experiment for the intensity ratio of
the 3s<SUP>21</SUP>S-3s3p <SUP>3</SUP>P<SUB>1</SUB> intercombination
line at 417.25 Åto the 3s<SUP>21</SUP>S-3s3p <SUP>1</SUP>P resonance
transition at 284.16 Å.
---------------------------------------------------------
Title: Effective collision strengths for transitions in Fe XIII
Authors: Aggarwal, K. M.; Keenan, F. P.
2005A&A...429.1117A Altcode:
Effective collision strengths for transitions
among the lowest 97 fine-structure levels belonging
to the (1s<SUP>2</SUP>2s<SUP>2</SUP>2p<SUP>6</SUP>)
3s<SUP>2</SUP>3p<SUP>2</SUP>, 3s3p<SUP>3</SUP>, 3s<SUP>2</SUP>3p3d,
3p<SUP>4</SUP>, 3s3p<SUP>2</SUP>3d and 3s<SUP>2</SUP>3d<SUP>2</SUP>
configurations of Fe XIII have been calculated using the fully
relativistic Dirac Atomic R-matrix Code (DARC) of Norrington &
Grant (\cite{Norrington04}). Resonances have been resolved in the
threshold region, and results are reported over a wide electron
temperature range up to log T<SUB>e</SUB> = 6.8 K. Comparisons are
made with the earlier available R-matrix results of Gupta &
Tayal (\cite{Gupta98}), and the accuracy of the data is assessed. <P
/>Tables 2 and 3 are available only in electronic form at the CDS via
anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http ://
cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/429/1117
---------------------------------------------------------
Title: Modeling X-Ray Photoionized Plasmas Produced at the Sandia
Z-Facility
Authors: Van Hoof, P. A. M.; Foord, M. E.; Heeter, R. F.; Bailey,
J. E.; Chung, H. -K.; Cuneo, M. E.; Goldstein, W. H.; Jonauskas, V.;
Keenan, F. P.; Kisielius, R.; Liedahl, D. A.; Ramsbottom, C.; Rose,
S. J.; Springer, P. T.; Thoe, R. S.
2005hedl.book..147V Altcode:
In experiments at the high-power Z-facility at Sandia National
Laboratory in Albuquerque, New Mexico, we have been able to produce a
low density photoionized laboratory plasma of Fe mixed with NaF. The
conditions in the experiment allow a meaningful comparison with X-ray
emission from astrophysical sources. The charge state distributions of
Fe, Na and F are determined in this plasma using high resolution X-ray
spectroscopy. Independent measurements of the density and radiation
flux indicate unprecedented values for the ionization parameter ξ =
20-25 erg cm s<SUP>-1</SUP> under nearly steady-state conditions. First
comparisons of the measured charge state distributions with X-ray
photoionization models show reasonable agreement, although many
questions remain.
---------------------------------------------------------
Title: Initial Results from Secis Observations of the 2001 Eclipse
Authors: Katsiyannis, A. C.; Williams, D. R.; Murtagh, F.; McAteer,
R. T. J.; Keenan, F. P.
2004ESASP.575..410K Altcode: 2004soho...15..410K; 2003astro.ph.11534K
SECIS observations of the June 2001 total solar eclipse were taken
using an Fe xiv 5303 A filter. Existing software was modified and new
code was developed for the reduction and analysis of these data. The
observations, data reduction, study of the atmospheric and instrumental
effects, together with some preliminary results are discussed. Emphasis
is given to the techniques used for the automated alignment of the 8000
images, the application of the a Trous algorithm for noise filtering
and the software developed for the automated detection of intensity
oscillations using wavelet analysis. In line with findings from the
1999 SECIS total eclipse observations, intensity oscillations with
periods in the range of 20-30 s, both inside and just outside coronal
loops are also presented.
---------------------------------------------------------
Title: New results about dust in the envelope of the symbiotic nova
RR Tel
Authors: Kotnik-Karuza, D.; Friedjung, M.; Exter, K.; Keenan, F. P.;
Pollacco, D. L.; Whitelock, P. A.
2004ASPC..318..363K Altcode: 2004ssrc.conf..363K
We have examined the changes of line fluxes of RR Tel in the optical
spectra taken in 2000 compared with the corresponding ones of the
spectra taken in 1996. The fading of the lines leading to the apparent
decrease of the radius of the line emitting region can be understood as
being spurious and explained by increased circumstellar dust absorption
in the stellar wind of the mira. This dust obscuration event has given
clues about stratification effects in the emitting region. In addition,
infrared photometry performed from SAAO shows a change in the nature
of colour behaviour. It is not yet clear if that is due to a change
in dust properties.
---------------------------------------------------------
Title: Spectroscopy: Spectroscopy of astrophysic al plasmas in
the laboratory
Authors: Keenan, F. P.; Rose, S. J.
2004A&G....45f..18K Altcode:
Most of the matter in the universe is in the form of a plasma. Over the
past few years physicists have produced laboratory plasmas that can
mimic those observed in astrophysics. The best known is probably the
tokamak, which has similar physical conditions and plasma processes to
those found in collisionally dominated solar and stellar transition
regions and coronae. Spectroscopy of such laboratory plasmas, in
particular at ultraviolet and X-ray wavelengths, has greatly aided
our understanding of their astrophysical counterparts. More recently,
experiments have been performed on the Z Machine at the Sandia National
Laboratory in the USA with the aim of creating, for the first time,
steady-state photoionization-dominated plasmas that recreate the
conditions found in some accretion-powered X-ray sources, such as X-ray
binaries. In the future, experiments are envisaged with laser-produced
plasmas at AWE Aldermaston that may be able to mimic the steady-state
conditions found in high-energy accretion-powered sources, including
the central regions of active galaxies.
---------------------------------------------------------
Title: The behaviour of the Fe II emission lines of the symbiotic
mira RR Tel during an obscuration event
Authors: Friedjung, M.; Kotnik-Karuza, D.; Exter, K.; Keenan, F. P.;
Pollacco, D. L.
2004sf2a.conf..289F Altcode: 2004sf2a.confE.311K
RR Tel, like other symbiotic miras, is a binary containing a giant,
which is a mira variable, and a compact component. According
to present day ideas, the latter is a white dwarf, accreting from
the mira wind. The wind contains dust; during "obscuration events"
absorption due to this dust increases temporarily. At present we are
comparing relative fluxes of optical Fe II emission lines at two dates,
of which one was during an obscuration event and the other not during
such an event, in order to obtain information on the changes in the
distribution of dust between the two dates and the physics involved.
---------------------------------------------------------
Title: Wavelet Phase Coherence Analysis: Application to a Quiet-Sun
Magnetic Element
Authors: Bloomfield, D. Shaun; McAteer, R. T. James; Lites, Bruce W.;
Judge, Philip G.; Mathioudakis, Mihalis; Keenan, Francis P.
2004ApJ...617..623B Altcode:
A new application of wavelet analysis is presented that utilizes
the inherent phase information residing within the complex Morlet
transform. The technique is applied to a weak solar magnetic network
region, and the temporal variation of phase difference between TRACE
1700 Å and SOHO/SUMER C II 1037 Å intensities is shown. We present,
for the first time in an astrophysical setting, the application of
wavelet phase coherence, including a comparison between two methods
of testing real wavelet phase coherence against that of noise. The
example highlights the advantage of wavelet analysis over more
classical techniques, such as Fourier analysis, and the effectiveness
of the former to identify wave packets of similar frequencies but
with differing phase relations is emphasized. Using cotemporal,
ground-based Advanced Stokes Polarimeter measurements, changes in the
observed phase differences are shown to result from alterations in
the magnetic topology.
---------------------------------------------------------
Title: Current Status of the SuperWASP Project
Authors: Clarkson, W. I.; Christian, D. C.; Collier-Cameron, A.;
Evans, N.; Fitzsimmons, A.; Haswell, C. A.; Hellier, C.; Hodgkin,
S. T.; Horne, K. D.; Kane, S. R.; Keenan, F. P.; Lister, T. A.; Norton,
A. J.; Pollacco, D. L.; Ryans, R.; Skillen, I.; Street, R. A.; West,
R. G.; Wheatley, P. J.
2004AAS...20517101C Altcode: 2005BAAS...37..375C
We present the current status of the SuperWASP project, an ultra-wide
angle search for exoplanetary transits. Each instrument consists of
up to eight cameras backed by high-quality passively-cooled CCDs,
to photometrically survey large numbers of stars in the magnitude
range 7-15. Each camera covers a largely distinct 7.8x7.8-degree
field of view, as a result of which roughly 25,000 stars brighter
than 13th magnitude are surveyed per field per camera for exoplanet
transit events. Located on La Palma, the SuperWASP-I instrument
has been observing the Northern Hemisphere with five cameras since
its April 2004 inauguration. The resulting dataset provides an
excellent opportunity to evaluate hardware and software performance,
to optimise observing efficiency and inform the construction of
the Southern-hemisphere SuperWASP-II instrument in 2005. <P />The
collaboration has developed a custom-built reduction pipeline and aims
to achive better than 1% photometric precision. Roughly four genuine
transiting exoplanetary systems per field per camera will be detected
through repeat transit events over the interval in which these systems
are visible, though perhaps ten times this number of false-positives
will also be observed. By monitoring a large number of fields over its
lifetime, SuperWASP will provide ephemerides for roughly 10<SUP>4</SUP>
systems exhibiting candidate exoplanet transits. These first-alarm
ephemerides will be used to perform incremental followup observations
of the candidates, separating out the false-positives and constraining
the properties of the true exoplanets. The resulting planet harvest
will increase the known exoplanet population by roughly an order of
magnitude. The pipeline will also produce well-sampled lightcurves for
all unblended objects in each field, providing a rich photometric
dataset to pursue the secondary science goals of the project,
including detection of optical transients and detailed studies of
stellar variability at the 1% level. <P />SuperWASP is a consortium
of Queen's University Belfast, The University of Cambridge, the Isaac
Newton Group of Telescopes, Keele University, Leicester University,
the Open University and St Andrews University.
---------------------------------------------------------
Title: Radiative rates for E1, E2, M1 and M2 transitions in Fe X
Authors: Aggarwal, K. M.; Keenan, F. P.
2004A&A...427..763A Altcode:
Energies of the 54 levels belonging to the
(1s<SUP>2</SUP>2s<SUP>2</SUP>2p<SUP>6</SUP>)
3s<SUP>2</SUP>3p<SUP>5</SUP>, 3s3p<SUP>6</SUP>,
3s<SUP>2</SUP>3p<SUP>4</SUP>3d and 3s3p<SUP>5</SUP>3d configurations
of Fe X have been calculated using the GRASP code of Dyall et
al. (\cite{Dyall89}). Additionally, radiative rates, oscillator
strengths, and line strengths are calculated for all electric dipole
(E1), magnetic dipole (M1), electric quadrupole (E2), and magnetic
quadrupole (M2) transitions among these levels. Comparisons are
made with results available in the literature, and the accuracy
of the data is assessed. Our energy levels are estimated to be
accurate to better than 3%, whereas results for other parameters are
probably accurate to better than 20%. Additionally, the agreement
between measured and calculated lifetimes is better than 10%. <P
/>Tables 2 and 3 are only available in electronic form at the CDS
via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via
http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/427/763
---------------------------------------------------------
Title: VizieR Online Data Catalog: Electron impact excitation of Al
XIII (Aggarwal+, 2005)
Authors: Aggarwal, K. M.; Keenan, F. P.; Rose, S. J.
2004yCat..34321151A Altcode:
Energy levels, radiative rates, collision strengths, and effective
collision strengths for all transitions up to and including the n=5
levels of Al XIII have been computed in the jj coupling scheme including
relativistic effects. All partial waves with angular momentum J<=60
have been included, and resonances have been resolved in a fine energy
grid in the threshold region. Collision strengths are tabulated at
energies above thresholds in the range 170.0<=E<=300.0Ryd,
and results for effective collision strengths, obtained after
integrating the collision strengths over a Maxwellian distribution
of electron velocities, are tabulated over a wide temperature range
of 4.4<=logT<SUB>e</SUB><=6.8K. The importance of including
relativistic effects in a calculation is disc ussed in comparison with
the earlier available non-relativistic results. <P />(4 data files).
---------------------------------------------------------
Title: Status of SuperWASP I (La Palma)
Authors: Street, R. A.; Christian, D. J.; Clarkson, W. I.; Collier
Cameron, A.; Evans, N.; Fitzsimmons, A.; Haswell, C. A.; Hellier,
C.; Hodgkin, S. T.; Horne, K.; Kane, S. R.; Keenan, F. P.; Lister,
T. A.; Norton, A. J.; Pollacco, D.; Ryans, R.; Skillen, I.; West,
R. G.; Wheatley, P. J.
2004AN....325..565S Altcode:
SuperWASP is an ultra-wide field (over 300 sq. degrees) photometric
survey project designed to monitor stars between 7 - 15 mag
to high precision and with high cadence over long (≥2 months)
timescales. The primary science goal of this project is the detection
of exoplanetary transits, as well as NEOs and optical transients. The
resulting photometric catalogue will be made public via a web-based
interface. The SuperWASP instrument consists of an array of cameras
each with a 7.8<SUP>°</SUP> × 7.8<SUP>°</SUP> field of view,
guided by a robotic fork mount and sited in a fibreglass enclosure
at the Observatorio de Roque de los Muchachos (ORM), La Palma, Canary
Islands. In this progress report, we describe the specifications of the
instrument, its semi-automated operation and pipeline data reduction.
---------------------------------------------------------
Title: Enhancement of Optically Thick to Thin Line Intensities in
Solar and Stellar Coronal Plasmas through Radiative Transfer Effects:
An Angularly Resolved Study
Authors: Kerr, F. M.; Rose, S. J.; Wark, J. S.; Keenan, F. P.
2004ApJ...613L.181K Altcode:
An analysis of radiative transfer effects present in the Fe XV
ion stage of solar and stellar coronal plasmas provides a general
explanation of line radiation intensity enhancement above the optically
thin limit. Full linearization radiation transfer is compared with
the escape factor method and found to be in good agreement at the
lower column densities. An angular study of the enhancement shows that
symmetry factors are of great importance. This gives a possible reason
for the indeterminate status of opacity in relation to coronal lines
of distant stellar sources, where only emission integrated across the
whole surface is detected.
---------------------------------------------------------
Title: A Detailed Study of Opacity in the Upper Atmosphere of
Proxima Centauri
Authors: Christian, D. J.; Mathioudakis, M.; Bloomfield, D. S.;
Dupuis, J.; Keenan, F. P.
2004ApJ...612.1140C Altcode:
We present far-UV and UV spectroscopic observations of Proxima Centauri
obtained as part of our continued investigation into the optically
thin approximation assumed for the transition regions of late-type
stars. Significant opacity is found in the C III lines during both
the quiescent and flaring states of Proxima Cen, with up to 70% of the
expected flux being lost in the latter. Our findings cast some doubt
on the suitability of the C III λ977 line for estimating the electron
density in stellar atmospheres. However, the opacity has no significant
effect on the observed line widths. We calculate optical depths for
homogeneous and inhomogeneous geometries and estimate an electron
density of 6×10<SUP>10</SUP> cm<SUP>-3</SUP> for the transition region
using the O IV line ratios at 1400 Å. The combination of electron
density and optical depth indicates path lengths as low as ~10 km,
which are in excellent agreement with estimates of the small-scale
structure seen in the solar transition region.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Fe XIII effective collision
strengths (Aggarwal+, 2005)
Authors: Aggarwal, K. M.; Keenan, F. P.
2004yCat..34291117A Altcode:
Effective collision strengths for transitions
among the lowest 97 fine-structure levels belonging
to the (1s<SUP>2</SUP>2s<SUP>2</SUP>2p<SUP>6</SUP>)
3s<SUP>2</SUP>3p<SUP>2</SUP>, 3s3p<SUP>3</SUP>, 3s<SUP>2</SUP>3p3d,
3p<SUP>4</SUP>, 3s3p<SUP>2</SUP>3d and 3s<SUP>2</SUP>3d<SUP>2</SUP>
configurations of Fe XIII have been calculated using the fully
relativistic Dirac Atomic R-matrix Code (DARC) of Norrington &
Grant (2004, Comput. Phys. Commun. - in prep.). Resonances have been
resolved in the threshold region, and results are reported over a wide
electron temperature range up to log T<SUB>e</SUB>=6.8K. Comparisons are
made with the earlier available R-matrix results of Gupta & Tayal
(1998ApJ...506..464G), and the accuracy of the data is assessed. <P
/>(4 data files).
---------------------------------------------------------
Title: High-resolution spectroscopic observations of B-type stars
from the Edinburgh-Cape Survey - III. Completion of a magnitude
range limited survey
Authors: Lynn, B. B.; Keenan, F. P.; Dufton, P. L.; Kilkenny, D.;
Rolleston, W. R. J.; Smoker, J. V.; Ryans, R. S. I.; Hambly, N.;
McGillivray, H. T.; O'Donoghue, D.
2004MNRAS.353..633L Altcode: 2004MNRAS.tmp..271L
High spectral resolution (R~ 40000) and signal-to-noise ratio
observations of five high Galactic latitude early-type stars taken from
the Edinburgh-Cape (EC) Faint Blue Object Survey are presented. These
were required to complete a magnitude range-limited survey of young
B-type objects with 11 < V < 15. Of the five stars, four were
rejected on the grounds that they are either subluminous (subdwarf or
horizontal branch), were part of a binary system or possessed colours
later than the (U-B) =-0.5 cut-off employed. The remaining star in the
data set, EC 19596-5356, is found to exhibit normal young B-type stellar
properties. A kinematic analysis reveals that an origin in the Galactic
disc appears likely for all the stars in the sample. Some statistics
are drawn about the number density of young stars in the Galactic halo.
---------------------------------------------------------
Title: Dirac-Fock energy levels and transition probabilities for
oxygen-like Fe XIX
Authors: Jonauskas, V.; Keenan, F. P.; Foord, M. E.; Heeter, R. F.;
Rose, S. J.; Ferland, G. J.; Kisielius, R.; van Hoof, P. A. M.;
Norrington, P. H.
2004A&A...424..363J Altcode:
Multiconfigurational Dirac-Fock calculations are reported
for 656 energy levels and the 214 840 electric dipole (E1),
electric quadrupole (E2) and magnetic dipole (M1) transition
probabilities in oxygen-like Fe XIX. The spectroscopic notations
as well as the total transition probabilities from each energy
level are provided. Good agreement is found with data compiled by
NIST. <P />Tables \ref{EnLevels} and \ref{RateLevels} are only
available in electronic form at http://www.edpsciences.org <P
/>Tables 6 to 8 are only available in electronic form at the CDS
via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via
http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/424/363
---------------------------------------------------------
Title: VizieR Online Data Catalog: Fe XIX transition probabilities
(Jonauskas+, 2004)
Authors: Jonauskas, V.; Keenan, F. P.; Foord, M. E.; Heeter, R. F.;
Rose, S. J.; Ferland, G. J.; Kisielius, R.; van Hoof, P. A. M.;
Norrington, P. H.
2004yCat..34240363J Altcode:
Energy levels and the corresponding transition probabilities as
well oscillator strengths and line strengths for allowed (E1)
and forbidden (E2, M1) transitions among the lowest 656 levels of
oxygen-like Fe XIX are presented. Calculations were performed using
the multiconfigurational Dirac-Fock GRASP code. <P />(3 data files).
---------------------------------------------------------
Title: CaII K interstellar observations towards early-type disc and
halo stars - distances to intermediate- and high-velocity clouds
Authors: Smoker, J. V.; Lynn, B. B.; Rolleston, W. R. J.; Kay,
H. R. M.; Bajaja, E.; Poppel, W. G. L.; Keenan, F. P.; Kalberla,
P. M. W.; Mooney, C. J.; Dufton, P. L.; Ryans, R. S. I.
2004MNRAS.352.1279S Altcode: 2004MNRAS.tmp..169S; 2004astro.ph..6038S
We compare existing high spectral resolution (R=λ/Δλ~ 40000) CaII K
observations (λ<SUB>air</SUB>= 3933.66 Å) towards 88 mainly B-type
stars, and new observations taken using the Intermediate dispersion
Spectrograph and Imaging System (ISIS) on the William Herschel
Telescope at R~ 10000 towards three stars taken from the Palomar-Green
Survey, with 21-cm HI emission-line profiles, in order to search
for optical absorption towards known intermediate- and high-velocity
cloud complexes. Given certain assumptions, limits to the gas phase
abundance of CaII are estimated for the cloud components. We use the
data to derive the following distances from the Galactic plane (z). (i)
Tentative lower z-height limits of 2800 and 4100 pc towards complex C
using lack of absorption in the spectra of HD341617 and PG0855+294,
respectively. (ii) A weak lower z-height of 1400 pc towards complex
WA-WB using lack of absorption in EC09470-1433 and a weak lower limit
of 2470 pc using lack of absorption in EC09452-1403. (iii) An upper
z-height of 2470 pc towards a southern intermediate-velocity cloud
(IVC) with v<SUB>LSR</SUB>=-55 km s<SUP>-1</SUP> using PG2351+198. (iv)
Detection of a possible IVC in CaII absorption at v<SUB>LSR</SUB>=+52
km s<SUP>-1</SUP> using EC20104-2944. No associated HI in emission
is detected. At this position, normal Galactic rotation predicts
velocities of up to ~+25 km s<SUP>-1</SUP>. The detection puts an
upper z-height of 1860 pc to the cloud. (v) Tentative HI and CaII K
detections towards an IVC at ~+70 km s<SUP>-1</SUP> in the direction
of high-velocity cloud (HVC) complex WE, sightline EC06387-8045,
indicating that the IVC may be at a z-height lower than 1770 pc. (vi)
Detection of CaII K absorption in the spectrum of PG0855+294 in the
direction of IV20, indicating that this IVC has a z-height smaller than
4100 pc. (vii) A weak lower z-height of 4300 pc towards a small HVC
with v<SUB>LSR</SUB>=+115 km s<SUP>-1</SUP> at l, b= 200°, + 52°,
using lack of absorption in the CaII K spectrum of PG0955+291.
---------------------------------------------------------
Title: VizieR Online Data Catalog: FeX E1, E2, M1 and M2 transitions
(Aggarwal+, 2004)
Authors: Aggarwal, K. M.; Keenan, F. P.
2004yCat..34270763A Altcode:
Energies of the 54 levels belonging to the
(1s<SUP>2</SUP>2s23p<SUP>5</SUP>, 3s3p<SUP>6</SUP>,
3s<SUP>2</SUP>3p<SUP>4</SUP>3d and 3s3p<SUP>5</SUP>3d configurations of
FeX have been calculated using the GRASP code of Dyall et al. (1989,
Comput. Phys. Commun, 55, 424). Additionally, radiative rates,
oscillator strengths, and line strengths are calculated for all
electric dipole (E1), magnetic dipole (M1), electric quadrupole (E2),
and magnetic quadrupole (M2) transitions among these levels. Comparisons
are made with results available in the literature, and the accuracy of
the data is assessed. Our energy levels are estimated to be accurate
to better than 3%, whereas results for other parameters are probably
accurate to better than 20%. Additionally, the agreement between
measured and calculated lifetimes is better than 10%. <P />(4 data
files).
---------------------------------------------------------
Title: Erratum: “Propagating Waves and Magnetohydrodynamic
Mode Coupling in the Quiet-Sun Network” (<A
href="/abs/2004ApJ...604..936B">ApJ, 604, 936 [2004]</A>)
Authors: Bloomfield, D. Shaun; McAteer, R. T. James; Mathioudakis,
Mihalis; Williams, David R.; Keenan, Francis P.
2004ApJ...609..465B Altcode:
Proof corrections were not carried correctly to the
final printed version of this paper, which resulted
in an extra set of overbars appearing in both terms
of the denominator of equation (3). The correct form of this equation
is:C(Δt,ν)=(Σ[P<SUB>λ<SUB>1</SUB></SUB>(t,ν)-P<SUB>λ<SUB>1</SUB></SUB>(t,ν)][P<SUB>λ<SUB>2</SUB></SUB>(t+Δt,ν)-P<SUB>λ<SUB>2</SUB></SUB>(t+Δt,ν)])/(sqrt(Σ[P<SUB>λ<SUB>1</SUB></SUB>(t,ν)-P<SUB>λ<SUB>1</SUB></SUB>(t,ν)]<SUP>2</SUP>Σ[P<SUB>λ<SUB>2</SUB></SUB>(t,ν)-P<SUB>λ<SUB>2</SUB></SUB>(t,ν)]<SUP>2</SUP>)).
(3)As noted in footnote 3, this correlation equation was stated
incorrectly in our previous paper (eq. [4] in R. T. J. McAteer et al.,
<A href="/abs/2004ApJ...604..936B">ApJ, 604, 936 [2004]</A>). However,
the correct form of equation (3), now given here, was used for the
analysis in both papers. <P />The press sincerely regrets this error.
---------------------------------------------------------
Title: High-resolution spectroscopy of globular cluster
post-Asymptotic Giant Branch stars
Authors: Mooney, C. J.; Rolleston, W. R. J.; Keenan, F. P.; Dufton,
P. L.; Smoker, J. V.; Ryans, R. S. I.; Aller, L. H.; Trundle, C.
2004A&A...419.1123M Altcode:
We present model atmosphere analyses of high resolution Keck and
VLT optical spectra for three evolved stars in globular clusters,
viz. ZNG-1 in M 10, ZNG-1 in M 15 and ZNG-1 in NGC 6712. The derived
atmospheric parameters and chemical compositions confirm the programme
stars to be in the post-Asymptotic Giant Branch (post-AGB) evolutionary
phase. Differential abundance analyses reveal CNO abundance patterns
in M 10 ZNG-1, and possibly M 15 ZNG-1, which suggest that both
objects may have evolved off the AGB before the third dredge-up
occurred. The abundance pattern of these stars is similar to the
third class of optically, bright post-AGB objects discussed by van
Winckel (\cite{van97}). Furthermore, M 10 ZNG-1 exhibits a large
C underabundance (with \bigtriangleup[C/O] ∼ -1.6 dex), typical
of other hot post-AGB objects. Differential \bigtriangleup[α/Fe]
abundance ratios in both M 10 ZNG-1 and NGC 6712 ZNG-1 are found to
be approximately 0.0 dex, with the Fe abundance of the former being
in disagreement with the cluster metallicity of M 10. Given that
the Fe absorption features in both M 10 ZNG-1 and NGC 6712 ZNG-1
are well observed and reliably modelled, we believe that these
differential Fe abundance estimates to be secure. However, our Fe
abundance is difficult to explain in terms of previous evolutionary
processes that occur on both the Horizontal Branch and the AGB. <P
/>Equivalent width data table is only available in electronic form
at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)
or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/419/1123
---------------------------------------------------------
Title: Radiative rates for transitions in Fe XVII
Authors: Aggarwal, K. M.; Keenan, F. P.; Kisielius, R.
2004A&A...420..783A Altcode:
Energies of the lowest 157 levels belonging to the (1s<SUP>2</SUP>)
2s<SUP>2</SUP>2p<SUP>6</SUP>, 2s<SUP>2</SUP>2p<SUP>5</SUP>3ℓ,
2s<SUP>2</SUP>2p<SUP>5</SUP>4ℓ, 2s<SUP>2</SUP>2p<SUP>5</SUP>5ℓ,
2s2p<SUP>6</SUP>3ℓ, 2s2p<SUP>6</SUP>4ℓ and 2s2p<SUP>6</SUP>5ℓ
configurations of Fe XVII have been calculated using the GRASP code
of Dyall et al. (\cite{Dya89}). Additionally, radiative rates,
oscillator strengths, and line strengths are calculated for all
electric dipole (E1), magnetic dipole (M1), electric quadrupole
(E2), and magnetic quadrupole (M2) transitions among these
levels. Comparisons are made with the results already available
in the literature, and the accuracy of the data is assessed. Our
energy levels are expected to be accurate to better than 1%, whereas
results for other parameters are probably accurate to better than
20%. <P />Tables 2-5 are only available in electronic form at the
CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via
http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/420/783
---------------------------------------------------------
Title: VizieR Online Data Catalog: Electron impact excitation of Fe
XVII (Aggarwal+, 2004)
Authors: Aggarwal, K. M.; Keenan, F. P.; Kisielius, R.
2004yCat..34200783A Altcode:
Energies of the lowest 157 levels belonging to the (1s<SUP>2</SUP>)
2s <SUP>2</SUP>2p<SUP>6</SUP>, 2s <SUP>2</SUP>2p <SUP>5</SUP>3l,
2s <SUP>2</SUP>2p <SUP>5</SUP>4l, 2s <SUP>2</SUP>2p <SUP>5</SUP>5l,
2s2p <SUP>6</SUP>3l, 2s2p <SUP>6</SUP>4l and 2s2p <SUP>6</SUP>5l
configurations of Fe XVII have been calculated using the GRASP code of
Dyall et al. (1989, Comput. Phys. Commun., 55, 424). Additionally,
radiative rates, oscillator strengths, and line strengths are
calculated for all electric dipole (E1), magnetic dipole (M1), electric
quadrupole (E2), and magnetic quadrupole (M2) transitions among these
levels. Comparisons are made with the results already available in
the literature, and the accuracy of the data is assessed. Our energy
levels are expected to be accurate to better than 1%, whereas results
for other parameters are probably accurate to better than 20%. <P />(6
data files).
---------------------------------------------------------
Title: Plasma Diagnostics of Active Region Evolution and Implications
for Coronal Heating
Authors: Milligan, R. O.; Gallagher, P. T.; Mathioudakis, M.;
Bloomfield, D. S.; Keenan, F. P.
2004AAS...204.9803M Altcode: 2004BAAS...36..984M
The decaying solar active region NOAA 10103 was observed during 2002
September 10--14 using the Coronal Diagnostic Spectrometer (CDS) onboard
the Solar and Heliospheric Observatory (SOHO). Electron density maps
were created using the Si X (356Å/347Å) ratio, which show densities
of ∼10<SUP>10</SUP>cm<SUP>-3</SUP> in the active region core, and
∼7x10<SUP>8</SUP>cm<SUP>-3</SUP> in the region boundaries. Over
the five days of observations, the average electron density fell by
approximately a factor of two. Temperature maps were created using
the Fe XVI (335.4Å)/Fe XIV (334.2Å) ratio, which show electron
temperatures of ∼2.2x10<SUP>6</SUP>K in the active region core,
and ∼2.0x10<SUP>6</SUP>K in the region boundaries. Similarly to the
electron density, the average electron temperature decreased over the
five days, but by only ∼3%. The radiative and conductive losses, and
resultant heating rate, were then calculated and compared to the total
unsigned magnetic flux (Φ <SUB>tot</SUB> = ∫ dA |B<SUB>z|</SUB>)
from Michelson Doppler Interferometer (MDI) magnetograms. Losses due to
radiation were found to exceed conductive losses by a factor of ten. As
the region decayed, the heating rate decreased by close to an order of
magnitiude between the first and last day of observations. In line with
several coronal heating theories, a power-law relationship of the form
P<SUB>tot} ∼Φ <SUB>{tot</SUB><SUP>0.95±0.07</SUP></SUB> was found
between the heating rate and the unsigned magnetic flux. This result
provides further observational evidence for wave rather than nanoflare
heating of solar active regions. <P />Ryan Milligan would like to
thank the Solar Physics Division for being awarded an SPD Studentship.
---------------------------------------------------------
Title: Early-type stars in the Galactic halo from the Palomar-Green
survey-III. Completion of a magnitude range limited sample
Authors: Lynn, B. B.; Keenan, F. P.; Dufton, P. L.; Saffer, R. A.;
Rolleston, W. R. J.; Smoker, J. V.
2004MNRAS.349..821L Altcode:
High-resolution (R~ 40000) echelle spectroscopic observations
of 13 high-latitude early-type stars are presented. These stars
comprise the final part of a complete magnitude range limited sample
based on low-resolution spectroscopy of targets drawn from the
Palomar-Green survey. The magnitude range under consideration is
13 <=B<SUB>PG</SUB><= 14.6, corresponding to an approximate
distance limit for main-sequence B-type objects of 5 <=d<=
40 kpc. Three stars are found to be apparently normal, young stars,
based on their positions on the (T<SUB>eff</SUB>, log g) diagram,
normal abundance patterns and relatively large projected rotational
velocities. A further star, PG 1209+263, was found to belong to the
chemically peculiar (CP) silicon star class of objects. The remainder
are evolved subluminous stars lying on post-horizontal branch (post-HB)
tracks, with the exception of PG 2120+062, which appears to be in a
post-asymptotic giant branch evolutionary stage. For the young stars
in the sample, we have derived distance and age estimates through
comparison of the atmospheric parameters with recent theoretical
evolutionary models. We discuss formation scenarios by comparing
times-of-flight and evolutionary time-scales. It is found that all
stars could have formed in the Galactic disc and been ejected from
there soon after their birth, with the exception of PG 1209+263. The
adopted proper motion is found to be a crucial factor in the kinematical
analysis. We also present some number densities for young B-type halo
stars, which indicate that they are extremely scarce objects.
---------------------------------------------------------
Title: Propagating Waves and Magnetohydrodynamic Mode Coupling in
the Quiet-Sun Network
Authors: Bloomfield, D. Shaun; McAteer, R. T. James; Mathioudakis,
Mihalis; Williams, David R.; Keenan, Francis P.
2004ApJ...604..936B Altcode:
High-cadence multiwavelength optical observations were taken with the
Dunn Solar Telescope at the National Solar Observatory, Sacramento Peak,
accompanied by Advanced Stokes Polarimeter vector magnetograms. A total
of 11 network bright points (NBPs) have been studied at different
atmospheric heights using images taken in wave bands centered on
Mg I b<SUB>1</SUB> - 0.4 Å, Hα, and Ca II K<SUB>3</SUB>. Wavelet
analysis was used to study wave packets and identify traveling
magnetohydrodynamic waves. Wave speeds were estimated through the
temporal cross-correlation of signals, in selected frequency bands
of wavelet power, in each wavelength. Four mode-coupling cases were
identified, one in each of four of the NBPs, and the variation of the
associated Fourier power with height was studied. Three of the detected
mode-coupling, transverse-mode frequencies were observed in the 1.2-1.6
mHz range (mean NBP apparent flux density magnitudes over 99-111 Mx
cm<SUP>-2</SUP>), with the final case showing 2.0-2.2 mHz (with 142 Mx
cm<SUP>-2</SUP>). Following this, longitudinal-mode frequencies were
detected in the range 2.6-3.2 mHz for three of our cases, with 3.9-4.1
mHz for the remaining case. After mode coupling, two cases displayed a
decrease in longitudinal-mode Fourier power in the higher chromosphere.
---------------------------------------------------------
Title: Electron impact excitation of Fe XIII
Authors: Aggarwal, K. M.; Keenan, F. P.
2004A&A...418..371A Altcode:
Energy levels and radiative rates for transitions
among the lowest 97 fine-structure levels belonging
to the (1s<SUP>2</SUP>2s<SUP>2</SUP>2p<SUP>6</SUP>)
3s<SUP>2</SUP>3p<SUP>2</SUP>, 3s3p<SUP>3</SUP>, 3s<SUP>2</SUP>3p3d,
3p<SUP>4</SUP>, 3s3p<SUP>2</SUP>3d and 3s<SUP>2</SUP>3d<SUP>2</SUP>
configurations of Fe XIII have been calculated using the fully
relativistic GRASP code. Additionally, collision strengths
for transitions among these levels have been computed using
the Dirac Atomic R-matrix Code (DARC) of Norrington & Grant
(\cite{Norrington04}). Radiative rates and oscillator strengths are
tabulated for all allowed transitions among the 97 fine-structure
levels, while collision strengths are reported for some transitions
at a few energies above thresholds. Comparisons are made with the
available results, and the accuracy of the data is assessed. <P
/>Table 2 is only available in electronic form at the CDS via
anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via
http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/418/371
---------------------------------------------------------
Title: Time signatures of impulsively generated coronal fast wave
trains
Authors: Nakariakov, V. M.; Arber, T. D.; Ault, C. E.; Katsiyannis,
A. C.; Williams, D. R.; Keenan, F. P.
2004MNRAS.349..705N Altcode:
Impulsively generated short-period fast magneto-acoustic wave
trains, guided by solar and stellar coronal loops, are numerically
modelled. In the developed stage of the evolution, the wave trains
have a characteristic quasi-periodic signature. The quasi-periodicity
results from the geometrical dispersion of the guided fast modes,
determined by the transverse profile of the loop. A typical feature
of the signature is a tadpole wavelet spectrum: a narrow-spectrum
tail precedes a broad-band head. The instantaneous period of the
oscillations in the wave train decreases gradually with time. The period
and the spectral amplitude evolution are shown to be determined by the
steepness of the transverse density profile and the density contrast
ratio in the loop. The propagating wave trains recently discovered
with the Solar Eclipse Coronal Imaging System (SECIS) instrument are
noted to have similar wavelet spectral features, which strengthens
the interpretation of SECIS results as guided fast wave trains.
---------------------------------------------------------
Title: Improved data for solar flare X-ray spectral analysis
Authors: Phillips, K. J. H.; Rainnie, J. A.; Harra, L. K.; Dubau,
J.; Keenan, F. P.; Peacock, N. J.
2004A&A...416..765P Altcode:
The inclusion of collisional rates for He-like Fe and Ca ions
is discussed with reference to the analysis of solar flare Fe
XXV and Ca XIX line emission, particularly from the Yohkoh Bragg
Crystal Spectrometer (BCS). The new data are a slight improvement
on calculations presently used in the BCS analysis software in that
the discrepancy in the Fe XXV y and z line intensities (observed
larger than predicted) is reduced. Values of electron temperature from
satellite-to-resonance line ratios are slightly reduced (by up to 1 MK)
for a given observed ratio. The new atomic data will be incorporated
in the Yohkoh BCS databases. The data should also be of interest for
the analysis of high-resolution, non-solar spectra expected from the
Constellation-X and Astro-E space missions. A comparison is made of a
tokamak S XV spectrum with a synthetic spectrum using atomic data in the
existing software and the agreement is found to be good, so validating
these data for particularly high-n satellite wavelengths close to the
S XV resonance line. An error in a data file used for analyzing BCS
Fe XXVI spectra is corrected, so permitting analysis of these spectra.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Equivalent widths of 3 post-AGB
(Mooney+, 2004)
Authors: Mooney, C. J.; Rolleston, W. R. J.; Keenan, F. P.; Dufton,
P. L.; Smoker, J. V.; Ryans, R. S. I.; Aller, L. H.; Trundle, C.
2004yCat..34191123M Altcode:
NGC 6712 ZNG-1 was observed on the 4 July 2000 with the 10m Keck I
telescope. M10 ZNG-1 and M15 ZNG-1 were observed during the period 01-03
July 2001 with the 8m VLT KUEYEN telescope. <P />The table presents
absorption line equivalent widths (in m{AA}) for the 3 globular cluster
stars: M10 ZNG-1, M15 ZNG-1 and NGC 6712 ZNG-1. The first column lists
the species, the second the rest wavelength for the line, and columns
3-5 list the equivalent widths (where measurable). Where 2 wavelengths
are given for a single species, the measured line equivalent width is
a blend. <P />(1 data file).
---------------------------------------------------------
Title: Search for 1-10 Hz modulations in coronal emission with SECIS
during the August 11, 1999 eclipse
Authors: Rudawy, P.; Phillips, K. J. H.; Gallagher, P. T.; Williams,
D. R.; Rompolt, B.; Keenan, F. P.
2004A&A...416.1179R Altcode:
Results of the search of the periodic changes of the 530.3 nm line
intensity emitted by selected structures of the solar corona in the
frequency range 1-10 Hz are presented. A set of 12 728 images of the
section of the solar corona extending from near the north pole to
the south-west were taken simultaneously in the 530.3 nm (“green”)
line and white-light with the Solar Eclipse Coronal Imaging System
(SECIS) during the 143-seconds-long totality of the 1999 August
11 solar eclipse observed in Shabla, Bulgaria. The time resolution
of the collected data is better than 0.05 s and the pixel size is
approximately 4 arcsec. Using classical Fourier spectral analysis tools,
we investigated temporal changes of the local 530.3 nm coronal line
brightness in the frequency range 1-10 Hz of thousands of points within
the field of view. The various photometric and instrumental effects
have been extensively considered. We did not find any indisputable,
statistically significant evidence of periodicities in any of the
investigated points (at significance level α=0.05).
---------------------------------------------------------
Title: Relativistic allowed and forbidden transition probabilities
for fluorine-like Fe XVIII
Authors: Jonauskas, V.; Keenan, F. P.; Foord, M. E.; Heeter, R. F.;
Rose, S. J.; van Hoof, P. A. M.; Ferland, G. J.; Aggarwal, K. M.;
Kisielius, R.; Norrington, P. H.
2004A&A...416..383J Altcode:
Energy levels and the corresponding transition probabilities for allowed
and forbidden transitions among the levels of the ground configuration
and first 23 excited configurations of fluorine-like Fe XVIII have been
calculated using the multiconfigurational Dirac-Fock GRASP code. A
total of 379 lowest bound levels of Fe XVIII is presented, and the
energy levels are identified in spectroscopic notations. Transition
probabilities, oscillator strengths and line strengths for
electric dipole (E1), electric quadrupole (E2) and magnetic dipole
(M1) transitions among these 379 levels are also presented. The
calculated energy levels and transition probabilities are compared with
experimental data. <P />Tables 5 to 8 are only available in electronic
form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)
or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/416/383
---------------------------------------------------------
Title: Ultraviolet Oscillations in the Chromosphere of the Quiet Sun
Authors: McAteer, R. T. James; Gallagher, Peter T.; Bloomfield,
D. Shaun; Williams, David R.; Mathioudakis, Mihalis; Keenan, Francis P.
2004ApJ...602..436M Altcode:
Quiet-Sun oscillations in the four Transition Region and Coronal
Explorer (TRACE) ultraviolet passbands centered on 1700, 1600,
1216, and 1550 Å are studied using a wavelet-based technique. Both
network and internetwork regions show oscillations with a variety of
periods and lifetimes in all passbands. The most frequent network
oscillation has a period of 283 s, with a lifetime of 2-3 cycles
in all passbands. These oscillations are discussed in terms of
upwardly propagating magnetohydrodynamic wave models. The most
frequent internetwork oscillation has a period of 252 s, again with
a lifetime of 2-3 cycles, in all passbands. The tendency for these
oscillations to recur in the same position is discussed in terms of
“persistent flashers.” The network contains greater oscillatory
power than the internetwork at periods longer than 300 s in the
low chromosphere. This value is shown to decrease to 250 s in the
high chromosphere. The internetwork also displays a larger number of
short-lifetime, long-period oscillations than the network, especially
in the low chromosphere. Both network and internetwork regions contain
a small number of nonrecurring long-lifetime oscillations.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Electron impact excitation of Fe
XIII (Aggarwal+, 2004)
Authors: Aggarwal, K. M.; Keenan, F. P.
2004yCat..34180371A Altcode:
Energy levels and radiative rates for transitions
among the lowest 97 fine-structure levels belonging
to the (1s<SUP>2</SUP>2s<SUP>2</SUP>2p<SUP>6</SUP>)
3s<SUP>2</SUP>3p<SUP>2</SUP>, 3s3p<SUP>3</SUP>, 3s<SUP>2</SUP>3p3d ,
3p<SUP>4</SUP>, 3s3p<SUP>2</SUP>3d and 3s<SUP>2</SUP>3d<SUP>2</SUP>
configurations of Fe XIII have been calculated using the fully
relativistic GRASP code. Additionally, collision strengths for
transitions among these levels have been computed using the Dirac
Atomic R-matrix Code (DARC) of Norrington & Grant (2004,
Comput. Phys. Commun., in prep.). Radiative rates and oscillator
strengths are tabulated for all allowed transitions among the 97
fine-structure levels, while collision strengths are reported for some
transitions at a few energies above thresholds. Comparisons are made
with the available results, and the accuracy of the data is assessed. <P
/>(5 data files).
---------------------------------------------------------
Title: A Comparison of Theoretical Si <Emphasis
Type="SmallCaps">VIII</Emphasis> Emission Line Ratios with
Observations from Serts
Authors: Keenan, F. P.; Katsiyannis, A. C.; Ramsbottom, C. A.; Bell,
K. L.; Brosius, J. W.; Davila, J. M.; Thomas, R. J.
2004SoPh..219..251K Altcode:
Recent R-matrix calculations of electron impact excitation rates in
N-like Si VIII are used to derive theoretical emission line intensity
ratios involving 2s<SUP>2</SUP>2p<SUP>3</SUP>-2s2p<SUP>4</SUP>
transitions in the 216-320 Å wavelength range. A comparison of these
with an extensive dataset of solar active region, quiet-Sun, sub-flare
and off-limb observations, obtained during rocket flights of the Solar
EUV Research Telescope and Spectrograph (SERTS), indicates that the
ratio R<SUB>1</SUB>= I(216.94 Å)/I(319.84 Å) may provide a usable
electron density diagnostic for coronal plasmas. The ratio involves
two lines of comparable intensity, and varies by a factor of about
5 over the useful density range of 10<SUP>8</SUP>-10<SUP>11</SUP>
cm<SUP>−3</SUP>. However R<SUB>2</SUB>= I(276.85 Å)/I(319.84 Å)
and R<SUB>3</SUB>=I(277.05 Å)/I(319.84 Å) show very poor agreement
between theory and observation, due to the severe blending of the 276.85
and 277.05 Å lines with Si VII and Mg VII transitions, respectively,
making the ratios unsuitable as density diagnostics. The 314.35 Å
feature of Si VIII also appears to be blended, with the other species
contributing around 20% to the total line flux.
---------------------------------------------------------
Title: Extreme-Ultraviolet Emission Lines of S X in Solar Flare and
Active Region Spectra
Authors: Keenan, F. P.; Katsiyannis, A. C.; Widing, K. G.
2004ApJ...601..565K Altcode:
R-matrix calculations of electron impact excitation rates in N-like S X
are used to derive theoretical emission-line intensity ratios involving
2s<SUP>2</SUP>2p<SUP>3</SUP>-2s2p<SUP>4</SUP> transitions in the 189-265
Å wavelength range. A comparison of these with observational data
for solar flares and active regions, obtained with the Naval Research
Laboratory's S082A spectrograph on board Skylab and the Solar EUV
Rocket Telescope and Spectrograph, reveals that many of the S X lines
in the spectra are badly blended with emission features from other
species. However, the intensity ratios I(228.70Å)/I(264.24Å) and
I(228.70Å)/I(259.49Å) are found to provide useful electron density
diagnostics for flares, although the latter cannot be employed for
active regions, because of blending of the 259.49 Å line with an
unidentified transition in these solar features.
---------------------------------------------------------
Title: Oscillatory Signatures above Quiet Sun Magnetic Elements
Authors: Bloomfield, D. S.; McAteer, R. T. J.; Lites, B. W.; Judge,
P. G.; Mathioudakis, M.; Keenan, F. P.
2004ESASP.547...51B Altcode: 2004soho...13...51B
A new application of wavelet analysis is presented. The data used are
part of Joint Observing Proposal 72 between SoHO and TRACE, obtained on
1998 May 16 with accompanying groundbased data taken with the Dunn Solar
Telescope at Sacramento Peak, New Mexico. A weak magnetic network region
is studied and the temporal variation of phase difference between TRACE
1700 Å and SoHO/SUMER C II intensities is shown. The example clearly
highlights the advantages of wavelet analysis over more classical
techniques such as Fourier analysis, where the effectiveness of the
technique to identify wavepackets with differing phase difference
relations is emphasised.
---------------------------------------------------------
Title: An Automated Wavelet Analysis Approach to TRACE Quiet Sun
Oscillations
Authors: McAteer, R. T. J.; Gallagher, P. T.; Williams, D. R. Williams
D. R.; Bloomfield, D. S.; Mathioudakis, M.; Keenan, F. P.
2004ESASP.547..139M Altcode: 2004soho...13..139M
An automated wavelet analysis approach to TRACE UV quiet Sun datasets
is discussed. Periodicity and lifetime of oscillations present in the
network and internetwork are compared and contrasted. This provides
a means of extending previous Fourier results into the time-localised
domain. The longest lifetime oscillations occur around the acoustic band
and the network tends to dominate over the internetwork at periods 4
mins. However, it is shown that the internetwork can dominate over the
network at long periods (7 - 20 mins), but only for short lifetimes
( 3 complete oscillations). These results are discussed in terms of
chromospheric heating theories.
---------------------------------------------------------
Title: Effect of Dust Obscuration on the Emission Lines of RR Tel
Authors: Kotnik-Karuza, D.; Friedjung, M.; Exter, K.; Keenan, F. P.;
Pollacco, D. L.
2004IAUS..219..888K Altcode: 2003IAUS..219E..76K
We continue our investigation of the emitting region of the symbiotic
nova RR Telescopii by analyzing the emission line fluxes from high
quality AAT optical spectra obtained in 2000 and comparing these
with previous observations. The fading found in the recent spectra
suggests increased circumstellar dust absorption in the stellar wind
of the mira. Differing absorption of lines formed in different regions
provides information on the geometry of the dust regions. The radii
of the Fe II emitting region obtained by the SAC method have been
corrected for the dust obscuration.
---------------------------------------------------------
Title: Initial Results from SECIS Observations of the 2001 Eclipse
Authors: Katsiyannis, A. C.; McAteer, R. T. J.; Williams, D. R.;
Gallagher, P. T.; Keenan, F. P.
2004ESASP.547..459K Altcode: 2004astro.ph.11722K; 2004soho...13..459K
SECIS observations of the June 2001 total solar eclipse were taken
using an Fe XIV 5303 Å filter. Existing software was modified and new
code was developed for the reduction and analysis of these data. The
observations, data reduction, study of the atmospheric and instrumental
effects, together with some preliminary results are discussed. Emphasis
is given to the techniques used for the automated alignment of the 8000
images, the application of the `a Trous algorithm for noise filtering
and the software developed for the automated detection of intensity
oscillations using wavelet analysis. In line with findings from the
1999 SECIS total eclipse observations, intensity oscillations with
periods in the range of 20-30 s, both inside and just outside coronal
loops are also presented.
---------------------------------------------------------
Title: CaII K interstellar observations towards early-type disc and
halo stars
Authors: Smoker, J. V.; Rolleston, W. R. J.; Kay, H. R. M.; Kilkenny,
D.; Morras, R.; Arnal, M.; Keenan, F. P.; Mooney, C. J.; Dufton,
P. L.; Ryans, R. S. I.; Hambly, N. C.; O'Donoghue, D.; McGillivray, H.
2003MNRAS.346..119S Altcode:
We present high-resolution (R=λ/Δλ~ 40000) CaII K interstellar
observations (λ<SUB>air</SUB>= 3933.66Å) towards 88 mainly B-type
stars, of which 74 are taken from the Edinburgh-Cape or Palomar-Green
surveys, and 81 have |b| > 25°. The majority of the data come from
previously existing spectroscopy, although also included are 18 new
observations of stars with echelle spectra taken with UVES on the Very
Large Telescope UT2 (Kueyen). Some 49 of the sample stars have distance
estimates above the Galactic plane (|z|) >= 1 kpc, and are thus
good probes of the halo interstellar medium. Of the 362 interstellar
Ca K components that we detect, 75 (21 per cent) have absolute values
of their LSR velocity values exceeding 40 km s<SUP>-1</SUP>. In terms
of the deviation velocity for the sightlines with distance estimates,
46/273 (17 per cent) of components have velocity values exceeding
those predicted by standard Galactic rotation by more than 40 km
s<SUP>-1</SUP>. Combining this data set with previous observations,
we find that the median value of the reduced equivalent width (REW)
of stars with |z| >= 1 kpc (EW×sin|b|) is ~115 mÅ (n= 80),
similar to that observed in extragalactic sightlines by Bowen. Using
data of all z distances, the REW at infinity is found to be ~130 mÅ,
with the scaleheight (l) of the CaII K column density distribution
being ~800 pc (n= 196) and reduced column density at infinity of
log[N(CaII K) cm<SUP>-2</SUP>]~12.24. This implies that ~30 per cent
of CaII K absorption occurs at distances exceeding ~1 kpc. For nine
sightlines with distance exceeding 1 kpc and with a companion object
within 5°, we find that all but two have values of CaII reduced
equivalent width the same to within ~20 per cent, when the REW of
the nearest object is extrapolated to the distance of the further
of the pair, and assuming l= 800 pc. For 29 of our sightlines with
|z| >= 1 kpc and a HI detection from the Leiden-Dwingeloo survey
(beamsize of 0.5°), we find log(N(CaII K)/N(HI)) ranging from -7.4
to -8.4. Values of the CaII K abundance relative to neutral hydrogen
(log[N(CaIIK)cm<SUP>-2</SUP>]-log[N(HI)cm<SUP>-2</SUP>]) are found
to be more than ~0.5dex higher in stars with distances exceeding
~100 pc, when compared with the (log[N(CaII K) cm<SUP>-2</SUP>]-
log[N(H<SUB>tot</SUB>) cm<SUP>-2</SUP>]) values found in nearby
sightlines such as those in Wakker & Mathis (2000). Finally, stellar
CaII K equivalent widths of the sample are determined for 26 objects.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Transition probabilities for Fe
XVIII (Jonauskas+, 2004)
Authors: Jonauskas, V.; Keenan, F. P.; Foord, M. E.; Heeter, R. F.;
Rose, S. J.; van Hoof, P. A. M.; Ferland, G. J.; Aggarwal, K. M.;
Kisielius, R.; Norrington, P. H.
2003yCat..34160383J Altcode:
Energy levels and the corresponding transition probabilities as well
oscillator strengths and line strengths for allowed (E1) and forbidden
(E2, M1) transitions among the lowest 379 levels of fluorine-like
Fe XVIII are presented. Calculations were performed using the
multiconfigurational Dirac-Fock GRASP code. <P />(4 data files).
---------------------------------------------------------
Title: Extreme ultraviolet emission lines of ArXIV in solar active
region and flare spectra
Authors: Keenan, F. P.; Katsiyannis, A. C.; Reid, R. H. G.; Pradhan,
A. K.; Zhang, H. L.; Widing, K. G.
2003MNRAS.346...58K Altcode:
New R-matrix calculations of electron impact excitation rates
for transitions among the 2s<SUP>2</SUP>2p, 2s2p<SUP>2</SUP>
and 2p<SUP>3</SUP> levels of ArXIV are presented. These data are
subsequently used to derive the theoretical electron density diagnostic
emission-line intensity ratios R<SUB>1</SUB>=I(187.95 Å)/I(194.41 Å)
and R<SUB>2</SUB>=I(257.40 Å)/I(243.78 Å) for a range of densities
(N<SUB>e</SUB>= 10<SUP>9</SUP>-10<SUP>13</SUP> cm<SUP>-3</SUP>) and
electron temperatures (T<SUB>e</SUB>= 10<SUP>6.3</SUP>-10<SUP>6.7</SUP>
K) appropriate to solar transition region and coronal plasmas. A
comparison of these diagnostics with observational data for solar
active regions and flares, obtained with the Naval Research Laboratory's
S082A spectrograph on board Skylab, reveals that the electron densities
determined from R<SUB>1</SUB> are in good agreement with those estimated
from line ratios in FeXIV or FeXV, which are formed at similar electron
temperatures to ArXIV. However, there are large discrepancies between
densities inferred from the R<SUB>2</SUB> ratio and those from FeXIV or
FeXV, confirming that the ArXIV 243.78- and 257.40-Å lines are badly
blended with FeXV 243.79 Å and FeXIV 257.38 Å, respectively. Hence,
R<SUB>2</SUB> cannot be employed as a density diagnostic, in contrast
to R<SUB>1</SUB>, which does provide reliable N<SUB>e</SUB> estimates.
---------------------------------------------------------
Title: Extreme Ultraviolet Emission Lines of ca xv in Solar and
Laboratory Spectra
Authors: Keenan, F. P.; Aggarwal, K. M.; Katsiyannis, A. C.; Reid,
R. H. G.
2003SoPh..217..225K Altcode:
New R-matrix calculations of electron impact excitation rates in Ca xv
are used to derive theoretical electron density diagnostic emission line
intensity ratios involving 2s<SUP>2</SUP>2p<SUP>2</SUP>-2s2p<SUP>3</SUP>
transitions, specifically R<SUB>1</SUB>=I(208.70 Å)/I(200.98 Å),
R<SUB>2</SUB>=I(181.91 Å)/I(200.98 Å), and R<SUB>3</SUB>=I(215.38
Å)/I(200.98 Å), for a range of electron temperatures
(T<SUB>e</SUB>=10<SUP>6.4</SUP>-10<SUP>6.8</SUP> K) and densities
(N<SUB>e</SUB>=10<SUP>9</SUP>-10<SUP>13</SUP> cm<SUP>−3</SUP>)
appropriate to solar coronal plasmas. Electron densities deduced from
the observed values of R<SUB>1</SUB>, R<SUB>2</SUB>, and R<SUB>3</SUB>
for several solar flares, measured from spectra obtained with the
Naval Research Laboratory's S082A spectrograph on board Skylab, are
found to be consistent. In addition, the derived electron densities
are in excellent agreement with those determined from line ratios
in Ca xvi, which is formed at a similar electron temperature to Ca
xv. These results provide some experimental verification for the
accuracy of the line ratio calculations, and hence the atomic data on
which they are based. A set of eight theoretical Ca xv line ratios
involving 2s<SUP>2</SUP>2p<SUP>2</SUP>-2s2p<SUP>3</SUP> transitions
in the wavelength range ∼ 140-216 Å are also found to be in good
agreement with those measured from spectra of the TEXT tokamak plasma,
for which the electron temperature and density have been independently
determined. This provides additional support for the accuracy of the
theoretical line ratios and atomic data.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Effective collision strengths in
Fe XV (Aggarwal+, 2003)
Authors: Aggarwal, K. M.; Keenan, F. P.; Msezane, A. Z.
2003yCat..34100349A Altcode:
Collision strengths for transitions among the energetically lowest 53
fine-structure levels belonging to the (1s<SUP>2</SUP> 2s<SUP>2</SUP>
2p<SUP>6</SUP>) 3l<SUP>2</SUP>, 3l3l', 3s4l and 3p4s configurations
of Fe XV are computed, over an electron energy range below 160Ryd,
using the Dirac Atomic R-matrix Code (DARC) of Norrington & Grant
(2003, Comput. Phys. Commun., in prep.). Effective collision strengths,
obtained after integrating the collision strengths over a Maxwellian
distribution of electron energies, have also been calculated. These
results of effective collision strengths are tabulated for all 1378
inelastic transitions over a wide temperature range of 10<SUP>5</SUP>
to 10<SUP>7</SUP>K. Comparisons are also made with other R-matrix
calculations and the accuracy of the results is assessed. <P />(3
data files).
---------------------------------------------------------
Title: Effective collision strengths for transitions in Fe XV.
Authors: Aggarwal, K. M.; Keenan, F. P.; Msezane, A. Z.
2003A&A...410..349A Altcode:
Collision strengths for transitions among the energetically
lowest 53 fine-structure levels belonging to the
(1s<SUP>2</SUP>2s<SUP>2</SUP>2p<SUP>6</SUP>) 3{l}<SUP>2</SUP>,
3{l}3{l}<SUP>'</SUP>, 3s4{l} and 3p4s configurations of Fe XV
are computed, over an electron energy range below 160 Ryd, using
the Dirac Atomic R-matrix Code (DARC) of Norrington & Grant
(\cite{Norrington03}). Effective collision strengths, obtained after
integrating the collision strengths over a Maxwellian distribution
of electron energies, have also been calculated. These results of
effective collision strengths are tabulated for all 1378 inelastic
transitions over a wide temperature range of 10<SUP>5</SUP> to
10<SUP>7</SUP> K. Comparisons are also made with other R-matrix
calculations and the accuracy of the results is assessed. <P
/>Table 4 is only available in electronic form at the CDS via
anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via
http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/410/349
---------------------------------------------------------
Title: VizieR Online Data Catalog: Excitation rates for transitions
in Ca XV (Aggarwal+, 2003)
Authors: Aggarwal, K. M.; Keenan, F. P.
2003yCat..34070769A Altcode:
Collision strengths for transitions among the energetically
lowest 46 fine-structure levels belonging to the (1s<SUP>2</SUP>)
2s<SUP>2</SUP>2p<SUP>2</SUP>, 2s2p<SUP>3</SUP>, 2p<SUP>4</SUP>, and
2s<SUP>2</SUP>2p3l configurations of Ca XV are computed, over a wide
electron energy range below 300Ryd, using the Dirac Atomic R-matrix
Code (DARC) of Norrington & Grant (2003, Comput. Phys. Comm., in
preparation). Resonances in the threshold region have been resolved in
a fine energy mesh, and excitation rates are determined over a wide
electron temperature range below 10<SUP>7</SUP>K. The results are
compared with those available in the literature, and the accuracy of
the data is assessed. <P />(2 data files).
---------------------------------------------------------
Title: Inner-shell photoexcitation of FeXV and FeXVI
Authors: Kisielius, R.; Hibbert, A.; Ferland, G. J.; Foord, M. E.;
Rose, S. J.; van Hoof, P. A. M.; Keenan, F. P.
2003MNRAS.344..696K Altcode:
The configuration-interaction method as implemented in the
computer code CIV3 is used to determine energy levels, electric
dipole radiative transition wavelengths, oscillator strengths and
transition probabilities for inner-shell excitation of transitions
in FeXV and FeXVI. Specifically, transitions are considered of the type
1s<SUP>2</SUP>2s<SUP>2</SUP>2p<SUP>6</SUP>3s<SUP>2</SUP>-1s<SUP>2</SUP>2s<SUP>2</SUP>2p<SUP>5</SUP>3l3l'3l”
(l, l' and l”= s, p or d) in FeXV and
1s<SUP>2</SUP>2s<SUP>2</SUP>2p<SUP>6</SUP>3s-1s<SUP>2</SUP>2s<SUP>2</SUP>2p<SUP>5</SUP>3l3l'
(l and l'= s, p or d) in FeXVI, using the relativistic Breit-Pauli
approach. An assessment of the accuracy of the derived atomic data
is performed.
---------------------------------------------------------
Title: Eclipse observations of high-frequency oscillations in active
region coronal loops
Authors: Katsiyannis, A. C.; Williams, D. R.; McAteer, R. T. J.;
Gallagher, P. T.; Keenan, F. P.; Murtagh, F.
2003A&A...406..709K Altcode: 2003astro.ph..5225K
One of the mechanisms proposed for heating the corona above solar active
regions is the damping of magnetohydrodynamic (MHD) waves. Continuing
on previous work, we provide observational evidence for the existence
of high-frequency MHD waves in coronal loops observed during the
August 1999 total solar eclipse. A wavelet analysis is used to identify
twenty 4x4 arcsec<SUP>2</SUP> areas showing intensity oscillations. All
detections lie in the frequency range 0.15-0.25 Hz (7-4 s), last for
at least 3 periods at a confidence level of more than 99% and arise
just outside known coronal loops. This leads us to suggest that they
occur in low emission-measure or different temperature loops associated
with the active region.
---------------------------------------------------------
Title: Excitation rates for transitions in Ca XV
Authors: Aggarwal, K. M.; Keenan, F. P.
2003A&A...407..769A Altcode:
Collision strengths for transitions among the energetically
lowest 46 fine-structure levels belonging to the (1s<SUP>2</SUP>)
2s<SUP>2</SUP>2p<SUP>2</SUP>, 2s2p<SUP>3</SUP>, 2p<SUP>4</SUP>, and
2s<SUP>2</SUP>2p3l configurations of Ca XV are computed, over a wide
electron energy range below 300 Ryd, using the Dirac Atomic R-matrix
Code (DARC) of Norrington & Grant (\cite{Norrington03}). Resonances
in the threshold region have been resolved in a fine energy mesh, and
excitation rates are determined over a wide electron temperature range
below 10<SUP>7</SUP> K. The results are compared with those available
in the literature, and the accuracy of the data is assessed. <P />Table
\ref{tab3} is also (and Table 4 only) available in electronic form
at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)
or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/407/769
---------------------------------------------------------
Title: Emission lines of Na-like ions in spectra obtained with the
Solar EUV Research Telescope and Spectrograph (SERTS)
Authors: Keenan, F. P.; Katsiyannis, A. C.; Brosius, J. W.; Davila,
J. M.; Thomas, R. J.
2003MNRAS.342..513K Altcode:
Theoretical emission-line ratios involving transitions in the 236-412
Å wavelength range are presented for the Na-like ions ArVIII, CrXIV,
MnXV, FeXVI, CoXVII, NiXVIII and ZnXX. A comparison of these with an
extensive data set of the solar active region, quiet-Sun, subflare and
off-limb observations, obtained during rocket flights by the Solar
EUV Research Telescope and Spectrograph (SERTS), reveals generally
very good agreement between theory and experiment. This indicates
that most of the Na-like ion lines are reliably detected in the
SERTS observations, and hence may be employed with confidence in
solar spectral analyses. However, the features in the SERTS spectra
at 236.34 and 300.25 Å, originally identified as the NiXVIII 3p
<SUP>2</SUP>P<SUB>3/2</SUB>-3d <SUP>2</SUP>D<SUB>3/2</SUB> and
CrXIV 3p <SUP>2</SUP>P<SUB>3/2</SUB>-3d <SUP>2</SUP>D<SUB>5/2</SUB>
transitions, respectively, are found to be due to emission lines of
ArXIII (236.34 Å) and possibly SV or NiVI (300.25 Å). The CoXVII
3s <SUP>2</SUP>S-3p <SUP>2</SUP>P<SUB>3/2</SUB> line at 312.55 Å is
always badly blended with an FeXV feature at the same wavelength, but
MnXV 3s <SUP>2</SUP>S-3p <SUP>2</SUP>P<SUB>1/2</SUB> at 384.75 Å may
not always be as affected by second-order emission from FeXII 192.37
Å as previously thought. On the other hand, we find that the ZnXX 3s
<SUP>2</SUP>S-3p <SUP>2</SUP>P<SUB>3/2</SUB> transition can sometimes
make a significant contribution to the ZnXX/FeXIII 256.43-Å blend, and
hence care must be taken when using this feature as an FeXIII electron
density diagnostic. A line in the SERTS-89 active region spectrum at
265.00 Å has been re-assessed, and we confirm its identification as
the FeXVI 3p <SUP>2</SUP>P<SUB>3/2</SUB>-3d <SUP>2</SUP>D<SUB>3/2</SUB>
transition.
---------------------------------------------------------
Title: Oscillator strengths for transitions in C-like ions between
K XIV and Mn XX
Authors: Aggarwal, K. M.; Keenan, F. P.; Msezane, A. Z.
2003A&A...401..377A Altcode:
Energy levels and oscillator strengths (transition probabilities) have
been calculated for transitions among 46 fine-structure levels of the
(1s<SUP>2</SUP>) 2s<SUP>2</SUP>2p<SUP>2</SUP>, 2s2p<SUP>3</SUP>,
2p<SUP>4</SUP>, 2s<SUP>2</SUP>2p3s, 2s<SUP>2</SUP>2p3p and
2s<SUP>2</SUP>2p3d configurations of C-like K XIV, Sc XVI, Ti XVII, V
XVIII, Cr XIX and Mn XX using the GRASP code. Configuration interaction
and relativistic effects have been included while generating the
wavefunctions. Calculated values of energy levels agree within 3% with
the experimentally compiled results, and the length and velocity forms
of oscillator strengths agree within 20% for a majority of allowed
transitions. <P />Tables \ref{tab4} to \ref{tab9} are only available
in electronic form at http://www.edpsciences.org
---------------------------------------------------------
Title: Observational Evidence for Mode Coupling in the Chromospheric
Network
Authors: McAteer, R. T. James; Gallagher, Peter T.; Williams, David R.;
Mathioudakis, Mihalis; Bloomfield, D. Shaun; Phillips, Kenneth J. H.;
Keenan, Francis P.
2003ApJ...587..806M Altcode:
Oscillations in network bright points (NBPs) are studied at a variety
of chromospheric heights. In particular, the three-dimensional
variation of NBP oscillations is studied using image segmentation
and cross-correlation analysis between images taken in light of Ca II
K<SUB>3</SUB>, Hα core, Mg I b<SUB>2</SUB>, and Mg I b<SUB>1</SUB>-0.4
Å. Wavelet analysis is used to isolate wave packets in time and
to search for height-dependent time delays that result from upward-
or downward-directed traveling waves. In each NBP studied, we find
evidence for kink-mode waves (1.3, 1.9 mHz), traveling up through the
chromosphere and coupling with sausage-mode waves (2.6, 3.8 mHz). This
provides a means for depositing energy in the upper chromosphere. We
also find evidence for other upward- and downward-propagating waves in
the 1.3-4.6 mHz range. Some oscillations do not correspond to traveling
waves, and we attribute these to waves generated in neighboring regions.
---------------------------------------------------------
Title: An analysis of the optical spectra of the post-asymptotic
giant branch stars LSIV -12 111 and HD 341617
Authors: Ryans, R. S. I.; Dufton, P. L.; Mooney, C. J.; Rolleston,
W. R. J.; Keenan, F. P.; Hubeny, I.; Lanz, T.
2003A&A...401.1119R Altcode:
High spectral resolution and signal-to-noise observations of the
absorption and emission line spectra in two post-asymptotic-giant-branch
(PAGB) stellar candidates, LSIV -12 111 and HD 314617 are discussed. The
absorption line spectra have been analysed using non-LTE model
atmosphere techniques to determine stellar atmospheric parameters
and chemical compositions, both in absolute terms and relative to
a standard star, HD 13841. The atmospheric parameters differ from
previous estimates based on LTE model atmospheres, probably due to
non-LTE effects. In turn these imply stellar masses that are generally
larger than have been previously estimated. Both PAGB candidates have
relative uniform underabundances of metals with mean values of -0.35
dex for LSIV -12 111 and -0.50 dex for HD 314617. <P />Furthermore,
their abundance patterns are remarkably similar to that observed
for optically bright, F-type PAGBs. From the emission spectra, the
plasma parameters and angular size of the circumstellar material are
constrained, and these are consistent with previous estimates and with
a PAGB evolutionary stage.
---------------------------------------------------------
Title: Effective collision strengths for transitions in Fe XI
Authors: Aggarwal, K. M.; Keenan, F. P.
2003A&A...399..799A Altcode:
Collision strengths for transitions among the lowest 48 fine-structure
levels belonging to the (1s<SUP>2</SUP>2s<SUP>2</SUP>2p<SUP>6</SUP>)
3s<SUP>2</SUP>3p<SUP>4</SUP>, 3s3p<SUP>5</SUP>,
3s<SUP>2</SUP>3p<SUP>3</SUP>3d and 3p<SUP>6</SUP> configurations of Fe
XI have been calculated using the Dirac Atomic R-matrix Code (DARC) of
Norrington & Grant (2003). Results are tabulated at energies above
thresholds in the range 10 <=E <=100 Ry, although resonances have
been resolved in a fine energy mesh in the thresholds region. Effective
collision strengths, obtained after integrating the collision
strengths over a Maxwellian distribution of electron velocities,
are also tabulated over a wide electron temperature range below 5x
10<SUP>6</SUP> K. Comparisons with other available results are made,
and the accuracy of the present data is assessed. <P />Tables 2 and
3 are only available in electronic form at http://www.edpsciences.org
---------------------------------------------------------
Title: Emission Lines of [Cl II] in the Optical Spectra of Gaseous
Nebulae
Authors: Keenan, F. P.; Aller, L. H.; Exter, K. M.; Hyung, S.;
Pollacco, D. L.
2003ApJ...584..385K Altcode:
Recent R-matrix calculations of electron impact excitation rates among
the 3s<SUP>2</SUP>3p<SUP>4</SUP> levels of Cl II are used to derive
the nebular emission-line intensity ratios R<SUB>1</SUB>=I(6161.8
Å)/I(8578.7 Å) and R<SUB>2</SUB>=I(6161.8 Å)/I(9123.6 Å)
as a function of electron temperature (T<SUB>e</SUB>) and density
(N<SUB>e</SUB>). The ratios are found to be very sensitive to changes
in T<SUB>e</SUB> but not N<SUB>e</SUB> for densities lower than
10<SUP>5</SUP> cm<SUP>-3</SUP>. Hence, they should, in principle,
provide excellent optical T<SUB>e</SUB> diagnostics for planetary
nebulae. The observed values of R<SUB>1</SUB> and R<SUB>2</SUB> for the
planetary nebulae NGC 6741 and IC 5117, measured from spectra obtained
with the Hamilton echelle spectrograph on the 3 m Shane Telescope,
imply temperatures in excellent agreement with those derived from
other diagnostic lines formed in the same region of the nebula as [Cl
II]. This provides some observational support for the accuracy of the
[Cl II] line ratio calculations and hence the atomic data on which
they are based. The [Cl II] 8578.7 and 9123.6 Å lines are identified
for the first time (to our knowledge) in a high-resolution spectrum
of the symbiotic star RR Telescopii, obtained with the University
College London Echelle Spectrograph on the 3.9 m Anglo-Australian
Telescope. However, the 6161.8 Å feature is unfortunately too weak
to be identified in the RR Telescopii observations, consistent with
its predicted line strength.
---------------------------------------------------------
Title: Electron impact excitation of S-like iron
Authors: Aggarwal, Kanti M.; Keenan, Francis P.
2003MNRAS.338..412A Altcode:
Energy levels and radiative rates for transitions
among the lowest 48 fine-structure levels belonging
to the (1s<SUP>2</SUP>2s<SUP>2</SUP>2p<SUP>6</SUP>)
3s<SUP>2</SUP>3p<SUP>4</SUP>, 3s3p<SUP>5</SUP>,
3s<SUP>2</SUP>3p<SUP>3</SUP>3d and 3p<SUP>6</SUP> configurations
of FeXI have been calculated using the fully relativistic GRASP
code. Additionally, collision strengths for transitions among these
levels have also been computed using the Dirac Atomic R-matrix Code
(DARC) of Norrington & Grant. Radiative rates and oscillator
strengths are tabulated for all allowed transitions among the 48
fine-structure levels, while collision strengths are reported
at three energies above thresholds, i.e. 8, 16 and 24 Ryd for
a few representative transitions. Furthermore, excitation rates
have been calculated in a wide electron temperature range below
5 × 10<SUP>6</SUP> K, and the contribution of resonances has been
included in the threshold regions. Comparisons are made with the earlier
available theoretical and experimental rates, and it is concluded that
the experimental rates are overestimated by up to a factor of 2.
---------------------------------------------------------
Title: Energy Levels, Radiative Rates, and Collision Strengths for
Transitions in Fe XVII
Authors: Aggarwal, K. M.; Keenan, F. P.; Msezane, A. Z.
2003ApJS..144..169A Altcode:
Energy levels and radiative rates have been calculated
for fine-structure transitions among the lowest 89 levels
of the (1s<SUP>2</SUP>) 2s<SUP>2</SUP>2p<SUP>6</SUP>,
2s<SUP>2</SUP>2p<SUP>5</SUP>3l, 2s<SUP>2</SUP>2p<SUP>5</SUP>4l,
2s2p<SUP>6</SUP>3l, and 2s2p<SUP>6</SUP>4l configurations of Fe XVII,
using the GRASP code of Dyall et al. Collision strengths have also
been calculated, for transitions among the lowest 55 levels, using the
recently developed Dirac atomic R-matrix code (DARC) of Norrington &
Grant. The results are compared with those available in the literature,
and the accuracy of the data is assessed.
---------------------------------------------------------
Title: Si IX Emission Lines in Spectra Obtained with the Solar euv
Research Telescope and Spectrograph (Serts)
Authors: Keenan, F. P.; Katsiyannis, A. C.; Aggarwal, K. M.;
Mathioudakis, M.; Brosius, J. W.; Davila, J. M.; Thomas, R. J.
2003SoPh..212...65K Altcode:
Theoretical electron-density-sensitive emission line ratios involving
2s<SUP>2</SUP>2p<SUP>2</SUP>-2s2p<SUP>3</SUP> transitions in Si ix
between 223 and 350 Å are presented. A comparison of these with
an extensive dataset of solar-active-region, quiet-Sun, subflare
and off-limb observations, obtained during rocket flights by the
Solar EUV Research Telescope and Spectrograph (SERTS), reveals
generally very good agreement between theory and experiment. This
provides support for the accuracy of the line-ratio diagnostics,
and hence the atomic data on which they are based. In particular,
the density-sensitive intensity ratio I(258.10 Å)/I(349.87 Å)
offers an especially promising diagnostic for studies of coronal
plasmas, as it involves two reasonably strong emission lines and
varies by more than an order of magnitude over the useful density
range of 10<SUP>9</SUP>-10<SUP>11</SUP> cm<SUP>−3</SUP>. The
2s<SUP>2</SUP>2p<SUP>2</SUP> <SUP>1</SUP>S<SUB>0</SUB>-2s2p<SUP>3</SUP>
<SUP>1</SUP>P<SUB>1</SUB> transition at 259.77 Å is very marginally
identified for the first time in the SERTS database, although it has
previously been detected in solar flare observations.
---------------------------------------------------------
Title: SuperWASP: Wide Angle Search for Planets
Authors: Street, R. A.; Pollaco, D. L.; Fitzsimmons, A.; Keenan, F. P.;
Horne, K.; Kane, S.; Collier Cameron, A.; Lister, T. A.; Haswell, C.;
Norton, A. J.; Jones, B. W.; Skillen, I.; Hodgkin, S.; Wheatley, P.;
West, R.; Brett, D.
2003ASPC..294..405S Altcode: 2002astro.ph..8233S
SuperWASP is a fully robotic, ultra-wide angle survey for planetary
transits. Currently under construction, it will consist of 5 cameras,
each monitoring a 9.5 by 9.5 degree field of view. The Torus mount
and enclosure will be fully automated and linked to a built-in weather
station. We aim to begin observations at the beginning of 2003.
---------------------------------------------------------
Title: New Results Concerning the Fe II Lines of RR Tel
Authors: Kotnik-Karuza, D.; Friedjung, M.; Exter, K.; Keenan, F. P.;
Pollacco, D. L.
2003ASPC..303..136K Altcode: 2003ssps.conf..136K
No abstract at ADS
---------------------------------------------------------
Title: The distance to high-velocity O VI absorption in the Galactic
halo
Authors: Keenan, F.
2003fuse.prop.D015K Altcode:
Previous FUSE studies have revealed the presence of large amounts of
high-velocity (midV<SUB>LSR</SUB>mid > 100 kms) hot gas towards
Galactic halo sightlines, detected via O VI absorption lines in
high-velocity clouds (HVCs). However, these sightlines are all
extragalactic, and hence the observations do not provide any insight
into a crucial HVC parameter -- the distance. As part of a continuing
program to investigate the distribution and origin of hot stars in
the Galactic halo, we have obtained high resolution (∼ 0.1Å FWHM)
optical echelle spectra of many faint B-type Post-AGB stars at high
Galactic latitudes. Detailed model atmosphere analyses of these spectra
have allowed us to derive reliable atmospheric parameters, and hence
determine stellar distances accurate to ∼ 20%. We have identified a
sample of our stars at distances from the Galactic plane (z) of up to 13
kpc, and which lie close in the sky (within 9°) to AGNs with HVC O VI
absorption in their sightlines. The detection of HVC O VI absorption in
our stellar sample will show that this hot gas lies close to the Galaxy,
and hence either originates from the Galaxy (e.g. a Galactic fountain
or wind), or arises via some interaction with the Galaxy (e.g. cloud
interactions with a Galactic corona). However null detections will also
provide useful constraints, indicating that the HVCs are extragalactic
in origin, such as intergalactic gas in the Local Group.
---------------------------------------------------------
Title: Multiwavelength observations of the M15 intermediate-velocity
cloud
Authors: Smoker, J. V.; Haffner, L. M.; Keenan, F. P.; Davies, R. D.;
Pollacco, D.
2002MNRAS.337..385S Altcode: 2002astro.ph..6373S
We present Westerbork Synthesis Radio Telescope HI images, Lovell
telescope multibeam HI wide-field mapping, William Herschel Telescope
long-slit echelle CaII observations, Wisconsin Hα Mapper (WHAM)
facility images, and IRAS ISSA 60- and 100-1μm co-added images towards
the intermediate-velocity cloud (IVC) at +70 km s<SUP>-1</SUP>,
located in the general direction of the M15 globular cluster. When
combined with previously published Arecibo data, the HI gas in the
IVC is found to be clumpy, with a peak HI column density of ~1.5 ×
10<SUP>20</SUP> cm<SUP>-2</SUP>, inferred volume density (assuming
spherical symmetry) of ~24 cm<SUP>-3</SUP>/D (kpc) and a maximum
brightness temperature at a resolution of 81 × 14 arcsec<SUP>2</SUP>
of ~14 K. The major axis of this part of the IVC lies approximately
parallel to the Galactic plane, as does the low-velocity HI gas and
IRAS emission. The HI gas in the cloud is warm, with a minimum value of
the full width at half-maximum velocity width of 5 km s<SUP>-1</SUP>
corresponding to a kinetic temperature, in the absence of turbulence,
of ~540 K. From the HI data, there are indications of two-component
velocity structure. Similarly, the CaII spectra, of resolution 7 km
s<SUP>-1</SUP>, also show tentative evidence of velocity structure,
perhaps indicative of cloudlets. Assuming that there are no unresolved
narrow-velocity components, the mean values of log<SUB>10</SUB>[N(CaII
K) cm<SUP>-2</SUP>]~ 12.0 and CaII/HI~2.5 × 10<SUP>-8</SUP> are typical
of observations of high Galactic latitude clouds. This compares with
a value of CaII/HI> 10<SUP>-6</SUP> for IVC absorption towards
HD 203664, a halo star of distance 3 kpc, some from the main M15 IVC
condensation. The main IVC condensation is detected by WHAM in Hα with
central local-standard-of-rest velocities of ~60-70 km s<SUP>-1</SUP>,
and intensities uncorrected for Galactic extinction of up to 1.3 R,
indicating that the gas is partially ionized. The FWHM values of the Hα
IVC component, at a resolution of 1°, exceed 30 km s<SUP>-1</SUP>. This
is some 10 km s<SUP>-1</SUP> larger than the corresponding HI value at
a similar resolution, and indicates that the two components may not be
mixed. However, the spatial and velocity coincidence of the Hα and
HI peaks in emission towards the main IVC component is qualitatively
good. If the Hα emission is caused solely by photoionization, the
Lyman continuum flux towards the main IVC condensation is ~2.7 ×
10<SUP>6</SUP> photon cm<SUP>-2</SUP> s<SUP>-1</SUP>. There is not
a corresponding IVC Hα detection towards the halo star HD 203664 at
velocities exceeding ~60 km s<SUP>-1</SUP>. Finally, both the 60- and
100-μm IRAS images show spatial coincidence, over a 0.675 × 0.625
deg<SUP>2</SUP> field, with both low- and intermediate-velocity HI
gas (previously observed with the Arecibo telescope), indicating that
the IVC may contain dust. Both the Hα and tentative IRAS detections
discriminate this IVC from high-velocity clouds, although the HI
properties do not. When combined with the HI and optical results,
these data point to a Galactic origin for at least parts of this IVC.
---------------------------------------------------------
Title: Search for short period coronal plasma oscillations. SECIS
results from 1999 and 2001 total eclipses
Authors: Rudawy, P.; Phillips, K. J. H.; Read, P.; Gallagher, P. T.;
Rompolt, B.; Berlicki, A.; Williams, D.; Keenan, F. P.; Buczylko, A.
2002ESASP.506..967R Altcode: 2002ESPM...10..967R; 2002svco.conf..967R
Results of the analysis of the high-cadence observations of the solar
corona, taken with the Solar Eclipse Coronal Imaging System instrument
during joint British-Polish expeditions during the total solar eclipses
of 1999 August 11 in Bulgaria (12768 images) and 2001 June 21 in Zambia
(16000 images) are presented. Using data collected during the both solar
eclipses we searched for possible periodic changes of the 530.3 nm line
intensity emitted by the selected points of the solar corona in the
frequency range up to 10 Hz. The time resolution of the collected data
is close to 0.05 sec and the pixel size is approximately 4 seconds of
arc. The standard photometric processing and correction of the image
motions caused by temporal drifts of the instrument pointing were
made. Using classical Fourier spectral analysis and wavelet analysis
tools we investigated temporal changes of the 530.3 nm coronal line
brightness of many thousands of points at various heights and position
angles above the solar limb. We did not find any statistically important
evidence of periodicity in the frequency range from 1 to 10 Hz in any
of the investigated points.
---------------------------------------------------------
Title: High-resolution Keck I spectroscopy of Galactic halo
post-asymptotic giant branch stars
Authors: Mooney, C. J.; Rolleston, W. R. J.; Keenan, F. P.; Dufton,
P. L.; Smoker, J. V.; Ryans, R. S. I.; Aller, L. H.
2002MNRAS.337..851M Altcode:
Absolute and differential abundance analyses have been performed from
high-resolution, high signal-to-noise ratio optical (Keck I) spectra
for three evolved Galactic halo stars, namely PG 1704 + 222, HD 341617
and LS IV -04 01. Their derived atmospheric parameters indicate that
all three objects are undergoing a post-asymptotic giant branch
(post-AGB) phase of evolution. A differential abundance analysis
reveals HD 341617 as having a mild carbon deficiency of 0.74 dex,
possibly due to the star having evolved off the AGB before the onset of
the third dredge-up. Although such carbon underabundances are typical
of hot post-AGB objects, the same trend is not observed in PG 1704 +
222, where the carbon abundance is found to be consistent with those
derived for nitrogen and oxygen. Hence, a dredge-up scenario need not
be invoked to explain the chemical composition of PG 1704 + 222. For
LS IV -04 01 no iron deficiency is apparent relative to magnesium and
silicon, and hence a gas-dust separation event in the AGB progenitor
need not be invoked for this star.
---------------------------------------------------------
Title: The OIV and SIV intercombination lines in the ultraviolet
spectra of astrophysical sources
Authors: Keenan, F. P.; Ahmed, S.; Brage, T.; Doyle, J. G.; Espey,
B. R.; Exter, K. M.; Hibbert, A.; Keenan, M. T. C.; Madjarska, M. S.;
Mathioudakis, M.; Pollacco, D. L.
2002MNRAS.337..901K Altcode:
New electron density diagnostic line ratios are presented for
the OIV 2s<SUP>2</SUP>2p <SUP>2</SUP>P-2s2p<SUP>24</SUP>P and SIV
3s<SUP>2</SUP>3p <SUP>2</SUP>P-3s3p<SUP>24</SUP>P intercombination
lines around 1400Å. A comparison of these with observational data
for the symbiotic star RR Telescopii (RR Tel), obtained with the
Space Telescope Imaging Spectrograph (STIS), reveals generally
very good agreement between theory and observation. However the
SIV<SUP>2</SUP>P<SUB>3/2</SUB>-<SUP>4</SUP>P<SUB>1/2</SUB> transition
at 1423.824Å is found to be blended with an unknown feature at
1423.774Å. The linewidth for the latter indicates that the feature
arises from a species with a large ionization potential. In addition,
the SIV<SUP>2</SUP>P<SUB>1/2</SUB>-<SUP>4</SUP>P<SUB>3/2</SUB>
transition at 1398.044Å is identified for the first time (to
our knowledge) in an astrophysical source other than the Sun,
and an improved wavelength of 1397.166 Å is measured for the
OIV<SUP>2</SUP>P<SUB>1/2</SUB>-<SUP>4</SUP>P<SUB>3/2</SUB> line. The
OIV and SIV line ratios in a sunspot plume spectrum, obtained with
the Solar Ultraviolet Measurements of the Emitted Radiation (SUMER)
instrument on the Solar and Heliospheric Observatory, are found to be
consistent, and remove discrepancies noted in previous comparisons of
these two ions.
---------------------------------------------------------
Title: A search for star formation around the Galactic halo B-type
star PHL 346 with the 2dF spectrograph
Authors: Lynn, B. B.; Dufton, P. L.; Keenan, F. P.; Hambly, N. C.;
Irwin, M. J.; Gilmore, G.; Rolleston, W. R. J.
2002MNRAS.336.1287L Altcode:
A preliminary search for stars that may have formed coevally with the
apparently young halo B-type star PHL 346 has been performed with
the 2dF multifibre spectrograph on the Anglo-Australian Telescope
(AAT). Candidates were selected for spectroscopy from APM scans of
B and R Schmidt plates centred on PHL 346. A total of 476 stars of
spectral type A or F were found; radial velocity estimates and more
accurate spectral type assignments narrowed the number of possible
coeval candidates to 6 A-type and 14 F-type stars. A statistical
analysis of these results using a comparison with a control field
suggests that the number of A-type or F-type candidate stars around
PHL 346 is not unexpected, and that they need not be associated with
PHL 346. A number of ways to improve the project are suggested.
---------------------------------------------------------
Title: An observational study of a magneto-acoustic wave in the
solar corona
Authors: Williams, D. R.; Mathioudakis, M.; Gallagher, P. T.; Phillips,
K. J. H.; McAteer, R. T. J.; Keenan, F. P.; Rudawy, P.; Katsiyannis,
A. C.
2002MNRAS.336..747W Altcode:
The Solar Eclipse Corona Imaging System (SECIS) observed a strong 6-s
oscillation in an active region coronal loop, during the 1999 August 11
total solar eclipse. In the present paper we show that this oscillation
is associated with a fast-mode magneto-acoustic wave that travels
through the loop apex with a velocity of 2100 km s<SUP>-1</SUP>. We use
near-simultaneous SOHO observations to calculate the parameters of the
loop and its surroundings such as density, temperature and their spatial
variation. We find that the temporal evolution of the intensity is in
agreement with the model of an impulsively generated, fast-mode wave.
---------------------------------------------------------
Title: A search for circumstellar material around B-type stars in
the Galactic halo
Authors: Magee, H. R. M.; Rolleston, W. R. J.; Dufton, P. L.; Keenan,
F. P.; Mooney, C. J.
2002MNRAS.336.1147M Altcode:
19 B-type stars, selected from the Palomar-Green Survey, have been
observed at infrared wavelengths to search for possible infrared
excesses, as part of an ongoing programme to investigate the nature
of early-type stars at high Galactic latitudes. The resulting infrared
fluxes, along with Strömgren photometry, are compared with theoretical
flux profiles to determine whether any of the targets show evidence of
circumstellar material, which may be indicative of post-main-sequence
evolution. Eighteen of the targets have flux distributions in good
agreement with theoretical predictions. However, one star, PG 2120+062,
shows a small near-infrared excess, which may be due either to a
cool companion of spectral type F5-F7, or to circumstellar material,
indicating that it may be an evolved object such as a post-asymptotic
giant branch star, in the transition region between the asymptotic
giant branch and planetary nebula phase, with the infrared excess due
to recent mass loss during giant branch evolution.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Effective collision strengths
for Fe XI trans. (Aggarwal+, 2003)
Authors: Aggarwal, K. M.; Keenan, F. P.
2002yCat..33990799A Altcode:
Collision strengths for transitions among the lowest 48 fine-structure
levels belonging to the (1s<SUP>2</SUP>2s<SUP>2</SUP>2p<SUP>6</SUP>)
3s<SUP>2</SUP>3p<SUP>4</SUP>, 3s3p<SUP>5</SUP>,
3s<SUP>2</SUP>3p<SUP>3</SUP>3d and 3p<SUP>6</SUP> configurations
of Fe XI have been calculated using the Dirac Atomic R-matrix Code
(DARC) of Norrington & Grant (2003, Comput. Phys. Commun., in
prep.). Results are tabulated at energies above thresholds in the range
10<=E<=100Ry, although resonances have been resolved in a fine
energy mesh in the thresholds region. Effective collision strengths,
obtained after integrating the collision strengths over a Maxwellian
distribution of electron velocities, are also tabulated over a wide
electron temperature range below 5x10<SUP>6</SUP>K. Comparisons with
other available results are made, and the accuracy of the present data
is assessed. <P />(5 data files).
---------------------------------------------------------
Title: Detections of high-frequency oscillations in solar active
region coronal loops
Authors: Katsiyannis, Athanassios C.; Williams, David R.; McAteer,
R. T. James; Gallagher, Peter T.; Mathioudakis, Mihalis; Keenan,
Francis P.
2002ESASP.505..441K Altcode: 2002IAUCo.188..441K; 2002solm.conf..441K
One of the mechanisms proposed as a possible solution to the
Sun's coronal heating problem is the damping of energy carried by
magnetohydrodynamic (MHD) waves that are expected to be present
in active regions. Continuing previous work on total solar eclipse
data, we provide further obervational evidence for the existence of
high-frequency MHD waves in coronal loops. Wavelet analysis is used to
identify 21 areas of 4×4 arcsec<SUP>2</SUP> with periodic intensity
oscillations. The frequency range of these detections was 0.2-0.3 Hz
and all last for at least 3 periods at a confidence level of more than
99%. All of the above detections are made just outside known coronal
loops, leading us to suggest a possible, unconventional mechanism.
---------------------------------------------------------
Title: Detection of propagating waves throughout the chromosphere
in network bright points
Authors: McAteer, R. T. James; Gallagher, Peter T.; Williams, David
R.; Mathioudakis, Mihalis; Phillips, Kenneth J. H.; Keenan, Francis P.
2002ESASP.505..305M Altcode: 2002IAUCo.188..305M; 2002solm.conf..305M
We analysed oscillations in individual Network Bright Points (NBPs)
in Ca II K<SUB>3</SUB>, Hα core, Mg I b<SUB>2</SUB>, and Mg I
b<SUB>1</SUB>-0.4 Å giving us a range of heights from the upper
to the lower chromosphere. Lightcurves, and hence power spectra,
were created by isolating distinct regions of the NBP via a simple
intensity thresholding technique. Using this technique, it was
possible to identify peaks in the power spectra with particular spatial
positions within the NBPs. This was extended into the time domain by
means of wavelet analysis. We track the temporal evolution of power
in particular frequency bands by creating power curves. These are
then cross-correlated across all observed wavelengths to search for
propagating waves. In particular, long-period waves with periods of
4-15 minutes (1-4 mHz) were found in the central portion of each NBP,
indicating that these waves are certainly not acoustic, but possibly
due to magneto-acoustic or magneto-gravity wave modes. We note the
possible existence of fast-mode MHD waves in the lower chromosphere,
coupling and transferring power top higher-frequency slow-mode MHD
waves in the upper chromosphere.
---------------------------------------------------------
Title: Macroturbulent and rotational broadening in the spectra of
B-type supergiants
Authors: Ryans, R. S. I.; Dufton, P. L.; Rolleston, W. R. J.; Lennon,
D. J.; Keenan, F. P.; Smoker, J. V.; Lambert, D. L.
2002MNRAS.336..577R Altcode:
The absorption-line spectra of early B-type supergiants show
significant broadening that implies that an additional broadening
mechanism (characterized here as `macroturbulence') is present in
addition to rotational broadening. Using high-resolution spectra
with signal-to-noise ratios of typically 500, we have attempted to
quantify the relative contributions of rotation and macroturbulence,
but even with data of this quality significant problems were
encountered. However, for all our targets, a model where macroturbulence
dominates and rotation is negligible is acceptable; the reverse scenario
leads to poor agreement between theory and observation. Additionally,
there is marginal evidence for the degree of broadening increasing with
line strength, possibly a result of the stronger lines being formed
higher in the atmosphere. Acceptable values of the projected rotational
velocity are normally less than or equal to 50 km s<SUP>-1</SUP>, which
may also be a typical upper limit for the rotational velocity. Our
best estimates for the projected rotational velocity are typically
10-20 km s<SUP>-1</SUP> and hence compatible with this limit. These
values are compared with those predicted by single star evolutionary
models, which are initially rapidly rotating. It is concluded that
either these models underestimate the rate of rotational breaking or
some of the targets may be evolving through a blue loop or are binaries.
---------------------------------------------------------
Title: Observations of a high-frequency, fast-mode wave in a
coronal loop
Authors: Williams, David R.; Mathioudakis, Mihalis; Gallagher, Peter
T.; Phillips, Kenneth J. H.; McAteer, R. T. James; Keenan, Francis P.;
Katsiyannis, Athanassios C.
2002ESASP.505..615W Altcode: 2002IAUCo.188..615W; 2002solm.conf..615W
The high-cadence Solar Eclipse Corona Imaging System (SECIS) observed
a strong 6-second oscillation in an active region coronal loop, during
the 1999 August 11 total solar eclipse. In the present paper we show
that this oscillation is associated with a fast-mode wave that travels
through the loop apex with a velocity of ~2000 km s<SUP>-1</SUP>. We
use near-simultaneous SoHO/CDS obervations to calculate the parameters
of the loop and its surroundings such as density, temperature and their
spatial variation. We also calculate radiative losses from the loop in
the temperature range 10<SUP>5.8</SUP> - 10<SUP>6.4</SUP>K, and compare
these losses with the wave energy density. Although the wave travels a
distance greater than λ/4π and therefore meets a necessary criterion
for slow dissipation, the dissipation length is well in excess of the
loop length. The temporal evolution of the intensity is found to be
in agreement with the model of an impulsively generated, fast-mode wave.
---------------------------------------------------------
Title: Opacity in the upper atmosphere of AU Mic
Authors: Bloomfield, D. S.; Mathioudakis, M.; Christian, D. J.;
Keenan, F. P.; Linsky, J. L.
2002A&A...390..219B Altcode:
In this paper we investigate the validity of the optically thin
assumption in the transition region of the late-type star AU Mic. We use
Far-Ultraviolet Spectroscopic Explorer (FUSE) observations of the C Iii
multiplet and O Vi resonance lines, hence yielding information at two
different levels within the atmosphere. Significant deviations from the
optically thin fluxes are found for C Iii in both quiescent and flare
spectra, where only 60% of the flux is actually observed. This could
explain the apparent deviation of C Iii observed in emission measure
distributions. We utilize escape probabilities for both homogeneous and
inhomogeneous geometries and calculate optical depths as high as 10 for
the C Iii 1175.71 Åcomponent of the multiplet. Using a lower limit
to the electron density (10<SUP>11</SUP> cm<SUP>-3</SUP>) we derive
an effective thickness of <100 km for the scattering layer. The
emission originates from very small and compact regions, consistent
with a filling factor of 10<SUP>-5</SUP> derived for the flare plasma.
---------------------------------------------------------
Title: Optical spectroscopy of the M 15 intermediate velocity cloud
Authors: Smoker, J. V.; Keenan, F. P.; Lehner, N.; Trundle, C.
2002A&A...387.1057S Altcode:
We present echelle spectrograph observations in the Na D lines, at
resolutions of 6.2-8.5 km s<SUP>-1</SUP>, for 11 stars located in
the line-of-sight to the M 15 intermediate velocity cloud (IVC),
which has a radial velocity of ~ +70 km s<SUP>-1</SUP> in the
Local Standard of Rest. This cloud is a part of IVC Complex gp. The
targets range in magnitude from m<SUB>V</SUB>=13.3-14.8. Seven of
the observed stars are in the M 15 globular cluster, the remaining
four being field stars. Three of the observed cluster stars are
located near a peak in intensity of the IVC H I column density as
observed at a resolution of ~ 1 arcmin. Intermediate velocity gas
is detected in absorption towards 7 stars, with equivalent widths
in Na D<SUB>2</SUB> ranging from ~ 0.09-0.20 Å, corresponding to
log<SUB>10</SUB>(N<SUB>Na</SUB> cm<SUP>-2</SUP>) ~ 11.8-12.5, and Na
I/H I column density ratios (neglecting the H II component) ranging
from ~ (1-3)x10<SUP>-8</SUP>. Over scales ranging from 30 arcsec to
1 arcmin, the Na I column density and the Na I/H I ratio varies by
upto 70 per cent and a factor of ~ 2, respectively. Combining the
current sightlines with previously obtained Na I data from Kennedy
et al. (\cite{Kennedy98}b), the Na I/H I column density ratio over
cluster sightlines varies by upto a factor of ~ 25, when using H I
data of resolution ~ 2x1 arcmin. One cluster star, M 15 ZNG-1, was
also observed in the Ca I (lambda<SUB>air</SUB> =4226.728 Å) and Ca II
(lambda<SUB>air</SUB> =3933.663 Å) lines. A column density ratio N(Ca
I)/N(Ca II) < 0.03 was found, typical of values seen in the warm
ionised interstellar medium. Towards this sightline, the IVC has a Na
I/Ca II column density ratio of ~ 0.25, similar to that observed in the
local interstellar medium. Finally, we detect tentative evidence for IV
absorption in K I (lambda<SUB>air</SUB> =7698.974 Å) towards 3 cluster
stars, which have N(K I)/N(H I) ratios of ~ 0.5-3x10<SUP>-9</SUP>. Based
on observations made with the Apache Point Observatory 3.5-m, USA, Very
Large Telescope, Chile, and William Herschel Telescope, La Palma, Spain.
---------------------------------------------------------
Title: Long-Period Chromospheric Oscillations in Network Bright Points
Authors: McAteer, R. T. James; Gallagher, Peter T.; Williams, David
R.; Mathioudakis, Mihalis; Phillips, Kenneth J. H.; Keenan, Francis P.
2002ApJ...567L.165M Altcode:
The spatial variation of chromospheric oscillations in network bright
points (NBPs) is studied using high-resolution observations in Ca II
K3. Light curves and hence power spectra were created by isolating
distinct regions of the NBP via a simple intensity thresholding
technique. Using this technique, it was possible to identify peaks in
the power spectra with particular spatial positions within the NBPs. In
particular, long-period waves with periods of 4-15 minutes (1-4 mHz)
were found in the central portions of each NBP, indicating that these
waves are certainly not acoustic but possibly due to magnetoacoustic
or magnetogravity wave modes. We also show that spatially averaged
or low spatial resolution power spectra can lead to an inability to
detect such long-period waves.
---------------------------------------------------------
Title: A Comparison of Theoretical mg vi Emission Line Strengths
with Active-Region Observations From Serts
Authors: Keenan, F. P.; Mathioudakis, M.; Katsiyannis, A. C.;
Ramsbottom, C. A.; Bell, K. L.; Thomas, R. J.; Brosius, J. W.
2002SoPh..205..265K Altcode:
R-matrix calculations of electron impact excitation
rates in N-like Mg vi are used to derive theoretical
electron-density-sensitive emission line ratios involving
2s<SUP>2</SUP>2p<SUP>3</SUP>−2s2p<SUP>4</SUP>transitions in
the 269-403 Å wavelength range. A comparison of these with
observations of a solar active region, obtained during the
1989 flight of the Solar EUV Rocket Telescope and Spectrograph
(SERTS), reveals good agreement between theory and observation for the
2s<SUP>2</SUP>2p<SUP>3</SUP><SUP>4</SUP>S−2s2p<SUP>4</SUP><SUP>4</SUP>Ptransitions
at 399.28, 400.67, and 403.30 Å, and the
2s<SUP>2</SUP>2p<SUP>3</SUP><SUP>2</SUP>P−2s2p<SUP>4</SUP><SUP>2</SUP>Dlines
at 387.77 and 387.97 Å. However, intensities for the other lines
attributed to Mg vi in this spectrum by various authors do not match the
present theoretical predictions. We argue that these discrepancies are
not due to errors in the adopted atomic data, as previously suggested,
but rather to observational uncertainties or mis-identifications. Some
of the features previously identified as Mg vi lines in the SERTS
spectrum, such as 291.36 and 293.15 Å, are judged to be noise, while
others (including 349.16 Å) appear to be blended.
---------------------------------------------------------
Title: Extreme-Ultraviolet Emission Lines of S XII in Solar Active
Region and Flare Spectra
Authors: Keenan, F. P.; Katsiyannis, A. C.; Ryans, R. S. I.; Reid,
R. H. G.; Zhang, H. L.; Pradhan, A. K.; Widing, K. G.
2002ApJ...566..521K Altcode:
New R-matrix calculations of electron impact excitation rates
for transitions among the 2s<SUP>2</SUP>2p, 2s2p<SUP>2</SUP>
and 2p<SUP>3</SUP> levels of S XII are presented. These data are
subsequently used to derive the theoretical electron density diagnostic
emission line intensity ratios R<SUB>1</SUB>=I(215.16 Å)/I(299.50
Å), R<SUB>2</SUB>=I(218.19 Å)/I(299.50 Å), R<SUB>3</SUB>=I(288.40
Å)/I(299.50 Å), and R<SUB>4</SUB>=I(221.41 Å)/I(299.50 Å). A
comparison of these with observational data for solar active regions
and flares, obtained with the Naval Research Laboratory's S082A
spectrograph on board Skylab and the Solar EUV Rocket Telescope
and Spectrograph (SERTS), reveals that the electron densities
determined from R<SUB>1</SUB>, R<SUB>3</SUB>, and R<SUB>4</SUB>
are consistent with each other. In addition, the densities deduced
from these ratios are in good agreement with those estimated from
diagnostic lines in Fe XIV or Fe XV, which are formed at similar
electron temperatures to S XII. However, the R<SUB>2</SUB> ratios
in the flare observations imply densities smaller than those from
Fe XIV/Fe XV, although the active region measurements do not show
such discrepancies, suggesting that the 218.19 Å line may be blended
with a transition from a high-temperature ion. An emission feature in
the SERTS active region spectrum at 215.29 Å, previously identified
as the 2s2p<SUP>3</SUP>P<SUB>2</SUB>-2s3s<SUP>3</SUP>S<SUB>1</SUB>
transition in O V, may be due primarily to the S XII 215.16 Å line.
---------------------------------------------------------
Title: Chemical Composition of Globular Cluster and Halo Post-AGB
Stars
Authors: Mooney, C. J.; Aller, L. H.; Rolleston, W. . R. J.; Dufton,
P. L.; Keenan, F. P.; Smoker, J. V.; Pollacco, D. L.
2002RMxAC..12..181M Altcode:
We present results of model atmosphere analyses of two post-AGB stars,
ZNG-1 in the globular cluster M10 and the halo star PG1704+222. A
differential abundance analysis reveals typical post-AGB abundance
patterns, both stars being generally metal poor with approximately
solar He. Large C depletions, observed in all hot post-AGB objects, are
confirmed. The C deficiency may suggest that hot post-AGB stars evolve
off the AGB before the third dredge-up begins. However, Fe depletions
observed in other similar stars suggest that gas-dust fractionation
in the AGB progenitor is responsible for the observed composition of
these objects.
---------------------------------------------------------
Title: Emission lines of [K V] in the optical spectra of gaseous
nebulae
Authors: Keenan, Francis P.; Aller, Lawrence H.; Espey, Brian R.;
Exter, Katrina M.; Hyung, Siek; Keenan, Michael T. C.; Pollacco,
Don L.; Ryans, Robert S. I.
2002PNAS...99.4152K Altcode:
Recent R-matrix calculations of electron impact excitation rates in
K V are used to derive the nebular emission line ratio R = I(4122.6
Å)/I(4163.3 Å) as a function of electron density (Ne). This ratio
is found to be very sensitive to changes in Ne over the density range
103 to 10<SUP>6</SUP> cm<SUP>-3</SUP>, but does not vary significantly
with electron temperature, and hence in principle should provide an
excellent optical N<SUB>e</SUB> diagnostic for the high-excitation
zones of nebulae. The observed value of R for the planetary nebula
NGC 7027, measured from a spectrum obtained with the Hamilton Echelle
spectrograph on the 3-m Shane Telescope, implies a density in excellent
agreement with that derived from [Ne IV], formed in the same region
of the nebula as [K V]. This observation provides observational
support for the accuracy of the theoretical [K V] line ratios, and
hence the atomic data on which they are based. However, the analysis
of a high-resolution spectrum of the symbiotic star RR Telescopii,
obtained with the University College London Echelle Spectrograph on
the 3.9-m Anglo-Australian Telescope, reveals that the [K V] 4122.6
Å line in this object is badly blended with Fe II 4122.6Å. Hence,
the [K V] diagnostic may not be used for astrophysical sources that
show a strong Fe II emission line spectrum.
---------------------------------------------------------
Title: Boron Abundances in B-Type Stars: A Test of Rotational
Depletion during Main-Sequence Evolution
Authors: Venn, K. A.; Brooks, A. M.; Lambert, David L.; Lemke, M.;
Langer, N.; Lennon, D. J.; Keenan, F. P.
2002ApJ...565..571V Altcode: 2001astro.ph..8263V
Boron abundances have been derived for seven main-sequence B-type
stars from Hubble Space Telescope STIS spectra around the B III
λ2066 line. In two stars, boron appears to be undepleted with
respect to the presumed initial abundance. In one star, boron is
detectable but is clearly depleted. In the other four stars, boron
is undetectable, implying depletions of 1-2 dex. Three of these four
stars are nitrogen enriched, but the fourth shows no enrichment
of nitrogen. Only rotationally induced mixing predicts that boron
depletions are unaccompanied by nitrogen enrichments. The inferred
rate of boron depletion from our observations is in good agreement
with these predictions. Other boron-depleted nitrogen-normal
stars are identified from the literature. In addition, several
boron-depleted nitrogen-rich stars are identified, and while all
fall on the boron-nitrogen trend predicted by rotationally induced
mixing, a majority have nitrogen enrichments that are not uniquely
explained by rotation. The spectra have also been used to determine
iron group (Cr, Mn, Fe, and Ni) abundances. The seven B-type stars
have near-solar iron group abundances, as expected for young stars in
the solar neighborhood. We have also analyzed the halo B-type star PG
0832+676. We find [Fe/H]=-0.88+/-0.10, and the absence of the B III
line gives the upper limit [B/H]<-2.5. These and other published
abundances are used to infer the star's evolutionary status as a
post-asymptotic giant branch star. Based on observations made with
the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope
Science Institute, which is operated by the Association of Universities
for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These
observations are associated with proposal GO 07400.
---------------------------------------------------------
Title: Flare Temperature from FE XXV and CA XIX: Improved Atomic Data
Authors: Phillips, K. J. H.; Rainnie, J. A.; Harra, L. K.; Dubau,
J.; Keenan, F. P.
2002mwoc.conf..293P Altcode:
For several years flare temperatures and emission measures have
been derived from comparison of observed Yohkoh BCS spectra with
theoretical spectra derived from atomic parameters based on distorted
wave approximation. In the case of Fe XXV and Ca XIX spectra, the
main lines used in the determination are dielectronic satellite lines
(j or k as appropriate) and the resonance line w. More accurate
close-coupling calculations from the R-matrix procedure have been
available in unpublished form, and in this work these new atomic data
were substituted for the distorted wave data. The intensities of
the Fe XXV and Ca XIX lines w, x, y, and z are affected -- all are
increased. However, the differences from the previously used atomic
data are very slight. We estimate that for a given j/w ratio in Fe
XXV, for instance, the temperature estimated from the new atomic data
will be about 1MK smaller than from the existing data in the standard
Yohkoh software at temperatures of around 20MK. Smaller differences
are expected for Ca XIX at typical temperatures of 14MK. The increase
in the Fe XXV y and z line intensities tends to reduce a well-known
discrepancy in these lines (more evident in the much better resolved SMM
BCS spectra) but not by a sufficient amount to explain the discrepancy.
---------------------------------------------------------
Title: Radiation damping effects on L-shell photoionization
cross-sections of O-like Fe XIX and N-like recombination rate
coefficients for Fe XX
Authors: McLaughlin, B. M.; Gorczyca, T. W.; Keenan, F. P.; Bell, K. L.
2001MNRAS.328..442M Altcode:
Photoionization cross-sections out of the fine-structure levels
(2s<SUP>2</SUP>2p<SUP>4</SUP> <SUP>3</SUP>P<SUB>2,0,1</SUB>) of the
O-like Fe ion FeXIX have been reinvestigated. Data for photoionization
out of each of these fine-structure levels have been obtained, where
the calculations have been performed with and without the inclusion
of radiation damping on the resonance structure in order to assess
the importance of this process. Recombination rate coefficients are
determined using the Milne relation, for the case of an electron
recombining with N-like Fe ions (FeXX) in the ground state to form
O-like Fe (FeXIX) existing in each of the fine-structure ground-state
levels. Recombination rates are presented over a temperature range
~4.0<=logT<SUB>e</SUB><=7.0, of importance to the modelling of
X-ray emission plasmas.
---------------------------------------------------------
Title: Boron Abundances in Main Sequence B-type Stars: A Test of
Rotational Depletion during Main Sequence Evolution
Authors: Venn, K. A.; Brooks, A. M.; Lambert, D. L.; Lemke, M.;
Langer, N.; Lennon, D. J.; Keenan, F. P.
2001AAS...19913703V Altcode: 2001BAAS...33.1512V
Boron abundances have been derived for seven main sequence B-type stars
from HST STIS spectra around the BIII 2066 A line. Boron abundances
range from normal to severly depleted. One boron depleted star shows no
nitrogen enrichment, which is an abundance pattern uniquely predicted
from the rotationally-induced mixing models, e.g., Heger and Langer
2000. Other stars show boron depletions that correlate with nitrogen
enrichments; this pattern is predicted by rotationally-induced mixing,
but also by other theories. The inferred rate of boron depletion (i.e.,
boron versus age) from our observations is also in good agreement with
the predictions. Based on observations made with the NASA/ESA Hubble
Space Telescope, obtained at the Space Telescope Science Institute,
which is operated by the Association of Universities for Research in
Astronomy, Inc., under NASA contract NAS 5-26555. These observations
are associated with proposal GO-7400.
---------------------------------------------------------
Title: HI observations of the high-velocity cloud in the direction
of M 92
Authors: Smoker, J. V.; Roger, R. S.; Keenan, F. P.; Davies, R. D.;
Lang, R. H.; Bates, B.
2001A&A...380..673S Altcode:
We present wide-field neutral hydrogen (H I) Lovell telescope multibeam,
and Dominion Radio Astrophysical Observatory H I synthesis observations,
of the high velocity cloud (HVC) located in the general direction of the
globular cluster M 92. This cloud is part of the larger Complex C and
lies at velocities between ~ -80 and -130 km s<SUP>-1</SUP> in the Local
Standard of Rest. The Lovell telescope observations, of resolution 12
arcmin spatially and 3.0 km s<SUP>-1</SUP> in velocity, fully sampling
a 3.1<SUP>deg</SUP> x12.6<SUP>deg</SUP> RA-Dec grid, have found that
this part of HVC Complex C comprises two main condensations, lying
approximately north-south in declination, separated by ~ 2<SUP>deg</SUP>
and being parallel to the Galactic plane. At this resolution, peak
values of the brightness temperature and H I column density of ~
1.4 K and ~ 5x10<SUP>19</SUP> cm<SUP>-2</SUP> are determined, with
relatively high values of the full width half maximum velocity (FWHM)
of ~ 22 km s<SUP>-1</SUP> being observed, equivalent to a gas kinetic
temperature, in the absence of turbulence and geometric effects of
~ 10 000 K. Each of these properties, as well as the sizes of the
clouds, are similar in the two components. The DRAO observations,
towards the Northern HVC condensation, are the first high-resolution
H I spectra of Complex C. When smoothed to a resolution of 3 arcmin,
they identify several H I intensity peaks with column densities in
the range 4-7x10<SUP>19</SUP> cm<SUP>-2</SUP>. Further smoothing of
these data to 6 arcmin resolution tentatively indicates that parts
of the HVC consist of two velocity components, of similar brightness
temperature, separated by ~ 7 km s<SUP>-1</SUP> in velocity, and
with FWHM velocity widths of ~ 5-7km s<SUP>-1</SUP>. No IRAS 60 or
100 micron flux is associated with the M 92 HVC. Cloud properties are
briefly discussed and compared to previous observations of HVCs. Based
on observations made with the Lovell telescope, Jodrell Bank, UK, the
Synthesis Telescope at the Dominion Radio Astrophysical Observatory,
Canada, and at the Isaac Newton Group of telescopes, La Palma, Spain.
---------------------------------------------------------
Title: Solar coronal observations at high frequencies
Authors: Katsiyannis, A. C.; Mathioudakis, M.; Phillips, K. J. H.;
Williams, D. R.; Keenan, F. P.
2001astro.ph.11447K Altcode:
The Solar Eclipse Coronal Imaging System (SECIS) is a simple and
extremely fast, high-resolution imaging instrument designed for studies
of the solar corona. Light from the corona (during, for example,
a total solar eclipse) is reflected off a heliostat and passes via
a Schmidt-Cassegrain telescope and beam splitter to two CCD cameras
capable of imaging at 60 frames a second. The cameras are attached via
SCSI connections to a purpose-built PC that acts as the data acquisition
and storage system. Each optical channel has a different filter allowing
observations of the same events in both white light and in the green
line (Fe XIV at 5303 A). Wavelet analysis of the stabilized images
has revealed high frequency oscillations which may make a significant
contribution on the coronal heating process. In this presentation we
give an outline of the instrument and its future development.
---------------------------------------------------------
Title: Electron Densities in the Coronae of the Sun and Procyon from
Extreme-Ultraviolet Emission Line Ratios in Fe XI
Authors: Pinfield, D. J.; Keenan, F. P.; Mathioudakis, M.; Widing,
K. G.; Gallagher, P. T.; Gupta, G. P.; Tayal, S. S.; Thomas, R. J.;
Brosius, J. W.
2001ApJ...562..566P Altcode:
New R-matrix calculations of electron impact excitation rates for Fe
XI are used to determine theoretical emission line ratios applicable
to solar and stellar coronal observations. These are subsequently
compared to solar spectra of the quiet Sun and an active region made
by the Solar EUV Rocket Telescope and Spectrograph (SERTS-95), as well
as Skylab observations of two flares. Line blending is identified,
and electron densities of 10<SUP>9.3</SUP>, 10<SUP>9.7</SUP>,
>=10<SUP>10.8</SUP>, and >=10<SUP>11.3</SUP> cm<SUP>-3</SUP>
are found for the quiet Sun, active region, and the two flares,
respectively. Observations of the F5 IV-V star Procyon, made with
the Extreme Ultraviolet Explorer (EUVE) satellite, are compared and
contrasted with the solar observations. It is confirmed that Procyon's
average coronal conditions are very similar to those seen in the quiet
Sun, with N<SUB>e</SUB>=10<SUP>9.4</SUP> cm<SUP>-3</SUP>. In addition,
although the quiet Sun is the closest solar analog to Procyon, we
conclude that Procyon's coronal temperatures are slightly hotter than
solar. A filling factor of 25<SUP>+38</SUP><SUB>-12</SUB>% was derived
for the corona of Procyon.
---------------------------------------------------------
Title: Extreme ultraviolet transitions of FeXXI in solar, stellar
and laboratory spectra
Authors: Keenan, F. P.; Aggarwal, K. M.; Williams, D. R.; Mathioudakis,
M.; Phillips, K. J. H.
2001MNRAS.326.1387K Altcode:
Recent <b><sansserif>R</sansserif></b>-matrix
calculations of electron impact excitation rates for transitions
among the 2s<SUP>2</SUP>2p<SUP>2</SUP>, 2s2p<SUP>3</SUP> and
2p<SUP>4</SUP> levels of FeXXI are used to derive theoretical electron
density (N<SUB>e</SUB>) sensitive emission-line ratios involving
2s<SUP>2</SUP>2p<SUP>2</SUP>-2s2p<SUP>3</SUP> transitions in the
~98-146Å wavelength range. A comparison of these with observations
from the PLT tokamak plasma, for which the electron density has been
independently determined, reveals generally very good agreement between
theory and experiment, and in some instances removes discrepancies
found previously. The observed FeXXI ratios for a solar flare,
obtained with the OSO-5 satellite, imply electron densities which are
consistent, with discrepancies that do not exceed 0.2dex. In addition,
the derived values of N<SUB>e</SUB> are similar to those estimated for
the high-temperature regions of other solar flares. The good agreement
between theory and observation, in particular for the tokamak spectra,
provides experimental support for the accuracy of the present line-ratio
calculations, and hence for the atomic data on which they are based.
---------------------------------------------------------
Title: Oscillator Strengths for Transitions in C-like Ions between
F IV and Ar XIII
Authors: Aggarwal, K. M.; Keenan, F. P.; Msezane, A. Z.
2001ApJS..136..763A Altcode:
Energy levels and oscillator strengths (transition probabilities) have
been calculated for the fine-structure transitions among the levels of
the (1s<SUP>2</SUP>) 2s<SUP>2</SUP>2p<SUP>2</SUP>, 2s2p<SUP>3</SUP>,
2p<SUP>4</SUP>, 2s<SUP>2</SUP>2p3s, 2s<SUP>2</SUP>2p3p, and
2s<SUP>2</SUP>2p3d configurations of C-like F IV, Na VI, Al VIII, P X,
Cl XII, and Ar XIII using the CIV3 program. The extensive configuration
interaction and relativistic effects have been included while generating
the wavefunctions. Calculated values of energy levels generally agree
within 5% with the experimentally compiled results, and the length and
velocity forms of oscillator strengths agree within 20% for a majority
of allowed transitions.
---------------------------------------------------------
Title: High-frequency oscillations in a solar active region coronal
loop
Authors: Williams, D. R.; Phillips, K. J. H.; Rudawy, P.; Mathioudakis,
M.; Gallagher, P. T.; O'Shea, E.; Keenan, F. P.; Read, P.; Rompolt, B.
2001MNRAS.326..428W Altcode:
The Solar Eclipse Corona Imaging System (SECIS) was used to record
high-cadence observations of the solar corona during the total solar
eclipse of 1999 August 11. During the 2min 23.5s of totality, 6364
images were recorded simultaneously in each of the two channels:
a white light channel, and the Fexiv (5303Å) `green line' channel
(T~2MK). Here we report initial results from the SECIS experiment,
including the discovery of a 6-s intensity oscillation in an active
region coronal loop.
---------------------------------------------------------
Title: A detailed abundance analysis of the hot post-AGB star ZNG-1
in M10
Authors: Mooney, C. J.; Rolleston, W. R. J.; Keenan, F. P.; Dufton,
P. L.; Pollacco, D. L.; Magee, H. R.
2001MNRAS.326.1101M Altcode:
We present a model-atmosphere analysis for the bright (V~13) star
ZNG-1, in the globular cluster M10. From high-resolution (R~40000)
optical spectra we confirm ZNG-1 to be a post-asymptotic giant
branch (post-AGB) star. The derived atmospheric parameters are
T<SUB>eff</SUB>=26500+/-1000K and logg=3.6+/-0.2dex. A differential
abundance analysis reveals a chemical composition typical of hot
post-AGB objects, with ZNG-1 being generally metal poor, although
helium is approximately solar. The most interesting feature is the
large carbon underabundance of more than 1.3dex. This carbon deficiency,
along with an observed nitrogen enhancement relative to other elements,
may suggest that ZNG-1 evolved off the AGB before the third dredge-up
occurred. Also, iron depletions observed in other similar stars
suggest that gas-dust fractionation in the AGB progenitor could be
responsible for the observed composition of these objects. However,
we need not invoke either scenario since the chemical composition of
ZNG-1 is in good agreement with abundances found for a Population II
star of the same metallicity.
---------------------------------------------------------
Title: The Extreme-Ultraviolet Structure and Properties of a Newly
Emerged Active Region
Authors: Gallagher, Peter T.; Phillips, Kenneth J. H.; Lee, Jeongwoo;
Keenan, Francis P.; Pinfield, David J.
2001ApJ...558..411G Altcode:
The structure and properties of a newly emerged solar active
region (NOAA Active Region 7985) are discussed using the Coronal
Diagnostic Spectrometer (CDS) and the Extreme-Ultraviolet Imaging
Telescope (EIT) on board the Solar and Heliospheric Observatory. CDS
obtained high-resolution EUV spectra in the 308-381 Å and 513-633
Å wavelength ranges, while EIT recorded full-disk EUV images in
the He II (304 Å), Fe IX/X (171 Å), Fe XII (195 Å), and Fe XV
(284 Å) bandpasses. Electron density measurements from Si IX,
Si X, Fe XII, Fe XIII, and Fe XIV line ratios indicate that the
region consists of a central high-density core with peak densities
of the order of 1.2×10<SUP>10</SUP> cm<SUP>-3</SUP>, which
decrease monotonically to ~5.0×10<SUP>8</SUP> cm<SUP>-3</SUP>
at the active region boundary. The derived electron densities
also vary systematically with temperature. Electron pressures as
a function of both active region position and temperature were
estimated using the derived electron densities and ion formation
temperatures, and the constant pressure assumption was found to be
an unrealistic simplification. Indeed, the active region is found
to have a high-pressure core (1.3×10<SUP>16</SUP> cm<SUP>-3</SUP>
K) that falls to 6.0×10<SUP>14</SUP> cm<SUP>-3</SUP> K just outside
the region. CDS line ratios from different ionization stages of iron,
specifically Fe XVI (335.4 Å) and Fe XIV (334.4 Å), were used to
diagnose plasma temperatures within the active region. Using this
method, peak temperatures of 2.1×10<SUP>6</SUP> K were identified. This
is in good agreement with electron temperatures derived using EIT
filter ratios and the two-temperature model of Zhang et al. The
high-temperature emission is confined to the active region core,
while emission from cooler (1-1.6)×10<SUP>6</SUP> K lines originates
in a system of loops visible in EIT 171 and 195 Å images. Finally,
the three-dimensional geometry of the active region is investigated
using potential field extrapolations from a Kitt Peak magnetogram. The
combination of EUV and magnetic field extrapolations extends the
“core-halo” picture of active region structure to one in which the
core is composed of a number of compact coronal loops that confine the
hot, dense, high-pressure core plasma while the halo emission emerges
from a system of cooler and more extended loops.
---------------------------------------------------------
Title: Solar coronal observations in high frequencies
Authors: Katsiyannis, A. C.; Mathioudakis, M.; Phillips, K. J. H.;
Williams, D. R.; Keenan, F. P.
2001hell.confE.174K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: X-ray and extreme-ultraviolet emission from the coronae
of Capella
Authors: Phillips, K. J. H.; Mathioudakis, M.; Huenemoerder, D. P.;
Williams, D. R.; Phillips, M. E.; Keenan, F. P.
2001MNRAS.325.1500P Altcode:
The primary objective of this work is the analysis and interpretation
of coronal observations of Capella obtained in 1999 September
with the High Energy Transmission Grating Spectrometer on the
Chandra X-ray Observatory and the Extreme Ultraviolet Explorer
(EUVE). He-like lines of O (Ovii) are used to derive a density of
1.7×10<SUP>10</SUP>cm<SUP>-3</SUP> for the coronae of the binary,
consistent with the upper limits derived from Fexxi, Neix and Mgxi
line ratios. Previous estimates of the electron density based on Fexxi
should be considered as upper limits. We construct emission measure
distributions and compare the theoretical and observed spectra to
conclude that the coronal material has a temperature distribution
that peaks around 4-6MK, implying that the coronae of Capella were
significantly cooler than in the previous years. In addition, we
present an extended line list with over 100 features in the 5-24Å
wavelength range, and find that the X-ray spectrum is very similar to
that of a solar flare observed with SMM. The observed to theoretical
Fexvii 15.012-Å line intensity reveals that opacity has no significant
effect on the line flux. We derive an upper limit to the optical depth,
which we combine with the electron density to derive an upper limit of
3000km for the size of the Fexvii emitting region. In the same context,
we use the Siiv transition region lines of Capella from HST/Goddard
High-Resolution Spectrometer observations to show that opacity can be
significant at T=10<SUP>5</SUP>K, and derive a path-length of ~75km
for the transition region. Both the coronal and transition region
observations are consistent with very small emitting regions, which
could be explained by small loops over the stellar surfaces.
---------------------------------------------------------
Title: Model atmosphere and kinematical analyses of early-type stars
from the Edinburgh-Cape Survey
Authors: Magee, H. R. M.; Dufton, P. L.; Keenan, F. P.; Rolleston,
W. R. J.; Kilkenny, D.; O'Donoghue, D.; Koen, C.; Stobie, R. S.
2001MNRAS.324..747M Altcode:
We present high-resolution spectroscopic observations of 21
B-type stars, selected from the Edinburgh-Cape Blue Object
Survey. Model atmosphere analyses confirm that 14 of these stars
are young, main-sequence B-type objects with Population I chemical
compositions. The remaining seven are found to be evolved objects,
including subdwarfs, horizontal branch and post-AGB objects. A
kinematical analysis shows that all 14 young main-sequence stars
could have formed in the disc and subsequently been ejected into
the halo. These results are combined with the analysis of a previous
subsample of stars taken from the Survey. Of the complete sample, 31
have been found to be young, main-sequence objects, with formation in
the disc, and subsequent ejection into the halo, again being found to
be a plausible scenario.
---------------------------------------------------------
Title: HST/STIS observations of the high-velocity interstellar cloud
HVC 291.2-41.2+80: a warm, mainly ionized high-velocity cloud
Authors: Lehner, N.; Keenan, F. P.; Sembach, K. R.
2001MNRAS.323..904L Altcode:
We present intermediate-resolution HST/STIS spectra of a high-velocity
interstellar cloud (v<SUB>LSR</SUB>=+80kms<SUP>-1</SUP>) towards DI1388,
a young star in the Magellanic Bridge located between the Small and
Large Magellanic Clouds. The STIS data have a signal-to-noise ratio
(S/N) of 20-45 and a spectral resolution of about 6.5kms<SUP>-1</SUP>
(FWHM). The high-velocity cloud absorption is observed in the lines
of Cii, Oi, Siii, Siiii, Siiv and Siii. Limits can be placed on
the amount of Sii and Feii absorption that is present. An analysis
of the relative abundances derived from the observed species,
particularly Cii and Oi, suggests that this high-velocity gas is warm
(T<SUB>k</SUB>~10<SUP>3</SUP>-10<SUP>4</SUP>K) and predominantly
ionized. This hypothesis is supported by the presence of absorption
produced by highly ionized species, such as Siiv. This sightline
also intercepts two other high-velocity clouds that produce weak
absorption features at v<SUB>LSR</SUB>=+113 and +130kms<SUP>-1</SUP>
in the STIS spectra.
---------------------------------------------------------
Title: Line identification in the Ca II K spectral region of
sharp-lined B-type stars
Authors: Lehner, N.; Trundle, C.; Keenan, F. P.; Sembach, K. R.;
Lambert, D. L.
2001A&A...370..996L Altcode:
Previous Ca Ii K observations of the B-type star HD 83206 have revealed
putative high-velocity interstellar clouds (HVCs) at Local Standard of
Rest (LSR) velocities of -80 and -110 kms<SUP>-1</SUP>. Similar results
were also found for the sightline towards HD 135485. In this article,
we show that these absorption lines are in fact due to stellar S Ii
features. As the Ca Ii K absorption line in B-type stars is often
used to assess the presence and distance of HVCs, we also present a
very high quality spectrum of HD 83206 in the Ca Ii K region ( ~ +/-
4 Å or +/- 300 kms<SUP>-1</SUP>), so that in the future confusion
between stellar lines and HVC features may be avoided.
---------------------------------------------------------
Title: Observations of the Interstellar Medium in the Magellanic
Bridge
Authors: Lehner, N.; Sembach, K. R.; Dufton, P. L.; Rolleston,
W. R. J.; Keenan, F. P.
2001ApJ...551..781L Altcode: 2001astro.ph..1548L
We present ultraviolet and optical spectra of DI 1388, a young star
in the Magellanic Bridge, a region of gas between the Small and Large
Magellanic Clouds. The data have signal-to-noise ratios of 20-45 and a
spectral resolution of 6.5 km s<SUP>-1</SUP>. Interstellar absorption
by the Magellanic Bridge at v<SUB>LSR</SUB>~200 km s<SUP>-1</SUP>
is visible in the lines of C I, C II, C II*, C IV, N I, O I, Al II,
Si II, Si III, Si IV, S II, Ca II, Fe II, and Ni II. The relative
gas-phase abundances of C II, N I, O I, Al II, Si II, Fe II, and Ni II
with respect to S II are similar to those found in Galactic halo clouds,
despite a significantly lower metallicity in the Magellanic Bridge. The
higher ionization species in the cloud have a column density ratio
N(C<SUP>+3</SUP>)/N(Si<SUP>+3</SUP>)~1.9, similar to that inferred
for collisionally ionized Galactic cloud interfaces at temperatures
~10<SUP>5</SUP> K. We identify substructure in the stronger interstellar
lines, with a broad component (FWHM~20 km s<SUP>-1</SUP>) at ~179
km s<SUP>-1</SUP> and a sharp component (FWHM~11 km s<SUP>-1</SUP>)
at 198 km s<SUP>-1</SUP>. The abundance analysis for these clouds
indicates that the feature at 198 km s<SUP>-1</SUP> consists of
a low electron density, mainly neutral gas that may be associated
with an interface responsible for the highly ionized gas. The 179
km s<SUP>-1</SUP> cloud consists of warmer, lower density gas that
is partially ionized. Based on observations with the NASA/ESA Hubble
Space Telescope, obtained at the Space Telescope Science Institute,
which is operated by the Association of Universities for Research in
Astronomy, Inc. under NASA contract NAS5-26555.
---------------------------------------------------------
Title: Hi and optical spectroscopy towards the M15
intermediate-velocity cloud
Authors: Smoker, J. V.; Lehner, N.; Keenan, F. P.; Totten, E. J.;
Murphy, E.; Sembach, K. R.; Davies, R. D.; Bates, B.
2001MNRAS.322...13S Altcode: 2002astro.ph..4464S
We present single-dish Arecibo 21-cm Hi observations, covering a
0.675°×0.625° RA-Dec. grid, of the intermediate-velocity cloud (IVC)
centred upon the M15 globular cluster. The velocity and positional
structure of the IVC gas at V<SUB>LSR</SUB>=70kms<SUP>-1</SUP> are
investigated; it is found to be clumpy and has a peak surface density
N<SUB>Hi</SUB>~8×10<SUP>19</SUP>cm<SUP>-2</SUP>. Additionally, we have
performed a long Hi integration towards HD 203664, a Galactic halo star
some 3.1° from M15, in which optical IVC absorption has previously
been detected. No Hi with a velocity exceeding 60kms<SUP>-1</SUP>
was found to a brightness temperature limit of 0.05K. However,
additional pointings did detect IVC gas approximately mid-way between
HD 203664 and M15. Finally, we present both Arecibo Hi pointings and
low-resolution spectra in the Caii H and K lines towards 15 field
stars in the general field towards M15, in an attempt to obtain the
distance to the IVC. Intermediate-velocity Hi is detected towards
seven sightlines. Stellar spectral types are derived for 12 of the
sample. Assuming that these stars lie on the main sequence, their
distances are estimated to lie in the range 150<=d<=1350pc. No
Caii absorption is observed, either because the IVC is further away
than ~1350pc or more likely because the gas along these sightlines is
of too low a density to be detected by the current observations.
---------------------------------------------------------
Title: Chemical abundances in the inner 5 kpc of the Galactic disk
Authors: Smartt, S. J.; Venn, K. A.; Dufton, P. L.; Lennon, D. J.;
Rolleston, W. R. J.; Keenan, F. P.
2001A&A...367...86S Altcode: 2000astro.ph..9157S
High-resolution, high signal-to-noise spectral data are presented for
four young B-type stars lying towards the Galactic Centre. Determination
of their atmospheric parameters from their absorption line profiles,
and uvby photometric measurement of the continua indicate that they
are massive objects lying slightly out of the plane, and were probably
born in the disk between 2.5-5 kpc from the Centre. We have carried out
a detailed absolute and differential line-by-line abundance analyses
of the four stars compared to two stars with very similar atmospheric
parameters in the solar neighbourhood. The stars appear to be rich in
all the well sampled chemical elements (C, N, Si, Mg, S, Al), except
for oxygen. Oxygen abundances derived in the atmospheres of these
four stars are very similar to that in the solar neighbourhood. If
the photospheric composition of these young stars is reflective of
the gaseous ISM in the inner Galaxy, then the values derived for the
enhanced metals are in excellent agreement with the extrapolation of
the Galactic abundance gradients previously derived by Rolleston et
al. (2000) and others. However, the data for oxygen suggests that the
inner Galaxy may not be richer than normal in this element, and the
physical reasons for such a scenario are unclear.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Chemical abundances of 5 Galactic
disk B stars (Smartt+, 2001)
Authors: Smartt, S. J.; Venn, K. A.; Dufton, P. L.; Lennon, D. J.;
Rolleston, W. R. J.; Keenan, F. P.
2001yCat..33670086S Altcode:
High-resolution, high signal-to-noise spectral data are presented for
four young B-type stars lying towards the Galactic Centre. Determination
of their atmospheric parameters from their absorption line profiles,
and uvby photometric measurement of the continua indicate that they
are massive objects lying slightly out of the plane, and were probably
born in the disk between 2.5-5kpc from the Centre. We have carried out
a detailed absolute and differential line-by-line abundance analyses
of the four stars compared to two stars with very similar atmospheric
parameters in the solar neighbourhood. The stars appear to be rich in
all the well sampled chemical elements (C, N, Si, Mg, S, Al), except
for oxygen. Oxygen abundances derived in the atmospheres of these
four stars are very similar to that in the solar neighbourhood. If
the photospheric composition of these young stars is reflective of
the gaseous ISM in the inner Galaxy, then the values derived for the
enhanced metals are in excellent agreement with the extrapolation of
the Galactic abundance gradients previously derived by Rolleston et
al. (2000A&A...363..537R) and others. However, the data for oxygen
suggests that the inner Galaxy may not be richer than normal in this
element, and the physical reasons for such a scenario are unclear. (2
data files).
---------------------------------------------------------
Title: Photoionization and Heating of a Well-characterized Iron Plasma
Authors: Foord, M. E.; Heeter, R. F.; Thoe, R. S.; Liedahl, D. A.;
Fournier, K. B.; Goldstein, W. H.; Springer, P. T.; Bailey, J. E.;
Cuneo, M. E.; Chandler, G. A.; Nash, T. J.; Phillips, M.; Keenan,
F.; Rose, S.
2001ASPC..247..117F Altcode: 2001scpp.conf..117F
No abstract at ADS
---------------------------------------------------------
Title: Photoionized Plasma Calculations using Laboratory and
Astrophysical Models
Authors: Phillips, M. E.; Keenan, F. P.; Rose, S. J.; Botha, G. J. J.;
Foord, M. E.; Heeter, R. F.; Ferland, G. J.
2001ASPC..247..123P Altcode: 2001scpp.conf..123P
No abstract at ADS
---------------------------------------------------------
Title: Cornoal Heating by MHD Waves: Results from the SECIS Instrument
during the 1999 Eclipse
Authors: Phillip, K. J. H.; Gallagher, P. T.; Williams, D. R.; Keenan,
F. P.; Rudawy, P.; Rompolt, B.; Berlicki, A.
2001IAUS..203..467P Altcode:
We report on observational evidence for the rôles that small flare-like
events and short-period MHD waves play in the heating of the solar
corona. In several studies of SOHO and Yohkoh data, we examine the
numbers and energies of small events in the EUV and in soft X-rays
can account for the necessary energetics of the quiet-Sun corona,
finding that EUV events at least might be sufficient to provide the
heating, at least in closed-field regions. Results will be summarized
in this paper. However, MHD waves may still play an important part,
and in a separate investigation we have used fast-cadence imaging of
the white-light and green-line corona during the total eclipse of 1999
August 11 to search for short-period modulations. The imaging system
is the Solar Eclipse Coronal Imaging System (SECIS), and consists of a
pair of CCD cameras and an adapted PC to form images of the corona at
a frame rate of 44 s<SUP>-1</SUP>. Preliminary analysis of the data
suggests the presence of fast changes over the 2-minute-long period
of eclipse totality. This paper will also report on the SECIS data.
---------------------------------------------------------
Title: Opacity Effects in the Transition Region of Active Stars
(CD-ROM Directory: contribs/williams)
Authors: Williams, D. R.; Mathioudakis, M.; McKenny, J.; Keenan, F. P.
2001ASPC..223..889W Altcode: 2001csss...11..889W
No abstract at ADS
---------------------------------------------------------
Title: Theoretical emission line ratios for [Fe III] and [Fe VII]
applicable to the optical and infrared spectra of gaseous nebulae
Authors: Keenan, Francis P.; Aller, Lawrence H.; Ryans, Robert S. I.;
Hyung, Siek
2001PNAS...98.9476K Altcode:
Recent calculations of electron impact excitation rates and Einstein
A-coefficients for transitions among the 3d6 levels of Fe III
and among the 3d2 levels of Fe VII are used to derive theoretical
emission line ratios applicable to the optical and infrared spectra
of gaseous nebulae. Results for [Fe III] are generated for electron
temperatures Te = 7,000-20,000 K and densities N<SUB>e</SUB> =
10<SUP>2</SUP>-10<SUP>8</SUP> cm<SUP>-3</SUP>, whereas those for [Fe
VII] are provided for T<SUB>e</SUB> = 10,000-30,000 K and N<SUB>e</SUB>
= 10<SUP>2</SUP>-10<SUP>8</SUP> cm<SUP>-3</SUP>. The theoretical line
ratios are significantly different in some instances from earlier
calculations and resolve discrepancies between theory and observation
found for the planetary nebulae IC 4997 and NGC 7027.
---------------------------------------------------------
Title: Emission-Line Ratios for [N II] in Gaseous Nebulae and a
Comparison between Theory and Observation
Authors: Keenan, F. P.; Crawford, F. L.; Feibelman, W. A.; Aller, L. H.
2001ApJS..132..103K Altcode:
R-matrix calculations of electron impact excitation rates among
the 2s<SUP>2</SUP>2p<SUP>2</SUP> <SUP>3</SUP>P, <SUP>1</SUP>D,
<SUP>1</SUP>S, and 2s2p<SUP>3</SUP> <SUP>5</SUP>S levels of
N II are presented. These results are used in conjunction with
other recent calculations of electron impact excitation rates and
Einstein A-coefficients for N II to derive the emission-line ratio:
ratio diagrams (R<SUB>1</SUB>, R<SUB>2</SUB>) and (R<SUB>1</SUB>,
R<SUB>3</SUB>), where R<SUB>1</SUB>=I(5756.2 Å)/I(6549.9+6585.2
Å), R<SUB>2</SUB>=I(2143.5 Å)/I(6549.9+6585.2 Å), and
R<SUB>3</SUB>=I(2139.7 Å)/I(6549.9+6585.2 Å), for a range of
electron temperatures (T<SUB>e</SUB>=5000-20,000 K) and electron
densities (N<SUB>e</SUB>=10<SUP>2</SUP>-10<SUP>7</SUP> cm<SUP>-3</SUP>)
appropriate to gaseous nebulae. These diagrams should, in principle,
allow the simultaneous determination of T<SUB>e</SUB> and N<SUB>e</SUB>
from measurements of the [N II] lines in a spectrum. Plasma parameters
deduced for a sample of gaseous nebulae, using observational data
obtained from ground-based telescopes plus the International Ultraviolet
Explorer and Hubble Space Telescope satellites, are found to show
generally excellent internal consistency and to be in good agreement
with the values of T<SUB>e</SUB> and N<SUB>e</SUB> estimated from
other line ratios. These results provide observational support for the
accuracy of the theoretical ratios and hence the atomic data adopted in
their derivation. Theoretical ratios are also presented for the infrared
line pair R<SUB>4</SUB>=I(122 μm)/I(205 μm), and the usefulness of
R<SUB>4</SUB> as an electron density diagnostic is briefly discussed.
---------------------------------------------------------
Title: S xi Emission Lines in Active Region Spectra Obtained with
the Solar euv Rocket Telescope and Spectrograph (Serts)
Authors: Keenan, F. P.; Pinfield, D. J.; Mathioudakis, M.; Aggarwal,
K. M.; Thomas, R. J.; Brosius, J. W.
2000SoPh..197..253K Altcode:
Theoretical electron density sensitive emission line ratios involving
a total of eleven 2s<SUP>2</SUP>2p<SUP>2</SUP>-2s2p<SUP>3</SUP>
transitions in S xi between 187 and 292 Å are presented. A
comparison of these with solar active region observations obtained
during rocket flights by the Solar EUV Rocket Telescope and
Spectrograph (SERTS) reveals generally good agreement between
theory and experiment. However, the 186.87 Å line is masked by
fairly strong Fe xii emission at the same wavelength, while 239.83
Å is blended with an unknown feature, and 285.58 Å is blended with
possibly N iv 285.56 Å. In addition, the 191.23 Å line appears to
be more seriously blended with an Fe xiii feature than previously
believed. The presence of several new S xi lines is confirmed in the
SERTS spectra, at wavelengths of 188.66, 247.14 and 291.59 Å, in
excellent agreement with laboratory measurements. In particular, the
detection of the 2s<SUP>2</SUP>2p<SUP>2</SUP><SUP>3</SUP>P<SUB>1</SUB>
-2s2p<SUP>3</SUP><SUP>3</SUP>P<SUB>0,1</SUB> transitions at 242.91
Å is the first time (to our knowledge) that this feature has been
identified in the solar spectrum. The potential usefulness of the S xi
line ratios as electron density diagnostics for the solar transition
region and corona is briefly discussed.
---------------------------------------------------------
Title: CO and optical observations of the Magellanic Bridge
Authors: Smoker, J. V.; Keenan, F. P.; Polatidis, A. G.; Mooney,
C. J.; Lehner, N.; Rolleston, W. R. J.
2000A&A...363..451S Altcode:
We present <SUP>12</SUP>CO(1-0) molecular line and BV CCD observations
towards 0311-7651, a region in the Magellanic Bridge where cold
atomic Hydrogen has previously been detected by Kobulnicky &
Dickey. Additionally, BV images of a comparison field 1<SUP>deg</SUP> to
the South were taken. No CO was detected to a limit of ~ 0.06 Kelvin,
and the colour-magnitude diagrams show no evidence for a stellar
association in either field. Based on observations made with the
Danish 1.54-m and SEST telescopes at the European Southern Observatory,
La Silla, Chile.
---------------------------------------------------------
Title: A developed stage of Alfvén wave phase mixing
Authors: Botha, G. J. J.; Arber, T. D.; Nakariakov, V. M.; Keenan,
F. P.
2000A&A...363.1186B Altcode:
Alfvén wave phase mixing is an extensively studied mechanism for
dissipating wave energy in an inhomogeneous medium. It is common in the
vast majority of phase mixing papers to assume that even though short
scale lengths and steep gradients develop as a result of phase mixing,
nonlinear wave coupling does not occur. However, weakly nonlinear
studies have shown that phase mixing generates magnetoacoustic
modes. Numerical results are presented which show the nonlinear
generation of magnetosonic waves by Alfvén wave phase mixing. The
efficiency of the effect is determined by the wave amplitude, the
frequency of the Alfvén waves and the gradient in the background
Alfvén speed. Weakly nonlinear theory has shown that the amplitude
of the fast magnetosonic wave grows linearly in time. The simulations
presented in this paper extend this result to later times and show
saturation of the fast magnetosonic component at amplitudes much lower
than that of the Alfvén wave. For the case where Alfvén waves are
driven at the boundary, simulating photospheric footpoint motion,
a clear modulation of the saturated amplitude is observed. All the
results in this paper are for a low amplitude (<= 0.1), single
frequency Alfvén wave and a uniform background magnetic field in
a two dimensional domain. For this simplified geometry, and with a
monochromatic driver, we concluded that the nonlinear generation of
fast modes has little effect on classical phase mixing.
---------------------------------------------------------
Title: Electron density diagnostics for solar ultraviolet lines of O V
Authors: O'Shea, E.; O'Neill, T.; Keenan, F. P.; Doyle, J. G.
2000SoPh..196..321O Altcode:
We determine the electron densities for a range of solar features using
new calculations for the O v line ratio, R=I(λ761.1)/I(λ760.4), in
conjunction with observational data obtained with the Solar Ultraviolet
Measurements of Emitted Radiation (SUMER) instrument on the Solar
and Heliospheric Observatory (SOHO). The densities obtained from this
diagnostic are in good agreement with earlier measured values. This
provides support for the theoretical diagnostics presented in this
paper, and hence the atomic data used in their derivation. We conclude
from these results that this particular O v ratio is a useful diagnostic
for many types of solar features.
---------------------------------------------------------
Title: Emission lines of O bt III in the optical and ultraviolet
spectra { } of planetary nebulae
Authors: Crawford, F. L.; Keenan, F. P.; Aggarwal, K. M.; Wickstead,
A. W.; Aller, L. H.; Feibelman, W. A.
2000A&A...362..730C Altcode:
Recent R-matrix calculations of electron impact excitation rates in O
Iii are used to calculate electron temperature and density-dependent
emission line ratios R<SUB>1</SUB> = I(4363 Å) / I(4960 Å+ 5007
Å), R<SUB>2</SUB> = I(1661 Å+ 1667 Å) / I(4960 Å+ 5007 Å)
and R<SUB>3</SUB> = I(2322 Å) / I(1661 Å+ 1667 Å), for a range
of electron temperatures (7500 <= T<SUB>e</SUB> <= 30 000 K)
and densities (10<SUP>4</SUP> <= N<SUB>e</SUB> <= 10<SUP>7</SUP>
cm<SUP>-3</SUP>) applicable to gaseous nebulae. The ratio-ratio diagrams
(R<SUB>1</SUB>, R<SUB>2</SUB>) and (R<SUB>1</SUB>, R<SUB>3</SUB>)
should, in principle, allow the simultaneous determination of
T<SUB>e</SUB> and N<SUB>e</SUB> from measurements of the O Iii features
in a spectrum. Plasma parameters derived for a sample of mid- to
high-excitation planetary nebulae from (R<SUB>1</SUB>, R<SUB>2</SUB>)
and (R<SUB>1</SUB>, R<SUB>3</SUB>) measurements, produced using a
combination of ultraviolet spectra obtained with the International
Ultraviolet Explorer (IUE) and optical data from a number of observing
runs, are found to show excellent internal consistency. They also
show, in general, good agreement with the values of T<SUB>e</SUB> and
N<SUB>e</SUB> estimated from other line ratios in the nebulae, therefore
providing observational support for the accuracy of the theoretical
ratios and hence the atomic data adopted in their derivation.
---------------------------------------------------------
Title: The Radial and Angular Variation of Electron Density in the
Solar Corona.
Authors: Gallagher, P. T.; Mathioudakis, M.; Phillips, K. J. H.;
Tsinganos, K.; Keenan, F. P.
2000SPD....31.0234G Altcode: 2000BAAS...32.1290G
We derive, for the first time, electron densities as a function of
both radius (R) and position angle (θ ) for the south-west quadrant of
the off-limb corona, using the density-sensitive Si ix (349.9 Å/341.9
Å) and Si x (356.0 Å/347.7 Å) extreme ultraviolet line ratios. The
observations were made with the Coronal Diagnostic Spectrometer (cds)
on board the Solar and Heliospheric Observatory (soho), over the range
1.00R<SUB>⊙ </SUB> < R < 1.20R<SUB>⊙ </SUB> and 180° <
θ < 270° . Within the south polar coronal hole, the density varies
from 2.3 x 10<SUP>8</SUP> cm<SUP>-3</SUP> at 1.0R<SUB>⊙ </SUB> to 8.3x
10<SUP>7</SUP> cm<SUP>-3</SUP> at 1.20R<SUB>⊙ </SUB>, while at the
equator the density varies from 6.3 x 10<SUP>8</SUP> cm<SUP>-3</SUP>
at 1.0R<SUB>⊙ </SUB> to 1.6x 10<SUP>8</SUP> cm<SUP>-3</SUP> at
1.20R<SUB>⊙ </SUB>. The density falloff with height is therefore
faster in the equatorial region. We also find that electron densities
are, on average, a factor of 2.7 larger in the equatorial regions than
in the polar coronal hole at a given radial distance. Finally, we find
remarkable agreement between our measured densities as a function of
radius and position angle and those predicted by a recent analytic
MHD model of the solar wind, strongly supporting its basic premises.
---------------------------------------------------------
Title: Extreme ultraviolet emission lines of Nixii in laboratory
and solar spectra
Authors: Keenan, F. P.; Botha, G. J. J.; Matthews, A.; Lawson, K. D.;
Coffey, I. H.
2000MNRAS.318...37K Altcode:
Wavelengths for emission lines arising from
3s<SUP>2</SUP>3p<SUP>5</SUP>-3s3p<SUP>6</SUP> and
3s<SUP>2</SUP>3p<SUP>5</SUP>-3s<SUP>2</SUP>3p<SUP>4</SUP>3d
transitions in Nixii have been measured in extreme ultraviolet
spectra of the Joint European Torus (JET) tokamak. The
3s<SUP>2</SUP>3p<SUP>5</SUP> <SUP>2</SUP>P<SUB>1/2</SUB>-
3s<SUP>2</SUP>3p<SUP>4</SUP>(<SUP>3</SUP>P)3d
<SUP>2</SUP>D<SUB>3/2</SUB> line is found to lie at 152.90+/-0.02Å,
a significant improvement over the previous experimental determination
of 152.95+/-0.5Å. This new wavelength is in good agreement with a solar
identification at 152.84+/-0.06Å, confirming the presence of this line
in the solar spectrum. The Nixii feature at 152.15Å may be a result
only of the 3s<SUP>2</SUP>3p<SUP>5</SUP> <SUP>2</SUP>P<SUB>3/2</SUB>-
3s<SUP>2</SUP>3p<SUP>4</SUP>(<SUP>3</SUP>P)3d
<SUP>2</SUP>D<SUB>5/2</SUB> transition, rather than a blend of this
line with 3s<SUP>2</SUP>3p<SUP>5</SUP> <SUP>2</SUP>P<SUB>3/2</SUB>-
3s<SUP>2</SUP>3p<SUP>4</SUP>(<SUP>3</SUP>P)3d
<SUP>2</SUP>P<SUB>1/2</SUB>, as previously
suggested. Unidentified emission lines at 295.32 and
317.61Å in solar flare spectra from the Skylab mission are
tentatively identified as the 3s<SUP>2</SUP>3p<SUP>5</SUP>
<SUP>2</SUP>P<SUB>3/2</SUB>-3s3p<SUP>6</SUP>
<SUP>2</SUP>S<SUB>1/2</SUB> and 3s<SUP>2</SUP>3p<SUP>5</SUP>
<SUP>2</SUP>P<SUB>1/2</SUB>-3s3p<SUP>6</SUP> <SUP>2</SUP>S<SUB>1/2</SUB>
transitions in Nixii, which have laboratory wavelengths of 295.33 and
317.50Å, respectively. Additional support for these identifications
is provided by the line intensity ratio for the solar features, which
shows good agreement between theory and observation.
---------------------------------------------------------
Title: K-Shell Photoionization of Fe
Authors: McLaughlin, B. M.; Donnelly, D.; Bell, K. L.; Scott, M. P.;
Keenan, F. P.
2000adnx.conf...85M Altcode:
The status of K-shell photoionization of neutral iron has been
reviewed. A comparison with the available experimental data and existing
theoretical work is made for this important element. Several anomalies
and features are illustrated and future directions of theoretical work
are indicated.
---------------------------------------------------------
Title: Radio continuum observations of possible B-type stars in the
halo of M 31
Authors: Smoker, J. V.; Keenan, F. P.; Marcha, M. J.; Watson, D.;
Irwin, M. J.
2000A&A...361...60S Altcode:
We present Very Large Array (VLA) 5 GHz continuum observations of
six point sources towards the halo of M 31, which have featureless
optical spectra and magnitudes ranging from V=21.5-22.2, in order
to determine whether these objects are BL Lacs. No radio emission
coincident with the optical positions is detected to a 5sigma noise
level of between 0.08 and 0.11 mJy. The resulting upper limits to
the two-point radio-to-optical spectral indexes from 5 GHz to 2500
&Aring (alpha_RO ) are less than 0.30 for all of the sample. These
observations make it highly likely that these objects are not BL Lacs,
and hence strengthens the case that they are normal B-type stars in
the halo of M 31. Based on observations taken at the National Radio
Observatory which is operated by Associated Universities, Inc., under
cooperative agreement with the National Science Foundation, USA
---------------------------------------------------------
Title: Multi-wavelength observations of the 1998 September 27
flare spray
Authors: Gallagher, Peter T.; Williams, David R.; Phillips, Kenneth
J. H.; Mathioudakis, Mihalis; Smartt, Raymond N.; Keenan, Francis P.
2000SoPh..195..367G Altcode:
We report on observations of a large eruptive event associated with a
flare that occurred on 27 September 1998 made with the Richard B. Dunn
Solar Telescope at Sacramento Peak Observatory (several wave bands
including off-line-center Hα), in soft and hard X-rays (GOES and
BATSE), and in several TRACE wave bands (including Fe ix/x 171 Å,
Fe xii 195 Å, and C iv 1550 Å). The flare initiation is signaled by
two Hα foot-point brightenings which are closely followed by a hard
X-ray burst and a subsequent gradual increase in other wavelengths. The
flare light curves show a complicated, three-component structure which
includes two minor maxima before the main GOES class C5.2 peak after
which there is a characteristic exponential decline. During the initial
stages, a large spray event is observed within seconds of the hard
X-ray burst which can be directly associated with a two-ribbon flare
in Hα. The emission returns to pre-flare levels after about 35 min,
by which time a set of bright post-flare loops have begun to form at
temperatures of about 1.0-1.5 MK. Part of the flare plasma also intrudes
into the penumbra of a large sunspot, generally a characteristic of
very powerful flares, but the flare importance in GOES soft X-rays is in
fact relatively modest. Much of the energy appears to be in the form of
a second ejection which is observed in optical and ultraviolet bands,
traveling out via several magnetic flux tubes from the main flare site
(about 60° from Sun center) to beyond the limb.
---------------------------------------------------------
Title: Six emission lines in spectra obtained with the Solar EUV
Rocket Telescope and Spectrograph (SERTS)
Authors: Keenan, F. P.; O'Shea, E.; Thomas, R. J.; Brosius, J. W.;
Katsiyannis, A.; Ryans, R. S. I.; Reid, R. H. G.; Pradhan, A. K.;
Zhang, H. L.
2000MNRAS.315..450K Altcode:
New R-matrix calculations of electron impact excitation rates
for transitions among the 2s<SUP>2</SUP>2p, 2s2p<SUP>2</SUP> and
2p<SUP>3</SUP> levels of Six are presented. These data are subsequently
used, in conjunction with recent estimates for proton excitation rates,
to derive theoretical electron density sensitive emission-line ratios
involving transitions in the ~253-356Å wavelength range. A comparision
of these with observations of a solar active region and subflare,
obtained during the 1989 flight of the Solar EUV Rocket Telescope and
Spectrograph (SERTS), reveals that the electron densities determined
from most of the Six line ratios are consistent with one another for
both solar features. In addition, the derived densities are also in good
agreement with the values of N<SUB>e</SUB> estimated from diagnostic
lines in other species formed at similar electron temperatures to Six,
such as Fexii and Fexiii. These results provide observational support
for the general accuracy of the adopted atomic data, and hence line
ratio calculations, employed in the present analysis. However, we find
that the Six 256.32-Å line is blended with the Heii transition at
the same wavelength, while the feature at 292.25Å is not due to Six,
but currently remains unidentified. The intensity of the 253.81-Å line
in the SERTS active region spectrum is about a factor of 3 larger than
expected from theory, but the reason for this is unclear, and requires
additional observations to explain the discrepancy.
---------------------------------------------------------
Title: Transition region and coronal structuring
Authors: O'Shea, E.; Gallagher, P. T.; Mathioudakis, M.; Phillips,
K. J. H.; Keenan, F. P.; Katsiyannis, A. C.
2000A&A...358..741O Altcode:
In this paper we examine regions of internetwork, network and bright
network emission, observed in the quiet Sun with the Coronal Diagnostic
Spectrometer (cds) onboard SoHO. The slopes of the emission measure
distributions, between 5.4 <= log T<SUB>e</SUB> <= 6.0, are
found to differ in each region, suggesting the presence of different
atmospheric structures. From an analysis of emission area the network
is shown to have two populations of structures, a low transition region
group and a coronal group. Using mdi magnetograms the bright network
emission is shown to originate from regions of strong magnetic field
composed of bipolar loops and unipolar funnels, that extend from the
low transition region up to the corona. Up to 30% of all radiative
losses between 5.7 <= log T<SUB>e</SUB> <= 6.3 are found to come
from these continuous bright network structures. Cross-sectional areas
calculated from redshift values suggest that the area expansion seen
in the bright network emission is the result of flux tube expansion
into the corona, accompanied by either a downflow or upflow of material.
---------------------------------------------------------
Title: Strömgren uvby photometry of B-type stars from the
Palomar-Green Survey
Authors: Mooney, C. J.; Rolleston, W. R. J.; Keenan, F. P.; Pinfield,
D. J.; Pollacco, D. L.; Dufton, P. L.; Katsiyannis, A. C.
2000A&A...357..553M Altcode:
We present Strömgren uvby photometry for a sample of 31 high Galactic
latitude stars selected from the Palomar-Green Survey. The data include
photometric magnitudes accurate to <= 0.01 mag in most cases,
plus colours and the reddening free [c_1] and [u-b] indices, which
possess a precision of better than 0.02 and 0.04 mag, respectively. The
latter should be suitable for the reliable determination of stellar
photometric temperatures.
---------------------------------------------------------
Title: High-resolution optical spectroscopy of the sharp-lined B-type
star HD83206
Authors: Lehner, N.; Dufton, P. L.; Lambert, D. L.; Ryans, R. S. I.;
Keenan, F. P.
2000MNRAS.314..199L Altcode:
Very-high-resolution (R~160000) spectroscopic observations are
presented for the early B-type star, HD83206. Because it has very
sharp metal lines, this star affords an opportunity to test theories
of model atmospheres and line formation. Non-LTE model atmosphere
calculations have been used to estimate the atmospheric parameters and
absolute metal abundances (C, N, O, Mg and Si); an LTE analysis was
also undertaken to investigate the validity of this simpler approach
and to estimate an iron abundance. For the non-LTE calculations,
there is excellent agreement with observations of the Balmer lines Hα
and Hδ and the lines of Siii and Siiii for atmospheric parameters of
T<SUB>eff</SUB>~=21700+/-600K and logg~=4.00+/-0.15dex. The agreement
is less convincing for the LTE calculations, and a higher gravity is
deduced. Careful comparison of the metal line profiles with non-LTE
calculations implies that the projected rotational and microturbulent
velocities have maximum values of ~=5 and ~=2kms<SUP>-1</SUP>,
respectively. The latter value is smaller than has often been adopted in
LTE model atmosphere analyses of main-sequence stars. Non-LTE absolute
metal abundances are estimated, and a comparison with those for
normal B-type stars (deduced using similar non-LTE techniques) shows
no significant differences. A comparison of the abundances deduced
using non-LTE and LTE calculations implies systematic differences
of 0.1-0.2dex, showing the importance of using a non-LTE approach
when accurate absolute abundances are required. Its location in the
Hertzsprung-Russell diagram and normal metal abundance lead us to
conclude that HD83206 is probably a main-sequence B-type star. As such,
it is among the sharpest-lined young B-type star discovered to date.
---------------------------------------------------------
Title: SECIS: The Solar Eclipse Coronal Eclipse Imaging System
Authors: Phillips, K. J. H.; Read, P. D.; Gallagher, P. T.; Keenan,
F. P.; Rudawy, P.; Rompolt, B.; Berlicki, A.; Buczylko, A.; Diego,
F.; Barnsley, R.; Smartt, R. N.; Pasachoff, J. M.; Babcock, B. A.
2000SoPh..193..259P Altcode:
The Solar Eclipse Coronal Imaging System (SECIS) is an instrument
designed to search for short-period modulations in the solar corona
seen either during a total eclipse or with a coronagraph. The CCD
cameras used in SECIS have the capability of imaging the corona at a
rate of up to 70 frames a second, with the intensities in each pixel
digitised in 12-bit levels. The data are captured and stored on a
modified PC. With suitable optics it is thus possible to search for
fast changes or short-period wave motions in the corona that will
have important implications for the coronal heating mechanism. The
equipment has been successfully tested using the Evans Solar Facility
coronagraph at National Solar Observatory/Sacramento Peak and during
the 11 August 1999 eclipse at a site in north-eastern Bulgaria. The
instrument is described and preliminary results are outlined.
---------------------------------------------------------
Title: Cross Sections for the K-Shell Photoabsorption of Neutral Iron
Authors: Donnelly, D. W.; Bell, K. L.; Scott, M. P.; Keenan, F. P.
2000ApJ...531.1168D Altcode:
The Fe I Kα emission lines are observed during solar flares and in
the emission spectra of other astrophysical sources, such as active
galactic nuclei. This paper presents cross sections for the K-shell
photoionization of neutral iron, which are urgently required for
the modeling of these astrophysical phenomena. A 16 target-state
representation is utilized, where each target state is represented
by an extensive configuration-interaction-type wave function. The
consequent introduction of electron correlation effects is seen to
significantly alter the magnitude of the background cross section in
comparison with earlier work, while extensive resonance structure is
also resolved near threshold for the first time.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Excitation rate coefficients for
O III (Aggarwal+, 1999)
Authors: Aggarwal, K. M.; Keenan, F. P.
2000yCat..21230311A Altcode:
Collision strengths for fine-structure transitions among the levels of
the (1s<SUP>2</SUP>) 2s<SUP>2</SUP>2p<SUP>2</SUP>, 2s2p<SUP>3</SUP>,
2p<SUP>4</SUP>, 2s<SUP>2</SUP>2p3s, 2s<SUP>2</SUP>2p3p, and
2s<SUP>2</SUP>2p3d configurations of O III have been computed over a
wide range of energies below 13.0 ryd using the R-matrix program. All
partial waves with L{<=}40 have been included to ensure the
convergence of results. Excitation rate coefficients, in the form of
dimensionless effective collision strengths, have also been computed at
temperatures below 200,000 K. The results are compared with available
calculations, and accuracy of the data is assessed. <P />(4 data files).
---------------------------------------------------------
Title: Fe II emission lines as a chronometer for high-redshift quasars
Authors: Espey, Brian; Ferland, Gary; Keenan, Francis; Verner, Dima
2000noao.prop..301E Altcode:
We have embarked on a project to fully simulate the physical conditions
within Fe II-emitting gas, and predict the resulting spectrum. The first
steps of generating the initial atomic database, and incorporating it
into the photoionization code CLOUDY, are complete. Here we request
echelle observations of the symbiotic star RR Telescopii (RR Tel), to
combine with HST/STIS data to give the first complete coverage of Fe II
emission lines in the 1150-10000 Arange. The Fe II emitting regions in
symbiotics have similar physical conditions to those in active galaxies,
and hence the RR Tel observations will provide a testbed for our Fe II
numerical simulations. Analysis of the RR Tel data using CLOUDY will
allow us to check the reliability and completeness of the atomic data
and processes considered, to investigate the sensitivity of emission
to temperature and density variations, and to assess the importance of
blending. Once calibrated against the RR Tel data, we will use our Fe II
simulations to deduce iron abundances in high-redshift quasars. This,
in conjunction with predictions of stellar evolution and galactic
nucleosynthesis, will result in a chronometer measuring the redshift
when the universe passed through an age of 1 Gyr, thus constraining
several cosmological parameters.
---------------------------------------------------------
Title: Strömgren uvby photometry of hot stars at high galactic
latitudes
Authors: Mooney, C. J.; Rolleston, W. R. J.; Keenan, F. P.; Pinfield,
D. J.; Pollacco, D. L.; Dufton, P. L.
2000LIACo..35..517M Altcode: 2000ghgc.conf..517M
No abstract at ADS
---------------------------------------------------------
Title: Identification of the [Al II] Forbidden Line at 2661 Å in
the Spectrum of RR Telescopii
Authors: Crawford, F. L.; Keenan, F. P.; Mathioudakis, M.; Aggarwal,
K. M.; McKenna, F. C.; Feibelman, W. A.; Espey, B. R.
2000ASPC..204..387C Altcode: 2000tiaf.conf..387C
No abstract at ADS
---------------------------------------------------------
Title: Nebular and auroral emission lines of [Cl III] in the optical
spectra of planetary nebulae
Authors: Keenan, Francis P.; Aller, Lawrence H.; Ramsbottom, Catherine
A.; Bell, Kenneth L.; Crawford, Fergal L.; Hyung, Siek
2000PNAS...97.4551K Altcode:
Electron impact excitation rates in Cl III, recently determined
with the R-matrix code, are used to calculate electron temperature
(T<SUB>e</SUB>) and density (N<SUB>e</SUB>) emission line ratios
involving both the nebular (5517.7, 5537.9 A) and auroral (8433.9,
8480.9, 8500.0 A) transitions. A comparison of these results with
observational data for a sample of planetary nebulae, obtained with the
Hamilton Echelle Spectrograph on the 3-m Shane Telescope, revelas that
the R<SUB>1</SUB> = I(5518)/I(5538) intensity ratio provides estimates
of N<SUB>e</SUB> in excellent agreement with values derived from
other line ratios in the echelle spectra. This agreement indicates
that R<SUB>1</SUB> is a reliable density diagnostic for planetary
nebulae, and it also provides observational support for the accuracy
of the atomic data adopted in the line ratio calculations. However
the [Cl III] 8433.9 line is found to be frequently blended with a weak
telluric emission feature, although in those instances when the [Cl III]
intensity may be reliably measured, it provides accurate determinations
of T<SUB>e</SUB> when ratioed against the sum of the 5518 and 5538
A line fluxes. Similarly, the 8500.0 A line, previously believed to
be free of contamination by the Earth's atmosphere, is also shown
to be generally blended with a weak telluric emission feature. The
[Cl III] transition at 8480.9 A is found to be blended with the He
I 8480.7 A line, except in planetary nebulae that show a relatively
weak He I spectrum, where it also provides reliable estimates of
T<SUB>e</SUB> when ratioed against the nebular lines. Finally, the
diagnostic potential of th near-UV [Cl III] lines at 3344 and 3354 A
is briefly discussed.
---------------------------------------------------------
Title: The Quiet Sun Atmosphere as Seen by Soho
Authors: Phillips, K. J. H.; Gallagher, P. T.; Harra-Murnion, L. K.;
Keenan, F. P.; Pres, P.
2000AdSpR..25.1747P Altcode:
The recent solar minimum has allowed studies to be made of quiet-Sun
structures with SOHO instruments with better resolution than
before. This paper reports on the morphology and dynamics of the EUV
emission, including the chromospheric and transition-region network
and coronal features, and how the photospheric magnetic field and
coronal bright points are related
---------------------------------------------------------
Title: Line Identifications and Intensitites for the Optical Spectrum
of RR Telescopi between 3180 and 9455 Å
Authors: Crawford, F. L.; McKenna, F. C.; Keenan, F. P.; Aller, L. H.;
Fiebelman, W. A.; Ryan, S. G.
2000ASPC..204..385C Altcode: 2000tiaf.conf..385C
No abstract at ADS
---------------------------------------------------------
Title: Modeling the Warm Ionized Interstellar Medium and Its Impact
on Elemental Abundance Studies
Authors: Sembach, Kenneth R.; Howk, J. Christopher; Ryans, Robert
S. I.; Keenan, Francis P.
2000ApJ...528..310S Altcode: 1999astro.ph..8051S
We present model calculations of ionization fractions for elements
in the warm (T~10<SUP>4</SUP> K), low-density photoionized
interstellar medium (WIM) of the Milky Way. We model the WIM as
a combination of overlapping low-excitation H II regions having
n(H<SUP>+</SUP>)/n(H)>~0.8. Our adopted standard model incorporates
an intrinsic elemental abundance pattern similar to that found
for warm neutral clouds in the Galaxy and includes the effects of
interstellar dust grains. The radiation field is characterized by
an ionizing spectrum of a star with T<SUB>eff</SUB>~35,000 K and an
ionization parameter log(q)~-4.0. The emergent emission-line strengths
are in agreement with the observed ratios of [S II]/Hα, [N II]/Hα,
[S II]/[N II], [O I]/Hα, [O III]/Hα, and He I/Hα in the Galactic
WIM. Although the forbidden emission-line intensities depend strongly
on the input model parameters, the ionization fractions of the 20
elements studied in this work are robust over a wide range of physical
conditions considered in the models. These ionization fractions have
direct relevance to absorption-line determinations of the elemental
abundances in the warm neutral and ionized gases in the Milky Way
and other late-type galaxies. We demonstrate a method for estimating
the WIM contributions to the observed column densities of singly and
doubly ionized atoms used to derive abundances in the warm neutral
gas. We apply this approach to study the gas-phase abundances of the
warm interstellar clouds toward the halo star HD 93521.
---------------------------------------------------------
Title: Model atmosphere and kinematical analyses of early-type stars
from the Edinburgh-Cape survey
Authors: Magee, H. R. M.; Dufton, P. L.; Keenan, F. P.; Rolleston,
W. R. J.; Kilkenny, D.; O'Donoghue, D.; Koen, C.; Stobie, R. S.
2000LIACo..35..249M Altcode: 2000ghgc.conf..249M
No abstract at ADS
---------------------------------------------------------
Title: HST/STIS Observations of the Interstellar Medium in the
Magellanic Bridge
Authors: Lehner, N.; Keenan, F. P.; Dufton, P. L.; Sembach, K. R.
2000dhst.conf...56L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: SUMER Measurements of Electron Density Enhancements in the
Solar Transition Region
Authors: Pérez, M. E.; Doyle, J. G.; O'Shea, E.; Keenan, F.
1999ESASP.448..629P Altcode: 1999mfsp.conf..629P; 1999ESPM....9..629P
No abstract at ADS
---------------------------------------------------------
Title: Evidence for Non-Maxwellian Electron Energy Distributions in
the Solar Transition Region: Si III Line Ratios from SUMER
Authors: Pinfield, D. J.; Keenan, F. P.; Mathioudakis, M.; Phillips,
K. J. H.; Curdt, W.; Wilhelm, K.
1999ApJ...527.1000P Altcode:
Recent calculations of Si III emission-line strengths are compared with
SUMER observations from a quiet solar region, a coronal hole, and an
active region. Diagnostic line ratios are used to derive T<SUB>e</SUB>
and N<SUB>e</SUB> for the emitting plasma in each region, and good
agreement between theory and observations is found. A major enhancement
in the intensity of the 1313 Å emission line is observed, as well
as some evidence of a small decrease in the temperature of maximum
ionization fraction, as one moves from the coronal hole to the active
region. Possible explanations for these effects are discussed, and
it is concluded that they may be caused by the presence of nonthermal
electrons in the transition region.
---------------------------------------------------------
Title: Optical observations of three Galactic halo stars: evidence
for cloudlets in intermediate- and high-velocity interstellar clouds
Authors: Lehner, N.; Sembach, K. R.; Lambert, D. L.; Ryans, R. S. I.;
Keenan, F. P.
1999A&A...352..257L Altcode:
Very high resolution (R ~ 160000) absorption line measurements of the
interstellar Ca Ii K and Na I D lines and medium resolution (R ~ 50000)
measurements of the interstellar Ti Ii (3384 Ä) line towards three
Galactic halo stars are presented. The data have signal-to-noise
ratios of ~ 90-240. The sightlines studied clearly show several
intermediate-high velocity interstellar clouds with local standard
of rest velocities in the range ~ - 40 to -110 \km. Two different
methods have been used to analyze these data. Line profile fitting
allows us to model multiple components for the different high-velocity
clouds separated by only a few km. The close proximity of the lines in
velocity space indicates that the cloudlets are related. Conversion
of the absorption profiles to apparent optical depth profiles also
allows us to examine the column densities and their ratios as a
function of velocity. Variations in N(ion {Ca}{ii})/N(ion {Na}i),
N(ion {Ca}{ii})/N(ion {Ti}{ii}) and N(ion {Ti}{ii})/N(ion {Na}i)
with cloud velocity are discussed.
---------------------------------------------------------
Title: Temporal variability in the electron density at the solar
transition region
Authors: Pérez, M. E.; Doyle, J. G.; O'Shea, E.; Keenan, F. P.
1999A&A...351.1139P Altcode:
The electron density as measured in the transition region of a coronal
hole, a `quiet' Sun region at disk center plus an active region shows
variations of up to a factor of two at T_e ~ 1.5 10<SUP>5</SUP> K,
lasting at most only a few minutes. There is remarkable agreement
between the number of such variations, their temporal variability
and duration in the coronal hole and `quiet' Sun datasets, consistent
with an earlier bright point study. There appears to be evidence of
super-granular cells, with the increases in electron density occurring
along the network boundaries. At some locations, periodicities of
between 8 and 16 min are visible in the electron density variations. We
associate these variations with the sites of explosive events.
---------------------------------------------------------
Title: The effects of opacity in the transition region of YZ CMi
Authors: Mathioudakis, M.; McKenny, J.; Keenan, F. P.; Williams,
D. R.; Phillips, K. J. H.
1999A&A...351L..23M Altcode:
It has generally been assumed that the emission from the upper
atmosphere of late-type stars is optically thin. In the present paper we
use the Si IV and C IV resonance lines to investigate this assumption
for the active dMe star YZ CMi. The significant deviations of the line
ratios from their optically thin values, demonstrate that opacity can
be quite important particularly in the case of stellar flares. These
deviations are combined with a method of escape probabilities to
derive optical depths of approximately unity for the lines under
consideration. We demonstrate that, if the electron density in the
atmosphere is known, opacity can provide important information on the
linear dimensions of the scattering layer. Using this technique, we
have estimated path lengths of a few kilometers for one of the flares
under consideration. Based on observations made with the NASA/ESA Hubble
Space Telescope, obtained from the data archive at the Space Telescope
Science Institute. STScI is operated by the Association of Universities
for Research in Astronomy, Inc. under NASA contract NAS 5-26555.
---------------------------------------------------------
Title: Line identifications and intensities for the optical spectrum
of <ASTROBJ>RR Telescopii</ASTROBJ> between 3180 and 9455 Å
Authors: Crawford, F. L.; McKenna, F. C.; Keenan, F. P.; Aller, L. H.;
Feibelman, W. A.; Ryan, S. G.
1999A&AS..139..135C Altcode:
The symbiotic nova <ASTROBJ>RR Telescopii</ASTROBJ> has been observed
with the 3.9 m telescope at the Anglo-Australian Observatory (AAO),
using the University College London Echelle Spectrograph (UCLES) in
conjunction with a Tek CCD. It displays a rich emission line spectrum,
ranging in excitation from N I to [Ni Viii]. We present a list of 811
measured lines, with their suggested identifications and absolute
line intensities, covering a wavelength range from 3180 Å to 9455
Å. The absolute line intensities have been derived by comparing the
high resolution data with a flux-calibrated low resolution spectrum
taken with the Australian National University 2.3 m telescope. All of
the lines have been successfully identified. Comparing our results with
those of previous studies indicates that the <ASTROBJ>RR Tel</ASTROBJ>
system is advancing towards higher degrees of ionisation. <P
/>Tables 2 and 3 are only available in electronic form at the CDS
via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via
http://cdsweb.u-strasbg.fr/Abstract.html
---------------------------------------------------------
Title: A New Study of the Quiet Sun
Authors: O'Shea, E.; Gallagher, P. T.; Mathioudakis, M.; Phillips,
K. J. H.; Keenan, F. P.
1999ESASP.446..519O Altcode: 1999soho....8..519O
In this paper we present results of an emission measure analysis
performed on regions of cell, network and bright network emission
which were observed in the quiet Sun at Sun centre with the Coronal
Diagnostic Spectrometer (CDS) on board SOHO. Seperate emission from
the three regions was obtained by a method of image segmentation
using a histogram modification technique. From the averaged emission
it was possible to produce emission measures over a broad temperature
range. These emission measures were then used to produce estimates of
radiative and conductive losses in the three regions considered. Using
a magnetogram obtained from the MDI instrument on SOHO we show that
the bright network emission originates from bipolar magnetic loops
and from what appear to be monopole regions, which could be the
remains of footpoints of larger loops. The bright network emission
shows significantly higher mean magnetic field strength as well as
significantly larger radiative energy losses than either of the other
two regions. We find some evidence suggesting the presence of cool
loops. The process of image segmentation also enabled us to obtain
the relative areas of the cell, network and bright network emission
as a function of temperature. We found that only the bright network
emission showed an expansion in area with temperature and therefore
height. Fitting this area curve with the functional form suggested
by Rabin (1991),i.e A(T)/A(T<SUB>h</SUB>) = [1 + (Gamma<SUP>2</SUP>
- 1)(T/T<SUB>h</SUB>)<SUP>nu</SUP>]<SUP>1/2</SUP>/Gamma , for the
cross-sectional area of a flux tube, we obtain a value of Gamma=7.1
and nu=2.5 for the constriction and shape factors respectively.
---------------------------------------------------------
Title: The Radial and Angular Variation of the Electron Density in
the Solar Corona
Authors: Gallagher, P. T.; Mathioudakis, M.; Keenan, F. P.; Phillips,
K. J. H.; Tsinganos, K.
1999ApJ...524L.133G Altcode:
We derive, for the first time, electron densities as a function
of both radius (R) and position angle (θ) for the southwest
quadrant of the off-limb corona, using the density-sensitive Si IX
λ349.9/λ341.9 and Si X λ356.0/λ347.7 extreme-ultraviolet line
ratios. The observations were made with the coronal diagnostic
spectrometer on board the Solar and Heliospheric Observatory over
the ranges of 1.00 R<SUB>solar</SUB><R<1.20 R<SUB>solar</SUB>
and 180<SUP>deg</SUP><θ<270<SUP>deg</SUP>. Within the south
polar coronal hole, the density varies from 2.3×10<SUP>8</SUP>
cm<SUP>-3</SUP> at 1.0 R<SUB>solar</SUB> to 8.3×10<SUP>7</SUP>
cm<SUP>-3</SUP> at 1.20 R<SUB>solar</SUB>, while at the equator,
the density varies from 6.3×10<SUP>8</SUP> cm<SUP>-3</SUP> at 1.0
R<SUB>solar</SUB> to 1.6×10<SUP>8</SUP> cm<SUP>-3</SUP> at 1.20
R<SUB>solar</SUB>. The density falloff with height is therefore faster
in the equatorial region. We also find that electron densities are,
on average, a factor of 2.7 larger in the equatorial regions than in
the polar coronal hole at a given radial distance. Finally, we find
remarkable agreement between our measured densities as a function of
radius and position angle and those predicted by a recent analytic
MHD model of the solar wind, strongly supporting its basic premises.
---------------------------------------------------------
Title: [Alii] in the ultraviolet spectrum of the symbiotic star
RR Telescopii
Authors: Keenan, F. P.; Espey, B. R.; Mathioudakis, M.; Aggarwal,
K. M.; Crawford, F. L.; Feibelman, W. A.; McKenna, F. C.
1999MNRAS.309..195K Altcode:
An inspection of a GHRS/HST spectrum of the symbiotic star RR Telescopii
reveals the presence of the [Alii] 3s^2 ^1S - 3s3p ^3P_2 line at a
vacuum wavelength of 2661.06+/-0.08Å, 8.89+/-0.08Å away from the Alii]
3s^2 ^1S - 3s3p ^3P_1 intercombination transition at 2669.95Å, in good
agreement with the theoretical prediction of Δλ=8.80Å. We also find
that the Alii] line profile is asymmetric, showing a strong low-density
component with a weak high-density wing, redshifted by 30kms^-1, in
agreement with the findings of Schild & Schmid, which were based
on optical observations. Our measurement of the emission-line ratio
RI(2661.06Å)/I(2669.95Å)=0.027+/-0.003 implies logN_e=5.8+/-0.2,
in good agreement with the densities found from other ions, such as
Siiii. These results provide strong evidence that we have detected the
[Alii] line, the first time (to our knowledge) that this feature has
been reliably identified in an astrophysical or laboratory spectrum.
---------------------------------------------------------
Title: Fexiixii emission lines in solar active regions observed by
the RES-C spectroheliograph on the CORONAS-I mission
Authors: Zhitnik, I. A.; Kuzin, S. V.; Urnov, A. M.; Keenan, F. P.;
Pinfield, D. J.
1999MNRAS.308..228Z Altcode:
Theoretical line intensity ratios involving Fexii transitions in the
186-201Å wavelength range are compared with observational data for five
solar active regions, obtained by the RES-C spectroheliograph on the
CORONAS-I mission. Generally good agreement is found between theory
and observation, hence resolving discrepancies previously found in
the comparison of calculations with active region and subflare spectra
from the Solar EUV Rocket Telescope and Spectrograph (SERTS). However,
the Fexii 190.06- and 201.12-Å lines are blended with Fex 190.04Å and
Fexiii 201.13Å, respectively. In addition, a weak feature at ~197Å,
tentatively identified as Fexii 196.87Å, does not appear to be due
to this ion.
---------------------------------------------------------
Title: Photoionization cross sections for Fe XVI and Fe XVII
recombination rate coefficients
Authors: Donnelly, D.; Bell, K. L.; Darlington, W. G. V.; Reid,
R. H. G.; Keenan, F. P.
1999A&A...349..996D Altcode:
The Breit-Pauli R-matrix codes are utilized in a detailed study of the
photoionization of the ground state of Fe XVI (2s(22p^63s) (2S_{1/2})
). High resolution total and partial cross sections are obtained using
37 Jpi configuration interaction type wavefunctions to represent the
residual ion, Fe XVII, after 3s, 2p and 2s photoionization. For the
total cross section, the work of Verner et al. and previous Opacity
Project calculations are in fair agreement with the present results,
while relativistic effects are seen to have a noticeable but not an
overly significant effect on the background cross section. The derived
partial cross sections are used in a calculation of rates for the
recombination of states of Fe XVII to the ground state of Fe XVI.
---------------------------------------------------------
Title: Effective collision strengths for forbidden transitions among
the 3s<SUP>2</SUP>3p<SUP>3</SUP> fine-structure levels of CL IIIIII
Authors: Ramsbottom, C. A.; Bell, K. L.; Keenan, F. P.
1999MNRAS.307..669R Altcode:
Effective collision strengths for the 10 astrophysically important
fine-structure forbidden transitions among the ^4S^o, ^2D^o and ^2P^o
levels in the 3s^23p^3 configuration of Cliii are presented. The
calculation employs the multichannel R-matrix method to compute the
electron-impact excitation collision strengths in a close-coupling
expansion, which incorporates the lowest 23 LS target eigenstates of
Cliii. These states are formed from the 3s^23p^3, 3s3p^4, 3s^23p^23d
and 3s^23p^24s configurations. The Maxwellian-averaged effective
collision strengths are presented graphically for all 10 fine-structure
transitions over a wide range of electron temperatures appropriate
for astrophysical applications [logT(K)=3.3-logT(K)=5.9]. Comparisons
are made with the earlier seven-state close-coupling calculation
of Butler & Zeippen, and in general excellent agreement is
found in the low-temperature region where a comparison is possible
[logT(K)=3.3-logT(K)=4.7]. However, discrepancies of up to 30 per
cent are found to occur for the forbidden transitions which involve
the ^4S^o ground state level, particularly for the lowest temperatures
considered. At the higher temperatures, the present data are the only
reliable results currently available.
---------------------------------------------------------
Title: Transient events in the EUV transition region and chromosphere
Authors: Gallagher, P. T.; Phillips, K. J. H.; Harra-Murnion, L. K.;
Baudin, F.; Keenan, F. P.
1999A&A...348..251G Altcode:
Rapid time cadence observations of the quiet Sun extreme
ultraviolet emission, observed by the cds instrument on soho, are
discussed. Numerous transient brightenings are observed in network
features in both a transition region line (O V 629.73 Ä) and a
chromospheric line (He I 584.33 Ä), indicating a dynamic coupling
between the chromospheric and transition region network. Their
durations are between 80 and 200 s and dimensions 6 000-10 000 km. A
wavelet analysis reveals a tendency for semi-periodic behaviour,
with excess power at a frequency of about 4 mHz. The variations are
much less evident in the internetwork or cell regions, although they
are again semi-periodic. Relative line-of-sight velocities have also
been derived from the data, the cds spectral resolution allowing a
precision of between 4.7 and 6 km s(-1) . There is a clear association
of brightenings in the network with downflows of ~ 13 km s(-1) at 250
000 K with some events having velocities of up to ~ 20 km s(-1) , these
being measured relative to the average quiet Sun emission. Within the
internetwork, we also find a weak correlation between events seen in
the He I (584.33 Ä) and the O V (629.73 Ä) lines. In this case, the
events have a smaller size (<= 2 000 km), amplitude (both in terms of
their intensity and velocity), and also show a higher frequency of about
6 mHz. The apparent differing properties of network and internetwork
events implies that both these regions are heated by two distinct
mechanisms. In the case of the internetwork, these results further
confirm that acoustic waves propagating up from the photosphere and
forming shocks in the overlying atmosphere are the most likely heating
mechanism. For the network, it is apparent that the heating required
must be in excess of that supplied by acoustic shocks. Our view is that
the network events are produced by nanoflare-like magnetic reconnections
in the corona, or possibly excitation due to a spicule-type event in
which there is a repeated rebound.
---------------------------------------------------------
Title: L-shell photoionization cross-sections for FeXIXXIX and FeXXXX
recombination rate coefficients
Authors: Donnelly, D.; Bell, K. L.; Keenan, F. P.
1999MNRAS.307..595D Altcode:
High-quality atomic data concerning the interaction of photons
with highly ionized ions of iron are an essential requirement in the
modelling of X-ray emission from astrophysical plasmas. Consequently a
detailed study of the photoionization of the ground-state fine-structure
levels (2s^22p^4 ^3P_2,0,1) of FeXIX has been undertaken, and a set
of high-resolution cross-sections for photoionization of each of
these levels obtained. We have considered both the total and partial
cross-section cases, with the latter restricted to those instances
where the residual ion is left in one of the energetically lowest 23
Jpi (12 LSpi) states of FeXX. The calculation was performed by applying
the Breit-Pauli R-matrix codes using a sophisticated representation of
these 23 target-states. This approach allows for the possibility of
fine-structure splitting in both thresholds and resonances, as well
as incorporating any coupling between target-states with different
LS symmetries through the inclusion of the spin-orbit operator. A
significant amount of such coupling is discovered in the present
investigation, and is responsible for a background cross-section
whose magnitude is lower than that determined in previous LS-coupling
calculations by more than a factor of 2. Extensive resonance structure
is also resolved, including shape resonances in the 133 -> 148Ryd
photon energy region. Such structure has not been resolved in any
previous investigation and is of extreme importance in the modelling of
X-ray emission plasmas. Using the derived photoionization cross-section
data, recombination rate coefficients are calculated using the Milne
relation, for the case of an electron recombining with FeXX in the
ground state to form FeXIX existing in each of the fine-structure
ground-state levels. These recombination rates are summarized over
a temperature range of 50 000 to 10^7K. To supplement these data
further we also present a set of energy levels and oscillator strengths
for FeXX.
---------------------------------------------------------
Title: Electron densities above a polar coronal hole based on improved
SI IX density diagnostics
Authors: Doyle, J. G.; Keenan, F. P.; Ryans, R. S. I.; Aggarwal,
K. M.; Fludra, A.
1999SoPh..188...73D Altcode:
Using new close-coupling excitation rates for the C-like ion Si ix,
density-diagnostic ratios based on Si ix lines have been re-evaluated
and applied to a sequence of CDS observations taken above a polar
coronal hole. The derived electron densities are in excellent agreement
with previous values of N<SUB>e</SUB>estimated from the N-like ion Si
viii for another coronal hole. The confirmed trend is for a fall-off
of one order of magnitude within the first 0.3 R<SUB>⊙</SUB>above the
limb. These densities are well fitted with an analytic formula for the
density profile out to at least 8 R<SUB>⊙</SUB>, by which stage the
electron density has fallen to ∼4×10<SUP>3</SUP> cm<SUP>−3</SUP>,
from 1.5×10<SUP>8</SUP> cm<SUP>−3</SUP>at 1.0 R<SUB>⊙</SUB>.
---------------------------------------------------------
Title: HR 1099 - A multi-wavelength study of a short period RS
CVn binary
Authors: Mathioudakis, Mihalis; Christian, Damian; Keenan, Francis
1999noao.prop...50M Altcode:
The launch of AXAF in the summer of 1999 will open a new era in the
study of stellar coronae. The active RS CVn binary HR 1099 is one of
the AXAF primary calibration targets that will be observed in the
first 3-4 months of the mission. We propose to carry out a ground
based spectroscopic study of HR 1099. With the combination of optical
and X- ray observations we will be able to : (i) Study the effects
of rotational modulation in photospheric (TiO bands), chromospheric
(H(alpha), Ca II H& K) and coronal lines (e.g. Fe XVII) (ii)
Carry out a near simultaneous estimate of photospheric and coronal
abundances (iii) Investigate whether the absorption features that
cross the H(alpha) profile are due to cool hydrogen prominences or mass
transfer between the components of the binary. The requested observing
time will allow us to cover ~ 3 rotational revolutions with an ~ 80%
phase coverage.
---------------------------------------------------------
Title: Source Tracing of Archeological Copper Smelting Ore by In Situ
Isotopic Measurements by Laser Ablation Inductively Coupled Plasma
Mass Spectrometry Using Quadrupole and Multicollector Techniques
Authors: Young, S. M. M.; Horn, I.; Miller, D.; Cantle, J.; Keenan,
F.; Bowen, I.
1999nag..conf.7662Y Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Search for Extraterrestrial Intelligence (SETI)
Authors: Keenan, F. P.; Phillips, M. E.; Rose, S. J.; Burgess, D. D.
1999IrAJ...26...87K Altcode:
A brief review is presented of the hypotheses inherent in searches for
extraterrestrial intelligence (SETI). Some of the problems associated
with such work at radio wavelengths are discussed, such as the optimal
choice of a search frequency. It is shown that pulsed laser signals sent
from an extraterrestrial civilisation should be observed to be brighter
than the parent star, even when conservative estimates are adopted
for the laser energy generation and detector time resolution. This is
still the case when the energy output from the parent star is summed
over all wavelengths. As a result, optical SETI programmes may be more
attractive than their radio counterparts.
---------------------------------------------------------
Title: Early-type stars in the Galactic halo from the Palomar-Green
Survey II: A sample of distant, apparently young Population I stars
Authors: Rolleston, W. R. J.; Hambly, N. C.; Keenan, F. P.; Dufton,
P. L.; Saffer, R. A.
1999A&A...347...69R Altcode:
We present échelle (R ~ 40 000) spectroscopic observations for
a sample of apparently normal, high Galactic latitude, early-type
stars drawn from the Palomar-Green Survey. The metal-line spectra
show evidence for rotational velocity broadening with values of vsin
i<=300 km s(-1) . In conjunction with Kurucz model atmospheres,
we derive stellar photospheric abundances that are consistent with
a Population i chemical composition; differential abundances with
respect to Galactic disk Population i stars indicate no abundance
differences outside the estimated errors. From a comparison of the
derived atmospheric parameters with recent theoretical evolutionary
models, we derive distance and age estimates for individual
stars. Using kinematical considerations, we conclude that all
these objects are `runaway' stars, formed in the Galactic disk and
subsequently ejected, possibly by supernovae explosions or dynamical
interactions. Tables 4 and 5 are only available in electronic form
at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)
or via http://cdsweb.u-strasbg.fr/Abstract.html
---------------------------------------------------------
Title: VizieR Online Data Catalog: The Optical Spectrum of RR Tel
(Crawford+ 1999)
Authors: Crawford, F. L.; McKenna, F. C.; Keenan, F. P.; Aller, L. H.;
Feibelman, W. A.; Ryan, S. G.
1999yCat..41390135C Altcode:
The symbiotic nova RR Telescopii has been observed with the 3.9
m telescope at the Anglo-Australian Observatory (AAO), using the
University College London Echelle Spectrograph (UCLES) in conjunction
with a Tek CCD. It displays a rich emission line spectrum, ranging in
excitation from NI to NiVIII. We present a list of 811 measured lines,
with their suggested identifications and absolute line intensities,
covering a wavelength range from 3180 to 9455 A. The absolute line
intensities have been derived by comparing the high resolution data with
a flux-calibrated low resolution spectrum taken with the Australian
National University 2.3 m telescope. All of the lines have been
successfully identified. Comparing our results with those of previous
studies indicates that the RR Tel system is advancing towards higher
degrees of ionisation. (2 data files).
---------------------------------------------------------
Title: Excitation Rate Coefficients for Fine-Structure Transitions
in O III
Authors: Aggarwal, Kanti M.; Keenan, Francis P.
1999ApJS..123..311A Altcode:
Collision strengths for fine-structure transitions among the levels of
the (1s<SUP>2</SUP>) 2s<SUP>2</SUP>2p<SUP>2</SUP>, 2s2p<SUP>3</SUP>,
2p<SUP>4</SUP>, 2s<SUP>2</SUP>2p3s, 2s<SUP>2</SUP>2p3p, and
2s<SUP>2</SUP>2p3d configurations of O III have been computed over a
wide range of energies below 13.0 ryd using the R-matrix program. All
partial waves with L<=40 have been included to ensure the convergence
of results. Excitation rate coefficients, in the form of dimensionless
effective collision strengths, have also been computed at temperatures
below 200,000 K. The results are compared with available calculations,
and accuracy of the data is assessed.
---------------------------------------------------------
Title: The interstellar medium near to and beyond the Galactic Center
Authors: Keenan, Francis
1999hst..prop.8096K Altcode: 1999hst..prop.4430K
We have recently identified a B-type supergiant, LS 4825, which lies
on the far side of the Galaxy, at a Galactocentric distance of R_G
= 12 kpc, and whose sightline passes within 1 kpc of the Galactic
Center. Optical ionCa2 and ionNa1 interstellar observations of LS 4825
reveal a miriad of intermediate and high velocity clouds, several of
which arise from gas near to and beyond the Galactic Center. We now
propose to obtain medium resolution STIS spectra, primarily to observe
the ultraviolet interstellar lines towards LS 4825. These data will
allow us to determine the abundances of important elements such as Mg,
Si, S, Cr, Mn, Fe, and Zn {and possibly C, N, and O} in interstellar
gas as a function of Galactocentric distance, from the Solar position
all the way in to the Galactic Center and beyond, which is vital for
testing the competing models for the chemical evolution of our Galaxy. A
secondary aim of the STIS observations will be to study the ultraviolet
stellar absorption lines in LS 4825, which will provide reliable element
abundances for this star, and hence the chemical composition of the
interstellar medium at R_G = 12 kpc on the far side of the Galaxy. This
will be compared with results at R_G = 12 kpc on the near side, to
investigate the azimuthal dependence of the Galactic abundance gradient.
---------------------------------------------------------
Title: Low Resolution Optical Spectroscopy of The M15 High Velocity
Interstellar Cloud
Authors: Smoker, J. V.; Lehner, N.; Keenan, F. P.; Totten, E. J.
1999IrAJ...26..105S Altcode:
We present low resolution optical spectra of 16 field stars in the CaII
H and K lines towards the high velocity cloud (HVC) at V=+80 kms-1,
observed in the direction of the M15 globular cluster. Stellar spectral
types and distances are estimated for 12 of the sample. Null detections
of HVC CaII absorption in the spectra, combined with an upper limit to
the HVC distance from observations of the Galactic halo star HD 203664,
tentatively imply that the HVC lies in the distance range 400 <=
d <= 3200 pc.
---------------------------------------------------------
Title: Fe II emission lines as a chronometer for high-redshift quasars
Authors: Keenan, Francis
1999hst..prop.8098K Altcode: 1999hst..prop.4432K
We request STIS observations of the symbiotic nova RR-TEL to give
complete coverage of FeII emission lines in the 1150- 9800 Angstrom
wavelength range. We have embarked on a long- term program to fully
simulate the physical conditions within FeII-emitting gas, and predict
the resulting spectrum. The first steps of generating the initial atomic
database and incorporating it into the photoionization code Cloudy,
are complete. Analysis of the FeII lines from RR-TEL using Cloudy will
allow us to check the r eliability and completeness of the atomic data
and processes considered, to investigate the sensitivity of emission
to temperature and density variations, and to assess the importance of
blending. Although emission lines from FeII are observed from a wide
variety of astronomical objects, including protostellar disks, novae,
supernovae, and quasars, these lines have been notoriously difficult
to interpret because of the great complexity of the FeII energy
level structure. We no w have the tools to quantify the abundances in
these objects and, once calibrated against the RR-TEL data, we will
apply the same technique to deduce iron abundances from FeII emission
in high-redshift quasars. This, in conjunction with predictions of
ste llar evolution and galactic nucleosynthesis, will result in a
chronometer measuring the redshift when the universe passed through
an age of 1 Gyr, thus constraining several cosmological parameters.
---------------------------------------------------------
Title: Book Review: The sun in eclipse / Springer, 1997 & 1998
Authors: Gallagher, P. T.; Keenan, F. P.; Phillips, K. J. H.; Read,
P. D.; Rudawy, P.; Mpolt, B. Ro
1999IrAJ...26..115G Altcode:
The Solar Eclipse Coronal Imaging System (SECIS) is an instrument
designed to search for short-period modulations in the solar corona seen
either during a total eclipse or with a coronagraph. The CCD cameras
used in SECIS have the capability of imaging a selected portion of the
corona at a rate of 50 frames per second, with the intensities in each
pixel digitised in 12-bit levels. The data are captured and stored on
a modified PC. It will thus be possible to search for fast changes
or short-period wave motions in the corona that will have important
implications for the coronal heating mechanism. Tests have been
carried out during the 1998 total solar eclipse visible in Guadeloupe
(French West Indies) and with the Evans Solar Facility coronagraph at
the National Solar Observatory, Sacramento Peak, with scientifically
useful results obtained from the latter.
---------------------------------------------------------
Title: Electron temperature diagnostics for the quiet Sun using SI
BT IV lines
Authors: Ahmed, S.; Pinfield, D. J.; Mathioudakis, M.; Keenan, F. P.;
Phillips, K. J. H.; Curdt, W.
1999A&A...346L..69A Altcode:
We compare SUMER observations of six Si riptsize IV emission lines
detected at the quiet Sun disk centre with recent theoretical line ratio
calculations. Good agreement is found between theory and observation
for ratios involving the 1394, 1403 and 818 Ä line intensities. This
agreement supports the theoretical prediction that the temperature
where Si riptsize IV has its maximum ionisation fraction in ionisation
equilibrium is T_max =~ 10(4.8) K, as well as showing that Lyman
continuum absorption does not significantly effect line intensities
for transitions with wavelengths below 912 Ä. We find that the 815,
1122 and 1128 Ä lines are blended by approximately 30, 55 and 45%,
respectively, in the SUMER transitions.
---------------------------------------------------------
Title: NE VII emission lines in the solar EUV spectrum
Authors: McKeown, M.; Keenan, F. P.; Ramsbottom, C. A.; Bell, K. L.;
Ryans, R. S. I.; Reid, R. H. G.
1999SoPh..186..231M Altcode:
Recent calculations of electron and proton impact excitation rates
in Ne vii are used to calculate theoretical emission line ratios
involving both Δn=0 (2-2) and Δn=1 (2-3) transitions in the ∼
97-895 Å wavelength range. A comparison of these with existing solar
observations, obtained by instruments on rocket flights and on the
Skylab mission, reveals generally good agreement between theory and
observation. This provides experimental support for the accuracy of
the atomic data adopted in the line ratio calculations, and implies
that the latter may be applied with confidence to the analysis of
solar and stellar spectra from current and future satellite missions.
---------------------------------------------------------
Title: Proton impact excitation of the 1s(2) 2s(2) 2p(2) (3) P
fine-structure transitions in carbon-like ions
Authors: Ryans, R. S. I.; Foster-Woods, V. J.; Reid, R. H. G.; Keenan,
F. P.
1999A&A...345..663R Altcode:
We present new cross sections and thermally averaged excitation rate
coefficients for proton impact excitation of the 1s(2) 2s(2) 2p(2)
(3) P fine-structure transitions for ions in the carbon isoelectronic
sequence. These data have been calculated using a close-coupled impact
parameter method that incorporates the effects of higher lying levels
of the triplet 2s2p(3) configuration. We find that the inclusion of
these additional states leads to significant reductions in excitation
rates for high-Z ions.
---------------------------------------------------------
Title: High-resolution stellar and interstellar spectra of HD 100340
Authors: Ryans, R. S. I.; Keenan, F. P.; Rolleston, W. R. J.; Sembach,
K. R.; Davies, R. D.
1999MNRAS.304..947R Altcode:
We present new, high-resolution, high signal-to-noise ratio, optical
and 21-cm HI observations of the faint blue halo star HD 100340. A
differential abundance analysis with respect to the Galactic disc star
HR 2387 shows no significant peculiarities. We find that HD 100340 lies
at a distance of 3 kpc, and a kinematical analysis strongly supports a
`runaway star' origin. We also present improved cloud models for three
intermediate velocity clouds seen in Ca II K or H I towards HD 100340.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Abundances of halo early-type stars
(Rolleston+, 1999)
Authors: Rolleston, W. R. J.; Hambly, N. C.; Keenan, F. P.; Dufton,
P. L.; Saffer, R. A.
1999yCat..33470069R Altcode:
We present echelle (R~40,000) spectroscopic observations for a sample
of apparently normal, high Galactic latitude, early-type stars drawn
from the Palomar-Green Survey. The metal-line spectra show evidence for
rotational velocity broadening with values of vsini<=300km/s. In
conjunction with Kurucz model atmospheres, we derive stellar
photospheric abundances that are consistent with a Population I
chemical composition; differential abundances with respect to Galactic
disk Population I stars indicate no abundance differences outside
the estimated errors. From a comparison of the derived atmospheric
parameters with recent theoretical evolutionary models, we derive
distance and age estimates for individual stars. Using kinematical
considerations, we conclude that all these objects are `runaway'
stars, formed in the Galactic disk and subsequently ejected, possibly
by supernovae explosions or dynamical interactions. (2 data files).
---------------------------------------------------------
Title: Soft X-ray emission lines of Ni XVIII in the solar spectrum
Authors: Keenan, F. P.; Mathioudakis, M.; Pinfield, D. J.; Brown,
W. A.; Bruner, M. E.
1999SoPh..185..289K Altcode:
R-matrix calculations of electron impact excitation rates in Ni xviii
are used to derive theoretical electron-temperature-sensitive emission
line ratios involving 3s−4p,3p−4d,3p −4s, and 3d−4f transitions
in the 41-53 Å wavelength range. A comparison of these with solar
flare observations from a rocket-borne X-ray spectrograph (XSST) reveals
generally excellent agreement between theory and experiment (within the
experimental and theoretical uncertainties), which provides support
for the atomic data adopted in the analysis. However the 3s 2S−4p
2P1/2 line of Ni xviii at 41.22 Å appears to be blended with the Fe
xix 13.74 Å feature observed by XSST in third order. In addition, the
measured Ni xviii intensity ratio I(3p 2P3/2− 4s 2S)/I(3p 2P1/2−4s
2S)=I(51.02 Å)/I(50.26 Å)=0.56, a factor of ∼3.8 smaller than the
theoretical (temperature and density-insensitive) value of 2.1. The
reason for this discrepancy is currently unexplained, but is unlikely
to be due to blending of the 50.26 Å line, as the intensity of this
feature is consistent with that expected from the other Ni xviii lines
in the XSST spectrum. Future observations of the Ni xviii lines by
the Advanced X-ray Astrophysics Facility (AXAF) should allow this
problem to be resolved, and may also permit the use of the lines as
electron-temperature diagnostics.
---------------------------------------------------------
Title: Emission lines of [O II] in the optical and ultraviolet
spectra of planetary nebulae
Authors: Keenan, F. P.; Aller, L. H.; Bell, K. L.; Crawford, F. L.;
Feibelman, W. A.; Hyung, S.; McKenna, F. C.; McLaughlin, B. M.
1999MNRAS.304...27K Altcode:
Recent R-matrix calculations of electron impact excitation rates in O
II are used to calculate the emission-line ratio-ratio diagrams (R_1,
R_2), (R_1, R_3) and (R_1, R_4), where R_1 = I(3729 A)/I(3726 A), R_2 =
I(7320 A)/I(3726 + 3729 A), R_3 = I(7330 A)/I(3726 + 3729 A) and R_4
= I(2470 A)/I(3726 + 3729 A), for a range of electron temperatures
(T_e = 7500-20 000 K) and electron densities (N_e = 10^1.5-10^5 cm^-3)
appropriate to planetary nebulae. These diagrams should, in principle,
allow the simultaneous determination of T_e and N_e from measurements
of the [O II] emission lines in a spectrum. Plasma parameters deduced
for a sample of planetary nebulae, using observational data obtained
with the IUE satellite and the Hamilton Echelle spectrograph on the 3-m
Shane Telescope at the Lick Observatory, are found to show excellent
internal consistency, and to be in generally good agreement with the
values of T_e and N_e estimated from other line ratios in the echelle
spectra. These results provide observational support for the accuracy
of the theoretical ratios, and hence the atomic data adopted in their
derivation.
---------------------------------------------------------
Title: Quiet Sun Bright Point Dynamics and Energetics as seen by
SOHO and Yohkoh
Authors: Gallagher, P.; Keenan, F.; Phillips, K.; Prés, P.;
Harra-Murnion, L.
1999ASPC..183..405G Altcode: 1999hrsp.conf..405G
No abstract at ADS
---------------------------------------------------------
Title: The Intersteliar Medium in the Magellanic Bridge
Authors: Lehner, N.; Keenan, F. P.; Smoker, J. V.; Dufton, P. L.;
Rolleston, W. R. J.; McKenna, F. C.; Sembach, K. R.; Tohline, J. E.;
White, G.; Stanimirovic, S.
1999IAUS..190..501L Altcode: 1998IAUS..190E.167L
We present high resolution ultraviolet (HST/STIS) and H I 21 cm (ATCA)
observations of the interstellar lines towards DI 1388, a B-type star in
the Bridge of gas between the Small and Large Magellanic Clouds (SMC,
LMC). Our observations provide a unique opportunity to investigate
the velocity structure, elemental abundances, and physical conditions
within the Bridge gas, which until this time has remained unexplored. We
compare the results obtained with information for the LMC and SMC, to
test the theory that the Bridge gas originated in the SMC. The presence
of young B-type stars in the Bridge implies ongoing star formation, and
our observations allow us to investigate the mechanisms responsible for
creating stars in this gas, and to determine whether they are similar
to the processes inferred for high velocity clouds within our Galaxy.
---------------------------------------------------------
Title: Cross Sections and Rate Coefficients for Excitation of the
1s<SUP>2</SUP>2s<SUP>2</SUP>2p<SUP>2</SUP> <SUP>3</SUP>P<SUB>J</SUB>
--> 1s<SUP>2</SUP>2s<SUP>2</SUP>2p<SUP>2</SUP>
<SUP>3</SUP>P<SUB>J'</SUB> Fine-Structure Transition in Carbon-like
Ions by Heavy Particle Impact
Authors: Ryans, R. S. I.; Foster-Woods, V. J.; Keenan, F. P.; Reid,
R. H. G.
1999ADNDT..73....1R Altcode:
We have calculated cross sections for excitation of the fine-structure
transitions in carbon-like ions by proton, deuteron, triton, and
α-particle impact via a close-coupled impact-parameter method. This
technique includes the effects of dipole coupling to the nearby triplet
2s2p<SUP>3</SUP> configuration by means of a polarization potential. We
consider the ions N II, O III, Ne V, Mg VII, Si IX, S XI, Ar XIII, Ca
XV, Ti XVII, Cr XIX, Fe XXI, and Ni XXIII. Excitation rate coefficients
have also been calculated for a range of temperatures.
---------------------------------------------------------
Title: High-velocity interstellar clouds towards the M 15 globular
cluster. I. Low resolution optical data
Authors: Lehner, N.; Rolleston, W. R. J.; Ryans, R. S. I.; Keenan,
F. P.; Bates, B.; Pollacco, D. L.; Sembach, K. R.
1999A&AS..134..257L Altcode:
We present low resolution interstellar spectra of the Ca Ii K and Na I
D lines towards 12 stars in the M 15 globular cluster. These sightlines
are used to study the small scale structure of the interstellar medium,
over scales of a few arcseconds to a few arcminutes. A high-velocity
cloud is detected in the Ca Ii and Na I lines at a LSR velocity
of approximately ~ 70 km s(-1) . Tentative velocity and equivalent
width variations are observed on scales of a few arcseconds; however,
higher resolution data are necessary to quantify the magnitude of these
variations. We discuss these observations and their importance for
future studies of this high velocity gas at high spectral resolution.
---------------------------------------------------------
Title: Photoionization cross sections for Fe XVIII
Authors: Donnelly, D.; Bell, K. L.; Keenan, F. P.
1998A&AS..133..249D Altcode:
A sophisticated R-matrix calculation is performed for the
photoionization of the fine-structure levels of the ground state of Fe
XVIII. High resolution total and partial cross sections are obtained
with the later restricted to the cases of the Fe XVIII ion being left
in one of the fine-structure levels corresponding to the energetically
lowest 11 LS states of Fe XIX after ionization. Both sets of cross
sections are obtained using the Breit-Pauli R-matrix approximation
which allows for the possibility of fine structure splitting in both
resonances and thresholds. We find extensive resonance structure in
the 99 to 113 Ryd photon energy range, a high percentage of which
arises from 2p photoionization leaving the ion in the 2s(2) 2p(4) (3)
P_2 state while the background cross section is constructed almost
exclusively of 2p and 2s photoionization with the former dominant
in both photoionization cases. Relativistic effects are found to be
important in obtaining accurate threshold positions as well as being
responsible for a significant drop in the background cross section in
comparison with various calculations done in LS coupling. We believe
that this is the first relativistic calculation for this ion.
---------------------------------------------------------
Title: The O V 1213.9 Angstroms forbidden line in the quiet Sun
Authors: Pinfield, D. J.; Mathioudakis, M.; Keenan, F. P.; Phillips,
K. J. H.; Curdt, W.
1998A&A...340L..15P Altcode:
We present the first unambiguous detection of the O v 1213.9 Angstrom
(2s(2) (1) S_0 -> 2s2p (3) P_2) forbidden line in the solar spectrum,
using observations obtained with the SUMER instrument on board SOHO. The
wavelength separation of the forbidden to the (2s(2) (1) S_0 ->
2s2p (3) P_1) intercombination line at 1218.35 Angstroms is 4.5+/-0.1
Angstroms in excellent agreement with theoretical predictions. The
observed line ratio, combined with the latest calculations, allows us
to derive an electron density of log {N_e/cm(-3}) = 8.5 +/- 0.15 for
the quiet Sun. However, the O v 1213.9 Angstroms line was not detected
in the HST spectra of Procyon and we can only place a lower limit of
log {N_e/cm(-3}) >= 7.8 to the electron density in this object.
---------------------------------------------------------
Title: Rotational velocities of B-type stars from the Edinburgh-Cape
survey
Authors: Magee, H. R. M.; Dufton, P. L.; Keenan, F. P.; Rolleston,
W. R. J.; Kilkenny, D.; O'Donoghue, D.; Koen, C.; Stobie, R. S.;
Peterson, R. C.
1998A&A...338...85M Altcode:
The projected rotational velocity distribution for a sample of 34
high Galactic latitude B-type stars from the Edinburgh-Cape Faint Blue
Object Survey is presented to investigate the evolutionary status of
the group as a whole. Statistical analyses of the distribution show it
to be similar to that expected if the sample contained mainly normal
Population i early B-type stars, although a contamination of up to 20 %
by evolved stars cannot be ruled out. This implies that a large fraction
of the sample consists of normal Population i B-type stars similar to
those found in the Galactic disk. Possible mechanisms explaining the
presence of these stars in the halo are briefly discussed.
---------------------------------------------------------
Title: The solar transition region: a time-varying interface between
the chromosphere and corona?
Authors: O'Shea, E.; Doyle, J. G.; Keenan, F. P.
1998A&A...338.1102O Altcode:
Using joint observations taken with the CDS and SUMER instruments
onboard SOHO, we re-examine the solar transition region in an attempt
to determine whether it is de-coupled from the over-lying coronal
region. Line ratios calculated from temporal series observations of
O iv and Fe xiii spectral lines were converted to electron density,
and hence electron pressure using theoretical line ratios. Little or no
evidence was found to support the constant electron density assumption,
and instead a constant electron pressure is found between the transition
region and corona. This lends support to the idea that the transition
region is a time varying interface between the chromosphere and corona,
and is not formed in unresolved fine-structures that are disconnected
from the corona.
---------------------------------------------------------
Title: K-shell photoejection cross section for neutral iron
Authors: Black, G. M.; Donnelly, D.; Bell, K. L.; Scott, M. P.;
Keenan, F. P.
1998A&A...337L..21B Altcode:
This Letter presents the first ab initio calculation, using the R-matrix
method, of the cross section for photoejection of a K-shell electron
from neutral iron. A 9-state target state approximation is employed,
and the results are compared with recent theoretical values, namely
the Hartree-Dirac-Slater method data of Verner and co-workers (1993,
1995). At the highest photon energy considered (640 Ryd), agreement is
excellent. However, with decreasing photon energy the two calculations
diverge, and the behaviour of the present cross section near threshold
shows a rapid rise from threshold in contrast to earlier work for which
the behaviour of the cross section as a function of photon energy is
approximately linear.
---------------------------------------------------------
Title: Proton impact excitation of the 1s(2) 2s2p (3) P fine-structure
transitions in the Be-like ions C iii, N iv, and O V
Authors: Ryans, R. S. I.; Foster-Woods, V. J.; Reid, R. H. G.; Keenan,
F. P.; Copeland, F.
1998A&A...336..393R Altcode:
Cross sections and thermally averaged excitation rate coefficients
are presented for proton impact excitations of the 1s(2) 2s2p (3) P
fine-structure transitions in the Be-like ions C iii, N iv, and O v. The
cross sections were calculated using a close-coupled impact parameter
method that has been modified to include the higher lying levels of the
triplet states of the 2p(2) , 2s3s, and 2s3d configurations. Excitation
rate coefficients have been calculated using these cross-sections for
a wide range of temperatures.
---------------------------------------------------------
Title: Extreme-Ultraviolet Transitions of Ca XVI in Solar Flare and
Laboratory Spectra
Authors: Keenan, F. P.; Pinfield, D. J.; Woods, V. J.; Reid, R. H. G.;
Conlon, E. S.; Pradhan, A. K.; Zhang, H. L.; Widing, K. G.
1998ApJ...503..953K Altcode:
New R-matrix calculations of electron impact excitation rates
for transitions among the 2s<SUP>2</SUP>2p, 2s2p<SUP>2</SUP>,
and 2p<SUP>3</SUP> levels of Ca XVI are presented. These data are
subsequently used, in conjunction with recent estimates for proton
excitation rates, to derive theoretical electron density sensitive
emission-line ratios involving 2s<SUP>2</SUP>2p-2s2p<SUP>2</SUP>
transitions in the ~155-225 Å wavelength range. A comparison of these
with observational data for solar flares, obtained with the Naval
Research Laboratory's S082A spectrograph on board Skylab, reveals
excellent agreement between theory and observation. In addition, the
theoretical ratios compare favorably with those measured from the TEXT
tokamak plasma, for which the electron temperature and density have
been independently determined. This provides experimental support for
the accuracy of the atomic data, and hence line ratio calculations,
employed in the present analysis.
---------------------------------------------------------
Title: Radio HI and optical absorption-line spectra of an
intermediate-velocity cloud in the general direction of the M15
globular cluster
Authors: Kennedy, D. C.; Bates, B.; Keenan, F. P.; Kemp, S. N.; Ryans,
R. S. I.; Davies, R. D.; Sembach, K. R.
1998MNRAS.297..849K Altcode:
Using HI spectra obtained with the Lovell telescope (FWHM ~ 12 arcmin)
we present maps showing the HI distribution and velocity structure
of an intermediate-velocity cloud (IVC; v_LSR~70 km s^-1) which is
observed in the general direction of the globular cluster M15. The
gas is shown to be clumpy in nature and we examine its position and
velocity structure. The IVC is detected in absorption in the CaII K line
towards five cluster stars in intermediate resolution spectra obtained
with ISIS/WHT and in high resolution UES/WHT NaI D line spectra of two
cluster stars (II-75; IV-38). The clumpy nature of the gas is indicated
by the NaI and KI spectra obtained in the II-75 and IV-38 sightlines,
which have angular separation ~ 3.5 arcmin. The IVC is detected in KI
in the higher column density II-75 sightline; this appears to be the
first detection of IVC or HVC gas in KI. The IVC gas towards M15 has
a similar velocity to that observed towards HD 203664, some 3.1 deg
away from the cluster. Similarities in the IVC gas velocity suggest a
gas structure that extends across both sightlines, although gas column
densities are considerably higher towards M15. For a common feature,
this would place the M15 IVC at a height above the Galactic plane
(z-distance) of <~1.5 kpc based on the Little et al. estimate
of the HD 203664 distance. From the fine-scale structure and column
density observations, estimates are made of the space density of the
small-scale concentrations. However, these remain uncertain and the
present observations emphasize the need for higher spatial and spectral
resolution studies to provide firmer estimates of cloud properties. We
report also on a radio HI and CaII line survey towards a sample of 24
stars over a wider field. This was carried out in an attempt to detect
any wider distribution of the IVC gas and to place better limits on
its distance. Although these observations are of sufficient spectral
quality, no new optical detections are reported.
---------------------------------------------------------
Title: Properties of the quiet Sun EUV network
Authors: Gallagher, P. T.; Phillips, K. J. H.; Harra-Murnion, L. K.;
Keenan, F. P.
1998A&A...335..733G Altcode:
Observations of the quiet Sun network in a small region at Sun
centre taken with the Coronal Diagnostic Spectrometer (CDS) on board
SOHO are reported for EUV lines with T_e between ~ 10(4) and 10(6)
K. The changing structure of the network in the upper chromosphere,
transition region, up to the corona was examined using intensity
distributions which were decomposed into two normal components using
a mixture-modelling technique. This enabled areas of high and low
intensities to be separated, and hence averaged network properties
including area, intensity, contrast, and fractal dimension to
be derived as a function of ion temperature. The network area and
emission were found to be more concentrated in the transition region
than in the chromosphere and in the corona, although the results
for the chromospheric He lines appear to be affected by resonance
scattering. At ~ 10(6) K, the area and emission of bright structures
dramatically increase, partly due to the appearance of small coronal
loops. There is also a discrete change in the fractal dimension at
coronal temperatures, signifying a change from network to simpler
coronal structures. Furthermore, the contrast of bright to dark regions
is at a maximum for T_e ~ 2.5x 10(5) K and falls to its lowest values
for coronal temperatures. The properties of several individual network
structures were found to follow the same general behaviour as in
the statistical analysis. Our results including physical dimensions
are broadly consistent with the transition region model of Gabriel,
although we cannot exclude the existence of low-lying loops as in the
model of Dowdy et al.
---------------------------------------------------------
Title: Beta Cephei type variability in the ultraviolet spectrum and
radial velocity of PHL 346
Authors: Dufton, P. L.; Keenan, F. P.; Kilkenny, D.; O'Donoghue, D.;
Parker, Q. A.; van Wyk, F.; van Leeuwen, F.
1998MNRAS.297..565D Altcode:
International Ultraviolet Explorer low-resolution and optical
moderate-resolution spectra are presented for the high galactic
latitude beta Cephei type star, PHL 346. Variability is identified
in both the ultraviolet flux and the radial velocity with periods
and phases consistent with those previously deduced from optical
photometry. The similarity of both the flux and the radial velocity
amplitude to those previously reported for the beta Cephei variable,
gamma Pegasus, is striking and provides evidence for PHL 346 being a
young core hydrogen burning star. A distance estimate for PHL 346 of
approximately 7 kpc (corresponding to a z-distance of approximately
6 kpc) is obtained by scaling the distance of gamma Pegasus obtained
from Hipparcos observations.
---------------------------------------------------------
Title: Photoionisation cross sections for Fe XVII
Authors: Leo, P. J.; Bell, K. L.; Keenan, F. P.
1998A&A...333..385L Altcode:
This paper reports the first close-coupling photoionisation
calculation of Fe XVII, and provides accurate total and partial
cross sections for photon energies up to 450 Ryd. The total and
first partial photoionisation cross sections, the latter obtained
when the Fe XVIII ion is left in the 2s(22p^5;^2P^o) ground state,
are dominated by resonance structure for photon energies in the range
from threshold to excitation of the first excited state (2s2p(6;^2S)
) of Fe XVIII. This is the first time that such structure has been
determined. The background cross section is found to be in good
agreement (to within 10%) with the results of Verner and co-workers
for the total cross section, and for the partial cross sections
corresponding to 2p and 2s photoejection, respectively.
---------------------------------------------------------
Title: Emission lines of [NeIV] in the optical and ultraviolet
spectra of gaseous nebulae
Authors: Keenan, F. P.; Aller, L. H.; Bell, K. L.; Espey, B. R.;
Feibelman, W. A.; Hyung, S.; McKenna, F. C.; Ramsbottom, C. A.
1998MNRAS.295..683K Altcode:
Recent R-matrix calculations of electron impact excitation rates
in Ne IV are used to calculate emission line ratio-ratio diagrams
involving both the ultraviolet (1602, 2422 and 2424 A) and optical
(4714, 4716, 4724 and 4726 A) [Ne IV] transitions, for a range of
electron temperatures (T_e=10 000-30 000 K) and electron densities
(N_e=10^2-10^6.5 cm^-3) appropriate to gaseous nebulae. These diagrams
should, in principle, allow the simultaneous determination of T_e
and N_e from measurements of the [Ne IV] lines in a spectrum. Plasma
parameters deduced for a sample of high-excitation planetary nebulae,
using a combination of observational data obtained with the IUE
satellite and the Hamilton Echelle Spectrograph (HES) on the 3-m Shane
Telescope at the Lick Observatory, are found to show generally excellent
internal consistency. In addition, they are in good agreement with
the values of T_e and N_e estimated from other high-excitation line
ratios in the HES spectra, and by previous authors using infrared and
ultraviolet transitions in [O IV] and [Ne V]. These results provide
observational support for the accuracy of the theoretical [Ne IV]
ratios, and hence the atomic data adopted in their derivation. An
inspection of IUE and GHRS/HST spectra of the symbiotic stars Z And
and RR Tel reveals asymmetries in the line profile of the [Ne IV]
2s^22p^3 ^4S-2s^22p^3 ^2P_1/2, 3/2 doublet at 1602 A, hence allowing
the measurement of the wavelength separation of the ^4S-^2P_1/2 and
^4S-^2P_3/2 components. The separation is found to be 0.21+/-0.02
A, in good agreement with the theoretical estimate of 0.16+/-0.03 A
this is the first time (to our knowledge) that this quantity has been
experimentally determined.
---------------------------------------------------------
Title: Effective Collision Strengths for Fine-Structure Transitions
from the 3s<SUP>2</SUP>3p<SUP>5</SUP> <SUP>2</SUP>P Ground State of
Chlorine-like Ni XII
Authors: Matthews, A.; Ramsbottom, C. A.; Bell, K. L.; Keenan, F. P.
1998ApJ...492..415M Altcode:
The R-matrix method is used to compute electron impact collision
strengths for transitions in Ni XII from its ground-state fine-structure
levels. Sophisticated configuration-interaction wave functions are
used to represent the 14 lowest LS target states employed in the
R-matrix expansion. By transforming the LS-coupled reactance matrices,
and by assuming a Maxwellian velocity distribution for the incident
electrons, the effective collision strengths are calculated for the
3s<SUP>2</SUP>3p<SUP>5</SUP><SUP>2</SUP>P<SUP>o</SUP><SUB>1/2</SUB>-3s<SUP>2</SUP>3p<SUP>5</SUP><SUP>2</SUP>P<SUP>o</SUP><SUB>3/2</SUB>
transition within the ground state and from both these fine-structure
levels to the 29 excited levels arising from states obtained
from 3s3p<SUP>6</SUP> and 3s<SUP>2</SUP>3p<SUP>4</SUP>3d
configurations. Effective collision strengths, obtained in the
temperature range log T<SUB>e</SUB> = 3.2-6.6 (K), are expected to
have an accuracy of better than 20%.
---------------------------------------------------------
Title: CDS observations of the quiet Sun EUV network
Authors: Gallagher, P. T.; Phillips, K. J. H.; Harra-Murnion, L. K.;
Keenan, F. P.
1998ESASP.421..365G Altcode: 1998sjcp.conf..365G
No abstract at ADS
---------------------------------------------------------
Title: Effective collision strengths for fine-structure forbidden
transitions among the 2s^22p^3 levels of Neiv
Authors: Ramsbottom, C. A.; Bell, K. L.; Keenan, F. P.
1998MNRAS.293..233R Altcode:
Effective collision strengths for electron-impact excitation of the
N-like ion Neiv are calculated in the close-coupling approximation
using the multichannel R-matrix method. Specific attention is given to
the 10 astrophysically important fine-structure forbidden transitions
among the ^4S^o, ^2D^o and ^2P^o levels in the 2s^22p^3 ground-state
configuration. The expansion of the total wavefunction incorporates
the lowest 11 LS eigenstates of Neiv, consisting of eight n=2 terms
with configurations 2s^22p^3, 2s2p^4 and 2p^5, together with three
n=3 states of configuration 2s^22p^23s. We present in graphical form
the effective collision strengths obtained by thermally averaging the
collision strengths over a Maxwellian distribution of velocities,
for all 10 fine-structure transitions, over the range of electron
temperatures log T(K) = 3.6 to log T(K) = 6.1 (the range appropriate
for astrophysical applications). Comparisons are made with the earlier,
less sophisticated close-coupling calculation of Giles, and excellent
agreement is found in the limited temperature region where a comparison
is possible [log T(K) = 3.7 to log T(K) = 4.3]. At higher temperatures
the present data are the only reliable results currently available.
---------------------------------------------------------
Title: Fe XVIII Emission Lines in Solar X-Ray Spectra
Authors: Warren, G. A.; Keenan, F. P.; Greer, C. J.; Phillips, K. J.;
Bruner, M. E.
1998smc..conf.....W Altcode:
We have calculated intensity ratios for emission lines of Fe XVIII in
the 19-94A wavelength range at electron temperatures characteristic
of the solar corona, Te = 2-10 x 10 to the 6th power K. Our model
ion includes data for transitions among the 2s22p5, 2s2p6, 2s22p43l,
and 2s2p53l (l = s, p, and d) states. Test calculations that omit the
2s2p53l levels show that cascades from these are important. We compare
our results with observed ratios determined from four solar X-ray
instruments, a rocket-borne spectrograph, and spectrometers on the
P78-1, OV1-17 and Solar Maximum Mission (SMM) satellites. In addition,
we have generated synthetic spectra which we compare directly with
flare observations from SMM. Agreement between theory and observation
is generally quite good, with differences that are mostly less than
30%, providing limited support for the accuracy of the atomic physics
data used in our calculations. However, large discrepancies are found
for ratios involving the 2s22p5 2P3/2-2s2p6 2S line at 93.84A, which
currently remain unexplained. Our analysis indicates that the Fe XVIII
feature at 15.83A is the 2s22p5 2P3/2-2s22p4(3P)3s4 P3/2 transition,
rather than 2s22p5 2P3/2-2s22p4(3P)3s 2P3/2, as suggested by some
authors.
---------------------------------------------------------
Title: Effective Collision Strengths for Electron-Impact Excitation
of Ni XII
Authors: Matthews, A.; Ramsbottom, C. A.; Bell, K. L.; Keenan, F. P.
1998ADNDT..70...41M Altcode:
Effective collision strengths computed by the R-matrix method
are presented for the electron-impact excitation of Cl-like
Ni XII. The total wave function used in the close-coupling
expansion includes the lowest 14 target states of Ni XII, arising
from the 3s<SUP>2</SUP>3p<SUP>5</SUP>, 3s3p<SUP>6</SUP>and
3s<SUP>2</SUP>3p<SUP>4</SUP>3dconfigurations. These 14LStarget
states corresponds to 31j-resolved fine-structure levels, connected
by 465 independent transitions. Effective collision strengths for all
possible transitions, calculated by averaging the electron collision
strengths over a Maxwellian distribution of electron velocities, are
tabulated over the electron temperature range logT(K) = 5.5 to logT(K)
= 6.6. This range includes the temperatures of particular interest
for many astrophysical applications.
---------------------------------------------------------
Title: The Structural Variability of the Solar EUV Network
Authors: Gallagher, P. T.; Phillips, K. J. H.; Harra-Murnion, L. K.;
Keenan, F. P.
1998ASPC..154..612G Altcode: 1998csss...10..612G
Observations of the quiet Sun with the Coronal Diagnostic Spectrometer
(CDS) on board the Solar and Heliospheric Observatory (SOHO) are
reported for the upper chromosphere, transition region, and corona. The
changing structure of the EUV network is examined over a temperature
range of 1.5 x 10^4 K to 1.2 x 10^6 K using a variety of properties
of the characteristic intensity distributions. The distribution of
intensity in small (4 x 4 arcmins^2) areas of the quiet Sun at Sun
centre has been examined. These distributions were found to consist of
both a low intensity core distribution combined with an extended tail
associated with the transition region EUV network. Network properties
such as relative area, emission, contrast, and fractal dimension
have been derived by fitting two Gaussians (one representing the cell
distribution, the other the network) to each frequency histogram and
then using the cross-over point of the two Gaussians as a boundary
point between the two components. The integrity of the network displays
a well defined relationship with temperature showing a noticeable
structural enhancement in the temperature range 1.1 x 10^5 K to 2.5 x
10^5 K together with a dramatic change in integrity at coronal (>=
10^6 K) temperatures.
---------------------------------------------------------
Title: Proton-Impact Excitation Data of Relevance to the SOHO Mission
Authors: Foster-Woods, V. J.; Copeland, F.; Reid, R. H. G.; Keenan,
F. P.
1998ASPC..154..608F Altcode: 1998csss...10..608F
Calculations of proton-impact fine-structure excitation of ions have
been compiled and assessed, listing references and accuracies for
individual transitions for each isoelectronic sequence. We present here
a summary of that compilation, which was carried out in line with the
recent exercise for the electron-impact excitation data for the SOHO
mission. We also report on new data for several B-like, Be-like and
C-like ions, calculated by the close-coupled impact-parameter method
modified to include higher states by means of a polarization potential.
---------------------------------------------------------
Title: Cross Sections and Rate Coefficients for Excitation of
the 1s<SUP>2</SUP>2s2p <SUP>3</SUP>P<SUP>o</SUP><SUB>J</SUB>
--> 1s<SUP>2</SUP>2s2p <SUP>3</SUP>P<SUP>o</SUP><SUB>J'</SUB>
Fine-Structure Transitions in Beryllium-like Ions by Heavy Particle
Impact
Authors: Ryans, R. S. I.; Foster-Woods, V. J.; Copeland, F.; Keenan,
F. P.; Matthews, A.; Reid, R. H. G.
1998ADNDT..70..179R Altcode:
Cross sections for excitation of the
1s<SUP>2</SUP>2s2p<SUP>3</SUP>P<SUP>o</SUP><SUB>J</SUB>→
1s<SUP>2</SUP>2s2p<SUP>3</SUP>P<SUP>o</SUP><SUB>J‧</SUB>fine-structure
transitions in beryllium-like ions by proton, deuteron, triton,
and α-particle impact have been calculated using a close-coupled
impact-parameter method. This technique includes the effects of
dipole coupling to the nearby triplet 2p<SUP>2</SUP>, 2s3s, and
2s3dconfigurations by means of a polarization potential. We consider
the ions C III, N IV, O V, Ne VII, Mg IX, Al X, Si XI, S XIII, Ar
XV, Ca XVII, Ti XIX, Cr XXI, Fe XXIII, and Ni XXV. Excitation rate
coefficients have also been calculated from the cross sections for a
range of temperatures.
---------------------------------------------------------
Title: Hubble Space Telescope Observations of an Intermediate-High
Velocity Cloud in the Low Galactic Halo
Authors: Sembach, K. R.; Keenan, F.; Ryans, Robert
1997AAS...191.5113S Altcode: 1997BAAS...29.1297S
For many years it has been realized that the existence of intermediate
and high velocity clouds in the Milky Way can provide information
about the nature of the gaseous halo that surrounds our Galaxy. Despite
this realization, there is still very little known about the chemical
compositions, physical properties, and origins of most interstellar
clouds that fall into these categories. Furthermore, the relationships
(or lack thereof) between intermediate velocity and high velocity
clouds themselves are poorly defined, though at least in some cases it
does appear that the intermediate velocity clouds may be more confined
to the Galactic plane than their higher velocity counterparts. Those
clouds that have velocities near the arbitrary velocity cutoff to be
considered high velocity (|v| ~ 100 km/s) are particularly worthy of
study, since they may contain clues to help distinguish between the
competing physical processes responsible for separating (or linking)
clouds in these two velocity regimes. Using the Goddard High Resolution
Spectrograph aboard the Hubble Space Telescope, we have obtained high
quality spectra (S/N > 50, R ~ 20,000-85,000) of a large number of
atomic transitions observable in the intermediate-high velocity cloud
in the direction of HD 203664 (l = 61.9, b = -27.5). This cloud has a
velocity (LSR) of about +80 km/s and displays absorption in a wide range
of ionization stages. Much of the observed absorption may arise in an
envelope of gas that extends across the face of the globular cluster
M 15, located ~ 3 degrees away from the sight line. In this poster,
we provide comparisons of the various ionization stages observed
and their velocity distributions, information about the chemical and
physical properties of the cloud, and some comments about the possible
origins of such clouds.
---------------------------------------------------------
Title: The calculation of photoionization of highly-ionized iron
using R-matrix theory.
Authors: Black, G.; Rose, S. J.; Bell, K. L.; Keenan, F. P.
1997JQSRT..58..491B Altcode:
Results of recent R-matrix calculations on the photoionization
cross-sections for Fe XXIII and Fe XXIV are presented. These, unlike
previous calculations, predict large resonance structure.
---------------------------------------------------------
Title: A Large-Scale Spectroscopic Survey of Early-Type Stars at
High Galactic Latitudes
Authors: Saffer, Rex A.; Keenan, F. P.; Hambly, N. C.; Dufton, P. L.;
Liebert, James
1997ApJ...491..172S Altcode:
We present new model atmosphere analyses of optical spectroscopy of a
large sample of B-type stellar candidates. Of a total of 298 objects,
the largest sample of its kind to date, 205 were drawn from the Palomar
Green Survey of high Galactic latitude ultraviolet-excess stellar
objects and comprise a complete magnitude-limited sample. Effective
temperatures, surface gravities, and helium abundances for the hot
subdwarf (high-gravity) component of the sample are derived from a
detailed line profile analysis of the hydrogen and helium absorption
lines in intermediate-resolution (3-5 Å FWHM) optical spectra. A
separate analysis of the lower gravity component is made using a
newly calculated grid of synthetic spectra. Additional estimates of
the effective temperatures are made from wide- and intermediate-band
photometry taken from the literature. We are currently undertaking two
follow-up programs. (1) Detailed abundance analyses of high-resolution
echelle spectra of the lower gravity component of the survey using
modern model atmosphere and synthetic spectrum techniques will
differentiate between massive Population I main-sequence B stars and
low-mass, lower luminosity Population II blue horizontal branch stars
and post-asymptotic giant branch stars. (2) The derived atmospheric
parameters for the higher gravity component, the field extended
horizontal branch stars, will be combined with radial velocity
measurements to determine their spatial and kinematic distributions,
which will distinguish between competing evolutionary scenarios for
this hot, evolved stellar population. <P />Observations obtained, in
part, at the Multiple Mirror Telescope Observatory (MMTO), operated
jointly by the University of Arizona and the Smithsonian Institution.
---------------------------------------------------------
Title: LS 4825: A Blue Supergiant on the Far Side of the Galaxy
Authors: Ryans, R. S. I.; Dufton, P. L.; Keenan, F. P.; Smartt, S. J.;
Sembach, K. R.; Lennon, D. J.; Venn, K. A.
1997ApJ...490..267R Altcode:
We present high-resolution spectroscopic observations of LS 4825, a V =
12 B-type star in the Galactic center direction. On the basis of its
stellar and interstellar spectra, we infer that it is likely to be
a young supergiant at a distance of 21 +/- 5 kpc, and hence lying on
the far side of the Galaxy. Adopting this hypothesis, a differential
abundance analysis shows LS 4825 to have a chemical composition that is
consistent with local B-type supergiants. These observations therefore
represent the first detailed investigation of a star on the far side
of the Galactic center. We trace multiple interstellar components in
Ca II K and Na I D spectra, with velocities -206 <= v<SUB>lsr</SUB>
<= +93 km s<SUP>-1</SUP>. We consider the likely origin of this gas
and find that some components appear to trace matter lying close to
the Galactic center. We discuss the possible use of such sight lines
in furthering our understanding both of the nature of gas around the
Galactic center and of the abundance gradient of the Galaxy. <P />Based
in part upon observations made at the European Southern Observatory,
La Silla, Chile.
---------------------------------------------------------
Title: Nebular and Auroral Emission Lines of [Ar IV] in the Optical
Spectra of Planetary Nebulae
Authors: Keenan, F. P.; McKenna, F. C.; Bell, K. L.; Ramsbottom,
C. A.; Wickstead, A. W.; Aller, L. H.; Hyung, S.
1997ApJ...487..457K Altcode:
Recent R-matrix calculations of electron impact excitation rates in
Ar IV are used to calculate the emission-line ratio: ratio diagrams
(R<SUB>1</SUB>, R<SUB>2</SUB>), (R<SUB>1</SUB>, R<SUB>3</SUB>), and
(R<SUB>1</SUB>, R<SUB>4</SUB>), where R<SUB>1</SUB> = I(4711 Å)/I(4740
Å), R<SUB>2</SUB> = I(7238 Å)/I(4711 + 4740 Å), R<SUB>3</SUB> =
I(7263 Å)/I(4711 + 4740 Å), and R<SUB>4</SUB> = I(7171 Å)/I(4711
+ 4740 Å), for a range of electron temperatures (T<SUB>e</SUB> =
5000-20,000 K) and electron densities (N<SUB>e</SUB> = 10-10<SUP>6</SUP>
cm<SUP>-3</SUP>) appropriate to gaseous nebulae. These diagrams should,
in principle, allow the simultaneous determination of T<SUB>e</SUB>
and N<SUB>e</SUB> from measurements of the [Ar IV] lines in a
spectrum. Plasma parameters deduced for a sample of planetary nebulae
from (R<SUB>1</SUB>, R<SUB>3</SUB>) and (R<SUB>1</SUB>, R<SUB>4</SUB>),
using observational date obtained with the Hamilton echelle spectrograph
on the 3 m Shane Telescope at the Lick Observatory, are found to show
excellent internal consistency and to be in generally good agreement
with the values of T<SUB>e</SUB> and N<SUB>e</SUB> estimated from other
line ratios in the echelle spectra. These results provide observational
support for the accuracy of the theoretical ratios and, hence, the
atomic data adopted in their derivation. In addition, they imply that
the 7171 Å line is not as seriously affected by telluric absorption
as previously thought. However, the observed values of R<SUB>2</SUB>
are mostly larger than the theoretical high-temperature and density
limit, which is due to blending of the Ar IV 7237.54 Å line with the
strong C II transition at 7236 Å.
---------------------------------------------------------
Title: [O V] in the Ultraviolet Spectra of Gaseous Nebulae
Authors: McKenna, F. C.; Keenan, F. P.; Aller, L. H.; Hyung, S.;
Feibelman, W. A.; Berrington, K. A.; Fleming, J.; Hibbert, A.
1997ApJ...486..571M Altcode:
Theoretical O V electron-density-sensitive emission line
ratios for R = I(2s<SUP>2</SUP> <SUP>1</SUP>S<SUB>0</SUB> - 2s2p
<SUP>3</SUP>P<SUB>2</SUB>)/I(2s<SUP>2</SUP> <SUP>1</SUP>S<SUB>0</SUB> -
2s2p <SUP>3</SUP>P<SUB>1</SUB>) are presented. Inspection of Goddard
High Resolution Spectrograph Hubble Space Telescope spectra of RR
Tel reveals the presence of the [O V] 2s<SUP>2</SUP> <SUP>1</SUP>S
- 2s2p <SUP>3</SUP>P<SUB>2</SUB> line at 1213.80 Å, which is
4.62 +/- 0.12 Å away from the 2s<SUP>2</SUP> <SUP>1</SUP>S - 2s2p
<SUP>3</SUP>P<SUB>2</SUB> intercombination transition at 1218.42 Å,
in good agreement with the theoretical prediction of Δλ = 4.54
Å. The resultant value of R = 0.82 +/- 0.11 implies a logarithmic
electron density, log N<SUB>e</SUB>, of 5.2 +/- 0.2 cm<SUP>-3</SUP>,
in good agreement with that found from other ions with high electron
temperature, such as Ne VI, which also provides support for the
identification.
---------------------------------------------------------
Title: High-resolution spectroscopic observations of B-type stars
from the Edinburgh-Cape survey
Authors: Rolleston, W. R. J.; Hambly, N. C.; Dufton, P. L.; Keenan,
F. P.; Little, J. E.; Kilkenny, D.; O'Donoghue, D.; Koen, C.; Stobie,
R. S.
1997MNRAS.290..422R Altcode:
High-resolution spectroscopy has been obtained for 25 high-latitude
stars identified from the Edinburgh-Cape faint blue object survey
as having B-type spectra. Five objects are found to be subluminous
(subdwarf or horizontal branch), chemically peculiar, or later
than B-type. We present model atmosphere analyses for the other
20 objects, and conclude that 17 stars exhibit stellar properties
typical of young B-type dwarfs. Photospheric abundances determined for
a subset of stars were also found to be consistent with a Population
I composition. Furthermore, we believe EC 05229-6058 to be an evolved
object currently on the post-asymptotic giant branch phase, whilst EC
20411-2704 and 11074-2912 are consistent with being zero-age horizontal
branch and post-blue horizontal branch objects respectively. A kinematic
analysis of the normal stars implies that all could have formed in,
and have been subsequently ejected from, the Galactic disc.
---------------------------------------------------------
Title: Star-forming Processes Far from the Galactic Disk: Inoperative
or Indolent Where Operative
Authors: Christodoulou, Dimitris M.; Tohline, Joel E.; Keenan,
Francis P.
1997ApJ...486..810C Altcode:
Highly supersonic collisions between gaseous clouds may effectively
trigger star formation in the disk of our Galaxy, but not in the
diffuse environment of the Galactic halo. This is because the observed
high-velocity clouds (HVCs) are not dominated by collisions: the
characteristic time between cloudlet collisions inside an HVC at an
assumed distance of 10 kpc is at least 1 Gyr for collective encounters
and at least 10 Gyr if a particular cloudlet is considered. In agreement
with this result, we also estimate that the observed cloudlets contain
smaller masses than the nonmagnetic Jeans mass that signals favorable
conditions for gravitational collapse and further fragmentation in
the isothermal regime. The diffuse environment observed around the
Magellanic Clouds (MCs) is more difficult to understand than HVCs. Six
sparse blue associations and two young B-type stars have been observed
in the H I bridge between the MCs, while no stars exist in the H I
cloud complexes that make up the Magellanic Stream. We discuss the
conditions under which spatially sporadic star formation took place
in the Magellanic Bridge during the past 16-25 Myr and the reasons
for the complete absence of star formation in the Stream during its
entire lifetime. We also estimate the angular resolutions that need
to be achieved by follow-up radio observations of these regions that
could detect cold cloudlets embedded in the gas.
---------------------------------------------------------
Title: Optical and HI studies of high- and intermediate-velocity
gas towards Complex A
Authors: Ryans, R. S. I.; Keenan, F. P.; Sembach, K. R.; Davies, R. D.
1997MNRAS.289..986R Altcode:
We present high-resolution optical and 21-cm Hi spectra of
seven early-type stellar sightlines towards the high-velocity
cloud Complex A, at distances of up to 4.6 kpc from the Galactic
plane. We do not optically detect the -160 kms^-1 interstellar gas
associated with Complex A, and so are unable to establish limits
on its distance. However, we do detect gas associated with the Low
Latitude Intermediate Velocity Arch, placing it at z<0.9kpc, and
also establish distance limits (z<=1.2-3.3kpc) on several other
intermediate- and high-velocity clouds in this region that have not
been catalogued previously.
---------------------------------------------------------
Title: FeXVII X-ray lines in solar coronal and laboratory plasmas.
Authors: Phillips, K. J. H.; Greer, C. J.; Bhatia, A. K.; Coffey,
I. H.; Barnsley, R.; Keenan, F. P.
1997A&A...324..381P Altcode:
Theoretical intensities of the Fe XVII X-ray lines due to transitions
2p^6^-2p^5^3d (near 15Å) and 2p^6^-2p^5^3s (near 17Å) are presented,
and compared with solar flare and active region spectra. The ratio
of the 15Å lines to the 17Å lines is a function of temperature
T_e_, but for solar spectra this is not of practical use because of
the resonance scattering of the intense 15.015Å line. Instead we
use the ratio of a nearby Fe XVIII line to obtain T_e_. We find very
satisfactory correspondence between solar spectra and synthetic spectra
based on calculated line intensities with appropriately chosen T_e_
apart from the 15.015Å line, which is sometimes less intense than its
theoretical value, apparently owing to resonance scattering. Spectra
emitted by DITE and JET tokamak plasmas with measured T_e_ and N_e_
are also considered. A predicted density variation of the ratio of
the Fe XVII lines at 17.051Å and 17.096 Å is confirmed, and using
Abel inversion techniques applied to a sequence of DITE spectra
with different radial distances good agreement is found between the
theoretical temperature variation of the I(15.015Å)/I(16.776Å)
line ratio and that derived from these spectra. We conclude that our
calculated Fe XVII line intensities are very reliable and may therefore
be used in future analysis.
---------------------------------------------------------
Title: Early-Type Stars in the Galactic Halo from the Palomar-Green
Survey. I. A Sample of Evolved, Low-Mass Stars
Authors: Hambly, N. C.; Rolleston, W. R. J.; Keenan, F. P.; Dufton,
P. L.; Saffer, R. A.
1997ApJS..111..419H Altcode:
We present high-resolution spectroscopic observations of early-type
stars drawn from a complete sample based on low-resolution spectroscopy
of targets from the Palomar-Green Survey by Green, Schmidt, &
Liebert. Qualitatively, the metal-line spectra are sharp and
are therefore indicative of extremely low projected rotational
velocities. Hence the objects are characterized as members of an
old, evolved population (for example, blue horizontal branch or
post-asymptotic giant branch). By careful choice of Population I,
Galactic disk B stars, we have computed differential abundances between
the targets and their main-sequence analogs. The CNO abundances from
model-atmosphere analyses suggest the presence of nucleosynthesis
dredge-up products in the stellar photospheres. With one exception,
the stars all have [Fe/H] abundances consistent with their progenitor
objects being metal deficient. Some conclusions are drawn as to the
previous evolution (red giant branch, horizontal branch, or asymptotic
giant branch) of the stars.
---------------------------------------------------------
Title: The Ar/Ca relative abundance in solar coronal plasma.
Authors: Young, P. R.; Mason, H. E.; Keenan, F. P.; Widing, K. G.
1997A&A...323..243Y Altcode:
The relative abundances of elements with low and high first
ionisation potentials (FIP) is a subject of much recent debate. In
situ measurements of the solar wind reveal a clear pattern of low
FIP enhancement that has been followed up with various spectroscopic
measurements of the solar corona. Argon is unique amongst the more
abundant high FIP elements in retaining several of its electrons at
the high temperatures seen in flares. This allows emission lines of
different ions to be compared with more confidence than for, say,
hydrogen-like high FIP ions such as OVIII and NeX. In this paper we
look at emission lines of the boron-like ion ArXIV; in particular,
the optical line at 4412Å, seen in eclipse observations, is compared
to the CaXIII 4086Å and CaXV 5445Å & 5694Å lines to yield an
Ar/Ca abundance of 0.85+/- 0.20. In the extreme ultra-violet (EUV),
the ArXIV lines at 187.94Å and 194.41Å can be compared with CaXIV
193.87 Å - flare data from Skylab giving values of 1.10+/-0.25 and
0.55+/-0.21. Analysis of previous work indicates a photospheric Ar/Ca
abundance of 1.31+/-0.30, hence supporting the conclusion that elements
with high FIP have lower coronal abundances.
---------------------------------------------------------
Title: Nonthermal Velocities in the Solar Transition Zone and Corona
Authors: Doyle, J. G.; O'Shea, E.; Erdélyi, R.; Dere, K. P.; Socker,
D. G.; Keenan, F. P.
1997SoPh..173..243D Altcode:
Nonthermal velocities are presented for spectral lines covering the
temperature range 10 4-10 6 K, measured from high-spectral-resolution
data for several solar features observed at the limb by the high
resolution telescope and spectrograph (HRTS), including a coronal hole,
`quiescent regions' and several small-scale active regions. These
results are compared with predictions based on acoustic waves and
heating via Alfvén waves. It is likely that more than one mechanism is
operating simultaneously, in particular, resonant Alfvén wave heating,
which is very sensitive to background plasma motions.
---------------------------------------------------------
Title: Heavy particle excitation of the fine-structure transitions
within the 2s2p^2^4P multiplet in boron-like ions
Authors: Foster, V. J.; Reid, R. H. G.; Keenan, F. P.
1997MNRAS.288..973F Altcode:
Cross-sections are presented for proton-impact excitation of the
fine-structure transitions within the 2s2p^2 ^4P multiplet in Cii,
Niii and Oiv. These have been calculated using the close-coupled impact
parameter method modified to include the 2p^3 ^4S^o states by means
of a polarization potential. Excitation rate coefficients have been
derived from the cross-sections for a wide range of temperatures.
---------------------------------------------------------
Title: Spectroscopy of the interstellar medium in the Magellanic
Bridge
Authors: Keenan, Francis
1997hst..prop.7511K Altcode:
Our optical observations of two B-type stars in the Magellanic Bridge,
a region of material between the Large and Small Magellanic Clouds {LMC,
SMC}, reveal strong interstellar Ca II K absorption arising from the
Bridge gas. We now propose to obtain medium resolution STIS spectra
of the ultraviolet interstellar lines toward both of the stars. The
proposed observations will provide an opportunity to investigate
the physical conditions within the Bridge gas, and to determine the
chemical composition of important elements such as C, N, O, Mg, Si, S,
and Fe. These abundances will be compared with those found for the LMC
and SMC, which will allow us to investigate if the Bridge gas originated
in the SMC, as current theory suggests. The presence of young B-type
stars in the Bridge implies that star formation is still occurring
in this region. It has been suggested that the formation mechanism
is similar to that believed to be responsible for some of the young
B-type stars found in the halo of our Galaxy, namely collisions between
cloudlets within high-velocity clouds {HVCs}. To investigate this, we
will compare our derived physical conditions for the Bridge gas with
those found for halo HVCs. We will also search for cloudlet structure
in the Bridge gas, through the identification of multicomponents in
the interstellar line profiles; such cloudlets have already been found
by us in an HVC.
---------------------------------------------------------
Title: The distance to Complex M and the Intermediate Velocity Arch
Authors: Ryans, R. S. I.; Keenan, F. P.; Sembach, K. R.; Davies, R. D.
1997MNRAS.289...83R Altcode:
The Intermediate Velocity Arch is an association of Hi clouds lying
within the broad limits l~110 deg-210 deg,b~50 deg-80 deg. We use
high-resolution optical, and single-dish 21-cm, observations of 10
early-type halo star sightlines in this region to establish distance
limits (0.4<=z<=3.5kpc) for seven IVCs that are part of the
Arch. We re-examine a previous determination of upper and lower
distance limits on the IVC Complex M using the closely aligned halo
stars BD+382182 and HD93521. Our Hi spectra show no evidence of emission
from Complex M, leading us to conclude that, while an upper distance
limit of z<=3.5 kpc may be established, no useful lower distance
determination can be made. Our new Hi observations allow new limits
to be established on the metallicity of Complex M, and show C, O and
Si variations with respect to solar abundances in the range +/-0.3 dex.
---------------------------------------------------------
Title: Photoionisation cross-sections for Fe XXIII and Fe XXIV.
Authors: Black, G. M.; Bell, K. L.; Keenan, F. P.
1997A&A...322..359B Altcode:
Photoionisation of Fe XXIII and Fe XXIV is investigated using
the R-matrix method, with particular attention being given to
photoejection of the 1s K-shell electron. In both cases, good agreement
(to within 5%) is found with earlier calculations of the background
cross-section. However, the present work is the first to determine
resonance structure just below and above the 1s photoejection threshold
energy.
---------------------------------------------------------
Title: Emission Lines of NI XVIII in the Solar EUV Spectrum
Authors: Keenan, F. P.; Foster, V. J.; Mohan, M.; Widing, K. G.
1997SoPh..171..337K Altcode:
Using electron excitation rates calculated with the R-matrix code,
theoretical Nixviii electron-temperature-sensitive emission line
ratios are presented for R<SUB>1</SUB> = I(220.41 Å)/I(320.56 Å) ,
R<SUB>2</SUB> = I(233.79 Å)/I(320.56 Å) , and R<SUB>3</SUB> = I(220.41
Å)/I(292.00 Å) . A comparison of these with observational data for
two solar flares, obtained by the Naval Research Laboratory's S082A
slitless spectrograph on board Skylab, reveals good agreement between
theory and observation for R<SUB>1</SUB> and R<SUB>2</SUB> in two
spectra, which provides limited support for the accuracy of the atomic
data adopted in the analysis. However, several of the measured ratios
are much larger than theory predicts, which is probably due mainly to
saturation of the strong 292.00 and 320.56 Å lines on the photographic
film used to record the S082A data. A comparison of our line ratio
calculations with active region observations made by the Solar EUV
Rocket Telescope and Spectrograph (SERTS) indicate that a feature at
236.335 Å, identified as the Nixviii 3p<SUP>2</SUP>P<SUB>3/2</SUB> -
3d<SUP>2</SUP>D<SUB>3/2</SUB> transition in the SERTS data, is actually
the Arxiii 2s<SUP>2</SUP>2p<SUP>2</SUP><SUP>3</SUP>P<SUB>0</SUB> -
2s2p<SUP>3</SUP><SUP>3</SUP>D<SUB>1</SUB> line. The potential usefulness
of the Nixviii line ratios as electron temperature diagnostics for
the solar corona is briefy discussed.
---------------------------------------------------------
Title: The Optical Spectral Line List of RR Telescopii
Authors: McKenna, F. C.; Keenan, F. P.; Hambly, N. C.; Allende Prieto,
C.; Rolleston, W. R. J.; Aller, L. H.; Feibelman, W. A.
1997ApJS..109..225M Altcode:
The symbiotic nova RR Telescopii has been observed with the 1.5
m telescope of the Cerro Tololo Inter-American Observatory (CTIO),
using the 1.5 m bench-mounted echelle spectrograph in conjunction with
a Tektronix CCD. It displays a rich emission-line spectrum, ranging in
excitation from O I to [Ni VIII]. We present a list of 491 measured
lines, with their suggested identifications, covering a wavelength
range from 3430 to 9320 Å. Of these, only nine are unidentified, and
70 lines are cataloged that were not given in the original line list of
Thackeray. Absolute line intensities are also given, which have been
derived by comparing the high-resolution data with a flux-calibrated
low-resolution spectrum taken with the Cassegrain spectrograph on the
1.0 m telescope at CTIO.
---------------------------------------------------------
Title: F XVIII Emission Lines in Solar X-Ray Spectra
Authors: Warren, G. A.; Keenan, F. P.; Greer, C. J.; Phillips,
K. J. H.; Bruner, M. E.; Brown, W. A.; McKenzie, D. L.
1997SoPh..171...93W Altcode:
We have calculated intensity ratios for emission lines of Fexviii
in the 13-94 Å wavelength range at electron temperatures
characteristic of the solar corona, T<SUB>e</SUB> = 2-10 x
10<SUP>6</SUP> K. Our model ion includes data for transitions
among the 2s<SUP>2</SUP>2p<SUP>5</SUP> , 2s2p<SUP>6</SUP>,
2s<SUP>2</SUP>2p<SUP>4</SUP>3l, and 2s2p<SUP>5</SUP>3l (l = s, p, and
d) states. Test calculations which omit the 2s2p<SUP>5</SUP>3l levels
show that cascades from these are important. We compare our results
with observed ratios determined from four solar X-ray instruments, a
rocket-borne spectrograph, and spectrometers on the P78-1, OV1-17 and
Solar Maximum Mission (SMM) satellites. In addition, we have generated
synthetic spectra which we compare directly with flare observations
from SMM. Agreement between theory and observation is generally
quite good, with differences that are mostly less than 30%, providing
limited support for the accuracy of the atomic physics data used in
our calculations. However, large discrepancies are found for ratios
involving the 2s<SUP>2</SUP>2p<SUP>5</SUP><SUP>2</SUP>P<SUB>3/2</SUB>-
2s2p<SUP>6</SUP><SUP>2</SUP>S line at 93.84 Å, which currently remain
unexplained. Our analysis indicates that the FeXVIII feature at 15.83
Å is the 2s<SUP>2</SUP>2p<SUP>5</SUP><SUP>2</SUP>P<SUB>3/2</SUB>
- 2s<SUP>2</SUP>2p<SUP>4</SUP>(<SUP>3</SUP>P)3s
<SUP>4</SUP>P<SUB>3/2</SUB> transition, rather than
2s<SUP>2</SUP>2p<SUP>5</SUP><SUP>2</SUP>P<SUB>3/2</SUB>
- 2s<SUP>2</SUP>2p<SUP>4</SUP>(<SUP>3</SUP>P)3s
<SUP>2</SUP>P<SUB>3/2</SUB>, as suggested by some authors.
---------------------------------------------------------
Title: M VIII Diagnostic Line Ratios in SKYLAB Solar Observations
Authors: Foster, V. J.; Keenan, F. P.; Reid, R. H. G.; Doyle, J. G.;
Zhang, H. L.; Pradhan, A. K.; Widing, K. G.
1997SoPh..170..217F Altcode:
Recent calculations of Mgviii electron and proton impact
excitations rates are used to derive theoretical electron temperature
(T<SUB>e</SUB>)- and density (N<SUB>e</SUB>)-sensitive emission line
ratios involving transitions in the 315-782 Å wavelength range. Some
of these ratios are presented in the form of ratio-ratio diagrams,
which should in principle allow both N<SUB>e</SUB> and T<SUB>e</SUB>
to be deduced. These results are compared with solar observational data
from Skylab, but agreement between theory and observation is very poor,
probably due to blending.
---------------------------------------------------------
Title: Oscillator Strengths for Transitions in Ca XV and Fe XXI
Authors: Aggarwal, K. M.; Hibbert, A.; Keenan, F. P.; Norrington, P. H.
1997ApJS..108..575A Altcode:
Energy levels and oscillator strengths (transition rates) have been
calculated for the fine-structure transitions among the levels of the
(1s<SUP>2</SUP>) 2s<SUP>2</SUP>2p<SUP>2</SUP>, 2s2p<SUP>3</SUP>,
2p<SUP>4</SUP>, 2s<SUP>2</SUP>2p3s, 2s<SUP>2</SUP>2p3p, and
2s<SUP>2</SUP>2p3d configurations of Ca XV and Fe XXI using the CIV3 and
GRASP programs. The results are compared with the recently available
theoretical values from the SuperStructure program. The differences
among the various calculations are discussed, and the accuracy of the
results is assessed.
---------------------------------------------------------
Title: Observations of Ob-Type Stars in the Halos of Galaxies
Authors: Keenan, F. P.
1997fbs..conf..199K Altcode: 1997LDP....22..199K
No abstract at ADS
---------------------------------------------------------
Title: Oscillator Strengths for Transitions in O III
Authors: Aggarwal, K. M.; Hibbert, A.; Keenan, F. P.
1997ApJS..108..393A Altcode:
Energy levels and oscillator strengths have been calculated for the
fine-structure transitions among the levels of the (1s<SUP>2</SUP>)
2s<SUP>2</SUP>2p<SUP>2</SUP>, 2s2p<SUP>3</SUP>, 2p<SUP>4</SUP>,
2s<SUP>2</SUP>2p3s, 2s<SUP>2</SUP>2p3p, and 2s<SUP>2</SUP>2p3d
configurations of O III using the CIV3 program. The extensive
configuration interaction and relativistic effects have been included
while generating the wave functions. The results are compared with
other recent theoretical estimates, and their accuracy is assessed.
---------------------------------------------------------
Title: Time Series Photometric and Spectroscopic Observations of
the β Cephei Halo Star PHL 346
Authors: Dufton, P. L.; Keenan, F. P.; Kilkenny, D.
1997fbs..conf..389D Altcode: 1997LDP....22..389D
No abstract at ADS
---------------------------------------------------------
Title: High Resolution Spectroscopic Observations of B-Type Stars
from the Edinburgh-Cape Survey
Authors: Rolleston, W. R. J.; Dufton, P. L.; Keenan, F. P.; Little,
J. E.; Hambly, N. C.; Kilkenny, D.; Koen, C.; Stobie, R. S.;
O'Donoghue, D.
1997fbs..conf..367R Altcode: 1997LDP....22..367R
No abstract at ADS
---------------------------------------------------------
Title: Abundance analyses of a sample of five faint blue stars in
the galactic halo.
Authors: Kendall, T. R.; Dufton, P. L.; Keenan, F. P.; Beers, T. C.;
Hambly, N. C.
1997A&A...317...82K Altcode:
High resolution optical spectra of five faint high galactic latitude
B-type stars, identified from a magnitude limited survey, have been
analysed using LTE model atmosphere calculations. All targets have
small projected rotational velocities (<=30km/s) and hence may be
evolved objects. This is supported by their chemical compositions,
which indicate that they are old Population II stars; two stars also
show enhanced nitrogen abundances probably due to the mixing of nuclear
processed material to their surfaces. Their atmospheric parameters are
consistent with a post-Asymptotic Giant Branch evolutionary status,
although two targets may have evolved directly off the horizontal
branch.
---------------------------------------------------------
Title: The identification of the O V forbidden line in the ultraviolet
spectrum of gaseous nebulae
Authors: McKenna, F. C.; Keenan, F. P.; Aller, L. H.; Hyung, S.;
Feibelman, W. A.; Berrington, K. A.; Fleming, J.
1997IAUS..180..259M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Radio HI and optical absorption-line studies of interstellar
gas
Authors: Bates, B.; Shaw, C. R.; Kemp, S. N.; Keenan, F. P.; Davies,
R. D.; Roger, R. S.
1997hsra.book..101B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: S II emission lines in Planetary Nebulae
Authors: McKenna, F. C.; Keenan, F. P.; Aller, L. H.; Hyung, S.;
Bell, K. L.; Ramsbottom, C. A.
1997IAUS..180..258M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Effective collision strengths for fine-structure forbidden
transitions among the 3s^23p^3 levels of AR IV
Authors: Ramsbottom, C. A.; Bell, K. L.; Keenan, F. P.
1997MNRAS.284..754R Altcode:
The multichannel R-matrix method is used to compute electron impact
excitation collision strengths in Ar iv for all fine-structure
transitions among the ^4S^o, ^2D^o and ^2P^o levels in the 3s^23p^3
ground configuration. Included in the expansion of the total
wavefunction are the lowest 13 LS target eigenstates of Ar iv formed
from the 3s^23p^3, 3s3p^4 and 3s^23p^23d configurations. The effective
collision strengths, obtained by averaging the electron collision
strengths over a Maxwellian distribution of electron velocities, are
presented for all 10 fine-structure transitions over a wide range
of electron temperatures of astrophysical interest (T_e=2000-100
000K). Comparisons are made with an earlier 7-state close-coupling
calculation by Zeippen, Butler & Le Bourlot, and significant
differences are found to occur for many of the forbidden transitions
considered, in particular those involving the ^4S^o ground state, where
discrepancies of up to a factor of 3 are found in the low-temperature
region.
---------------------------------------------------------
Title: CDS Observations of the Quiet Sun EUV Network
Authors: Gallagher, P. T.; Phillips, K. J. H.; Harra-Murnion, L. K.;
Keenan, F. P.
1997ESASP.404..395G Altcode: 1997cswn.conf..395G
No abstract at ADS
---------------------------------------------------------
Title: Cross Sections and Rate Coefficients for Excitation
within the 1s<SUP>2</SUP>2s<SUP>2</SUP>2p <SUP>2</SUP>P and
1s<SUP>2</SUP>2s2p<SUP>2</SUP> <SUP>4</SUP>P Multiplets in Boron-like
Ions C II-Ni XXIV by Heavy Particle Impact
Authors: Foster, V. J.; Keenan, F. P.; Reid, R. H. G.
1997ADNDT..67...99F Altcode:
Cross sections for excitation of the fine-structure transitions
within the 1s<SUP>2</SUP>2s<SUP>2</SUP>2p<SUP>2</SUP>P<SUP>o</SUP>and
1s<SUP>2</SUP>2s2p<SUP>2 4</SUP>P<SUP>e</SUP>multiplets in boron-like
ions by proton, deuteron, triton, and α-particle impact have been
calculated using a close-coupled impact-parameter method, which
includes the effects of dipole coupling to nearby configurations
by means of a polarization potential. The ions considered are C II,
N III, O IV, Ne VI, Mg VIII, Al IX, Si X, S XII, Ar XIV, Ca XVI, Ti
XVIII, Cr XX, Mn XXI, Fe XXII, Co XXIII, and Ni XXIV. Excitation rate
coefficients have been calculated from the cross sections for a wide
range of temperatures.
---------------------------------------------------------
Title: On the Variability of Forming Stars in the Galactic Halo and
in the Gas around the Magellanic Clouds
Authors: Christodoulou, Dimitris M.; Tohline, Joel E.; Keenan,
Francis P.
1997fbs..conf..105C Altcode: 1997LDP....22..105C
No abstract at ADS
---------------------------------------------------------
Title: A Large Scale Spectroscopic Survey of Early-Type Stars at
High Galactic Latitudes
Authors: Saffer, Rex A.; Keenan, F. P.; Hambly, N. C.; Dufton, P. I.;
Liebert, James W.
1997fbs..conf...97S Altcode: 1997LDP....22...97S
No abstract at ADS
---------------------------------------------------------
Title: Assessment of Proton-Impact Excitation Rate-Coefficient Data
of Relevance to the SOHO Mission
Authors: Copeland, F.; Reid, R. H. G.; Keenan, F. P.
1997ADNDT..67..179C Altcode:
Calculations of proton-impact fine-structure excitation of the Be-
to Cl-like ions for elements from C to Ni are compiled and assessed,
in line with the exercise recently carried out for electron-impact
excitation data relevant to the analysis of experiments on the Solar and
Heliospheric Observatory (SOHO) spacecraft and published in this journal
[Vol.57,Nos. 1/2 (1994)]. References for individual transitions are
presented in tabular form for each isoelectronic sequence considered,
together with their estimated relative accuracy.
---------------------------------------------------------
Title: Evolved Stars in the Halo of Our Galaxy from the Palomar-Green
Survey
Authors: Rolleston, W. R. J.; Keenan, F. P.; Dufton, P. L.; Hambly,
N. C.; Saffer, R.
1997fbs..conf..363R Altcode: 1997LDP....22..363R
No abstract at ADS
---------------------------------------------------------
Title: Fe XVII X-ray lines in solar coronal plasmas
Authors: Phillips, K. J. H.; Greer, C. J.; Bhatia, A. K.; Coffey,
I. H.; Barnsley, R.; Keenan, F. P.
1997AdSpR..20.2267P Altcode:
Calculated intensities of the Fe xvii X-ray lines due to transitions
2p^6 - 2p^53d lines (near 15 A˚) and 2p^6 - 2p^53s lines (near 17
A˚) are compared with measured line intensities in solar and tokamak
spectra. For the solar spectra, temperature T_e is obtained from the
ratio of the Fe xvii 16.776 A˚ line to a nearby Fe xviii line. We
find excellent agreement for all the major Fe xvii line features in
the 15-17 A˚ region except the Fe xvii 15.015 A˚ line, the observed
flux of which is less than the theoretical by a factor f. We find that
f strongly depends on the heliocentric angle theta of the emitting
region, being smallest (0.2) when the region is nearest Sun centre,
but nearly 1 near the limb. Attributing this to resonance scattering,
we are able to deduce the path length and electron density from the
observations. Possible application to stellar active regions is given.
---------------------------------------------------------
Title: Fe X Emission Lines in Solar and Stellar Spectra
Authors: Foster, V. J.; Mathioudakis, M.; Keenan, F. P.; Drake, J. J.;
Widing, K. G.
1996ApJ...473..560F Altcode:
Theoretical electron density sensitive emission line ratios involving
Fe X 3s<SUP>2</SUP>3p<SUP>5</SUP>-3s<SUP>2</SUP>3p<SUP>4</SUP>3d
transitions in the 170-190 Å wavelength range are compared with
observational data for a solar active region and flares, obtained
during the Skylab mission, and Cen and Procyon observations from the
Extreme Ultraviolet Explorer (EUVE) satellite. Electron densities
derived from the majority of the ratios are consistent for the events
but are in poor agreement with the values of N<SUB>e</SUB> estimated
from diagnostic lines in other species observed in the spectra, casting
doubt on the accuracy of the theoretical line ratio calculations and,
hence, the atomic data of Mohan et al. used in their derivation. At
low N<SUB>e</SUB>, the present ratios are significantly different
from those of Young et al., while the latter imply densities that
are in somewhat better agreement with densities derived from other
diagnostics. This would appear to indicate that the electron impact
excitation rates of Bhatia & Doschek adopted by Young et al. are
to be preferred over the Mohan et al. results.
---------------------------------------------------------
Title: The Structure and Properties of an Intermediate-Velocity
Cloud in the Direction of the Globular Cluster M13
Authors: Shaw, C. R.; Bates, B.; Kemp, S. N.; Keenan, F. P.; Davies,
R. D.; Roger, R. S.
1996ApJ...473..849S Altcode:
A study of an intermediate-velocity cloud (IVC; V<SUB>LSR</SUB> ≍ -70
km s<SUP>-1</SUP>) detected in the foreground of the globular cluster
M13 has been made using H I spectra obtained with the Lovell Telescope,
Jodrell Bank (FWHP beamwidth 12') and H I spectral maps derived
from Dominion Radio Astrophysical Observatory Synthesis Telescope
observations (FWHP synthesised beamwidth ≍2'.8 x 2.'0). The radio
data complement the optical absorption line spectroscopy of M13 cluster
stars reported by Bates et al. The H I data obtained with the Lovell
Telescope show extended emission from a broad-velocity component (FWHM
30 km s<SUP>-1</SUP>) of H I column density≥ 7 x 1O18<SUP></SUP>. Two
cloudlets are revealed in the H I observations lying on either side
of M13 and having a two-component structure; the broad component
(FWHM ≍ 32 km s<SUP>-1</SUP>) has an H I column density of 5 x
1O<SUP>19</SUP> cm<SUP>-2</SUP>, while the narrow component (FWHM ≍
8 km s<SUP>-1</SUP>) has a column density of ≍6 x 1O<SUP>18</SUP>
cm<SUP>-2</SUP> as seen in the Synthesis Telescope observations. The
cloudlets have an angular size ≍2' and are only partially resolved in
the synthesis telescope data. Fine-scale gas structure is also evident
from the cluster star spectroscopy with variations in Na I column
density of a factor of ≥10 observed across the several arcminutes of
the cluster face; there is also evidence for structure on an angular
scale of several arcseconds. A column density ratio Na I/H I≍ 4
× 10<SUP>-8</SUP> is measured for a cloudlet in the foreground of
the cluster near the strongest Na I detection. Estimates are made
of cloudlet gas density that are comparable with those reported
for high-velocity cloud (HVC) concentrations. However, the present
observations emphasize further the need for higher spatial resolution
H I studies to provide firmer estimates of cloud properties.
---------------------------------------------------------
Title: Fe XXI Emission Line Ratios as Electron Temperature Diagnostics
for the Coronae of Cool Stars
Authors: Keenan, F. P.; Foster, V. J.; Aggarwal, K. M.; Widing, K. G.
1996SoPh..169...47K Altcode:
Theoretical Fe XXI electron temperature and density
sensitive emission line ratios are presented for
R<SUB>1</SUB> = I(2s<SUP>2</SUP>2p<SUP>23<SUP>P<SUB>1</SUB> -
2s2p<SUP>35</SUP>S)/I(2s<SUP>2</SUP>2p<SUP>23</SUP>P<SUB>0</SUB>
- 2s<SUP>2</SUP>2p<SUP>23</SUP>P<SUB>1</SUB>) and
R<SUB>2</SUB> = T(2s<SUP>2</SUP>2p<SUP>23</SUP>P<SUB>1</SUB> -
2s2p<SUP>21</SUP>S)/T(2s<SUP>2</SUP>2p<SUP>23</SUP>P<SUB>0</SUB> -
2s<SUP>2</SUP>2p<SUP>23</SUP>P<SUB>1</SUB>). <P /></SUP></SUP>
---------------------------------------------------------
Title: UHRF observations of the interstellar medium towards two
stars in the Galactic Halo.
Authors: Ryans, R. S. I.; Sembach, K. R.; Keenan, F. P.
1996A&A...314..609R Altcode:
We present interstellar Na I and Ca II spectra of the halo stars HD
18100 and HD 203664, obtained with the Ultra-High Resolution Facility
on the Anglo-Australian Telescope. These observations have spectral
resolutions R=~210,000 and signal-to-noise ratios in the range 20-75. We
find multiple absorbing components along both sightlines and resolve the
velocity structure within the high velocity cloud toward HD 203664. We
discuss these spectra and their use in future Hubble Space Telescope
studies of HD 18100 and HD 203664.
---------------------------------------------------------
Title: Active Region Electron Density and Dimensions from Fe XVII
X-Ray Lines
Authors: Phillips, K. J. H.; Greer, C. J.; Bhatia, A. K.; Keenan, F. P.
1996ApJ...469L..57P Altcode:
The Fe XVII 2p6 1S0--2p53d 1P1 X-ray line at 15.015 A is
resonance-scattered in solar active region and flare spectra, as has
been deduced by comparing theoretical intensities of lines in the Fe
XVII 2p6--2p53l (l = s, d) arrays with intensities observed by the
flat crystal spectrometer (FCS) on the Solar Maximum Mission. We show
that the amount of resonance scattering is strongly dependent on the
heliocentric distance of the emitting plasma, disk regions showing
much larger scattering than limb regions. Average values for electron
density Ne and path length l can be derived for various heliocentric
distances using the X-ray line intensities. We find Ne ~ 109 cm-3 and
l ~ 100,000 km (region on the disk) to Ne ~ 1011 cm-3 and l ~ 1000 km
(region on the limb) for active region AR 4787, as it rotated across
the solar disk to the limb. These lengths appear to be consistent with
FCS images. We note, from our findings, that the approximate extent of
stellar X-ray active regions could be determined, if high-resolution
Fe XVII or equivalent observations were available.
---------------------------------------------------------
Title: Auroral and nebular emission lines of [SII] in the optical
spectra of planetary nebulae
Authors: Keenan, F. P.; Aller, L. H.; Bell, K. L.; Hyung, S.; McKenna,
F. C.; Ramsbottom, C. A.
1996MNRAS.281.1073K Altcode:
R-matrix calculations of electron impact excitation rates among
the 3s^23p^3 levels of SII are presented, which are found to be
up to a factor ~2 different from those of Cai & Pradhan. The
present results are subsequently used to calculate emission-line
ratio-ratio diagrams involving the 4068-, 4076-, 6717- and 6730-A
transitions, for a range of electron temperatures (T_e=5000-20000 K)
and electron densities (N_e=10-10^5 cm^-3) appropriate to gaseous
nebulae. These diagrams should, in principle, allow the simultaneous
determination of T_e and N_e from measurements of the [SII] lines
in a spectrum. Plasma parameters deduced for a sample of planetary
nebulae, using observational data obtained with the Hamilton Echelle
spectrograph on the 3-m Shane Telescope at Lick Observatory, are found
to show excellent internal consistency, and to be in generally good
agreement with the values of T_e and N_e estimated from other line
ratios in the echelle spectra. These results provide observational
support for the accuracy of the theoretical ratios, and hence the
atomic data adopted in their derivation.
---------------------------------------------------------
Title: High-Resolution Optical Spectroscopy of PG 0832+676: A
Sharp-lined, Evolved Low-Mass Star
Authors: Hambly, N. C.; Keenan, F. P.; Dufton, P. L.; Brown, P. J. F.;
Saffer, R. A.; Peterson, R. C.
1996ApJ...466.1018H Altcode:
We present high-resolution spectroscopic observations of the faint,
hot star PG 0832+676, identified in a previous paper as an extremely
distant young B-type object. A differential abundance analysis with
respect to the Galactic B-type star HR 1886 shows near normal helium,
nitrogen, and oxygen abundances while there is a systematic depletion
of ∼0.4 dex in the abundances of other elements. Furthermore, our
new high-resolution observations show this object to be extremely sharp
lined (v sin i ∼ 1 km s<SUP>-1</SUP>), and we therefore conclude that
the star is an old, evolved low-mass star, either in the postasymptotic
giant branch phase or more probably evolving off the blue horizontal
branch. We suggest that such sharp-lined spectra from hot stars
provide a unique and critical test for model atmospheric analyses,
particularly with respect to the micro turbulent velocity parameter.
---------------------------------------------------------
Title: [N II] and [O III] Mean Electron Temperatures in Planetary
Nebulae
Authors: McKenna, F. C.; Keenan, F. P.; Kaler, J. B.; Wickstead,
A. W.; Bell, K. L.; Aggarwal, K. M.
1996PASP..108..610M Altcode:
Mean electron tempertures for 106 planetary nebulae are presented,
which have been derived using calculations of the values of electron
temperature-sensitive line ratios involving forbidden transitions
among the 2s^2 2p^2 3P, 1D, and 1S levels of N+ and O++, based on
new electron impact rates and transition probabilities. Comparison
of these results with values of T_e[N II] and T_e[O III] determined
previously by Kaler reveal that the present electron temperatures
are systematically lower for both ions, and that this discrepancy
is correlated with the electron density in the nebula. It is also
shown that the average difference tween T_e[N II] and T_e[O III] in
a planetary nebula is somewhat smaller than that derived by Kaler,
with the present results implying that the N II and O III temperatures
disagree on average by 2070 K as opposed to the 2210 K average found
by Kaler. (SECTION: Interstellar Medium and Nebulae)
---------------------------------------------------------
Title: New Line Identifications in the Optical Spectrum of the Slow
Nova RR Telescopii
Authors: McKenna, F. C.; Keenan, F. P.; Hambly, N. C.; Allende Prieto,
C.; Aller, L. H.; Feibelman, W. A.
1996IrAJ...23..157M Altcode:
The symbiotic nova RR~Telescopii has been observed with the 1.5m
telescope of the Cerro Tololo Inter-American Observatory (CTIO),
using the 1.5m Bench-Mounted Echelle Spectrograph (BME) in conjunction
with a Tek CCD. It displays a rich emission line spectrum, ranging
in excitation from O I to [Ni VIII]. The result is a list of 483
measured lines, with their suggested identifications, covering a
range from 3430 A to 9320 A. Of these, only nine are unidentified,
and 70 lines are catalogued that were not given in the original line
list of Thackeray. We have also obtained absolute line intensities,
which have been derived by comparing the high-resolution data with
a flux calibrated low-resolution spectrum taken with the Cassegrain
Spectrograph on the 1.0m at the CTIO.
---------------------------------------------------------
Title: NE V and NE VI Lines in the Ultraviolet Spectrum of the
Symbiotic Star RR Telescopii
Authors: Espey, B.; Keenan, F. P.; McKenna, F. C.; Feibelman, W. A.;
Aggarwal, K. M.
1996ApJ...465..965E Altcode:
New theoretical Ne VI] electron density-sensitive ratios are
presented for the intercombination transitions R<SUB>1</SUB> =
I(1006.1 Å)/I(999.6 Å) and R<SUB>2</SUB> = 1(1010.6 Å)/I(999.6
Å). Temperature-sensitive ratios are also given for the Ne V] ratio
R = 1(1137.0 Å)/I(1574.8 Å). We discuss the potential usefulness of
these line ratios for studying hot gas and apply them to the case of
the symbiotic system RR Telescopii. Using far-UV data that has recently
been acquired with the Hopkins Ultraviolet Telescope, we conclude that
the Ne V and Ne VI emission in RR Tel is due to photoionization, with
the temperature and density of the emitting region being approximately
T<SUB>e</SUB> ≃ 18,000 K and N<SUB>e</SUB> ≃ 10<SUP>6</SUP>
cm<SUP>-3</SUP>, respectively. These results are similar to those
estimated using other high ionization line diagnostics of the nebular
material, such as O V I(1371 Å)/I(1644 Å) and Ne IV] I(1602 Å)/I(2423
Å). Although these Ne V] and Ne VI] lines have been used as diagnostics
for solar physics, we believe that this is the first instance in which
they have been applied to another astrophysical object.
---------------------------------------------------------
Title: Proton impact excitation of the ground state fine-structure
transition in C II, N III and O IV.
Authors: Foster, V. J.; Keenan, F. P.; Reid, R. H. G.
1996A&A...308.1009F Altcode:
Cross sections and thermally averaged excitation rate coefficients
are presented for proton impact excitation of the ground 1s^2^2s^2^2p
^2^P_1/2_-1s^2^2s^2^2p ^2^P_3/2_ transition, in C II, N III and O
IV. Cross sections were calculated using the close-coupled impact
parameter method which has been modified to include the higher lying
levels of the doublet states of the 2s2p^2^ configuration by means of
a polarization potential. Excitation rate coefficients, calculated
over a wide range of temperatures, are also presented and compared
with previous results.
---------------------------------------------------------
Title: Helium like sulphur X-ray emission in solar flares and
laboratory plasmas.
Authors: Harra-Murnion, L. K.; Phillips, K. J. H.; Lemen, J. R.;
Zarro, D. M.; Greer, C. J.; Foster, V. J.; Barnsley, R.; Coffey,
I. H.; Dubau, J.; Keenan, F. P.; Fludra, A.; Rachlew-Kaellne, E.;
Watanabe, T.; Wilson, M.
1996A&A...308..670H Altcode:
Theoretical X-ray spectra of He-like sulphur (S xv) derived from the
General Relativistic Atomic Structure Package, the Dirac R-matrix code
and other calculations are compared to laboratory spectra obtained
from the Alcator C tokamak and JET, and solar flare spectra obtained
from the Yohkoh Bragg Crystal Spectrometer (BCS) and with the SMM Flat
Crystal Spectrometer. The spectra depend on electron temperature and
electron density for plasma densities greater than 10^14^ cm^-3^. The
fits of the derived synthetic spectra to the laboratory spectra at
measured density and temperature are in fair agreement. Very good
agreement can be achieved with the solar flare spectra, which are
in general consistent with the S xv low-density limit, by adjusting
temperature. Thus, S xv line spectra can be used to determine the
temperatures of relatively weak flares for which diagnostics from
higher-temperature ions are unavailable. Using the synthetic spectra,
a search for density effects in Yohkoh BCS data at the time of compact
flares was made. None was found, so that it can be deduced that for
such flares the electron density is less than 10^14^cm^-3^. Density
estimates are made from emission measures and image sizes using
Yohkoh Soft X-ray Telescope data. Research has been carried out with
the results of laboratory spectra which indicate a variation of the
I_x_/I_y_ line intensity ratio across the tokamak minor radius. We
have studied various flares which occur at different locations across
the solar disk to determine if the same effect exists on the Sun.
---------------------------------------------------------
Title: A Search for Star Formation around the Galactic Halo B-type
Star PHL 346
Authors: Totten, E.; Wood, K. D.; Keenan, F. P.; Dufton, P. L.;
Kilkenny, D.; Miller, L.; Hambly, N. C.; Gilmore, G.; Irwin, M. J.
1996ASPC...92..196T Altcode: 1996fogh.conf..196T
A search is presented for stars that may have formed coevally with
the apparently young halo star PHL 346. Candidates were selected for
spectroscopy from UBR Schmidt Telescope plates scanned with the COSMOS
facility at the Royal Observatory, Edinburgh. Spectroscopic observations
at 3.5 Angstroms resolution were made of 72 field stars using the 1.9m
telescope at the South Africa Astronomical Observatory; 16 A- and B-type
stars were found, one of which had the appropriate spectral type and
radial velocity to be associated with PHL 346. Further photometry and
spectroscopy confirmed this identification. The remaining low gravity
early-type stars have a mean LSR radial velocity of --75 kms(-1) ,
consistent with a non-rotating halo population.
---------------------------------------------------------
Title: Spectroscopic Diagnostics Applicable to the UV and EUV Spectra
of Astrophysical Sources
Authors: Keenan, F. P.
1996SSRv...75..537K Altcode:
A bibliography is provided of the most reliable emission and absorption
line ratio diagnostic calculations currently available for application
to the spectra of astrophysical sources in the UV and EUV wavelength
region (50 3000 Å). References are listed containing diagnostics for
species in the Li through P isoelectronic sequences, as well as the
iron ions Fe ii-Fe xxiii and nickel ions Ni xvii-Ni xxv. Also given is
the wavelength range for which diagnostic calculations are presented
in each reference, along with the type of diagnostic considered. These
include, for example, emission line ratios for determining electron
temperatures and densities, and absorption line diagnostics for
evaluating hydrogen densities.
---------------------------------------------------------
Title: Atomic data for the X-ray lines of iron.
Authors: Black, G.; Bell, K. L.; Keenan, F. P.
1996rftu.proc..671B Altcode:
Iron is an astrophysically abundant element, and the X-ray lines of
iron and its ions (especially the K lines in some cases) are important
sources of information on the structure of and processes in and around
certain astronomical objects. To interpret these lines one needs
accurate atomic data about the atoms and ions from which they arise:
photoionisation cross-sections are one of the most important sources
of such information. This paper presents the results of R-matrix
calculations on the photoionisation cross-section of Fe XXIV (total,
1s photoejection and partial cross-sections), which is the start of
a series of such calculations on the ions of iron.
---------------------------------------------------------
Title: FeXII emission lines in spectra obtained with the Solar EUV
Rocket Telescope and Spectrograph (SERTS)
Authors: Keenan, F. P.; Thomas, R. J.; Neupert, W. M.; Foster, V. J.;
Brown, P. J. F.; Tayal, S. S.
1996MNRAS.278..773K Altcode:
Many intensity ratios involving FeXII 3s^23p^3-3s3p^4 and
3s^23p^3-3s^23p^23d transitions in the 186-383A wavelength range are
known to be sensitive to electron density. We compare calculations
for these lines with observations of a solar active region and of
a subflare obtained during the 1989 flight of the Solar EUV Rocket
Telescope and Spectrograph (SERTS). Electron densities derived from
the majority of such ratios are consistent with one another for both
solar features, and are also in good agreement with the values of N_e
estimated from diagnostic lines in other species formed at similar
electron temperatures to FeXII, such as FeXIII and FeXIV. These results
provide observational support for the general accuracy of the diagnostic
calculations, and imply that they may be applied to future observations
planned with the Coronal Diagnostic Spectrometer on the SOHO mission. In
addition, our analysis indicates that the line at 283.70A in the active
region data is the 3s^23p^3 ^2D_3/2-3s3p^4 2P_1/2 transition in FeXII,
the first time (to the best of our knowledge) that this line has been
identified in the solar spectrum. Five of the line ratios considered
are predicted to be relatively insensitive to the adopted electron
temperature and density, and the good agreement found between theory
and observation for three of these provides evidence for the reliability
of the SERTS instrument calibration. However, for one of the remaining
ratios the large discrepancies between theory and observation cannot
be attributed to blending, and may be due to errors in the adopted
atomic data.
---------------------------------------------------------
Title: EUV emission lines of O IV observed in solar spectra by the
S-055 instrument on Skylab.
Authors: O'Shea, E.; Foster, V. J.; Keenan, F. P.; Doyle, J. G.;
Reid, R. H. G.; Zhang, H. L.; Pradhan, A. K.
1996A&A...306..621O Altcode:
Recent calculations of electron and proton impact excitation rates
in O IV are used to derive the intensity ratios of lines in the
~340-1350A wavelength range as a function of electron temperature
(T_e_) and density (N_e_). These results are presented in the form of
ratio-ratio diagrams, which should in principle allow both N_e_ and T_e_
to be deduced for the O IV line emitting region of a plasma. Electron
temperatures derived from ratio-ratio diagrams involving the 790A/554A
ratio, in conjunction with observational data for several solar
features obtained with the Harvard S-055 spectrometer on board Skylab,
are found to be in reasonable agreement with the value of T_e_ expected
from ionization equilibrium calculations. This provides some support
for the theoretical diagnostics presented in this paper, and hence
the atomic data used in their derivation. However other temperature
and density sensitive ratios involving the O IV multiplets at 609A,
625A and 787A could not be used to derive plasma parameters from the
ratio-ratio diagrams, due to blending with lines of Mg X and S V.
---------------------------------------------------------
Title: On the nature of the high-latitude B-type star CPD-61 deg455
Authors: Hambly, N. C.; Dufton, P. L.; Keenan, F. P.; Lumsden, S. L.
1996MNRAS.278..811H Altcode:
High-resolution, high-signal-to-noise optical and near-infrared
spectra, along with lower resolution infrared spectra, of the
high-latitude, faint B-type star CPD-61 deg455 have been obtained
using the 3.9-m Anglo-Australian Telescope. Using LTE model atmosphere
codes to compute optical absorption profiles in the hot star, we find
atmospheric parameters of T_eff=25000k and logg~3.6 furthermore, the
abundance pattern of metals as measured differentially with respect
to the Galactic disc B-type star xi^1CMa is not that expected for
a normal young object. We show that the previous interpretation of
this object as a composite consisting of a B-type star with a possible
early K-type giant secondary is consistent with the near-infrared and
infrared data. We hypothesize that CPD-61 deg455 is in fact an evolved,
post-asymptotic giant branch (post-AGB) star in a binary system, and
is possibly a hotter analogue of the binary systems containing younger,
cooler post-AGB stars discussed by van Winckel, Waelkens & Waters.
---------------------------------------------------------
Title: A search for star formation around the Galactic halo B-type
star PHL 346.
Authors: Hambly, N. C.; Wood, K. D.; Keenan, F. P.; Kilkenny, D.;
Dufton, P. L.; Miller, L.; Gilmore, G.; Irwin, M. J.; Totten, E. J.
1996A&A...306..119H Altcode:
A search is presented for stars that may have formed coevally with
the apparently young halo star PHL 346. Candidates were selected
for spectroscopy from UBR Schmidt Telescope plates in U.K. Schmidt
Telescope survey field 603 scanned with the COSMOS facility at the Royal
Observatory, Edinburgh. Spectroscopic observations at ~3.5A resolution
were made of 72 field stars using the 1.9m telescope at the South
African Astronomical Observatory; 16 A- and B-type stars were found,
one of which had the appropriate spectral type and radial velocity
to be associated with PHL 346. Further photometry and spectroscopy
confirmed this identification. The remaining low gravity early-type
stars have a mean LSR radial velocity of -75km/s, consistent with a
non-rotating halo Population.
---------------------------------------------------------
Title: On IV diagnostic line ratios in solar EUV spectra.
Authors: Foster, V. J.; O'Shea, E.; Keenan, F. P.; Doyle, J. G.;
Reid, R. H. G.; Zhang, H. L.; Pradhan, A. K.
1996uxsa.conf..425F Altcode: 1996uxsa.coll..425F
Recent calculations of electron and proton impact excitation rates in
O IV are used to derive the intensity ratios of lines in the ≡340
- 1350 Å wavelength range as a function of electron temperature
(T<SUB>e</SUB>) and density (N<SUB>e</SUB>). These results are
presented in the form of ratio-ratio diagrams, which should in
principle allow both N<SUB>e</SUB> and T<SUB>e</SUB> to be deduced
for the O IV line emitting region of a plasma. Electron temperatures
derived from ratio-ratio diagrams involving the 790 Å/554 Å ratio,
in conjunction with observational data for several solar features
obtained with the Harvard S-055 spectrometer on board Skylab, are
found to be in reasonable agreement with the value of T<SUB>e</SUB>
expected from ionization equilibrium calculations. This provides
some support for the theoretical diagnostics presented in this paper,
and hence the atomic data used in their derivation.
---------------------------------------------------------
Title: Nonthermal velocities in the solar transition and coronal
region observed with the high-resolution telescope and spectrograph
Authors: O'Shea, E.; Doyle, J. G.; Dere, K. P.; Keenan, F. P.
1996ASPC..109..145O Altcode: 1996csss....9..145O
No abstract at ADS
---------------------------------------------------------
Title: Fe XVII X-Ray Lines in Solar Coronal Plasmas
Authors: Greer, C. J.; Phillips, K. J. H.; Bhatia, A. K.; Keenan, F. P.
1996ASPC..111..125G Altcode: 1997ASPC..111..125G
Calculated intensities of the Fe XVII X-ray lines in the 15 - 17
Å wavelength range are compared with measured line intensities in
solar spectra. The intensity ratio of the Fe XVII 16.776 Å line to
any one of several nearby Fe XVIII 2p<SUP>5</SUP>-2p<SUP>4</SUP>3s
transitions is suitable for determining temperature. Using this ratio,
and comparing theory and observed solar spectra, excellent agreement is
found for all the major Fe XVII and Fe XVIII features in this region,
apart from the Fe XVII 15.015 Å line, which is resonance scattered
in solar active region and flare spectra. The observed flux of this
line is less than the theoretical value by a factor R<SUB>2</SUB>
which varies between 0.2 and 0.9. The relation of R<SUB>2</SUB> to
the heliographic position and shape of the emitting feature is examined.
---------------------------------------------------------
Title: Solar EUV Rocket Telescope and Spectrograph (SERTS)
Observations of Fe XII Emission Lines
Authors: Keenan, F. P.; Thomas, R. J.; Neupert, W. M.; Foster, V. J.;
Greer, C. J.; Tayal, S. S.
1996aeu..conf..531K Altcode: 1996IAUCo.152..531K
No abstract at ADS
---------------------------------------------------------
Title: Fe XIII Emission Lines Observed by EUVE and the S082A
Instrument On-Board SKYLAB
Authors: Keenan, F. P.; Drake, J. J.; Foster, V. J.; Greer, C. J.;
Tayal, S. S.; Widing, K. C.
1996aeu..conf..525K Altcode: 1996IAUCo.152..525K
No abstract at ADS
---------------------------------------------------------
Title: Cl XV and Cl XVI in the jet and COMPASS-D tokamaks.
Authors: Coffey, I. H.; Barnsley, R.; Keenan, F. P.; Melnick, I.;
McGinnity, P.; O'Mullane, M. G.; Peacock, N. J.
1996uxsa.conf..431C Altcode: 1996uxsa.coll..431C
Studies of the soft X-ray emission spectrum of He-like Cl XVI and its
associated Li-like Cl XV satellites from the JET (Joint European Torus)
and COMPASS-D tokamaks are reported.
---------------------------------------------------------
Title: A differential abundance analysis of the early-type halo star
PHL 346
Authors: Ryans, R. S. I.; Hambly, N. C.; Dufton, P. L.; Keenan, F. P.
1996MNRAS.278..132R Altcode:
A differential abundance analysis is presented of the faint halo star
PHL 346 with respect to gammaPegasus, based on high-resolution optical
spectra. PHL 346 is found to have absolute abundances consistent
with Population I values, and a differential analysis also shows no
significant peculiarities. The evolutionary status and kinematics of
PHL 346 are considered, and we conclude that while formation in the
halo remains a likely origin, it is also possible that PHL 346 could
have been ejected from the disc.
---------------------------------------------------------
Title: Helium-like sulfur emission in solar flares and laboratory
plasmas.
Authors: Harra-Murnion, L. K.; Phillips, K. J. H.; Lemen, J. R.;
Zarro, D. M.; Greer, C. J.; Foster, V. J.; Barnsley, R.; Coffey,
I. H.; Dubau, J. D.; Keenan, F. P.; Fludra, A.; Rachlew-Källne, E.;
Watanabe, T.; Wilson, M.
1996uxsa.conf..417H Altcode: 1996uxsa.coll..417H
Theoretical X-ray spectra of S XV derived from the General Relativistic
Structure Package, the Dirac R-matrix code and other calculations are
compared to laboratory spectra obtained from the Alcator C tokamak and
JET, and solar flare spectra obtained from the Yohkoh Bragg Crystal
Spectrometer (BCS) and with the SMM Flat Crystal Spectrometer. The
spectra depend on electron temperature and, electron density for
plasma densities greater than 10<SUP>14</SUP>cm<SUP>-3</SUP>. The
fits of the derived synthetic spectra to the laboratory spectra at
measured density and temperature are in fair agreement. Very good
agreement can be achieved with the solar flare spectra, which are
in general consistent with the S XV low-density limit, by adjusting
temperature. Thus, S XV line spectra can be used to determine the
temperatures of relatively weak flares for which diagnostics from
higher-temperature ions are unavailable.
---------------------------------------------------------
Title: Excitation of boron-like ions by heavy particle impact.
Authors: Foster, V. J.; Reid, R. H. G.; Keenan, F. P.
1996uxsa.conf..421F Altcode: 1996uxsa.coll..421F
Cross sections and rate coefficients for the excitation
of the 2s<SUP>2</SUP>2p <SUP>2</SUP>P<SUB>1/2</SUB> -
2s<SUP>2</SUP>2p <SUP>2</SUP>P<SUB>3/2</SUB> and 2s2p<SUP>2</SUP>
<SUP>4</SUP>P<SUB>J</SUB> - 2s2p<SUP>2</SUP> <SUP>4</SUP>P<SUB>J</SUB>,
transitions in boron-like ions by proton, deuteron, triton and
α-particle impact have been calcualted suing the close-coupled
impact parameter method, with a number of ions between C II and Pb
LXXVIII being considered. Cross sections were calculated for a range of
impact energies, with higher lying states being included by means of a
polarization potential. There are major differences between the authors'
results and previous calculations, due mainly to the emission of higher
lying state in the latter. Excitation rate coefficients have been
calculated from the cross sections for a wide range of temperatures. In
this paper results are presented for a few of the ions considered.
---------------------------------------------------------
Title: Fine-structure population ratios for the <SUP>3</SUP>P ground
state of N II.
Authors: McKenna, F. C.; Keenan, F. P.; Foster, V. J.; Jenkins, E. B.;
Bell, K. L.; Stafford, R. P.
1996uxsa.conf..499M Altcode: 1996uxsa.coll..499M
R-matrix calculations of electron impact excitation rates for
the 2s<SUP>2</SUP>2p<SUP>2</SUP> <SUP>3</SUP>P<SUB>J</SUB> -
2s<SUP>2</SUP>2p<SUP>2</SUP> <SUP>3</SUP>P<SUB>J</SUB>, fine-structure
transitions in N II are used to derive the electron density
(n<SUB>e</SUB>) and temperature (T<SUB>e</SUB>) sensitive population
ratios f<SUB>1</SUB> = n(<SUP>3</SUP>P<SUB>1</SUB>)/n(<SUP>3</SUP>P)
and f<SUB>2</SUB> = n(<SUP>3</SUP>P<SUB>2</SUB>)/n(<SUP>3</SUP>P) for
a range of n<SUB>e</SUB> and T<SUB>e</SUB> appropriate to H II regions.
---------------------------------------------------------
Title: Line Ratio Diagnostics Applicable to Astronomical Spectra in
the 50-3000 Angstrom Wavelength Region
Authors: Keenan, F. P.
1996aeu..conf..595K Altcode: 1996IAUCo.152..595K
No abstract at ADS
---------------------------------------------------------
Title: SKYLAB Observations of Temperature and Density Sensitive
Emission Line Ratios in NE VI
Authors: Greer, C. J.; Foster, V. J.; Keenan, F. P.; Reid, R. H. G.;
Doyle, J. G.; Zhang, H. L.; Pradhan, A. K.
1996aeu..conf..537G Altcode: 1996IAUCo.152..537G
No abstract at ADS
---------------------------------------------------------
Title: Ar XVII and Ar XVIII in the JET tokamak.
Authors: McGinnity, P.; Barnsley, R.; Coffey, I. H.; Keenan, F. P.;
O'Mullane, M. G.; Peacock, N. J.
1996uxsa.conf..447M Altcode: 1996uxsa.coll..447M
Observations of H-like Ar XVIII and He like Ar XVII and its associated
Li-like satellite spectra have been made on the JET tokamak. G, α
and β intensity ratios have been derived from recently calculated
atomic data and, after extensive transport modelling to account for
diffusive effects in the plasma, compared with measured values. The
measured G-ratio disagrees with the calculated ratio and with a
previously published ratio and some possible reasons are given. The
α and β ratios show the expected temperature and density sensitivity
respectively.
---------------------------------------------------------
Title: Extreme Ultraviolet Emission Lines of Fe XIII in Solar and
Stellar Spectra
Authors: Keenan, F. P.; Foster, V. J.; Drake, J. J.; Tayal, S. S.;
Widing, K. G.
1995ApJ...453..906K Altcode:
Recent R-matrix calculations of electron impact excitation
rates for Fe XIII are used to derive the theoretical electron
density sensitive emission line ratios R<SUB>1</SUB> =
I(3s<SUP>2</SUP>3p<SUP>2</SUP> <SUP>1</SUP>D-3s3p<SUP>3</SUP>
<SUP>1</SUP>D)/I(3s<SUP>2</SUP>3p<SUP>2</SUP>
<SUP>3</SUP>P<SUB>2</SUB>-3s3p<SUP>3</SUP> <SUP>3</SUP>P<SUB>2</SUB>)
= I(318.12 Å)/I(320.80 Å) and R<SUB>2</SUB> =
I(3s<SUP>2</SUP>3p<SUP>2</SUP> <SUP>1</SUP>D-3s3p<SUP>3</SUP>
<SUP>1</SUP>P)/I(3s<SUP>2</SUP>2p<SUP>2</SUP>
<SUP>3</SUP>P<SUB>2</SUB>-3s3p<SUP>3</SUP> <SUP>3</SUP>S) = 1(256.42
Å)/I(251.95 Å), which are found to be up to 70% different from earlier
diagnostics. A comparison of the current line ratios with both solar
flare and active region observations, obtained by the Naval Research
Laboratory's S082A spectrograph on board Skylab, reveals generally good
agreement between densities deduced from Fe XIII and those estimated
from diagnostic line ratios in species formed at similar temperatures,
such as I(219.12 Å)/I(211.32 Å) in Fe XIV. This provides experimental
support for the accuracy of the line ratio calculations, and hence the
atomic data adopted in their derivation. In Extreme Ultraviolet Explorer
satellite (EUVE) spectra the Fe XIII emission lines are found to be
severely blended. However, an analysis of these lines measured in the
spectra of Procyon and α Cen demonstrates that they still allow very
approximate values of the electron density to be inferred. Moreover,
it should be possible to increase the accuracy of the measured line
fluxes, and hence of the inferred densities, if longer exposures of
the stars concerned can be obtained.
---------------------------------------------------------
Title: The OV 1371.29A/1218.35A emission-line ratio in solar and
stellar spectra
Authors: Keenan, F. P.; Brekke, P.; Byrne, P. B.; Greer, C. J.
1995MNRAS.276..915K Altcode:
New calculations of the theoretical electron-density-sensitive
emission-line ratio R=I(2s2p ^1P-2p^2 ^1D)/I(2s^2 ^1S-2s2p
^3P_1)=I(1371.29A)/I(1218.35A) in OV are presented, which are
significantly different from those deduced previously, principally
due to the adoption of improved atomic data in the present
analysis. Electron densities estimated from the current diagnostics,
in conjunction with observed values of R measured from solar spectra
obtained by the S082B spectrograph on board Skylab and by the High
Resolution Telescope and Spectrograph (HRTS) on board a sounding rocket
flight, are found to be in good agreement with densities determined from
line ratios in species formed at similar electron temperatures to OV,
such as OIV and NIV. These results provide experimental support for
the accuracy of the diagnostic calculations presented in this paper,
and hence the atomic data used in their derivation. The observed value
of R for the M0Ve flare star AU Mic, determined from observations made
by the Goddard High Resolution Spectrometer on board the Hubble Space
Telescope, is within 4 per cent of the expected low-density limit,
implying that logN_e<=10.4 for the OV emitting region of the AU
Mic atmosphere. This is similar to density estimates made for AU Mic
using other methods.
---------------------------------------------------------
Title: Emission Line Ratios for SI XI Applicable to CDS/SUMER
Observations from SOHO
Authors: Keenan, F. P.; Greer, C. J.; Foster, V. J.; Widing, K. G.
1995SoPh..161..159K Altcode:
Calculations of electron temperature (T<SUB>e</SUB>) and density
(N<SUB>e</SUB>) sensitive line ratios in SiXI involving transitions in
the ∼ 358-604 å wavelength range are presented. These are shown
in the form of ratio-ratio diagrams, which should in principle
allow bothN<SUB>e</SUB> andT<SUB>e</SUB> to be deduced for the
SiXI line-emitting region of a plasma. However a comparison of
these with observational data for two solar flares, obtained with
the Naval Research Laboratory's S082A spectrograph on boardSkylab,
reveals that the experimental ratios are much larger than expected
from theory, which is probably due to the SiXI lines in the S082A
spectra being blended with transitions from species including NeV,
FeXI, and FeXII. Possible future applications of the SiXI results to
spectral data from the Coronal Diagnostic Spectrometer on the Solar
and Heliospheric Observatory are briefly discussed.
---------------------------------------------------------
Title: A Photometric and Spectroscopic Survey for Young Stars in
the Halo of M31
Authors: Hambly, N. C.; Fitzsimmons, A.; Keenan, F. P.; Dufton, P. L.;
Brown, P. J. F.; Irwin, M. J.; Rolleston, W. R. J.
1995ApJ...448..628H Altcode:
We have obtained UBV CCD photometry of a 0.5 deg<SUP>2</SUP> field
toward the halo of M31 (the Andromeda Galaxy), using the 2.5 m Isaac
Newton Telescope on La Palma. These observations have allowed us
to identify nine blue stellar objects, with (U - B) < - 0.4 and
(B - V) < 0.0, in the magnitude range B = 21.5-22.5, typical of
main-sequence early B-type stars at the distance of Andromeda. Hence
these objects may be normal Population I stars at large distances
(>3 kpc) from the plane of M31. Follow-up low-resolution spectra of
these objects obtained with the William Herschel Telescope, also on La
Palma, do not have the requisite signal-to-noise ratios for a definitive
conclusion regarding their nature, although one source appears to be a
degenerate star in the halo of our Galaxy and has thus been eliminated
from the candidate list. Positive identification of Balmer absorption
features in the stellar spectra at the known radial velocity shift of
the Andromeda system would provide very strong evidence for the general
existence of normal B-type stars in the halos of spiral galaxies.
---------------------------------------------------------
Title: Theoretical emission line intensity ratios for NE ^44^Sc VI
compared to EUV solar observations.
Authors: Keenan, F. P.; Foster, V. J.; Reid, R. H. G.; Doyle, J. G.;
Zhang, H. L.; Pradhan, A. K.
1995A&A...300..534K Altcode:
Recent calculations of electron and proton impact excitation rates
in Ne ^44^Sc VI are used to derive the intensity ratios of lines in
the ~402-1006A wavelength range as a function of electron temperature
(T_e_) and density (N_e_). These results are presented in the form
of ratio-ratio diagrams, which should in principle allow both N_e_
and T_e_ to be deduced for the Ne ^44^Sc VI line emitting region of a
plasma. Electron temperatures and densities derived from ratio-ratio
diagrams involving the 562.7, 997.4, 999.6 and 1006.1A lines, in
conjunction with observational data for a sunspot obtained with
the Harvard S-055 spectrometer on board Skylab, are found to be
compatible, and in good agreement with plasma parameters determined
using other methods. This provides some support for the diagnostic
calculations presented in this paper, and hence the atomic data used
in their derivation. However agreement between theory and observation
is very poor for other Ne ^44^Sc VI lines in the sunspot spectrum,
and for most transitions observed in S-055 active region and flare
data, which is probably due to blending with lines from N ^44^Sc III,
Mg ^44^Sc VI and Mg ^44^Sc VII.
---------------------------------------------------------
Title: Observations of an intermediate velocity cloud in the direction
of the globular cluster M13.
Authors: Shaw, C. R.; Bates, B.; Kemp, S. N.; Keenan, F. P.; Davies,
R. D.; Roger, R. S.
1995JRASC..89..178S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A 325 Square Degree Survey of B-Type Stars at High Galactic
Latitudes
Authors: Little, J. E.; Dufton, P. L.; Keenan, F. P.; Hambly, N. C.;
Conlon, E. S.; Brown, P. J. F.; Miller, L.
1995ApJ...447..783L Altcode:
Final results from model atmosphere analyses of all blue stars in
a ∼325 square degree region of the Galactic halo are presented. A
kinematic analysis reveals the presence of one star which cannot have
been ejected from the disk according to contemporary theories. Ten other
objects have, however, evolutionary times consistent with classification
as disk runaway stars. Our results therefore imply the existence of
some 200 stars in the Galaxy unexplainable in terms of disk ejection
models, and set a lower limit of 10,000 runaway halo B-type stars.
---------------------------------------------------------
Title: Properties of the High-Velocity Cloud Towards HD 203664
Authors: Keenan, Francis
1995hst..prop.5883K Altcode: 1995hst..prop.2356K
We will obtain high- and intermediate-resolution GHRS spectra of
the +70 km/sec HVC seen toward HD 203664 in optical and radio
spectra. The observations will provide a unique opportunity to
quantify the ionization structure of a HVC and accurately determine
the chemical abundances of important elements such as C, N, O, Mg, Si,
S, Cr, Mn, Fe, and Zn in high velocity interstellar material. Our high
spectral resolution optical data suggest that substructure may exist
within the HVC which, if confirmed, would support the possibility
that early-type stars at large distances from the Galactic plane are
formed through star formation induced by collisions between cloudlets
within HVCs. We will test this hypothesis on the HD 203664 HVC with
high S/N absorption line measurements made by the GHRS in its highest
resolution mode. By combining a supporting set of optical and radio
data with the ultraviolet observations, we will study the velocity
structure of the HVC, morphology, distance, and physical conditions
of this HVC in greater detail than has been possible for any other
high velocity cloud in the sky.
---------------------------------------------------------
Title: The O IV and S IV Intercombination Lines in Solar and Stellar
Ultraviolet Spectra
Authors: Cook, J. W.; Keenan, F. P.; Dufton, P. L.; Kingston, A. E.;
Pradhan, A. K.; Zhang, H. L.; Doyle, J. G.; Hayes, M. A.
1995ApJ...444..936C Altcode:
New calculations of O IV electron density diagnostic emission-line
ratios involving the 1399.8, 1401.2, 1404.8, and 14076.4 A transitions
are presented. A comparison of these calculations with observational
data from a quiet solar region, a sunspot, and an active region obtained
with the High Resolution Telescope and Spectrograph (HRTS), two flares
observed with the SO82B spectrograph on board Skylab, and Hubble Space
Telescope (HST) observations by the Goddard High Resolution Spectrograph
(GHRS) of Capella, gives good results using the ratio R<SUB>1</SUB> =
I(1407.4 A)/I(1401.2 A). However, the electron density obtained using
the ratio R<SUB>2</SUB> = I(1407.4 A)/I(1404.8 A) is often an order
of magnitude smaller. The O IV 1404.8 A line is blended with the S
IV 1404.8 A line, and we investigate whether this ratio may still be
used as a density diagnostic if the S IV 1406.1 A line intensity is
used to correct for the presence of S IV 1404.8 A, using previous S
IV calculations by Dufton et al. We still find systematic differences
compared to density determinations from line ratios that do not involve
the O IV 1404.8 A line, which we suggest are due to errors in earlier
theoretical calculations of the S IV atomic data, and also possibly
to previously unconsidered fluorescent pumping of the upper level of
the S IV 1404.8 A transition.
---------------------------------------------------------
Title: Optical and H i Observations of the Low-Velocity and
Intermediate-Velocity Gas toward the Globular Cluster M13
Authors: Bates, B.; Shaw, C. R.; Kemp, S. N.; Keenan, F. P.; Davies,
R. D.
1995ApJ...444..672B Altcode:
High-resolution spectra of interstellar lines toward 11 stars in
the globular cluster M13 and toward three foreground stars which lie
within 3 deg from the cluster are reported. The optical spectra are
compared with an H I profile of the gas recorded in the direction
of the cluster. The principal interstellar components have LSR
radial velocities centered near +10 km/s and -4km/s, but there is a
considerable variation in the velocities and the column densities of
both components across the face of the cluster. The positive velocity
gas has a high Na I/H I column density ratio, and it lies beyond the
foreground stars at a distance approximately greater than 200 pc;
this gas may be associated with the receding part of the Hercules
shell discussed in detail by Lilienthal et al. The negative velocity
gas is detected toward the foreground stars, and the observed Na
I/Ca II ratios suggest an association with gas at the approaching
side of the Hercules shell. Gas at a velocity approximately equal
-80 km/s has been previously reported in H I emission in the M13
direction and in UV spectra of the post-AGB cluster star, Barnard
29. This intermediate-velocity clouds in the lower halo. We discuss
also evidence for the detection of this gas in Na I and show that it
is most likely located at a distance.
---------------------------------------------------------
Title: Forbidden Lines of [O I] in the High-Resolution Optical
Spectra of Planetary Nebulae
Authors: Keenan, F. P.; Aller, L. H.; Hyung, S.; Brown, P. J. F.
1995PASP..107..148K Altcode:
Electron impact excitation rates for transitions in O I, calculated
with the R-matrix code, are used to derive the electron temperature
sensitive emission line ratio R = I(2s^2p^4 1D - 2s^2 2p^4 1S)/I(2s^2
2p^4 3P_1,2 - 2x^2 2p^4 1D) = I(5577 A)/I(6300 + 6365 A), for a range
of electron temperatures (T_e = 5000 - 20000 K) and d 2ensities (n_e =
10^4 - 10^6 cm^-3) applicable to planetary nebulae. Experimental values
of R for a number of planetaries have been measured from high resolution
(~0.6 A FWHM) spectra obtained with the Hamilton Echelle spectrograph
on the 3 m telescope at the Lick Observatory. These measurements
should be particularly reliable, as the sample of planetaries was
restricted to those with large enough radial velocities for the nebular
[O I] 5577 A emission to be red- or blue-shifted from the atmospheric
airglow feature by a sufficient amount for the former to be reliably
determined. Electron temperatures deduced from the observed values of R
are generally in good agreement with those derived from T_e sensitive
line ratios in other species, providing observational support for the
accuracy of the atomic data adopted in the calculations. (SECTION:
Interstellar Medium and Nebulae)
---------------------------------------------------------
Title: High-resolution optical observations of two early-type stars
towards the high-velocity cloud Complex M
Authors: Keenan, F. P.; Shaw, C. R.; Bates, B.; Dufton, P. L.; Kemp,
S. N.
1995MNRAS.272..599K Altcode:
High-resolution optical spectra of the early-type stars HD 93521
and BD +38 deg2182, which lie only 27 arcmin apart on the sky in
the direction of the high-velocity cloud (HVC) Complex M, reveal the
presence of weak HVC absorption in the Ca K line towards BD +38 deg2182,
with a velocity of V_LSR=-96.0+/-1.5 km s^-1 and an equivalent width
W_lambda=11+/-2 mA. However, the HVC is not detected either in the
Na D line for BD +38 deg2182 or in the Ca K and Na D lines towards
HD 93521. These observations, combined with revised stellar distance
estimates, imply that the HVC is at a distance from the Galactic plane
of 1.8<=z<=4.6 kpc. The Ca/H abundance in the HVC is found to be
at least ~=2 per cent of the solar value, consistent with the material
being returning condensations from a Galactic fountain flow.
---------------------------------------------------------
Title: N IV Emission Lines in the Ultraviolet Spectra of Gaseous
Nebulae
Authors: Keenan, F. P.; Ramsbottom, C. A.; Bell, K. L.; Berrington,
K. A.; Hibbert, A.; Feibelman, W. A.; Blair, W. P.
1995ApJ...438..500K Altcode:
Theoretical electron density sensitive emission-line ratios,
determined using electron impact excitation rates calculated with
the R-matrix code, are presented for R = I(2s<SUP>2</SUP> (1)S-2s2p
3P<SUB>2</SUB>)/I(2s<SUP>2</SUP> (1)S-2s2p 3P<SUB>1</SUB> = 1(1483
A)/I(1486 A) in N IV. These are found to be up to an order of magnitude
different from those deduced by previous authors, principally due to
the inclusion of excitation rates for transitions among the 2s2p (3)p
fine-structure levels. The observed values of R for several planetary
nebulae, symbiotic stars and the Cygnus Loop supernova remnant, measured
from spectra obtained with the International Ultraviolet Explorer
(IUE) satellite and the Hopkins Ultraviolet Explorer (HUT), lead to
electron densities which are in excellent agreement with those deduced
from line ratios in other species. This provides observational support
for the accuracy of the atomic data adopted in the present calculations.
---------------------------------------------------------
Title: Observations of a possible companion to the high-latitude
B-type star PG 0832+676.
Authors: Hambly, N. C.; Keenan, F. P.; Dufton, P. L.; Brown, P. J. F.;
Irwin, M. J.; Fitzsimmons, A.
1994MNRAS.271..729H Altcode:
We present photometric and spectroscopic observations of a faint star
4 arcsec away from the apparently normal, young early B-type star PG
0832+676, which was previously identified as being approximately 18
kpc above the Galactic plane. The differential radial velocity of the
two is found to be consistent with zero within the measurement errors,
suggesting physical association; however, the other available evidence
implies that the companion is a low-luminosity, metal-deficient early
G-type star. The implications of these data for the evolutionary status
and Galactic z-distance of PG 0832+676 are discussed, and we conclude
that this is a chance alignment of two unrelated objects. Key words:
stars: early-type - stars: individual: PG 0832+676.
---------------------------------------------------------
Title: Book-Review - Hot Stars in the Galactic Halo
Authors: Adelman, S. J.; Upgren, A. R.; Adelman, C. J.; Keenan, F. P.
1994Ap&SS.222..269A Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Book reviews
Authors: Burgess, D.; Kahn, F. D.; Dyson, John; Roche, Patrick;
Priest, E. R.; Budding, Edwin; Keenan, F. P.
1994Ap&SS.222..263B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Cross Sections and Excitation Rate Coefficients for the
2s<SUP>2</SUP>2p<SUP>5</SUP><SUP>2</SUP>P<SUB>3/2</SUB>-2s<SUP>2</SUP>2p<SUP>5</SUP><SUP>2</SUP>P<SUB>1/2</SUB>
Transition in Fluorine-Like Ions by p,d,t and α Impact
Authors: Foster, V. J.; Keenan, F. P.; Reid, R. H. G.
1994ADNDT..58..227F Altcode:
Cross sections and rate coefficients for excitation of the
2s<SUP>2</SUP>2p<SUP>5</SUP><SUP>2</SUP>P<SUB>3/2</SUB>-2s<SUP>2</SUP>2p<SUP>5</SUP><SUP>2</SUP>P<SUB>1/2</SUB>
transition in fluorine-like ions by proton, deuteron, triton, and
α-particle impact have been calculated using the close-coupled impact
parameter method. The ions considered are Ne II, S VIII, Ti XIV, Ni
XX, Zn XXII, Ge XXIV, Se XXVI, Kr XXVIII, Mo XXXIV, Ag XXXIX, and Pb
LXXIV. Cross sections were calculated for a range of impact energies,
and the 2s2p<SUP>6</SUP><SUP>2</SUP>S State was included by means
of a polarization potential. Excitation rate coefficients have been
calculated from the cross sections for a wide range of temperatures.
---------------------------------------------------------
Title: Optical observations of the hot post-asymptotic giant branch
star, HD 177566.
Authors: Kendall, T. R.; Brown, P. J. F.; Conlon, E. S.; Dufton,
P. L.; Keenan, F. P.
1994A&A...291..851K Altcode:
An LTE model atmosphere analysis of optical and ultra-violet spectra
is presented for a hot high galactic latitude star, HD 177566,
previously identified as a post-asymptotic giant branch candidate
from its ultra-violet spectrum. The derived atmospheric parameters
and chemical composition confirm that HD 177566 is a low mass
(M=~0.55M<SUB>sun</SUB>_) post-AGB star; a general heavy element
underabundance of approximately -1.3 dex is found. The possibility
that it is the central star of a young, compact planetary nebula is
briefly discussed.
---------------------------------------------------------
Title: CA X Line Ratios in Solar Flares
Authors: Keenan, F. P.; Foster, V. J.; Roche, I. J.; Mohan, M.;
Widing, K. G.
1994SoPh..154..309K Altcode:
Theoretical Ca X electron temperature sensitive emission line
ratios, derived using electron excitation rates interpolated from
accurateR-matrix calculations, are presented forR<SUB>1</SUB> =I(419.74
å)/I(574.02 å,),R<SUB>2</SUB> =I(411.65 å)/I(574.02 å),R<SUB>3</SUB>
=I(419.74 å)/I(557.75 å), andR<SUB>4</SUB> =I(411.65 å)/I(557.75
å). A comparison of these with observational data for three solar
flares, obtained by the Naval Research Laboratory's S082A slitless
spectrograph on boardSkylab, reveals good agreement between theory
and observation forR<SUB>1</SUB> andR<SUB>3</SUB> in one event, which
provides limited support for the accuracy of the atomic data adopted
in the analysis. However, in the other flares the observed values
ofR<SUB>1</SUB> -R<SUB>4</SUB> are much larger than the theoretical
high-temperature limits, which is probably due to blending of the 419.74
å line with CIV 419.71 å, and 411.65 å with possibly CIII 411.70 å.
---------------------------------------------------------
Title: Relative Emission-Line Strengths for the 146 and 63 Micron
Transitions in O i and a Comparison with Far-Infrared Observations
of Photodissociation Regions
Authors: Keenan, F. P.; Conlon, E. S.; Rubin, R. H.
1994ApJ...434..811K Altcode:
Theoretical O I density-sensitive emission-line ratios R =
I(2s<SUP>2</SUP>)(2p<SUP>4</SUP>)(<SUP>3</SUP>P<SUB>0</SUB>)-((2s<SUP>2</SUP>)(2p<SUP>4</SUP>)(<SUP>3</SUP>P<SUB>1</SUB>))/I((2s<SUP>2</SUP>)(2p<SUP>4</SUP>)(<SUP>3</SUP>P<SUB>1</SUB>)-(2s<SUP>2</SUP>)(2p<SUP>4</SUP>)(<SUP>3</SUP>P<SUB>2</SUB>))
= I(146 micrometers)/I(63 micrometers) are presented for a range
of temperatures (T = 100-10,000 K), neutral hydrogen densities
(N<SUB>H</SUB> = 10<SUP>-2</SUP> to 10<SUP>7</SUP>/cu cm) and
radiation fields (G<SUB>0</SUB> = 1-10<SUP>6</SUP>) applicable to both
photodissociation regions (PDRs) and H II regions and the diffuse
ionized medium (DIM). The observed values of R for several PDRs,
measured from far-infrared spectra obtained with the Kuiper Airborne
Observatory (KAO), imply hydrogen densities which are in good agreement
with those determined using other methods. This provides observational
support for the validity of the theoretical O I line ratios, and hence
the atomic data used in their derivation.
---------------------------------------------------------
Title: Abundance analysis of the hot post-AGB star Barnard 29.
Authors: Conlon, E. S.; Dufton, P. L.; Keenan, F. P.
1994A&A...290..897C Altcode:
We present a model atmosphere analysis for the relatively bright
(V~13) globular cluster post-AGB star, Barnard 29, using IUE and
high resolution (0.06A FWHM) optical spectra. The derived atmospheric
parameters are T_eff_=20000+/-1000K and logg=3.0+/-0.1dex, which imply a
current mass of ~0.55M<SUB>sun</SUB>_. The chemical composition provides
important constraints on the post-AGB evolutionary stage. We find an
overall metal deficiency of 1.46+/-0.11dex, which is compatible with the
mean [Fe/H] obtained from previous M13 studies. The most interesting
feature is the severe carbon deficiency of more than 2.0dex which has
also been observed in a number of high latitude B-type low gravity
stars. Hence the present results supports the recent classification
of these objects as hot post-AGB stars. Relative to the overall
metallicity, the observed carbon deficiency of Barnard 29 coupled with
a significant nitrogen overabundance indicates that this star has left
the AGB before the third dredge-up has occurred. The implications for
AGB and post-AGB evolution are briefly discussed.
---------------------------------------------------------
Title: Optical and UV spectroscopy towards stars in the direction
of the Cohen high-velocity H I stream.
Authors: Kemp, S. N.; Bates, B.; Dufton, P. L.; Keenan, F. P.;
Montgomery, A. S.
1994MNRAS.270..597K Altcode:
We present high-resolution, high signal-to-noise ratio optical spectra
and UV spectra obtained with lUE for several stars that lie within and
adjacent to the Cohen high- velocity (Hv) stream, which is considered
by Cohen to lie within 300 pc. From spectral classifications, published
photometry and LTE model atmosphere analysis of our stellar spectra,
the programme stars are shown to lie at distances from 50 to at least
600 pc. On the basis of the H I column densities for the HV stream,
it is expected that gas at corresponding velocity should be observed
in Na I and Ca ii in our high- quality spectra, but no such detections
are made. Low-velocity (LV) filament gas, which is spatially coincident
with the Hv stream in the directions studied, is detected, and is shown
to lie within 160 pc. The observations suggest that the HV stream lies
beyond our programme stars. Alternatively, if the stream is closer
and lies at a similar distance to the LV filament, then possible
explanations for the non-detection are (i) the HV gas is depleted
in the species observed (for example, for Ca lithe depletion would
be significantly greater than the average Ca ii depletion observed
for HVCs), (ii) the Na and Ca in the gas is mostly in the form of Na
ii and Ca iii, and (iii) the gas is very clumpy on a fine scale. In
the last context, our observations of the LV filament also indicate a
clumpy distribution for this gas. Key words: stars: distances - ISM:
clouds - ISM: structure - radio lines: ISM - ultraviolet: ISM.
---------------------------------------------------------
Title: Ultraviolet FeIII lines in the spectra of high galactic
latitude early-type stars
Authors: Kendall, T. R.; Conlon, E. S.; Dufton, P. L.; Keenan, F. P.
1994A&A...290..563K Altcode:
Using high resolution spectral data from the International Ultraviolet
Explorer satellite, we present qualitative and quantitative
comparisons of blends of Fe III absorption lines in the region
1890A<=λ<=1930A for a sample of fifteen high latitude B-type
and standard stars. Standard and halo stars were matched in effective
temperature and surface gravity using Stroemgren [c_1_] and Hβ
photometry, and LTE model atmosphere codes were used to investigate
whether they had similar iron abundances. We conclude that while
most of the halo stars have Population I iron abundances and may be
young objects, one star, HD 177566, has significant iron and silicon
depletions and is most probably an old, evolved star. In view of the
coincidence of the atmospheric parameters of this star with those of
young B-type stars, we consider a post-AGB evolutionary status to be
likely for HD 177566.
---------------------------------------------------------
Title: The Determination of Electron Densities in the Solar Atmosphere
from the 1718.56 Angstrom /1486.51 Angstrom Emission-Line Ratio in
N IV
Authors: Keenan, F. P.; Harra, L. K.; Doschek, G. A.; Cook, J. W.
1994ApJ...432..806K Altcode:
The theoretical electron density sensitive emission-line ratio
R = I(1718.56 a)/I(1486.51 A) in N IV is presented for a range of
N<SUB>e</SUB>(approximately equals 10<SUP>10</SUP> - 10<SUP>12</SUP>/cu
cm) applicable to higher density solar plasmas, such as active
regions. A comparison of these calculations with the observed values
of R of several solar features obtained with the Naval Research
Laboratory's S082B spectrograph on board Skylab reveals general
agreement between theory and observation at pointings just above the
limb, where line blends with N IV 1718.56 A should be insignificant,
which provides experimental support for the accuracy of the line
ratio calculations.
---------------------------------------------------------
Title: The distance to HVC complex M.
Authors: Shaw, C. R.; Keenan, F. P.; Bates, B.; Dufton, P. L.
1994IEEES...3....8S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Fe XVI Line Ratios in the Sun
Authors: Keenan, F. P.; Conlon, E. S.; Foster, V. J.; Tayal, S. S.;
Widing, K. G.
1994ApJ...432..809K Altcode:
Recent R-matrix calculations of electron impact excitation rates in
Fe XVI are used to derive the emission-line ratios R<SUB>1</SUB>
= I(251.07 A)/I(335.40 A), R<SUB>2</SUB> = I(262.98 A)/I(335.40
A), and R<SUB>3</SUB> = I(265.00 A)/I(335.40 A). A comparison of
these with solar observational data obtained by the Naval Research
Laboratory's S082A slitless spectrograph on board Skylab reveals
generally good agreement between theory and observation, which provides
experimental support for the accuracy of the atomic data adopted
in the analysis. However, several of the measured ratios are much
larger than theory predicts, which is probably due to saturation of
the strong 335.40 A line on the photographic film used to record the
S082A data. The potential usefulness of R<SUB>1</SUB>, R<SUB>2</SUB>,
and R<SUB>3</SUB> as electron temperature diagnostics for the solar
corona is briefly discussed.
---------------------------------------------------------
Title: Book Review: Luminous high-latitude stars / Astronomical
Society of the Pacific, 1993
Authors: Keenan, F.
1994Obs...114..182K Altcode: 1994Obs...114..182S
No abstract at ADS
---------------------------------------------------------
Title: Coronal Electron Density Diagnostic from Fe XII
Authors: Cook, J. W.; Keenan, F. P.; Harra, L. K.; Tayal, S. S.
1994ApJ...429..924C Altcode:
We present observations of the forbidden coronal lines Fe XII 1242 A and
1349 A from active regions and from two flares, obtained by the SO82B
slit spectrograph onboard Skylab. The line intensity ratio R = I(1242
A)/I(1349 A) is sensitive to electron density. We have calculated this
ratio using recent atomic data, and obtained coronal electron densities
at T = 1.5 x 10<SUP>6</SUP> K for our observations. We find a range
in N<SUB>e</SUB> of (0.5 to 7.2) x 10<SUP>9</SUP>/cm<SUP>-3</SUP> for
active regions, which is in good agreement with previous results from
other diagnostic ratios in this temperature range, and of approximately
(0.9 to 12) x 10<SUP>9</SUP>/cm<SUP>-3</SUP> (or higher) for flares,
which is generally low compared to previous flare results. The flare
values employ particularly weak 1349 A observations and may not be
reliable. From an observation of an active region just inside the solar
limb, giving the best coverage in our data of both line profiles, we
find a line width (FWHM) for both lines of 0.20 A, which corresponds
to a nonthermal velocity of 18 km/sec.
---------------------------------------------------------
Title: High-resolution spectroscopy of two young stars between the
Magellanic Clouds
Authors: Hambly, N. C.; Dufton, P. L.; Keenan, F. P.; Rolleston,
W. R. J.; Howarth, I. D.; Irwin, M. J.
1994A&A...285..716H Altcode:
High-resolution echelle spectra of one main sequence B-type star and
one B-type supergiant in the Bridge between the Magellanic Clouds have
been obtained using the 3.9-m Anglo-Australian Telescope. These spectra
have been analyzed in conjunction with IUE low-resolution observations
by using ATLAS9 LTE model atmosphere techniques, to derive the stellar
atmospheric parameters and photospheric chemical compositions; the
latter should reflect that of the current interstellar medium within
the Bridge. From a differential analysis performed relative to the
Galactic B-type stars τ Sco and 67 Oph, the stars appear to have a
mild helium deficiency of 0.1-0.2 dex, and a general heavy element
depletion of at least -0.5 dex for one star, and as much as -1.0 dex
for the other. These chemical compositions thus reflect those of SMC
rather than LMC stars while the evolutionary status of these objects
implies significant star formation is currently underway in the region.
---------------------------------------------------------
Title: SI XIII Emission Lines in Solar Flare X-Ray Spectra Obtained
with the P78-1 Satellite
Authors: Keenan, F. P.; McKenzie, D. L.; Phillips, K. J. H.; Conlon,
E. S.
1994ApJ...426..454K Altcode: 1994STIN...9529279K
Theoretical Si XIII electron-temperature-sensitive
emission-line ratios, which include satellite-line
contributions to the intensities of the forbidden (f)
(1s<SUP>2</SUP>)(<SUP>1</SUP>S) goes to (1s2s)(<SUP>3</SUP>S),
intercombination (i) (1s<SUP>2</SUP>(<SUP>1</SUP>S) goes
to (1s2p)(<SUP>3</SUP>P<SUB>1,2</SUB>), and resonance (r)
(1s<SUP>2</SUP>)(<SUP>1</SUP>S) goes to (1s2p)(<SUP>1</SUP>P)
transitions, are presented for G = (I(f) + I(r), R = I(f)/I(i),
R<SUB>1</SUB> = I((1s<SUP>2</SUP>)(<SUP>1</SUP>S) goes to
(1s3p)(<SUP>1</SUP>P))/I(r). These ratios are significantly different
from those calculated assuming that satellites do not contribute to
f, i, and r, and, in addition, are more temperature-sensitive over
the range log T<SUB>e</SUB> = 6.4-7.4. Electron temperatures deduced
using the new diagnostics in conjunction with observed values of G,
R<SUB>1</SUB>, and R<SUB>2</SUB> from solar-flare spectra obtained
by the SOLEX spectrometers aboard the P78-1 satellite are found
to be generally consistent. This provides support for the validity
of the theoretical R<SUB>1</SUB> and R<SUB>2</SUB> diagnostics and
also resolves discrepancies noted previously when the line ratios
were compared with observations from the Solar Maximum Mission
spectrometers. The R ratio, which is in the low-density limit under
solar flare conditions, is found not to be a useful T<SUB>e</SUB>
diagnostic when satellite contributions to f and i are included in
the theoretical line ratios. However, the observed values of R from
the SOLEX spectra are in good agreement with theoretical predictions,
which provides additional support for the accuracy of the line-ratio
calculations.
---------------------------------------------------------
Title: Optical and H i Observations of High-Velocity Gas toward
HD 203664
Authors: Little, J. E.; Dufton, P. L.; Keenan, F. P.; Conlon, E. S.;
Davies, R. D.
1994ApJ...427..267L Altcode:
High-resolution optical stellar and interstellar observations toward
the halo star HD 203664 and six surrounding early-type stars have been
combined with a 21 cm mapping of the region to investigate a 70 km
s<SUP>-1</SUP> between 200 and 1500 pc; upper limits to temperature
and velocity dispersion of 4600 K and 2.2 km s<SUP>-1</SUP> have been
estimated; and a column density ratio N(Na II)/N (Ca II) approx. equal
to 0.32 has been deduced. These parameters are consistent with the
material being shocked gas, possibly arising from an old supernova
remnant. The N(Na I)/N(H I) and N(Ca II)/N(H I) ratios are anomalously
large by factors of approximately 20 and 100, respectively, with
respect to normal diffuse gas; several scenarios are presented as
possible explanations of this phenomenon.
---------------------------------------------------------
Title: The Fe XIV Spectrum: Predicted Line Intensities and Solar
Identifications
Authors: Bhatia, A. K.; Kastner, S. O.; Keenan, F. P.; Conlon, E. S.;
Widing, K. G.
1994ApJ...427..497B Altcode:
Level populations and line intensities have been calculated
in a 40-level model of Fe XIV which includes the configuations
3p<SUP>3</SUP> and 3s3p3d. The results have been compared against
intensities of weaker, unidentified, or tentatively classified
lines in published solar line lists including a recent Goddard Space
Flight Center/Solar Extreme Ultraviolet Telescope and Spectrograph
(GSFC/SERTS) high-resolution list, and in presently measured archival
Naval Research Laboratory (NRL)/S082A active region spectra. Seven
new lines are identified as Fe XIV transitions; five other observed,
unidentified lines are considered to be Fe XIV transitions on the
basis of wavelength coincidence, but require further observations to
obtain photometric intensities for verification; one line at 216.93
A is shown to be due to some other ion than Fe XIV. In addition, a
unique forbidden infrared (approx. equal to 1.25 micrometer(s)) line
originating in the high metastable level 3s3p3d(F<SUB>9/2</SUB>-4)
is found to have an unusual intensity dependence on electron density.
---------------------------------------------------------
Title: Heavy-particle excitation of fluorinelike Fe xviii
Authors: Foster, V. J.; Keenan, F. P.; Reid, R. H. G.
1994PhRvA..49.3092F Altcode:
Cross sections and rate coefficients for
excitation of the 2s<SUP>2</SUP>2p<SUP>5</SUP>
<SUP>2</SUP>P<SUB>3/2</SUB>-2s<SUP>2</SUP>2p<SUP>5</SUP>
<SUP>2</SUP>P<SUB>1/2</SUB> transition in fluorinelike Fe xviii by
proton (p), deuteron (d), triton (t), and α-particle (α) impact
have been calculated using the close-coupled impact-parameter
method. These data, in conjunction with R-matrix calculations
of electron-impact excitation rates, are used to derive the
theoretical emission line ratio R=I(2s<SUP>2</SUP>2p<SUP>5</SUP>
<SUP>2</SUP>P<SUB>3/2</SUB>-2s<SUP>2</SUP>2p<SUP>5</SUP>
<SUP>2</SUP>P<SUB>1/2</SUB>)/I(2s<SUP>2</SUP>2p<SUP>5</SUP>
<SUP>2</SUP>P<SUB>3/2</SUB>-2s2p<SUP>6</SUP>
<SUP>2</SUP>S<SUB>1/2</SUB>)=I(974.8 Å)/I(93.4 Å) as a function
of electron and heavy-particle number density, and electron and ion
temperature, for values applicable to tokamak plasmas. A comparison
of our results with observations of R from the JIPP T-II-U tokamak
at the Institute of Plasma Physics, Nagoya, Japan, for which the
plasma parameters have been independently determined, reveals excellent
agreement between theory and experiment, with discrepancies of typically
<=10%. This provides observational support for the accuracy of the
atomic data adopted in the line ratio calculations.
---------------------------------------------------------
Title: The Allowed Lines of O IV near 1340 Angstrom in High Electron
Density Solar Flares
Authors: Cook, J. W.; Keenan, F. P.; Bhatia, A. K.
1994ApJ...425..861C Altcode:
Intersystem lines of O IV near 1400 A have long been used as electron
density diagnostics for solar plasmas at temperatures of around 160,000
K. In addition, however, several allowed lines of O IV near 1340 A
should become visible in conditions of high plasma electron number
density (greater than 10<SUP>12</SUP>/cu cm), such as during a solar
flare. We present observations of the 1340 A and 1400 A regions of the
solar spectrum for two solar flares, obtained by the SO82B spectrograph
on board Skylab. We examine three candidate lines for allowed O IV
in the flare spectra which occur at the correct wavelengths, but show
that two of these are actually blends dominated by resonantly excited
molecular lines of H2. The third candidate line, at 1343.51 A, we
identify as the O IV allowd line. We present the density and temperature
sensitivity of the ratio of allowed and intersystem O IV lines R =
I(1343.51 A)/I(1407.39 A). The 1343.51 A line is clearly present in
the first solar flare spectrum, and the ratio value implies an electron
density of log N<SUB>e</SUB> = 12.6. The second flare has a much weaker
1343.51 A profile, but again the ratio value implies a high electron
density. Both these electron density values are in good agreement
with estimates for each flare from independent diagnostic ratios. The
simple presence alone of a clearly observed O IV 1343.51 A emission
line implies an electron density greater than 10<SUP>12</SUP>/cu cm.
---------------------------------------------------------
Title: A Search for Beta-Cephei Type Variability in a Sample of
Intermediate Galactic Latitude to High Galactic Latitude B-Type Stars
Authors: Hambly, N. C.; Kilkenny, D.; Keenan, F. P.; van Wyk, F.;
Marang, F.; Roberts, G.; Dufton, P. L.
1994MNRAS.267.1103H Altcode:
We have photometrically monitored nine intermediate- to
high-Galactic-latitude B-type stars for β Cephei-type variability. One
star, HD 204076, shows a clearly sinusoidal variation with an
amplitude of 0.015 mag and a period of a few hours, typical of β
Cephei stars. One other (HD 206144) is possibly a longer term variable
at the 2 per cent level, while two objects, HD 219188 and HD 118246,
may be variable at a smaller amplitude of < 0.0t mag. The remaining
five stars show no signs of any periodic changes above 0.0t mag and
are therefore unlikely to belong to the β Cephei class of variable.
---------------------------------------------------------
Title: Theoretical Emission Line Strengths for OV Compared to Extreme
Ultraviolet Solar Observations
Authors: Keenan, F. P.; Warren, G. A.; Doyle, J. G.; Berrington,
K. A.; Kingston, A. E.
1994SoPh..150...61K Altcode:
Recent R-matrix calculations of electron impact excitation
rates in OV are used to derive the emission line intensity
ratios (in energy units) R<SUB>1</SUB> = I(2s2p<SUP>3</SUP>P -
2p<SUP>2</SUP><SUP>3</SUP>P)/I(2s<SUP>2</SUP><SUP>1</SUP>S<SUB>0</SUB>
- 2s2p<SUP>1</SUP>P<SUB>1</SUB> = I(761.1 A)/I(629.7 A),
R<SUB>2</SUB> = I(2s<SUP>2</SUP><SUP>1</SUP>S<SUB>0</SUB> -
2s2p<SUP>3</SUP>P<SUB>1</SUB>/I(2s<SUP>2</SUP><SUP>1</SUP>S<SUB>0</SUB>
- 2s2p<SUP>1</SUP>P<SUB>1</SUB> = I(1218.4 A)/I(629.7
A), and R<SUB>3</SUB> = I(2s2p<SUP>1</SUP>)P<SUB>1</SUB> -
2p<SUP>2</SUP><SUP>1</SUP>S<SUB>0</SUB>/I(2s<SUP>2</SUP><SUP>1</SUP>S<SUB>0</SUB>
- 2s2p<SUP>1</SUP>P<SUB>1</SUB>) = I(774.5 A)/I(629.7 A) as
a function of electron temperature (T<SUB>e</SUB>) and density
(N<SUB>e</SUB>). These results are presented as plots of R<SUB>1</SUB>
vsR<SUB>2</SUB>, andR<SUB>1</SUB> vsR<SUB>3</SUB>, which should
allowboth N<SUB>e</SUB> andT<SUB>e</SUB> to be deduced for the OV
line emitting region of a plasma. Electron densities derived from the
(R<SUB>1</SUB>,R<SUB>2</SUB>) and (R<SUB>1</SUB>,R<SUB>3</SUB>) diagrams
in conjunction with observational data for several solar features
obtained with the Harvard S-055 spectrometer on boardSkylab are found
to be compatible, and in good agreement with values ofN<SUB>e</SUB>
estimated from line ratios in species formed at similar electron
temperatures to OV. In addition, values ofT<SUB>e</SUB> determined
from (R<SUB>1</SUB>,R<SUB>2</SUB>) and (R<SUB>1</SUB>,R<SUB>3</SUB>)
are generally close to that expected theoretically. These results
provide experimental support for the accuracy of the diagnostic
calculations presented in this paper, and hence the atomic data used
in their derivation.
---------------------------------------------------------
Title: N III Intercombination Lines in the IUE Spectra of Gaseous
Nebulae
Authors: Keenan, F. P.; Dufton, P. L.; Feibelman, W. A.; Bell, K. L.;
Hibbert, A.; Stafford, R. P.
1994ApJ...423..882K Altcode:
Theoretical N III electron density-sensitive emission-line ratios
involving intercombination transitions, derived using recent
calculations of electron impact excitation rates and oscillator
strengths, are presented for R<SUB>1</SUB> = I(1754.0 Å)/I(1749.7 Å),
R<SUB>2</SUB> = I(1752.2 Å)/I(1749.7 Å), R<SUB>3</SUB> = I(1748.6
Å)/I(1749.7 Å), and R<SUB>4</SUB> = I(1746.8 Å)/I(1749.7 Å). The
observed values of R<SUB>1</SUB>, R<SUB>2</SUB>, and R<SUB>3</SUB>
for several gaseous nebulae, measured from high-resolution spectra
obtained with the International Ultraviolet Explorer (IUE) satellite,
imply electron densities that are compatible. However, values of
N<SUB>e</SUB> derived from the R<SUB>4</SUB> ratio are up to several
orders of magnitude smaller than those deduced from R<SUB>1</SUB>,
R<SUB>2</SUB>, and R<SUB>3</SUB>, which is probably due to the N
III 1746.8 Å line being blended with Fe II 1746.8 Å. The electron
densities deduced from the N III diagnostics are, in some objects,
much larger than those estimated from line ratios in nebular ions
such as O III, but are in good agreement with values deduced from the
chromospheric C II intercombination transitions at ∼2325 Å. These
results suggest that in these nebulae the N III emission may also be
chromospheric in origin.
---------------------------------------------------------
Title: Mgix Emission Lines in an Active Region Spectrum Obtained
with the Solar Extreme Ultraviolet Rocket Telescope and Spectrograph
/ SERTS
Authors: Keenan, F. P.; Conlon, E. S.; Thomas, R. J.; Neupert, W. M.
1994SoPh..149..301K Altcode:
Theoretical electron-temperature-sensitive MgIX emission line ratios are
presented forR<SUB>I</SUB> =I(443.96 å)/I(368.06 å),R<SUB>2</SUB>
=I(439.17 å)/I(368.06 å),R<SUB>3</SUB> =I(443.37 å)/I(368.06
å),R<SUB>4</SUB> =I(441.22 å)/I(368.06 å), andR<SUB>5</SUB> =I(448.28
å)/I(368.06 å). A comparison of these with observational data for a
solar active region, obtained during a rocket flight by the Solar EUV
Rocket Telescope and Spectrograph (SERTS), reveals excellent agreement
between theory and observation forR<SUB>1</SUB> throughR<SUB>4</SUB>,
with discrepancies that average only 9%. This provides experimental
support for the accuracy of the atomic data adopted in the line ratio
calculations, and also resolves discrepancies found previously when
the theoretical results were compared with solar data from the S082A
instrument on boardSkylab. However in the case ofR<SUB>5</SUB>, the
theoretical and observed ratios differ by almost a factor of 2. This may
be due to the measured intensity of the 448.28 å line being seriously
affected by instrumental effects, as it lies very close to the long
wavelength edge of the SERTS spectral coverage (235.46−448.76 å).
---------------------------------------------------------
Title: NE VI Line Ratios in the Sun
Authors: Keenan, F. P.; Conlon, E. S.; Warren, G. A.; Pradhan, A. K.;
Zhang, H. L.; Sampson, D. H.; Widing, K. G.
1994ApJ...421..851K Altcode:
Recent calculations of electron impact excitation rates for Ne VI
are used to derive theoretical electron density sensitive emission
line ratios involving transitions in the wavelength range 399-563
A. Electron densities deduced from the observed line ratios for solar
flares, obtained with the Naval Research Laboratory's SO82A slitless
spectrograph on-board Skylab, are in excellent internal agreement and,
furthermore, compare favorably with densities estimated from line ratios
in O V and Ne VII, which are formed at similar electron temperatures
to Ne VI. These results provide experimental support for the accuracy
of the atomic data adopted in the analysis.
---------------------------------------------------------
Title: Emission Line Ratios for Fexxi Applicable to the Extreme
Ultraviolet Spectra of Solar Flares
Authors: Keenan, F. P.; Conlon, E. S.; Warren, G. A.; Aggarwal, K. M.
1994SoPh..149..129K Altcode:
Electron impact excitation rates for FeXXI, calculated with theR-matrix
code, are used to determine theoretical electron density sensitive
emission line ratios involving transitions in the 121-146 å wavelength
range. The observed ratios for a solar flare, obtained with a grazing
spectrometer on board the OSO-5 satellite, imply electron densities
which are consistent, with discrepancies that do not exceed 0.3
dex. In addition, the derived values ofN<SUB>e</SUB> are similar
to those estimated for the high temperature regions of other solar
flares. This provides experimental support for the accuracy of the
atomic data adopted in the line ratio calculations.
---------------------------------------------------------
Title: Alix Emission Line Ratios in Solar Flares Observed with the
S:082A Spectrograph on Board SKYLAB
Authors: Keenan, F. P.; Conlon, E. S.; Bowden, D. A.; Dwidvedi, B. N.;
Widing, K. G.
1994SoPh..149..137K Altcode:
Theoretical electron-density-sensitive emission line ratios in B-like
AIIX are presented forR =I(385.01 å)/I(392.42 å). A comparison of
these with high spectral resolution solar flare data, obtained with the
S082A slitless spectrograph on boardSkylab, reveals agreement between
theory and observation for those spectra that were observed during
the later stages of the flares. These results provide experimental
support for the accuracy of the line-ratio calculations, and also
resolves discrepancies found previously when the theoretical results
were compared with solar observations from the S-055 instrument on
boardSkylab. However, the agreement between theory and observation for a
spectrum obtained during the early stages of a flare is very poor, which
probably indicates that the 392.42 å line is blended with a transition
arising from a species formed at a very high electron temperature.
---------------------------------------------------------
Title: UBV CCD Photometry of the Halo of M31
Authors: Fitzsimmons, A. P.; Keenan, F. P.; Dufton, P. L.; Little,
J. E.; Irwin, M. J.
1994hsgh.conf..326F Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Interstellar Detection of the Intersystem Line SI ii] lambda
2335 toward zeta Ophiuchi
Authors: Cardelli, Jason A.; Sofia, Ulysses J.; Savage, Blair D.;
Keenan, Francis P.; Dufton, Philip L.
1994ApJ...420L..29C Altcode:
We report on the detection of the weak intersystem transistion of Si
II lambda 2335 A in the sight line toward zeta Oph using the Ech-B mode
(3.5 km/s resolution) of the Goddard High Resolution Spectrograph. The
high-quality spectrum is characterized by an empirically measured
signal-to-noise of 450, in excellent agreement with that expected
from photon-statistics. The measured equivalent width of the Si
II line is W<SUB>lambda</SUB> = 0.48 +/- 0.12 mA. Using the new
experimental f-value of Calamai, Smith, and Bergeson, we find a Si
II column density of 2.34 (+/- 0.58) x 10<SUP>15</SUP> atoms/sq cm
and (Si/H)<SUB>zeta Oph</SUB> = 1.78 (+/- 0.44) x 10<SUP>-6</SUP>
for the principal absorbing component(s) at v<SUB>sun</SUB> approx. =
-15 km/s. Analysis of the Si II lambda 1808 absorption over the same
velocity range using the new experimental f-value of Bergeson &
Lawler yields a column density (corrected for saturation) that is
consistent within the weak line errors and confirms the relative
accuracies of these new f-values. Furthermore, these results indicate
that accurate abundances can now be derived for Si II, particularly from
the weak Si II lambda 2335 A since it is free of saturation effects. For
the zeta Oph v<SUB>sun</SUB> approx. = -15 km/s component(s), we find
that greater than 95% of the available cosmic abundance (i.e. the
1989 meteoritic abundances of Anders & Grevesse) of Mg, Fe,
and Si is 'missing' from the gas phase and is presumably locked up
in the dust. These elements are present in the dust grains in ratios
of Fe/Si approximately equals 0.9 and Mg/Si approximately equals 1.1,
consistent with the ratio of their cosmic abundances. These ratios are
in sharp contrast to more diffuse clouds like those seen toward the
high-latitude halo star HD 93521 where in the dust Fe/Si approximately
equals 1.8 and Mg/Si approximately equals 2.1.
---------------------------------------------------------
Title: Theoretical Line Ratios for Carbon Like Ar XIII and a
Comparison with XUV Observations of Solar Flares
Authors: Foster, V. J.; Keenan, F. P.; Conlon, E. S.; Aggarwal, K. M.;
Widing, K. G.
1994emsp.conf...73F Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A 300 Square Degree Survey of Young Stars at High Galactic
Latitudes
Authors: Eamon Little, J.; Dufton, P. L.; Keenan, F. P.; Hambly,
N. C.; Conlon, E. S.; Miller, L.
1994hsgh.conf...79E Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Calculated He-Like Argon Line Intensities and Comparison
with Solar Flare Spectra from the FCS Instrument on the Solar
Maximum Mission
Authors: Harra, L. K.; Phillips, K. J. H.; Keenan, F. P.; Zarro,
D. M.; Wilson, M.
1994emsp.conf...77H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Allowed Lines of O IV Near 1340 Angstroms in High Electron
Density Solar Flares
Authors: Cook, J. W.; Keenan, F. P.; Bhatia, A. K.
1993AAS...183.6805C Altcode: 1993BAAS...25.1396C
Intersystem lines of O IV near 1400 Angstroms have long been used as
electron density diagnostics for solar plasmas at temperatures of
around 160,000 K. In addition, however, several allowed lines of O
IV near 1340 Angstroms should become visible in conditions of high
plasma electron number density (N<SUB>e</SUB> > 10(12) cm(-3) ),
such as during a solar flare. We present observations of the 1340
Angstroms and 1400 Angstroms regions of the solar spectrum for two
solar flares, obtained by the S082B spectrograph on board Skylab. We
examine three candidate lines for allowed O IV in the flare spectra
which occur at the correct wavelengths, but show that two of these
are actually blends dominated by resonantly excited molecular lines
of H<SUB>2</SUB>. The third candidate line, at 1343.51 Angstroms,
we identify as the O IV allowed line. We present the density and
temperature sensitivity of the ratio of allowed and intersystem O
IV lines R = I(1343.51 Angstroms)/I(1407.39 Angstroms). The 1343.51
Angstroms line is clearly present in the first solar flare spectrum,
and the ratio value implies an electron density of log N<SUB>e</SUB>
= 12.6. The second flare has a much weaker 1343.51 Angstroms profile,
but again the ratio value implies a high electron density. Both these
electron density values are in good agreement with estimates for each
flare from independent diagnostic ratios. The simple presence alone
of a clearly observed O IV 1343.51 Angstroms emission line implies an
electron density greater than 10(12) cm(-3) .
---------------------------------------------------------
Title: Helium-like Argon Line Emission in Solar Flares
Authors: Phillips, K. J. H.; Harra, L. K.; Keenan, F. P.; Zarro,
D. M.; Wilson, M.
1993ApJ...419..426P Altcode:
Theoretical X-ray spectra of Ar XVII lines and Ar XVI satellites
at ∼4 Å, derived from R-matrix code and other calculations, are
compared with solar-flare observations obtained with the SMM Flat
Crystal Spectrometer. There is good agreement between the observed
line features and those in the theoretical spectra, and the comparison
leads to best-fit values of electron temperature for the observed solar
flares. We present wavelengths for the Ar XVII and some Ar XVI lines,
measured from the observed spectra, which have better precision than
previous values. In addition, the coronal Ar/S abundance is determined
from the relative intensities of Ar XVII lines to those of nearby S
XV transitions, and the value of this ratio is discussed in the light
of previous work.
---------------------------------------------------------
Title: Model Atmosphere and Kinematical Analyses of Early-Type,
High Galactic Latitude Stellar Candidates from the UKST UBVRI Survey
Authors: Hambly, N. C.; Conlon, E. S.; Dufton, P. L.; Keenan, F. P.;
Little, J. E.; Miller, L.
1993ApJ...417..706H Altcode:
From the UKST UBVRI survey, six high Galactic latitude stars have
been previously identified which may be young hydrogen-burning
objects. Using high-dispersion optical spectra, model atmosphere
analyses are presented for these targets. Two have normal or nearly
normal Population I chemical compositions, one appears to be subluminous
while the remaining three are possibly normal late B-type stars. A
kinematic analysis indicates that one star having normal parameters
is an excellent candidate for formation in the halo, having an
evolutionary age an order of magnitude less than the time required for
it to attain its current position following ejection from the Galactic
disk. A preliminary analysis implies that there may currently be a
few thousand normal B-type stars in the Galactic halo with z-distances
from the plane of the Galaxy in the range 3 < Ζ < 22 kpc.
---------------------------------------------------------
Title: The nature of the high latitude B-type binary, SU Piscium.
Authors: Dufton, P. L.; Holmgren, D.; Conlon, E. S.; Keenan, F. P.
1993A&A...278...68D Altcode:
A spectroscopic orbit is presented for the early-type eclipsing
binary star SU Psc and minimum masses of approximately 11 solar mass
are deduced for both components. Photometric colors and intermediate
dispersion spectra are used to deduce a composite spectral type for
this system. The relative strengths of the hydrogen lines in the two
components implies a magnitude difference of Delta B approximates to
1.0 and allows spectral types of B3III and B5III to be estimated for
the primary and secondary stars, respectively. The SU Psc system would
therefore appear to consist of a pair of normal young hydrogen burning
B-type stars; their high galactic latitude (b approximates to 48 deg)
would then imply that they are at a distance of more than 3 kpc from the
galactic plane. Evolutionary ages of approximately 10<SUP>7</SUP> years
for both components are smaller than the estimated time (approximates
to 4 x 10<SUP>7</SUP> years) for the system to have been moved from the
galactic disk to its current position. However given the uncertainties,
these estimates are still consistent with SU Psc having been ejected
from the galactic plane, possibly via dynamical interactions in a
young open cluster.
---------------------------------------------------------
Title: Electron Density Diagnostics for Gaseous Nebulae Involving
the O IV Intercombination Lines near 1400 Angstrom
Authors: Keenan, F. P.; Conlon, E. S.; Bowden, D. A.; Feibelman,
W. A.; Pradhan, A. K.
1993ApJS...88..169K Altcode:
The Bloom and Pradhan (1992) results on the excitation rates for
transitions in O IV matrix are used to derive emission-line ratios
near 1400 A, applicable to gaseous nebulae. The results are compared
with the values measured from high-resolution spectra obtained by the
IUE satellite.
---------------------------------------------------------
Title: S XI Line Ratios in the Sun
Authors: Keenan, F. P.; Foster, V. J.; Conlon, E. S.; Aggarwal, K. M.;
Widing, K. G.
1993ApJ...413..826K Altcode:
Recently, Conlon et al. (1992) used Aggarwal's (1986) R-matrix
calculations of electron excitation rates for Si IX, Ca XV, and Fe XXI
to interpolate atomic data for other C-like ions, including S XI. Here,
the results of Conlon et al. are used to derive diagnostic line ratios
for S XI, and the ratios are compared with solar flare observational
data obtained with the S082A instrument aboard Skylab. The experimental
ratios are generally much larger than those predicted by theory,
probably because of blending of the S XI 215.97 A line with Ni XVII
215.91 A and S XI 190.37 A with an unidentified feature at a coincident
wavelength. These observations indicate that photoexcitation of S XI
by Fe XII 191.26 A is probably not an important process in the solar
atmosphere under flare conditions.
---------------------------------------------------------
Title: Emission line ratios for C III in the sun
Authors: Keenan, F. P.; Warren, G. A.
1993SoPh..146...19K Altcode:
Theoretical electron-density-sensitive C III emission line
ratios are presented forR<SUB>1</SUB> =I(2s2p<SUP>3</SUP>P
− 2p<SUP>2</SUP><SUP>3</SUP>P)/I(2s2p<SUP>1</SUP>P
− 2p<SUP>2</SUP><SUP>1</SUP>S) =I(1176
Å)/I(1247 Å),R<SUB>2</SUB> =I(2s2p<SUP>3</SUP>P −
2p<SUP>2</SUP><SUP>3</SUP>P)/I(2s<SUP>2</SUP><SUP>1</SUP>S
− 2s2p<SUP>3</SUP>P<SUB>1</SUB>) =I(1176 Å)/I(1908
Å), andR<SUB>3</SUB> =I(2s2p<SUP>1</SUP>P −
2p<SUP>2</SUP><SUP>1</SUP>S)/I(2s<SUP>2</SUP><SUP>1</SUP>S −
2s2p<SUP>3</SUP>P<SUB>1</SUB>) =I(1247 Å)/I(1908 Å). These are
significantly different from those deduced previously, principally
due to the adoption of improved electron impact excitation rates in
the present analysis. Electron densities deduced from the present
theoretical line ratios, in conjunction with observed values
ofR<SUB>1</SUB>,R<SUB>2</SUB>, andR<SUB>3</SUB> measured from
solar spectra obtained by the Naval Research Laboratory's S082B
instrument on boardSkylab, are found to be generally compatible. In
contrast, previous diagnostic calculations imply electron densities
fromR<SUB>1</SUB>,R<SUB>2</SUB>, andR<SUB>3</SUB> that differ by up to
two orders of magnitude. These results provide observational support for
the accuracy of the atomic physics adopted in the present calculations,
and the methods employed in the derivation of the theoretical line
ratios.
---------------------------------------------------------
Title: A Search for Young Stars in the Halo of M31
Authors: McCausland, R. J. H.; Conlon, E. S.; Dufton, P. L.;
Fitzsimmons, A.; Irwin, M. J.; Keenan, F. P.
1993ApJ...411..650M Altcode:
Previous studies have identified young hot stars that appear to have
been formed in the halo of our Galaxy. Here we present preliminary
results of a spectroscopic search for similar objects in the halo of
M31. Radial velocities have been measured for 23 apparently blue objects
(selected from APM measurements of Schmidt plates) in a magnitude
range B_v_ ~ 17-21. For one of these targets, AND 0029+413, the radial
velocity suggests that the object is gravitationally bound to M31 and
hence that it may be in its halo. However, recent CCD photometry for
this object indicates that it is redder than implied by the original
photographic observations. A number of possible scenarios are presented
to explain this object, including one consistent with it being a young
star in the halo of M31.
---------------------------------------------------------
Title: Ar XIII line ratios in solar flares
Authors: Keenan, F. P.; Conlon, E. S.; Foster, V. J.; Aggarwal, K. M.;
Widing, K. G.
1993SoPh..145..291K Altcode:
Theoretical ArXIII electron-density-sensitive emission line ratios,
derived using electron impact excitation rates interpolated from
accurateR-matrix calculations, are presented forR<SUB>1</SUB>
=I(242.22 å)/I(236.27 å),R<SUB>2</SUB> =I(210.46 å)/I(236.27 å),
andR<SUB>3</SUB> =I(248.68 å)/I(236.27 å). Electron densities deduced
from the observed values ofR<SUB>1</SUB>,R<SUB>2</SUB>, andR<SUB>3</SUB>
for solar flares obtained with the NRL S082A slitless spectrograph
on boardSkylab are in excellent agreement, and furthermore compare
favorably with those determined from line ratios in CaXV, which is
formed at a similar electron temperature to that of ArXIII. These
results provide experimental support for the accuracy of the atomic
data adopted in the analysis, as well as for the techniques used to
calculate the line ratios.
---------------------------------------------------------
Title: Fe III Emission Lines in the Optical Spectrum of the Planetary
Nebula IC 4997
Authors: Keenan, F. P.; Aller, L. H.; Hyung, S.; Conlon, E. S.;
Warren, G. A.
1993ApJ...410..430K Altcode:
Relative populations for the 17 fine-structure levels in the 5D, 3P, 3H,
3F, and 3G states of the 3d6 configuration in Fe III, calculated using
electron impact excitation rates derived with the R-matrix code, are
used to derive theoretical electron temperature and density sensitive
emission-line ratios applicable to the spectra of astronomical objects
in the 4607-5412 A wavelength range. A comparison of these with high
spectral resolution observational data for the PN IC 4997 reveals
generally good agreement between theory and observation. This provides
experimental support for the accuracy of the theoretical ratios and
illustrates their usefulness in determining plasma parameters for the
Fe III-emitting region of a gaseous nebula.
---------------------------------------------------------
Title: The Ratio of Optical-to-Infrared Emission Line Strengths in
AR III as Electron Density Diagnostics for Planetary Nebulae
Authors: Keenan, F. P.; Conlon, E. S.
1993ApJ...410..426K Altcode:
The Johnson and Kingston (1990) results are used to derive theoretical
line ratios for Ar III, and these are compared with optical and
infrared observations of planetary nebulae. It is shown that this
approach makes it possible to investigate the accuracy of the atomic
data and evaluate the potential usefulness of optical/infrared line
ratios in Ar III as electron density diagnostics.
---------------------------------------------------------
Title: Infrared observations of possible hot post-asymptotic giant
branch stars.
Authors: Conlon, E. S.; Dufton, P. L.; Keenan, F. P.; McCausland,
R. J. H.; Little, J. E.
1993A&A...272..243C Altcode:
Infrared photometry of seventeen high latitude early-type stars,
that have either been identified as post-AGB objects or are post-AGB
candidates, has been obtained at JHKL and nbM wavelengths. This has been
combined with optical and IRAS observations, and compared with LTE model
atmosphere fluxes; infrared excesses are found for five stars. Of the
known post-AGB stars, only the highest mass objects reveal an infrared
excess, suggesting a correlation between the presence of circumstellar
material and mass. This may be explained in terms of the very different
transition times for high and low mass post-AGB stars from the AGB to
becoming a planetary nebula.
---------------------------------------------------------
Title: LSIV -12 degrees 111: A Candidate Halo Proto--Planetary Nebula
Authors: Conlon, E. S.; Dufton, P. L.; McCausland, R. J. H.; Keenan,
F. P.
1993ApJ...408..593C Altcode:
We report on multiwavelength observations of LSIV -12 deg 111, which
may be an emerging halo planetary nebula. This object was previously
classified as a young emission-line B-type star, but a model atmosphere
abundance analysis of high-resolution optical spectra has revealed it
to be an evolved object, probably in the postasymptotic giant branch
(AGB) evolutionary phase. The presence of an infrared excess and
low-excitation nebular emission lines implies that the central star may
just have started to photoionize the circumstellar material ejected
during the AGB phase. In this paper we discuss the nebular and dust
properties of LSIV -12 deg 111 and redetermine some metal abundances
for the central star. These are used to constrain the evolutionary
status of this unusual object.
---------------------------------------------------------
Title: A Comparison of Theoretical CIV Emission Line Strengths with
Active Region Observations Obtained with the Solar Extreme Ultraviolet
Rocket Telescope and Spectrograph / SERTS
Authors: Keenan, F. P.; Thomas, R. J.; Neupert, W. M.; Conlon, E. S.;
Burke, V. M.
1993SoPh..144...69K Altcode:
Theoretical line ratios involving 2s<SUP>2</SUP>S - 3p<SUP>2</SUP>P,
2p<SUP>2</SUP>P - 3s<SUP>2</SUP>S, and 2p<SUP>2</SUP>S - 3d<SUP>2</SUP>D
transitions inCIV between 312 and 420 Å are presented. A comparison
of these with solar active region observational data obtained during
a rocket flight by the Solar EUV Rocket Telescope and Spectrograph
(SERTS) reveals good agreement between theory and experiment, with
discrepancies that average only 22%. This provides experimental
support for the accuracy of the atomic data adopted in the line ratio
calculations, and also resolves discrepancies found previously when
the theoretical results were compared with solar data from the S082A
instrument on boardSkylab. The potential usefulness of theCIV line
ratios as electron temperature diagnostics for the solar transition
region is briefly discussed.
---------------------------------------------------------
Title: Identification of the Fe XV 3 s3p 1P--3p 2 1S Line in Solar
Flare Spectra and Its Use as an Electron Density Diagnostic
Authors: Keenan, F. P.; Dufton, P. L.; Conlon, E. S.; Foster, V. J.;
Kingston, A. E.; Widing, K. G.
1993ApJ...405..798K Altcode:
We have examined EUV spectra of solar flares and measured the
intensities of the 324.97 A and 323.57 A emission lines relative to that
of the Fe XV 3s3p 3P2-3p2 3P1 transition at 321.76 A. A comparison
of these line ratios with theoretical predictions indicates that
the Fe XV 3s3p 1P-3p2 1S transition is the line observed at 324.97
A, rather than the feature at 323.57 A as previously suggested. In
addition, we show that the I(324.97 A)/I(321.76 A) intensity ratio
is an excellent electron density diagnostic for the Fe XV emitting
region of the solar atmosphere. The relative intensities of other Fe
XV lines in the 290-330 A wavelength region of the S082A spectra are
also analyzed and briefly discussed.
---------------------------------------------------------
Title: Three stars at high galactic latitudes with peculiar helium
abundances.
Authors: Dufton, P. L.; Conlon, E. S.; Keenan, F. P.; McCausland,
R. J. H.; Holmgren, D. E.
1993A&A...269..201D Altcode:
High resolution optical observations have been obtained for three high
Galactic latitude hot stars (CD-43 14300 deg, PHL 382, and Feige 56)
which have abnormal helium spectra. An LTE model atmosphere analysis
indicates that CD-43 14300 deg is probably an intermediate helium star
with relatively normal metal abundances, while PHL 382 and Feige 56
are helium weak stars with silicon and magnesium underabundances. A
kinematic analysis implies that Feige 56 could have been ejected from
the Galactic plane; for the other two stars, the analysis is ambiguous
but favors them having been formed away from the Galactic plane. The
identification of such objects provides additional evidence for the
existence of young hot stars at large distances from the Galactic plane.
---------------------------------------------------------
Title: Theoretical Emission-Line Strengths for Fe XXIII and a
Comparison with Solar Observational Data
Authors: Keenan, F. P.; Conlon, E. S.; Warren, G. A.; Boone, A. W.;
Norrington, P. H.
1993ApJ...406..350K Altcode:
Electron impact excitation rates, calculated with a relativistic
version of the R-matrix code, are presented for all transitions among
the 2s2, 2s2p, and 2p2 levels of Fe XXIII. These data are used to
derive theoretical T(e) sensitive emission-line ratios involving Fe
XXIII transitions in the 132-1100 A wavelength range. A comparison of
our theoretical results for the ratio R1 = I(2s2 1S-2s2p 1P)/I(2s2 1
1S-2s2p 3Pi) = I(132.81 A)/I(263.79 A) with the observed value for a
solar flare, obtained with the Goddard Space Flight Center's grating
spectrometer on the OSO 5 satellite, reveals good agreement between
theory and observation. This provides some experimental support for
the accuracy of the atomic data adopted in the line ratio calculations.
---------------------------------------------------------
Title: An abundance and kinematic analysis from high dispersion
spectroscopy of early-type, high galactic latitude stellar candidates
from the UKST UBVRI survey.
Authors: Hambly, N. C.; Conlon, E. S.; Dufton, P. L.; Keenan, F. P.;
McCausland, R. J. H.
1993WFINw...3...18H Altcode:
The authors have identified four excellent young, high galactic latitude
candidates from the UKST UBVRI survey by model atmospheric analysis
from high resolution spectra.
---------------------------------------------------------
Title: Proton and Heavy Particle Excitation of the
2s<SUP>2</SUP>2p<SUP>5</SUP> <SUP>2</SUP>P<SUB>{3/2}</SUB> -
2s<SUP>2</SUP>2p<SUP>5</SUP> <SUP>2</SUP>P<SUB>½ </SUB>Transition
in Fluorine-Like Zn XXII, Kr XXVIII and Mo XXXIV
Authors: Reid, R.; Foster, V.; Keenan, F.
1993uxrs.conf..154R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: C IV emission lines in an active region spectrum obtained
with SERTS.
Authors: Keenan, F. P.; Thomas, R. J.; Neupert, W. M.; Conlon, E. S.;
Burke, V. M.
1993uxrs.conf..337K Altcode: 1993uxsa.conf..337K
Theoretical line ratios involving 2s <SUP>2</SUP>S-3p <SUP>2</SUP>P,
2p <SUP>2</SUP>P-3s <SUP>2</SUP>S and 2p <SUP>2</SUP>S-3d <SUP>2</SUP>D
transitions in C IV between 312 and 420 Å are presented. A comparison
of these with observations of a solar active region obtained during
a rocket flight by the Solar EUV Rocket Telescope and Spectrograph
(SERTS) reveals good agreement between theory and experiment, with
discrepancies that average only 19%. This provides experimental
support for the accuracy of the atomic data adopted in the line ratio
calculations, and also resolves discrepancies found previously when
the theoretical results were compared with solar data from the S082A
instrument on board Skylab. The potential usefulness of the C IV line
ratios as electron temperature diagnostics for the solar transition
region is briefly discussed.
---------------------------------------------------------
Title: Preliminary Results of Two Spectroscopic Surveys to Investigate
Star Formation in the Galactic Halo
Authors: Conlon, E. S.; Little, J. E.; Dufton, P. L.; Keenan, F. P.;
McCausland, R. J. H.; Holmgren, D.; Kilkenny, D.; Stobie, R. S.;
Miller, L.
1993ASPC...45..375C Altcode: 1993lhls.work..375C
No abstract at ADS
---------------------------------------------------------
Title: Abundance Analyses of Hot Post-Agb Stars at High Galactic
Latitude
Authors: Conlon, E. S.; McCausland, R. J. H.; Dufton, P. L.; Keenan,
F. P.
1993ASPC...45..146C Altcode: 1993lhls.work..146C
No abstract at ADS
---------------------------------------------------------
Title: Electron density diagnostics applicable to IUE spectra of
gaseous nebulae.
Authors: Keenan, F. P.; Feibelman, W. A.; Harra, L. K.; Conlon, E. S.;
Aggarwal, K. M.
1993uxrs.conf..341K Altcode: 1993uxsa.conf..341K
Observed values of the emission line ratios R = I(3s<SUP>2</SUP>
<SUP>1</SUP>S - 3s3p <SUP>3</SUP>P<SUB>2</SUB>)/ I(3s<SUP>2</SUP>
<SUP>1</SUP>S - 3s3p <SUP>3</SUP>P<SUB>1</SUB>) = I(2660 Å)/I(2669
Å) in Al II, R<SUB>1</SUB> = I(2s<SUP>2</SUP> <SUP>1</SUP>S -
2s2p <SUP>3</SUP>P<SUB>2</SUB>)/ I(2s<SUP>2</SUP> <SUP>1</SUP>S
- 2s2p <SUP>3</SUP>P<SUB>1</SUB>) = I(1907 Å)/I(1909 Å) in C
III, and R<SUB>2</SUB> = I(3s<SUP>2</SUP> <SUP>1</SUP>S - 3s3p
<SUP>3</SUP>P<SUB>2</SUB>)/ I(3s<SUP>2</SUP> <SUP>1</SUP>S - 3s3p
<SUP>3</SUP>P<SUB>1</SUB>) = I(1883 Å)/I(1892 Å) in Si III, measured
from high resolution spectra obtained with the International Ultraviolet
Explorer (IUE) satellite, are presented for several planetary nebulae
and symbiotic stars. Electron densities deduced from these ratios in
conjunction with new theoretical R, R<SUB>1</SUB> and R<SUB>2</SUB>
diagnostics (which are significantly different from those calculated
by previous authors), are found to be compatible, and are also in good
agreement with those derived from line ratios in other species. This
provides observational support for the accuracy of the atomic data
adopted in the line ratio calculations.
---------------------------------------------------------
Title: Ar XVII X-ray lines emitted by solar flares.
Authors: Phillips, K. J. H.; Keenan, F. P.; Harra, L. K.; McCann, S. M.
1993uxrs.conf..579P Altcode: 1993uxsa.conf..579P
Recent calculations of electron impact excitation rates in helium-like
argon (Ar XVII) have been used to derive emission line intensities
for the resonance (1s<SUP>2</SUP> <SUP>1</SUP>S<SUB>0</SUB> -
1s2p <SUP>1</SUP>P<SUB>1</SUB>), intercombination (1s<SUP>2</SUP>
<SUP>1</SUP>S<SUB>0</SUB> - 1s2p <SUP>3</SUP>P<SUB>1,2</SUB>)
and forbidden (1s<SUP>2</SUP> <SUP>1</SUP>S<SUB>0</SUB> - 1s2s
<SUP>3</SUP>S<SUB>1</SUB>) lines that appear in the X-ray region
(≍4 Å). These have been combined with calculations of nearby
dielectronic satellites of Ar XVI to synthesize spectra that can be
compared with observations. The synthetic spectra are sensitive to
electron temperature T<SUB>e</SUB> but not electron density unless
extremely large (>10<SUP>14</SUP>cm<SUP>-3</SUP>). Comparisons have
been made using observations taken during solar flares with the Flat
Crystal Spectrometer (part of the X-ray Polychromator) on Solar Maximum
Mission and with spectra from the Alcator tokamak. The observed spectra
show good agreement with the theoretical spectra, and demonstrate the
feasibility of using Ar XVII line ratios for determining T<SUB>e</SUB>.
---------------------------------------------------------
Title: Diffusion Effects on Diagnostic X-Ray Emission Line Ratio
Measurements in Laboratory Plasmas
Authors: Coffey, I.; Barnsley, R.; Hughes, I.; Keenan, F.; Lawson,
K.; Peacock, N.
1993uxrs.conf..533C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Line ratio diagnostics for astrophysical plasmas.
Authors: Keenan, F. P.
1993uxrs.conf...44K Altcode: 1993uxsa.conf...44K
In this paper the conditions under which emission (or absorption)
line intensity ratios are sensitive to variations in the physical
conditions of a plasma, such as electron temperature and density,
are discussed. More importantly, a bibliography is provided of the
most reliable line ratio diagnostic calculations currently available
for application to the IR, optical, UV and X-ray spectra of a wide
range of astrophysical sources. These include the solar chromosphere,
transition region and corona, late-type stellar atmospheres, gaseous
nebulae (such as H II regions and planetary nebulae), active galactic
nuclei, supernova remnants and the interstellar medium.
---------------------------------------------------------
Title: LSIV 12 degree 111 - A Newly Emerging Halo Planetary Nebula
Authors: Conlon, E. S.; Dufton, P. L.; Keenan, F. P.; McCausland,
R. J. H.
1993IAUS..155..356C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The determination of solar coronal electron temperatures from
Mg XI emission lines in SMM-FCS spectra of flares and active regions.
Authors: Harra, L. K.; Phillips, K. J. H.; Keenan, F. P.; Conlon,
E. S.; Kingston, A. E.
1993uxrs.conf..551H Altcode: 1993uxsa.conf..551H
Recent atomic physics calculations for Mg XI are used to derive
the electron temperature sensitive emission line ratios G =
[I(1s<SUP>2</SUP> <SUP>1</SUP>S - 1s2s <SUP>3</SUP>S) + I(1s<SUP>2</SUP>
<SUP>1</SUP>S - 1s2p <SUP>3</SUP>P<SUB>1,2</SUB>)]/ I(1s<SUP>2</SUP>
<SUP>1</SUP>S - 1s2p <SUP>1</SUP>P), R<SUB>1</SUB> = I(1s<SUP>2</SUP>
<SUP>1</SUP>S - 1s3p <SUP>1</SUP>P)/ I(1s<SUP>2</SUP> <SUP>1</SUP>S
- 1s2p <SUP>1</SUP>P), and R<SUB>2</SUB> = I(1s<SUP>2</SUP>
<SUP>1</SUP>S - 1s4p <SUP>1</SUP>P)/ I(1s<SUP>2</SUP> <SUP>1</SUP>S -
1s2p <SUP>1</SUP>P), which are found to be significantly different from
earlier results. Values of T<SUB>e</SUB> deduced from G, R<SUB>1</SUB>
and R<SUB>2</SUB> ratios measured from solar flare and active region
spectra obtained with the Flat Crystal Spectrometer (FCS) on board the
Solar Maximum Mission (SMM) satellite are consistent. This provides
support both for the validity of the theoretical G, R<SUB>1</SUB>
and R<SUB>2</SUB> diagnostics, and for the FCS calibration curve in
the wavelength region covering the Mg XI transitions, 7.472-9.314 Å.
---------------------------------------------------------
Title: Solar O IV and S IV lines from the High Resolution Telescope
and Spectrograph (HRTS) and the S082B spectrograph on board Skylab.
Authors: Keenan, F. P.; Cook, J. W.; Doyle, J. G.; Dufton, P. L.;
Hayes, M. A.; Kingston, A. E.
1993uxrs.conf..345K Altcode: 1993uxsa.conf..345K
A comparison of theoretical O IV electron density diagnostics with
observational data from a quiet solar region, a sunspot and an active
region obtained with the High Resolution Telescope and Spectrograph
(HRTS), and a flare observed with the S082B instrument on board Skylab,
reveals that the O IV 1404.8 Å line is not only blended with the S IV
1404.8 Å transition, but also with an unknown feature that contributes
a significant amount to the blend. It is therefore suggested that
line ratios which include the O IV 1404.8 Å transition should not be
employed as density diagnostics.
---------------------------------------------------------
Title: EUV lines of Mg IX as n<SUB>e</SUB>-diagnostics for high
density flares.
Authors: Harra, L. K.; Keenan, F. P.; Widing, K. G.; Conlon, E. S.
1993uxrs.conf..320H Altcode: 1993uxsa.conf..320H
Theoretical Mg IX electron density sensitive emission line ratios,
derived using electron impact excitation rates interpolated from
accurate R-matrix calculations, are presented for R<SUB>1</SUB> =
I(443.97 Å)/I(368.07 Å), R<SUB>2</SUB> = I(439.17 Å)/I(368.07 Å),
R<SUB>3</SUB> = I(443.40 Å)/I(368.07 Å) and R<SUB>4</SUB> = I(441.20
Å)/I(368.07 Å). A comparison of these with observational data for
solar flares, obtained with the Naval Research Laboratory's S082A
spectrograph on board Skylab, reveals excellent agreement between theory
and observation for R<SUB>1</SUB> and R<SUB>2</SUB>, which confirms
the usefulness of these ratios as N<SUB>e</SUB>-diagnostics for solar
flares, as well as providing experimental support for the accuracy
of the atomic data adopted in the line ratio calculations. However
the observed values of both R<SUB>3</SUB> and R<SUB>4</SUB> generally
imply unrealistically high electron densities, which is probably due
to blending in the 443.40 and 441.20 Å lines, possibly with Ar IV
443.44 Å and Mg VI/Mg VII 441.22 Å, respectively.
---------------------------------------------------------
Title: Helium-like Ne IX in the JET tokamak.
Authors: Coffey, I. H.; Barnsley, R.; Keenan, F. P.; Lawson, K. D.;
Peacock, N. J.
1993uxrs.conf..537C Altcode: 1993uxsa.conf..537C
New calculations are presented of the electron density sensitive
emission line ratio R = I(1s<SUP>2</SUP> <SUP>1</SUP>S<SUB>0</SUB>
- 1s2s <SUP>3</SUP>S<SUB>1</SUB>)/ I(1s<SUP>2</SUP>
<SUP>1</SUP>S<SUB>0</SUB> - 1s2p <SUP>3</SUP>P<SUB>1,2</SUB>),
and the electron temperature sensitive emission line
ratios G = [I(1s<SUP>2</SUP> <SUP>1</SUP>S<SUB>0</SUB> - 1s2s
<SUP>3</SUP>S<SUB>1</SUB>) + (1s<SUP>2</SUP> <SUP>1</SUP>S<SUB>0</SUB>
- 1s2p <SUP>3</SUP>P<SUB>1,2</SUB>)]/ I(1s<SUP>2</SUP>
<SUP>1</SUP>S<SUB>0</SUB> - 1s2p <SUP>1</SUP>P<SUB>1</SUB>) and
R<SUB>1</SUB> = I(1s<SUP>2</SUP> <SUP>1</SUP>S<SUB>0</SUB> - 1s3p
<SUP>1</SUP>P<SUB>1</SUB>)/ I(1s<SUP>2</SUP> <SUP>1</SUP>S<SUB>0</SUB>
- 1s2p <SUP>1</SUP>P<SUB>1</SUB>). They are compared with measured
ratios from the JET (Joint European Torus) plasma where the
electron temperature and density have been determined by independent
means. Consideration is given to diffusion effects which cause a
departure from coronal equilibrium conditions, resulting in significant
changes to the G ratio. These measurements are made in the absence
of blending with Fe XVIII, Fe XIX and Na X lines which are sources
of error in solar measurements. Good agreement with theory is found,
with discrepancies of typically less than 10%. This implies that the
theoretical results may be applied to the analysis of remote plasma
sources for which no independent electron density and temperature
estimates exist, such as solar flares and active regions.
---------------------------------------------------------
Title: Energy levels and oscillator strengths for transitions in
helium-like Fe XXV and Ni XXVII.
Authors: Harra, L. K.; Boone, A. W.; Norrington, P. H.; Keenan, F. P.;
Kingston, A. E.
1993uxrs.conf..122H Altcode: 1993uxsa.conf..122H
Configuration interaction (CI) wavefunctions are used to calculate
energy levels and oscillator strengths for all significant electric
dipole (E1), electric quadrupole (E2), magnetic dipole (M1) and magnetic
quadrupole (M2) transitions among the 1s<SUP>2</SUP>, 1s2l and 1s3l
states of He-like Fe XXV and Ni XXVII. Accurate wavefunctions are also
obtained using the fully relativistic MCDF method and similarly employed
to calculate these same energy levels and oscillator strenths. Derived
energy levels are compared to each other and with previous results,
and indicate that the MCDF method gives data which are closer to the
experimental energies. The calculated CI and MCDF A-values are found
to be in good agreement, but differ significantly in some cases from
these and previous authors.
---------------------------------------------------------
Title: Star formation in the galactic halo.
Authors: Keenan, F. P.
1992QJRAS..33..325K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Extreme Ultraviolet Line Ratios for CA XV Applicable to Solar
Flare Spectra
Authors: Keenan, F. P.; Conlon, E. S.; Foster, V. J.; Aggarwal, K. M.;
Widing, K. G.
1992ApJ...401..411K Altcode:
New R-matrix calculations of electron impact excitation rates in
Ca XV are used to derive theoretical electron density diagonstic
emission-line ratios involving 2s2 2p2 - 2s 2p3 transitions in the
wavelength range 180-215 A. A comparison of these with observational
data for solar flares obtained with the Naval Research Laboratory's
S082A spectrograph on board Skylab reveals excellent agreement
between theory and observation, as does a comparison with line ratio
measurements from the TEXT tokamak plasma, for which the electron
temperature and density have been independently determined. This
provides experimental support for the accuracy of the atomic data,
and hence line ratio calculations, employed in the present analysis.
---------------------------------------------------------
Title: Electron density diagnostics for gaseous nebulae involving
the O 4 intercombination lines near 1400 A
Authors: Keenan, F. P.; Conlon, E. S.; Bowden, D. A.; Feibelman,
W. A.; Pradhan, Anil K.
1992STIN...9314762K Altcode:
Theoretical O IV electron density sensitive emission line ratios,
determined using electron impact excitation rates calculated with the
R-matrix code, are presented for R<SUB>1</SUB> = I(1407.4 A)/I(1401.2
A), R<SUB>2</SUB> = I(1404.8 A)/I(1401.2A), R<SUB>3</SUB> = I(1399.8
A)/(1401.2 A), and R<SUB>4</SUB> = I(1397.2 A)/I(1401.2 A). The observed
values of R<SUB>1</SUB>-R<SUB>4</SUB>, measured from high resolution
spectra obtained with the International Ultraviolet Explorer (IUE)
satellite, lead to electron densities that are compatible, and which
are also in good agreement with those deduced from line ratios in
other species. This provides observational support for the accuracy
of the atomic data adopted in the present calculations.
---------------------------------------------------------
Title: The Origin of Distant B-Type Stars in the Galactic Halo
Authors: Conlon, E. S.; Dufton, P. L.; Keenan, F. P.; McCausland,
R. J. H.; Holmgren, D.
1992ApJ...400..273C Altcode:
Model atmosphere analyses of seven high-latitude faint blue stars
reveal them to be normal Population I objects at typical z-distances
of 4 kpc or more. A comparison of the stellar ages with the time that
would be required to reach their present locations following ejection
from the disk shows that the four objects, PB 5418, TS 195, TS 308,
and PHL 2018 could have formed in the disk. The most likely ejection
mechanism appears to be close gravitational encounters within stellar
clusters, in agreement with previous results (Conlon et al., 1990). The
kinematics of the remaining three stars (SB 357, BD - 15 deg 115, and
BD - 2 deg 3766) are further investigated, together with those of five
high-latitude B-type stars that appear to have formed in the halo,
to establish if disk ejection is possible. For three stars (SB 357,
PG 0832 + 676, and BD - 15 deg 115), star formation in the halo is
the only feasible explanation.
---------------------------------------------------------
Title: Low-dispersion spectroscopy of blue stars from UK Schmidt
Telescope UBVRI survey.
Authors: Holmgren, D. E.; McCausland, R. J. H.; Dufton, P. L.; Keenan,
F. P.; Kilkenny, D.
1992MNRAS.258..521H Altcode:
We present analyses of SAAO low-dispersion spectra and COSMOS
photographic photometry of 49 B-type stellar candidates selected
from the United Kingdom Schmidt Telescope UBVRI survey. Four of the
stars are possibly normal B-type stars at large z-distances from the
galactic plane. For these objects, we present approximate atmospheric
parameters based on a comparison of the stellar H-gamma lines with
theoretical profiles, and spectral types based on MK classification
and the Johnson Q parameter. Spectral types are also provided for the
remaining stars, which are OB-type subdwarfs.
---------------------------------------------------------
Title: A recalculation of the line emissivities for the strongest
UV and extreme-UV lines in the 400-2800 A wavelength range
Authors: Doyle, J. G.; Keenan, F. P.
1992A&A...264..173D Altcode:
Using the most recent atomic data we re-calculate line emissivities
for the strongest transitions in the 400-2800 A region. These line
emissivities may be used to construct emission measure curves for
either observed ultraviolet/extreme ultraviolet solar features or
ultraviolet observations of stellar sources. The new tables contain
several lines not in the original Raymond and Doyle tables.
---------------------------------------------------------
Title: X-Ray Emission-Line Ratios in MG XI as Electron Temperature
Diagnostics for Solar Flares and Active Regions
Authors: Keenan, F. P.; Phillips, K. J. H.; Harra, L. K.; Conlon,
E. S.; Kingston, A. E.
1992ApJ...393..815K Altcode:
Electron temperature-sensitive emission-line ratios are derived via
electron impact excitation rates for transitions in helium-like Mg
XI, calculated with the R-matrix code. These ratios are found to be
significantly different from earlier diagnostic calculations of Keenan
et al. (1984, 1991), and lead to electron temperature estimates up to
a factor of about 1.6 larger. Values of Te deduced from R<SUB>1</SUB>
and R<SUB>2</SUB> ratios measured from solar flare and active region
spectra obtained with the FCS on board the SMM satellite are consistent
and in good agreement with temperatures estimated from the observed
G ratios for these solar features. This provides support both for the
validity of the theoretical R<SUB>1</SUB> and R<SUB>2</SUB> diagnostics,
and for the FCS calibration curve in the wavelength region covering
the Mg XI transitions 7.472-9.314 A.
---------------------------------------------------------
Title: Hot Post--Asymptotic Giant Branch Stars at High Galactic
Latitudes
Authors: McCausland, R. J. H.; Conlon, E. S.; Dufton, P. L.; Keenan,
F. P.
1992ApJ...394..298M Altcode:
Model atmosphere analyses are presented for high-resolution spectra
of four stars at high Galactic latitudes. Although their derived
atmospheric parameters are consistent with their previous classification
as early B-type stars, their chemical compositions are significantly
different from those expected for Population I objects. However both
the chemical compositions and atmospheric parameters appear to be
consistent with a post-asymptotic giant branch evolutionary status.
---------------------------------------------------------
Title: AI II as an electron density diagnostic for the upper
chromosphere/lower transition region in late-type stars.
Authors: Doyle, J. G.; Keenan, F. P.; Harra, L. K.; Aggarwal, K. M.;
Tayal, S. S.
1992A&A...261..285D Altcode:
The ratio of the Al II resonance line 3s2 1S-3sp 1P1 at 1670 A to the
inter-system line 3s2 1S-3s3p 3P1 at 2669 A is a useful electron density
diagnostic for N(e) greater than 10 exp 10/cu cm. However, it is also
sensitive to the adopted electron temperature, and, in fact, should
be a useful electron temperature diagnostic when Ne is not greater
than 10 exp 9/cu cm. In particular, we present observational data for
the RS CVn star II Peg and show that this ratio implies an electron
pressure substantially less than that implied from other diagnostic
line ratios but in good agreement with the pressure derived from the
C III 1176/C III 1908 ratio. We suggest additional observational and
theoretical work that may be required.
---------------------------------------------------------
Title: Improved Calculations for the C III lambda lambda 1907,1909
and SI III lambda lambda 1883,1892 Electron Density Sensitive
Emission-Line Ratios, and a Comparison with IUE Observations
Authors: Keenan, F. P.; Feibelman, W. A.; Berrington, K. A.
1992ApJ...389..443K Altcode:
Atomic data are used in conjunction with the statistical equilibrium
code of Dufton (1977) to calculate relative C III and Si III level
populations, and hence emission-line strengths for a range of electron
temperatures and densities. It is assumed that photoexcitation and
deexcitaton rates are negligible in comparison with the corresponding
collisional rates, that ionization to and recombination from other
ionic levels are slow compared with bound-bound rates, and that all
transitions are optically thin. The observed values of R1 and R2
for several planetary nebulae and a symbiotic star, measured from
high-resolution spectra obtained with the IUE satellite, lead to
electron densities that are compatible, and are also in good agreement
with those deduced from line ratios in other species.
---------------------------------------------------------
Title: NE V Line Ratios in the EUV Spectra of Solar Flares
Authors: Keenan, F. P.; Conlon, E. S.; Harra, L. K.; Aggarwal, K. M.;
Widing, K. G.
1992ApJ...389..440K Altcode:
Theoretical line ratios involving 2s22p2-2s2p3 transitions in Ne
V between 359 and 572 A are presented. A comparison of these with
solar-flare observational data from the spectrograph on board Skylab
reveals excellent agreement between theory and experiment, with
discrepancies that average only 8 percent. This provides experimental
support for the accuracy of the atomic data adopted in the line-ratio
calculations, and in addition resolves discrepancies between theory
and observations previously found for this species. The potential
usefulness of the Ne V line ratios as electron temperature diagnostics
for the solar transition region is briefly discussed.
---------------------------------------------------------
Title: The Oscillator Strength of the SI II 3s 23p 2P--3 s3p 2 2D
Multiplet and the Interstellar Abundance of Silicon
Authors: Dufton, P. L.; Keenan, F. P.; Hibbert, A.; Ojha, P. C.;
Stafford, R. P.
1992ApJ...387..414D Altcode:
Spontaneous radiative rates, calculated using sophisticated
configuration interaction wavefunctions, are presented
for Si II resonance transitions in the 3s<SUP>2</SUP>3p
<SUP>2</SUP>P<SUB>j</SUB>-3s3p<SUP>2</SUP> <SUP>2</SUP>D<SUB>j</SUB>
multiplet. For the J = 1/2 to J' = 3/2 transition, an oscillator
strength of 0.0020 (with an estimated uncertainty of 25%) is
deduced. This value is significantly lower than those found in some
previous studies; the reasons for this and in particular the crucial
role of the energy splitting of the 3s<SUP>3</SUP>P<SUP>2</SUP>
<SUP>2</SUP>D and 3s<SUP>2</SUP>3d <SUP>2</SUP>D levels are
investigated. The implication of these new atomic data for gas phase
silicon abundances in the interstellar medium is briefly discussed.
---------------------------------------------------------
Title: Solar SI II Line Ratios from the High-Resolution Telescope
and Spectrograph
Authors: Keenan, F. P.; Cook, J. W.; Dufton, P. L.; Kingston, A. E.
1992ApJ...387..726K Altcode:
Theoretical emission-line ratios involving multiplets near 1262,
1306, and 1530 A are derived on the basis of new calculations of
electron-impact excitation rates for allowed transition in Si II. A
comparison of these line ratios with observational data from a quiet
solar region, a sunspot, and an active region, obtained with the HIRTS
on board a sounding rocket flight reveals that the 1530-A multiplet
is optically thick, which is consistent with a calculation of the
optical depth of these lines through a model atmosphere. The 1262-
and 1306-A multiplets appear to be effectively optically thin. The
average discrepancy between the theoretical and observed ratios is
about 40 percent, which may not be significant, since the estimated
uncertainties in both the calculated and experimental data are
approximately 30 percent.
---------------------------------------------------------
Title: MG IX Line Ratios in the Sun
Authors: Keenan, F. P.; Conlon, E. S.; Harra, L. K.; Widing, K. G.
1992ApJ...386..371K Altcode:
Attention is given to theoretical Mg IX electron density sensitive
emission-line ratios derived using electron impact excitation rates
interpolated from accurate R-matrix calculations, which are presented
for R1 = I(443.97 A)/I(368.07 A), R2 = I(439.17 A)/I(368.07 A), R3 =
I(368.07 A)/I(443.07 A), and R4 = I(441.20 A)/I(368.07 A). A comparison
of these with observational data for solar flares on board Skylab
reveals excellent agreement between theory and observation for R1 and
R2, which confirms the usefulness of these ratios as Ne-diagnostics for
solar flares, as well as providing experimental support for the accuracy
of the atomic data adopted in the line ratio calculations. The observed
values of both R3 and R4 generally imply unrealistically high electron
densities, which is argued to be due to blending in the 443.40- and
441.20-A lines, probably with Ar IV 443.44 A and Mg VI/Mg VII 441.22
A, respectively.
---------------------------------------------------------
Title: AL II Emission-Line Strengths in Low-Density Astrophysical
Plasmas
Authors: Keenan, F. P.; Harra, L. K.; Aggarwal, K. M.; Feibelman, W. A.
1992ApJ...385..375K Altcode:
Theoretical values of the emission-line ratio R are derived for the
transitions 3s2 1S-3s3p 3P2 and 3s2 1S-3s3p 3P1 in Al II, at 2660 and
2669 A, respectively. These ratios are compared with IUE observations
of the planetary nebula NGC 7027 and the symbiotic star RR Tel, to
illustrate the usefulness of the R as an electron density diagnostics. A
value of R = 0.72 was deduced for NGC 7027, which implies log Ne =
4.2 for Te = 14,000 K. This is consistent with densities deduced
earlier for this planetary nebula.
---------------------------------------------------------
Title: Fe XVIII Emission-Line Intensities in the Sun
Authors: McKenzie, D. L.; Keenan, F. P.; McCann, S. M.; Berrington,
K. A.; Hibbert, A.; Mohan, M.
1992ApJ...385..378M Altcode:
Recently calculated electron-impact excitation rates among the 2s2 2p5,
2s2p6, and 2s2 2p4nl levels of Fe XVIII are used to derive theoretical
emission-line ratios applicable to solar X-ray spectra. Oscillator
strengths for all levels with n of less than or equal to 3 are used
to take cascade involving the levels fully into account. Overall,
the agreement between the theory and spectra measured by crystal
spectrometers aboard the OV 1-17, P78-1, and SMM satellites is good. The
effects of cascade from levels for which n is at least 4 are small, at
least for the strongest lines. The labor required to take into account
these higher levels is not justified by the current discrepancies
between theory and observation.
---------------------------------------------------------
Title: Level Populations for Fe III Applicable to Astrophysical
Plasmas and a Comparison with Planetary Nebula Observations
Authors: Keenan, F. P.; Berrington, K. A.; Burke, P. G.; Zeippen,
C. J.; Le Dourneuf, M.; Clegg, R. E. S.
1992ApJ...384..385K Altcode:
Recent R-matrix calculations of electron impact excitation rates in
Fe III, which are significantly different from the earlier results of
Garstang, Robb, & Rountree, are used to derive relative populations
for the 17 fine-structure levels in the <SUP>5</SUP>D, <SUP>3</SUP>P,
<SUP>3</SUP>H, <SUP>3</SUP>F, and <SUP>3</SUP>G states of the
3d<SUP>6</SUP> configuration. Populations are presented for a wide range
of electron temperatures (T<SUB>e</SUB> = 5000-20,000 K) and densities
(N<SUB>e</SUB> = 10<SUP>2</SUP>-10<SUP>9</SUP> cm<SUP>-3</SUP>)
applicable to astrophysical plasmas. A comparison of theoretical
emission-line ratios generated using these results with observational
data for the planetary nebulae DDDM-1, Vy 2-2, and NGC 7027 reveals
general agreement between theory and observation, with discrepancies
that average only 10%. In addition, the present calculations remove
the disagreement found between theory and observation for the I(4881
Å)/I(4658 Å) line intensity ratio in DDDM-1 when the theoretical
ratios of Garstang et al. are adopted, which provides experimental
support for the accuracy of the current results.
---------------------------------------------------------
Title: C IV Line Ratios in the Sun
Authors: Keenan, F. P.; Conlon, E. S.; Harra, L. K.; Burke, V. M.;
Widing, K. G.
1992ApJ...385..381K Altcode:
Theoretical electron temperature-sensitive emission-line ratios are
calculated with R-matrix analysis of electron-impact excitation
rates for transitions in C IV. Two of the emission-line ratios
are found to agree with observational data on the sun taken with
a slitless spectrograph aboard Skylab, and the two remaining lines
have inaccuracies that can be attributed to blending of the 312.43
A line. The agreement between the observational and analytical data
lends credence to the accuracy of the atomic data used in the analysis.
---------------------------------------------------------
Title: X-ray emission-line ratios in He-like ions as
electron-temperature diagnostics for solar flares and active regions
(abstract)
Authors: Harra, L. K.; Phillips, K. J. H.; Keenan, F. P.; Bromage,
B. J. I.; McCann, S. M.
1992sccw.conf..144H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Spectroscopic Line Diagnostics (abstract)
Authors: Keenan, F. P.
1992sccw.conf..143K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The origin of distant B-type stars in the galactic halo
Authors: Conlon, E. S.; McCausland, R. J. H.; Dufton, P. L.; Keenan,
F. P.; Holmgren, D. E.
1992LNP...401...37C Altcode: 1992aets.conf...37C
Using model atmosphere analyses of high resolution optical spectra,
we have identified a group of young B-type stars at large distances
from the galactic plane. A study of the kinematics and evolutionary
ages of these objects reveals two groups of stars: those that could
have formed in the disc and travelled to their present locations
in their lifetimes and those that could not. The kinematics of the
first group are in agreement with results from N-body simulations of
dynamical ejection from young galactic star clusters. For the stars
that could not have formed in the disc, star formation in the halo
via collisions within intermediate and high velocity clouds appears
the most likely explanation.
---------------------------------------------------------
Title: The determination of accurate cosmic abundances from B-type
stellar spectra
Authors: Brown, P. J. F.; Dufton, P. L.; Keenan, F. P.; Holmgren,
D. E.; Warren, G. A.
1992LNP...401...33B Altcode: 1992aets.conf...33B
We have obtained high-resolution, high-signal-to noise observations
of weak A II and O II absorption lines formed in the atmospheres of
main-sequence early-type stars. The observed line strengths have
been combined with equally well determined oscillator strengths,
in an analysis which used both LTE and non-LTE model atmosphere
techniques. Cosmic argon and oxygen abundances (on a logarithmic scale
with hydrogen = 12) of [A] = 6.49 and [O] 8.93 have been determined;
these should have an accuracy of ±0.05 dex.
---------------------------------------------------------
Title: Blue post-asymptotic giant branch stars at high galactic
latitude
Authors: McCausland, R. J. H.; Conlon, E. S.; Dufton, P. L.; Keenan,
F. P.
1992LNP...401..301M Altcode: 1992aets.conf..301M
Model atmosphere analyses are presented for high resolution spectra of
six stars at high galactic latitude. Although their derived atmospheric
parameters are consistent with their previous classification as early
B-type stars, their metal abundances are significantly different from
those expected for Population I objects. However both their chemical
composition and atmospheric parameters appear consistent with a Post
Asymptotic Giant Branch evolutionary status. Additional evidence for
this hypothesis is present in the spectra of one star (LS IV-12° 111),
where its higher effective temperature is sufficient to excite emission
lines from the surrounding nebula.
---------------------------------------------------------
Title: The SI II intercombination multiplet in late-type stars.
Authors: Dufton, P. L.; Keenan, F. P.; Hibbert, A.; Stafford, R. P.;
Byrne, P. B.; Agnew, D.
1991MNRAS.253..474D Altcode:
New atomic data are used to calculate the relative intensities of
transitions within the Si II 3s(2)3p(2)P-3s3p(2) 4P intercombination
multiplet for plasma parameters appropriate to late-type stellar
atmospheres. These ratios are found to be significantly different from
those of Dufton and Kingston, (1991), principally due to changes in
the radiative rates. A comparison with line ratios for the sun (from
Skylab S082B spectra) and late-type stars (from IUE data) indicates
that although the new theoretical line ratios are in better agreement
with observation, significant discrepancies still exist. Possible
explanations for these discrepancies are briefly discussed.
---------------------------------------------------------
Title: The Ratio of Optical to Near Infrared Emission Line Strengths
in SII as Electron Density Diagnostics for Planetary Nebulae
Authors: Keenan, F. P.
1991Ap&SS.186..277K Altcode:
EinsteinA-coefficients for transitions in Sii, calculated with
the atomic structure package CIV3, are used to derive the electron
density sensitive emission line ratio {{R_1 = I(3s^2 3p^3 {}^2D_{{5
{/ {5 2}} 2}} - 3s^2 3p^3 {}^2P_{{3 {/ {3 2}} . 2}} )} {/ {{R_1 =
I(3s^2 3p^3 {}^2D_{{5 {/ {5 2}} . 2}} - 3s^2 3p^3 {}^2P_{{3 {/
{3 2}} 2}} )} {I(3s^2 3p^3 {}^4S_{{3 {/ {3 2}} right. 2}} - 3s^2
3p^3 {}^2D_{{3 {/{3 2}} 2}, {5 {/ {5 2}} 2}} ) = }}} {I(3s^2 3p^3
{}^4S_{{3 {/ {3 2}} 2}} - 3s^2 3p^3 {}^2D_{{3 {/ {3 2}} 2}, {5 {/
{5 2}} 2}} ) = }} \ {{ = I(10320{Å})} {/ {{ = I(10320{Å})} {I(6717
+ 6730{Å})}}} {I(6717 + 6730{Å})}} \ for a range of electron
temperatures (T <SUB> e </SUB>=5000 20000K) and densities (N <SUB>
e </SUB>=10<SUP>2</SUP> 10<SUP>5</SUP> cm <SUP>-3</SUP>) applicable to
planetary nebulae. Electron densities deduced from the observed values
ofR <SUB>1</SUB> in several planetaries are in excellent agreement
with those derived fromN <SUB> e </SUB>-sensitive line ratios in other
species, which provides observational support for the accuracy of the
atomic data adopted in the calculations.
---------------------------------------------------------
Title: Effective collision strengths among fine-structure levels of
CA XV: erratum
Authors: Aggarwal, K. M.; Berrington, K. A.; Keenan, F. P.
1991ApJS...77..441A Altcode:
An error has been found in the calculation of Aggarwal et al. made
in 1990, due to a mistake in the term coupling coefficients used to
transform the collision strengths to intermediate coupling. The 190
fine-structure transitions among the 1s(2)2s(2)2p(2), 1s(2)2s2p(3),
and 1s(2)2p(4) configurations of Ca XV are therefore corrected and
retabulated. Major differences between the R-matrix calculation of
Aggarwal et al. and the distorted wave method of Dere et al. have now
been resolved though minor differences still remain. The effective
collision strengths obtained after averaging the collision strengths
over a Maxwellian distribution of electron velocities are also presented
in the temperature range below 10 exp 7 K.
---------------------------------------------------------
Title: Improved Line Ratio Calculations Involving Delta N = 1
(2--3) Transitions in O V and a Reanalysis of SKYLAB Observations
of Solar Flares
Authors: Keenan, F. P.; Dufton, P. L.; Harra, L. K.; Conlon, E. S.;
Berrington, K. A.; Kingston, A. E.; Widing, K. G.
1991ApJ...382..349K Altcode:
R-matrix calculations of electron-impact-excitation rates in O
V are used to rederive theoretical electron-density diagnostic
emission-line ratios involving transitions between the n = 2 and 3
levels, which includes lines at 192.80, 192.90, 215.10, 215.25, 220.35,
and 248.46 A. A comparison of these diagnostics with observational
data for two solar flares obtained with the spectrograph on board
Skylab reveals better agreement between theory and observation than was
found previously. This provides experimental support for the improved
accuracy of the atomic data employed in the present analysis.
---------------------------------------------------------
Title: A comparison of theoretical Fe xii emission line strengths
with EUV observations of a solar active region
Authors: Keenan, F. P.; Doyle, J. G.; Tayal, S. S.; Henry, R. J. W.
1991SoPh..135..353K Altcode:
New theoretical electron-density-sensitive Fe XII emission line
ratios R<SUB>1</SUB> = I(3s<SUP>2</SUP>3p<SUP>34</SUP>S<SUB>3/2</SUB> -
3s3p<SUP>44</SUP>P<SUB>5/2</SUB>)/I(3s<SUP>2</SUP>3p<SUP>32</SUP>P<SUB>3/2</SUB>
- 3s3p<SUP>4</SUP>D<SUB>5/2</SUB> and R<SUB>2</SUB>
= I(3s<SUP>2</SUP>3p<SUP>32</SUP>P<SUB>3/2</SUB> -
3s3p<SUP>42</SUP>D<SUB>5/2</SUB>)/I(3s<SUP>2</SUP>3p<SUP>34</SUP>S<SUB>3/2</SUB>
- 3s3p<SUP>2</SUP>P<SUB>3/2</SUB>) are derived using R-matrix electron
impact excitation rate calculations. We have identified the FeXII and
transitions in an active region spectrum obtained with the Harvard
S-055 spectrometer on board Skylab at wavelengths of 364.0, 382.8,
1241.7, and 1349.4 Å, respectively. Electron densities determined
from the observed values of R<SUB>1</SUB> (log N<SUB>e</SUB> ≃ 11.0)
and R<SUB>2</SUB>(log N<SUB>e</SUB> ≃ 11.4) are significantly larger
than the typical active region measurements, but are similar to those
derived from some active region spectra observed with the Skylab 2082A
instrument, which provides observational support for the atomic data
adopted in the line ratio calculations, and also for the identification
of the Fe XII transitions in the S-055 spectrum. However the observed
value of R<SUB>3</SUB> = I(1349.4 Å)/I(1241.7 Å) is approximately
a factor of two larger than one would expect from theory which,
considering that the 1349.4 Å line lies at the edge of the S-055
wavelength coverage, may reflect errors in the instrument efficiency
curve. Another possibility is that the 1349.4 Å transition is blended,
probably with Si II 1350.1 Å.
---------------------------------------------------------
Title: Heliumlike Mg xi in the divertor-injected tokamak experiment
Authors: Keenan, F. P.; McCann, S. M.; Kingston, A. E.; Barnsley,
R.; Dunn, J.; Peacock, N. J.
1991PhRvA..44.3831K Altcode:
Electron-impact excitation rates for transitions in heliumlike
Mg xi, calculated with the R-matrix code, are used to derive
the electron-density-sensitive emission line ratio R (=f/i)
and temperature-sensitive ratio G [=(f+i)/r], where f is
the forbidden 1s<SUP>2</SUP> <SUP>1</SUP>S-1s2s <SUP>3</SUP>S
transition, i the intercombination 1s<SUP>2</SUP> <SUP>1</SUP>S-1s2p
<SUP>3</SUP>P<SUB>1,2</SUB> lines, and r the resonance 1s<SUP>2</SUP>
<SUP>1</SUP>S-1s2p <SUP>1</SUP>P transition. A comparison of these with
R and G ratios determined from x-ray spectra of the divertor-injected
tokamak experiment reveals excellent agreement between theory and
observation, with discrepancies of typically 3% and 9% in R and
G, respectively. These discrepancies correspond to variations in
N<SUB>e</SUB> and T<SUB>e</SUB> of approximately 0.1 and 0.15 dex,
respectively, and hence it should be possible to use the theoretical
results to derive plasma parameters to this level of accuracy for
remote sources for which no independent electron temperature and
density estimates exist, such as solar flares.
---------------------------------------------------------
Title: The 3s 23p 2 P--3s3p 2 4P Intercombination Lines of Fe XIV
in the Sun
Authors: Keenan, F. P.; Dufton, P. L.; Conlon, E. S.; Boylan, M. B.;
Kingston, A. E.; Widing, K. G.
1991ApJ...379..406K Altcode:
The EUV spectra of solar flares obtained with the Naval Research
Laboratory's S082A slitless spectrograph on board Skylab were
examined, and the five components of the Fe XIV 3s2 3p 2P-3s3p2 4P
intercombination multiplet were previsionally identified. A comparison
of the observed Fe XIV line intensities with theoretical predictions
reveals good agreement between theory and experiment, which tends to
confirm the identifications and those made previously by Trabert, et
al. (1987). The potential usefulness of the lines as electron density
diagnostics is briefly discussed.
---------------------------------------------------------
Title: IUE Observations of Early-Type Stars at High Galactic Latitudes
Authors: Quin, D. A.; Brown, P. J. F.; Conlon, E. S.; Dufton, P. L.;
Keenan, F. P.
1991ApJ...375..342Q Altcode:
High- and low-resolution IUE spectra of 14 apparently normal
high-Galactic latitude B-type stars, together with visual fluxes
determined from Stroemgren four-color photometry, are compared with
theoretical spectra deduced from LTE model atmosphere calculations. Ten
of the program stars have normal flux distributions, with only four of
the stars exhibiting UV flux deficiency. For the latter, PHL 346 has
been identified as a beta Cepheid variable, SB 357 is a Be-type star,
and the ultraviolet flux deficiency for HD 214080 can be removed by
increasing the E(B-V) from 0.09 to 0.12. In the case of HD 100340,
the four-color photometry is inconsistent with the ultraviolet flux
distribution, but this inconsistency vanishes when UBV photometry is
employed in the analysis, implying that the uvby measurements may be in
error. The normal flux distributions found for the program star provide
support for their being Population I objects in the Galactic halo.
---------------------------------------------------------
Title: On the nature of HD 93521, a high galactic latitude O-star.
Authors: Lennon, D. J.; Dufton, P. L.; Keenan, F. P.; Holmgren, D. E.
1991A&A...246..175L Altcode:
Classical non-LTE model atmosphere techniques are used to analyze a high
signal-to-noise, high-resolution spectrum of HD 93521 in the wavelength
region 4070-4510 A. Abundances of nitrogen, oxygen, magnesium, and
silicon were all found to be approximately solar. Attempts to fit the
UV continuum flux with model fluxes imply a UV deficiency relative
to the V-band. The present results are consistent with HD 93521
being a Population I late O-type shell star. It is inferred that the
overabundance of helium is the result of turbulent diffusion, induced
by the star's large rotational velocity, mixing CNO-cycled material
into its atmosphere. It is suggested that HD 93521 is evolving on a
track intermediate between homogeneous and normal evolutionary tracks
and may exhibit moderate changes in CNO surface abundances which are
masked by the star's large projected rotational velocity of 400 km/s.
---------------------------------------------------------
Title: Fe XIV Line Ratios in the Sun
Authors: Keenan, F. P.; Dufton, P. L.; Boylan, M. B.; Kingston, A. E.;
Widing, K. G.
1991ApJ...373..695K Altcode:
Recent R-matrix calculations of electron-impact excitation rates
for Fe XIV are used to derive theoretical electron density-sensitive
emission-line ratios involving transitions in the wavelength range
211-274 A. Electron densities deduced from the observed line ratios
for solar flares and active regions, obtained with the Naval Research
Laboratory's SO82A slitless spectrograph on board Skylab, are in
excellent internal agreement and, furthermore, compare favorably with
densities determined independently from line ratios in Fe XII and Fe
XIII. These results provide experimental support for the accuracy of
the atomic data adopted in the analysis, as well as for the techniques
used to calculate the line ratios.
---------------------------------------------------------
Title: NE V in Planetary Nebulae
Authors: Keenan, F. P.; Burke, V. M.; Aggarwal, K. M.
1991ApJ...371..636K Altcode:
The improved atomic data of Lennon and Burke (1991) are used there to
rederive Ne V diagnostic line ratios applicable to PNe for a range of
electron temperatures and densities. These results are found to be
somewhat different from those determined when the earlier R-matrix
atomic data of Baluja et al. (1980) and Aggarwal (1983) are used in
the line ratio calculations. It is shown that it is unwise to use
R1 or R3 alone as a temperature or density diagnostic, unless the
density or temperature of the Ne V emitting region of the plasma has
been independently determined. However, reliable estimates of both Ne
and Te may be found when R1 and R3 are used together, while R2 may be
used by itself as an accurate Ne diagnostic.
---------------------------------------------------------
Title: Radio and optical observations of high- and
intermediate-velocity gas in the nearby interstellar medium.
Authors: Bates, B.; Catney, M. G.; Gilheany, S.; Keenan, F. P.;
Davies, R. D.; Hummel, E.
1991MNRAS.249..282B Altcode:
Using observations at the 21-cm wavelength obtained with the Lovell
Telescope the authors report on the detection of a weak H I emission
feature at a velocity +100 km s<SUP>-1</SUP> LSR and of column density
log N(H I) = 18.5±0.2) towards the star 4 Lac. The feature corresponds
in velocity with a high-velocity gas component which the authors have
observed in several UV resonance lines in IUE spectra of this star. The
component gas temperature which is derived from radio, optical and UV
spectra lies in the range 5000 to 9000K and the line-of-sight column
thickness is estimated to be less than 10 pc. The relationship between
this observed feature and the widely distributed High-Velocity Clouds
(HVCs) is considered briefly. H I components are detected also at
intermediate velocities (between -20 and +25 km s<SUP>-1</SUP>) which
vary significantly on an angular scale ≍0°1. Towards the star 4 Lac,
components are observed in Na I within the same velocity range. If,
as the authors suggest, the H I and Na I components correspond, then
the intermediate-velocity gas lies in the foreground to the star and
the observed spatial variations occur on a scale ⪉2 pc.
---------------------------------------------------------
Title: Infrared observations of high galactic latitude early-type
stars.
Authors: Fitzsimmons, A.; Keenan, F. P.; Conlon, E. S.; Dufton, P. L.;
Williams, P. M.
1991MNRAS.249..336F Altcode:
Infrared photometry of four relatively faint (8.5 ≤ V ≤ 11.0)
early-type stars at high galactic latitude has been made in the J,
H, K, L' and narrow-band M wavelengths. This has been combined with
previously published ultraviolet and visible observations to enable
a comparison with LTE model atmosphere fluxes. The results imply that
at least three of the stars are normal main-sequence B-stars at large
distances from the galactic plane.
---------------------------------------------------------
Title: Fe XII Line Ratios in Solar Flares
Authors: Tayal, S. S.; Henry, Ronald J. W.; Keenan, F. P.; McCann,
S. M.; Widing, K. G.
1991ApJ...369..567T Altcode:
Relative level populations and the density-sensitive emission-line
ratios R1 = I(186.87 A)/I(193.51 A), R2 = I(196.64 A)/I(193.51 A),
and R3 = I(191.05 A/I(193.51 A) are derived using the recent R-matrix
calculations of electron impact excitation rates for Fe XII over a
wide range of electron densities (10 to the 9th - 10 to the 12th/cu
cm) and at an electron temperature of 1.5 x 10 to the 6th K. These
results are applied to solar active region and flare spectra obtained
by the Naval Research Laboratory's S082A slitless spectrograph on board
Skylab. Excellent agreement is found with observations. The electron
densities deduced from Fe XII line ratios are also in agreement with
those determined from Fe XIII and Fe XIV.
---------------------------------------------------------
Title: Theoretical Emission Line Strengths for Nevii Compared to
Extreme Ultraviolet Solar Observations
Authors: Keenan, F. P.
1991SoPh..131..291K Altcode:
Theoretical electron-temperature-sensitive Ne VII emission line ratios,
calculated using accurate R-matrix electron impact excitation rates, are
presented for R<SUB>1</SUB> = I(895.2 Å)/I(465.2 Å), R<SUB>2</SUB>
= I(561.7 Å)/I(465.2 Å) and R<SUB>3</SUB> = I(564.5 Å)/I(465.2
Å). A comparison of these with observational data for several solar
features obtained with the Harvard S-055 spectrometer on board Skylab
reveals good agreement between theory and experiment. This provides
observational support for the accuracy of the atomic physics adopted
in the calculations, and the methods employed in the derivation of
the theoretical diagnostics.
---------------------------------------------------------
Title: Two early-type POST AGB stars at high galactic latitudes.
Authors: Conlon, E. S.; Dufton, P. L.; Keenan, F. P.; McCausland,
R. J. H.
1991MNRAS.248..820C Altcode:
Two high galactic latitude B-type stars, PHL 1580 and PHL 174,
originally identified as distant early-type objects from low-resolution
spectroscopy and photometry are re-analyzed using high-resolution
spectra. The results of LTE and non-LTE model atmosphere analyses reveal
general metal underabundances relative to solar values of typically
0.6 and 1.0 dex for PHL 1580 and PHL 174, respectively. For both stars
carbon is significantly more underabundant. The anomalous compositions
are compatible with those of other high galactic latitude post-AGB
objects, while the derived atmospheric parameters are coincident with
post-AGB evolutionary tracks. Thus it appears that PHL 1580 and PHL 174
are low-mass post-AGB objects at an evolutionary stage intermediate
between those of the A-, F- and G-type objects and planetary nebulae
previously identified. The severe carbon deficiency may be evidence
that both objects left the AGB before the products of the CNO bi-cycle
were mixed to the stellar surface.
---------------------------------------------------------
Title: Relative Populations for Levels in the 3d 2 Ground
Configuration of Fe VII
Authors: Keenan, F. P.; Norrington, P. H.
1991ApJ...368..486K Altcode:
R-matrix calculations of electron impact exxcitation rates in Fe VII are
used to derive relative populations for all levels in the 3d2 ground
configuration. Results are presented for a wide range of electron
temperatures and densities applicable to astrophysical plasmas. The
calculations are used in conjunction with observed emission-line ratios
for the planetary nebula NGC 7027 to derive the electron temperature
of the Fe VII-emitting region, which is found to be in good agreement
with the values of Te deduced from other highly ionized species in
the planetary.
---------------------------------------------------------
Title: Electron density diagnostics for Ti XIV in high temperature
plasmas
Authors: Keenan, F. P.; Hibbert, A.; Reid, R. H. G.; Mohan, M.;
Baluja, K. L.
1991PhyS...43..147K Altcode:
Recent R-matrix calculations of electron excitation rates for
transitions in Ti XIV are used to derive two different theoretical
emission-line ratios as a function of the electron density values
from 10 to the 10 to 10 to the 14/cu cm. The density values are
applicable to astrophysical and tokamak plasmas. The results
are found to be significantly different from those deduced if the
distorted-wave electron rates of Bhatia et al. (1985) are adopted in
the calculations. The results also lead to electron density estimates
between a factor of 1.6 larger and 30 percent smaller for electron
temperatures in the 1.5-6 x 10 to the 6 K range.
---------------------------------------------------------
Title: The Determination of Element Abundances in the Solar
Neighborhood from B-Type Stellar Spectra. II. Non--LTE Calculations
for AR II
Authors: Holmgren, D. E.; Brown, P. J. F.; Dufton, P. L.; Keenan, F. P.
1990ApJ...364..657H Altcode:
Non-LTE radiative transfer calculations for argon are presented for
models with effective temperatures in the range 17,500-30,000 K and a
logarithmic argon abundance of 6.50 on the scale log (H) = 12. These
are used to analyze high-resolution and signal-to-noise observations of
weak Ar II lines in the spectra of B-type stars. A mean argon abundance
of 6.50 + or - 0.05 dex is found, providing a reliable estimate of
the current cosmic argon abundance in the solar neighborhood.
---------------------------------------------------------
Title: The 1 1S--n 1P/1 1S--2 1P Emission-Line Ratios in SI XIII as
Electron Temperature Diagnostics for Solar Flares and Active Regions
Authors: Keenan, F. P.; McCann, S. M.; Phillips, K. J. H.
1990ApJ...363..310K Altcode:
Theoretical Si XIII emission-line ratios R1, R2, and R3 are presented
as a function of electron temperature. These ratios are found to be
more electron temperature sensitive than the commonly used diagnostic
for He-like ions (G), with, for example, R1, R2, and R3 varying by
factors of approximately 6, 12, and 17 between log Te = 6.2 and 7.2,
while G only changes by a factor of 1.8. In addition, R1, R2, and R3
are less dependent on whether or not the Si XIII-emitting plasma is in
ionization equilibrium. Electron temperatures deduced using the observed
values of R1, R2, and R3 from OV 1-17 and OSO 8 satellite spectra of
solar flares and active regions are in good agreement and, in general,
compared favorably with those determined from G. However, in the case of
measurements made with the Flat Crystal Spectrometer on board the Solar
Maximum Mission satellite there are large discrepancies between theory
and observation. Possible explanations for these are briefly discussed.
---------------------------------------------------------
Title: NE VII Line Ratios in the Sun
Authors: Keenan, F. P.; McCann, S. M.; Widing, K. G.
1990ApJ...363..315K Altcode:
Theoretical Ne VII electron density sensitive emission-line ratios,
derived using electron impact excitation rates calculated with the
R-matrix code, are presented for R1 = I(561.7 A)/I(465.2 A) and R2 =
I(561.4 A)/I(465.2 A). A comparison of these with observational data
for solar flares, obtained with the Naval Research Laboratory's S082A
spectrograph on board Skylab, reveals excellent agreement between
theory and observation, which confirms the usefulness of R1 and R2
as Ne diagnostics for solar flares, as well as providing experimental
support for the accuracy of the atomic data adopted in the line ratio
calculations.
---------------------------------------------------------
Title: The runaway nature of distant early-type stars in the
galactic halo.
Authors: Conlon, E. S.; Dufton, P. L.; Keenan, F. P.; Leonard, P. J. T.
1990A&A...236..357C Altcode:
The kinematics of a sample of 32 distant halo B-stars with masses
in the range 3-21 solar masses are investigated using the current
'runaway star' hypotheses to establish if they belong to this group
of stars. Whether postmass transfer secondaries in evolved massive
close binaries can be normal low mass B-stars is discussed, but
support for this idea is not found. Thus it appears that the lower
mass stars could not have been ejected out of the disk as a result
of supernova explosions in massive close binaries, while the higher
mass objects do not in general reveal a binary nature as expected from
this theory. The results of recent N-body simulations of the purely
dynamical ejection of runaway stars from young galactic star clusters
are in excellent agreement with the observations. Thus it appears that
these halo stars are the most distant subgroup of OB runaways produced
by cluster ejection yet observed.
---------------------------------------------------------
Title: Determination of Cosmic Abundances
Authors: Keenan, F. P.
1990IrAJ...19..158K Altcode:
Accurate contemporary cosmic abundances are derived using weak stellar
absorption lines observed in the spectra of main sequence early-type
stars. Initially, weak lines of argon are observed by comparing measured
stellar Stromgren colors, beta indices, and Ar II equivalent widths with
those predicted by local thermodynamic equilibrium model atmosphere
codes. A mean abundance of 6.49 + or - 0.04 dex is obtained, and this
value is considered to represent an accurate assessment of the current
cosmic abundance value of argon in the solar neighborhood. This result
is compared with those of experiments, and it is pointed out that the
error estimate in this study is 12 percent or less.
---------------------------------------------------------
Title: IUE, optical and radio observations of high-velocity gas
components in the nearby interstellar medium
Authors: Gilheany, S.; Bates, B.; Catney, G.; Keenan, F. P.; Davies,
R. D.
1990ESASP.310..489G Altcode: 1990eaia.conf..489G
No abstract at ADS
---------------------------------------------------------
Title: A Comparison of Theoretical SV Emission Line Strengths with
Extreme Ultraviolet Observations of a Sunspot
Authors: Keenan, F. P.; Doyle, J. G.
1990SoPh..128..345K Altcode: 1990IAUCo.121P.345K
Electron impact excitation rates for transitions in the S v ion,
calculated with theR-matrix code, are used to derive the electron
temperature sensitive emission line ratiosR<SUB>1</SUB> =I(854.8
Å)/I(786.9 Å),R<SUB>2</SUB> =I(852.2 Å)/I(786.9 Å),R<SUB>3</SUB>
=I(849.2 Å)/I(786.9 Å), andR<SUB>4</SUB> =I(1199.1 Å)/I(786.9 Å),
which are found to be significantly different from previous estimates. A
comparison of the present results with observational data for a sunspot
obtained with the Harvard S-055 spectrometer on boardSkylab reveals
generally good agreement between theory and experiment, except in the
case ofR<SUB>1</SUB>, which is probably due to blending in the 854.8
Å feature. The possible effects of Lyman continuum absorption on the
observed line ratios is briefly discussed.
---------------------------------------------------------
Title: Solar chlorine abundance from an X-ray flare spectrum
Authors: Phillips, K. J. H.; Keenan, F. P.
1990MNRAS.245P...4P Altcode:
The solar coronal chlorine abundance is estimated from a weak X-ray line
seen during a flare. The line intensity is compared with a nearby sulfur
line with very similar contribution function. The chlorine abundance
obtained is very similar to the only other positive determination for
the sun, from HCl lines in a sunspot spectrum.
---------------------------------------------------------
Title: High Resoltuion Interstellar and Stellar Line Profiles of
the Stars in the Globular Cluster M22
Authors: Bates, B.; Catney, M. G.; Keenan, F. P.
1990MNRAS.245..238B Altcode:
High-resolution (∼5 km s<SUP>-1</SUP> FWHM) spectra have been
obtained for stars in the globular cluster M22 using the University
College London echelle spectrograph (UCLES) at the coudé focus of
the AAT. The prime objective was a study of the fine-scale spatial
structure of the line-of-sight gas through observations of the Na
D lines. Essentially the gas towards the cluster at distance ∼ 6
kpc is concentrated in two components at the approximate velocities
(LSR) of + 6 and + 37 km s<SUP>-1</SUP>. The lower velocity material
is likely to be part of a nearby H I cloud, first mapped in the radio
region, in which case the spatial sampling in the present study has
a scale < 0.3 pc. The higher velocity gas varies from a single
component to a multiple component structure over the angular extent
of the cluster. The distance to this material is less certain but
it may be associated with the Sagittarius arm. New observations are
presented also for the stellar Hα and Na D lines. Time variability of
Hα emission and Na D line asymmetry are detected for two stars. The
present data are in qualitative agreement with models for mass loss
occurring in expanding, circumstellar envelopes.
---------------------------------------------------------
Title: N IV line ratios in the Sun
Authors: Keenan, F. P.
1990SoPh..126..311K Altcode:
Theoretical NIV emission line ratios, which incorporate several
improvements over previous estimates, are presented for R<SUB>1</SUB> =
I(923.2 Å)/I(765.1 Å) and R<SUB>2</SUB> = I(1718.6 Å)/I(1486.5 Å),
which are electron density and temperature sensitive, respectively. A
comparison of R<SUB>1</SUB> with observational data for several solar
features obtained with the Harvard S-055 spectrometer on board Skylab
reveals generally good agreement between theory and observation, except
for the quiet Sun, which is probably due to the 923.2 Å line being
blended with an FeIII transition in this instance. The observed value
of R<SUB>2</SUB>, determined from a quiet-Sun spectrum obtained by the
S082-B spectrograph on board Skylab, implies an electron temperature
in excellent agreement with that of maximum NIV fractional abundance
in ionisation equilibrium, which provides observational support for
the accuracy of the diagnostic calculations.
---------------------------------------------------------
Title: Interspecies Emission-Line Ratios as Electron Density
Diagnostics for Late-Type Stellar Atmospheres
Authors: Keenan, F. P.; Dufton, P. L.; Kingston, A. E.
1990ApJ...353..636K Altcode:
Electron-impact excitation rates for transitions in S IV, Al III,
and N IV, determined with the R-matrix code, are used to calculate
relative level populations for electron temperatures log Te = 4.4 - 5.4
and densities Ne between 10 to the 8th and 10 to the 12th/cu cm. These
data are combined with similar results for C III and O III to derive
emission-line ratios which should be useful as electron-density
diagnostics when applied to the UV spectra of late-type stellar
atmospheres.
---------------------------------------------------------
Title: Effective Collision Strengths among Fine-Structure Levels of
CA XV
Authors: Aggarwal, K. M.; Berrington, K. A.; Keenan, F. P.
1990ApJS...72..815A Altcode:
The R-matrix program is used to calculate collision strengths Omega
for 190 fine-structure transitions among the 1s2 2s2 2p2, 1s2 2s 2p3,
and 1s2 2p4 configurations of Ca XV in the energy range of 0-100
Ry. Relativistic effects are included in the computations of Omega
through term coupling coefficients. The effective collision strengths
Tau, obtained by averaging Omega over a Maxwellian distribution of
electron velocities, are listed for all transitions in the temperature
range of 10 to the 6th to 10 to the 7th K. The effects on the calculated
Omega and Tau values of term coupling and configuration-interaction in
the target are examined, and the importance of including relativistic
effects is noted, particularly for spin and parity changing transitions
at the higher energies and temperatures.
---------------------------------------------------------
Title: The Ratio of Optical to Infrared Emission-Line Strengths in
O III as Electron Temperature Diagnostics for Planetary Nebulae
Authors: Keenan, F. P.; Aggarwal, K. M.
1990ApJ...350..262K Altcode:
Electron impact excitation rates for transitions in O III, calculated
with the R-matrix code, are used to derive electron temperature
diagnostics involving the ratio of optical (4363, 4959, 5007 A)
to infrared (52, 88 microns) emission-line strengths, for a range
of Ne( = 0.01-0.0001/cu cm) and Te( = 6000-20,000 K) applicable to
planetary nebulae. Temperatures deduced from the observed values of
these ratios for several planetaries show good internal agreement
and are also similar to those estimated from the I(7135 A)/I(5192 A)
ratio in Ar III, which provides observational support for the accuracy
of the theoretical O III diagnostics.
---------------------------------------------------------
Title: Determination of stellar and interstellar abundances from
weak absorption lines
Authors: Keenan, F. P.; Brown, P. J. F.; Dufton, P. L.; Holmgren, D. E.
1990asos.conf...44K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Determination of Element Abundances in the Solar
Neighborhood from B-Type Stellar Spectra. I. Argon
Authors: Keenan, F. P.; Bates, B.; Dufton, P. L.; Holmgren, D. E.;
Gilheany, S.
1990ApJ...348..322K Altcode:
The coude spectrograph and CCD camera on the coude feed telescope at the
Kitt Peak National Observatory, have been used to obtain high-resolution
(0.09 A FWHM), high signal-to-noise (200) observations of weak A II
absorption lines formed in the atmospheres of main-sequence early-type
stars. These have been analyzed using LTE model atmosphere techniques
to derive a mean argon-to-hydrogen abundance ratio of 6.49, which is
believed to be accurate to + or - 0.1 dex. As the stellar atmospheres
should be uncontaminated by the products of interior reactions,
this abundance should be that of the interstellar medium from which
the stars formed some 1-10 million yrs ago, and hence reflects the
current chemical composition of the solar neighborhood. The result is
compatible with that of Veck and Parkinson (1981).
---------------------------------------------------------
Title: High-velocity gas components towards 4 Lac.
Authors: Bates, B.; Catney, M. G.; Keenan, F. P.
1990MNRAS.242..267B Altcode:
A comparison of IUE ultraviolet spectra of the star 4 Lac with
observations of a suitable comparison star have confirmed the presence
of 'high-velocity gas components' in the former which are redshifted
by a velocity about 100 km/s from the low-velocity interstellar gas. In
addition to providing an unambiguous identification of the species which
show high-velocity components, the new data yield improved values for
equivalent widths. The derived column densities, element depletions and
ionization balances all lie within the range of values obtained from the
UV spectroscopy of old supernova remnants. Firmer predictions of the
gas electron and hydrogen densities may be possible from observations
of fine structure levels in species such as C II and Si II although,
as is shown, these will require substantial IUE exposure times even
for the brighter stars.
---------------------------------------------------------
Title: An investigation of oscillator strength calculations for
interstellarlines of CL I.
Authors: Keenan, F. P.; Dufton, P. L.
1990MNRAS.242P..52K Altcode:
Recent oscillator strength calculations for the 1088.062, 1097.369
and 1347.240 A interstellar lines of Cl I by Ojha and Hibbert
(1990) are found to be incompatible with high quality Copernicus
observations. Possible explanations are discussed, including severe
blending in the observational data, and misidentification of the
1088.062 and 1097.369 A transitions. Until these discrepancies are
resolved, column densities deduced from these two transitions should
be treated with caution.
---------------------------------------------------------
Title: The Fe xii 195.1 Å/1242 Å emission line ratio in the
solar corona
Authors: Keenan, F. P.; Tayal, S. S.; Henry, R. J. W.
1990SoPh..125...61K Altcode:
Recent R-matrix calculations of electron impact excitation rates
in Fe XII are used to derive the theoretical emission line ratio
R<SUB>1</SUB> = I(195.1 Å)/I(1242 Å), which is potentially a useful
electron density diagnostic for the solar inner corona (r ≤ 1.05
61-01). These results are found to be significantly different from
the earlier estimates of Withbroe and Raymond (1984), but are in good
agreement with the observed values of R<SUB>1</SUB>, for the quiet Sun
and an active region. Adoption of the R-matrix atomic data for the 1242
Å line in the coronal iron abundance determination removes an existing
discrepancy between results derived from the EUV transition and other
iron lines in the solar XUV spectrum. The R-matrix calculations confirm
the prediction of Withbroe and Raymond that the earlier discrepancies
in R<SUB>1</SUB> and the iron abundance were due to the 1242 Å line
excitation rates being underestimated by a factor of ~2. Withbroe and
Raymond's paper is, therefore, an excellent example of how astronomical
observations can be used to accurately predict atomic physics data.
---------------------------------------------------------
Title: Peculiar and normal early-type stars in the galactic halo.
Authors: Conlon, E. S.; Brown, P. J. F.; Dufton, P. L.; Keenan, F. P.
1989A&A...224...65C Altcode:
High resolution optical spectra of eight high latitude blue stars have
been obtained. Three of the sample are identified as subdwarfs. The
remaining five are analyzed for atmospheric parameters and metal and
He abundances using model atmosphere techniques. Four of the sample
appear to be normal B type stars 2 kpc or more from the plane. With a
logarithmic surface gravity estimated to be 4.6 + or - 0.3 dex, PB 166
could be either a main sequence, horizontal branch or cool subdwarf. The
nature of this star is discussed in view of its approximately normal
Population I chemical composition.
---------------------------------------------------------
Title: Use of Al xii and Mg xi lines as solar plasma diagnostics
Authors: Bromage, B. J. I.; Phillips, K. J. H.; Keenan, F. P.; McCann,
S. M.
1989SoPh..124..289B Altcode:
We present three sets of observations of n = 1 to n = 2 lines due
to helium-like aluminium (AlXII), made during two solar flares (25
August, 1980 and 19 October, 1986), using the X-Ray Polychromator on
the SMM satellite. The observed temperature-sensitive line ratio G is
shown to be consistent with the close-coupling calculations of Keenan
and McCann (1987), although the ratio R, which is both temperature
and density-sensitive for lower-Z elements, is not sufficiently well
determined from these data to say more than that the observed values
of R are not inconsistent with the theoretical calculations. This
region of the spectrum also includes the helium-like magnesium (Mgxi)
1<SUP>1</SUP>S - 3<SUP>1</SUP>P line, and it is shown that the ratio
of this line to the AlXII resonance (1<SUP>1</SUP>S - 2<SUP>1</SUP>P)
line is a more sensitive indicator of electron temperature than are
the AlXIIG and R ratios. We demonstrate that the three ratios may be
used together in order to derive values of emission measure, electron
temperature and electron density during these flares.
---------------------------------------------------------
Title: On III Line Ratios in the Sun
Authors: Keenan, F. P.; Aggarwal, K. M.
1989ApJ...344..522K Altcode:
The R-matrix code is used to calculated electron impact excitation
rates for transitions in O III. The calculated rates are used to
determine the theoretical electron sensitive emission-line ratios R(1)
and R(2). The ratios are up to a factor of 2 smaller than those of
Bhatia et al. (1982). The results are compared with solar observations
from Skylab, showing good agreement.
---------------------------------------------------------
Title: Electron Density Diagnostics of Fe XII in the Solar Plasma
Authors: Tayal, S. S.; Henry, Ronald J. W.; Keenan, F. P.; McCann,
S. M.; Widing, K. G.
1989ApJ...343.1004T Altcode:
Density-sensitive emission-line ratios R1 = I(338.27 A)/I(364.47 A)
and R2 = I(338.27 A)/I(352.10 A) are calculated for Fe XII using new
electron collisional excitation rates which are substantially larger
than those previously published. Electron densities deduced from the
values of R1 and R2 for solar active regions and flares obtained by
the NRL S082A slitless spectrograph on Skylab are in good agreement.
---------------------------------------------------------
Title: On III electron temperatures in planetary nebulae.
Authors: Keenan, F. P.; Aggarwal, K. M.
1989JApA...10..147K Altcode:
The electron-temperature-sensitive emission-line ratio I(2s2 2p2 1D -
2s2 2p2 1S)/I(2s2 2p2 3P1,2 - 2s2 2p2 1D) = I(4363 A)/I(4959 + 5007 A)
has been determined based upon relative level populations for O III
obtained using impact excitation rates calculated with the R-matrix
code. Results are presented for a temperature range which is applicable
to planetary nebulae. Electron temperatures derived from the observed
R values of several planetary nebulae agree well with those determined
from electron-temperature-sensitive line ratios is such other species as
(semiforbidden C III)/C II, forbidden N II, and forbidden Ar II.
---------------------------------------------------------
Title: Solar SI III Line Ratios from the High-Resolution Telescope
and Spectrograph on Board Spacelab 2: The Effects of Non-Maxwellian
Electron Distribution Function
Authors: Keenan, F. P.; Cook, J. W.; Dufton, P. L.; Kingston, A. E.
1989ApJ...340.1135K Altcode:
Electron impact excitation rates for transitions in Si III,
incorporating the effects of non-Maxwellian electron velocity
distribution functions (EVDFs), are presented for a range of
electron temperatures appropriate to the solar transition region. A
comparison of theoretical line ratios with observational data for a
quiet solar region, a sunspot, and an active region obtained with the
high-resolution telescope and spectrograph (HRTS) on board Spacelab
2 indicates that non-Maxwellian EVDFs may exist in the transition
region. Non-Maxwellian effects appear to be larger for the sunspot
than for the quiet sun, implying that the temperature gradient may be
greater in the former.
---------------------------------------------------------
Title: Fine-Structure Population Ratios for the 3P Ground States of
C i
Authors: Keenan, F. P.
1989ApJ...339..591K Altcode:
Results of recent R-matrix calculations of electron impact excitation
rates for the 2s2 2p2 3Pj-2s2 2p2 3Pj, fine-structure transition in C
I are used to derive density sensitive population ratios n(3P1)/n(3Po)
and n(3P2)/n(3Po) for a range of temperatures and electron and neutral
hydrogen densities. The present data differ appreciably from those of
Smeding and Pottasch (1979) and illustrate the importance of adopting
accurate electron excitation rates in population ratio calculations,
even in the case of neutrals.
---------------------------------------------------------
Title: Electron density and temperature-sensitive x-ray-emission-line
ratios for heliumlike Si xiii in the DITE tokamak
Authors: Keenan, F. P.; McCann, S. M.; Barnsley, R.; Dunn, J.; Evans,
K. D.; Peacock, N. J.
1989PhRvA..39.4092K Altcode:
Analyses of such remote X-ray sources as solar flares, for which
no independent electron density and temperature estimates exist,
may be undertaken in light of the present derivation of the electron
density-sensitive emission line ratio R and the temperature-sensitive
ratio G from calculations of the electron-impact excitation rates in
He-like Si XIII atoms. These results are compared with R and G values
obtained from X-ray spectra of the divertor-injected tokamak experiment;
good agreement is obtained between theory and experiment, thereby
supporting the accuracy of the atomic data used in the line-ratio
calculations.
---------------------------------------------------------
Title: PG 0832+676: an Apparently Normal B1 V Star 18 Kiloparsecs
above the Galactic Plane
Authors: Brown, Paul J. F.; Dufton, Philip L.; Keenan, Francis P.;
Boksenberg, Alec; King, David L.; Pettini, Max
1989ApJ...339..397B Altcode:
Stellar equivalent widths and line profiles, measured from optical
spectra obtained with the 5 m Hale telescope and the 2.5 m Isaac Newton
telescope, are used in conjunction with model atmosphere calculations
to determine the atmospheric parameters and chemical composition
of the faint, blue, high-galactic latitude star PG 0832 + 676. The
effective temperature (Teff = 25,000 K), surface gravity (log g = 3.9),
and abundances of He, C, N, O, Mg, Al, and Si are similar to those of
Population I OB-type stars, from which it is concluded that PG 0832 +
676 is a normal star at a distance from the galactic plane of about
18 kpc. The star's kinematics and evolutionary age suggest that it
formed in the halo, possibly from galactic fountain material.
---------------------------------------------------------
Title: A comparison of theoretical line strengths for the
2s<SUP>2</SUP>2p<SUP>2</SUP> − 2s2p<SUP>3</SUP> transitions in Ne
V with solar data
Authors: Keenan, F. P.; Aggarwal, K. M.
1989SoPh..122....1K Altcode:
Results are presented for several theoretical line ratios
in Nev involving transitions between multiplets in the
2s<SUP>2</SUP>2p<SUP>2</SUP> and 2s2p<SUP>3</SUP> configurations. A
comparison of these with solar data from the S082A and S-055 instruments
on board Skylab reveals generally good agreement between theory and
experiment, especially in the case of the high-resolution (S082A)
observations. However the 2s<SUP>2</SUP>2p<SUP>2</SUP><SUP>1</SUP>D
− 2s2p<SUP>3</SUP><SUP>1</SUP>P (365.6 Å)
and 2s<SUP>2</SUP>2p<SUP>2</SUP><SUP>3</SUP>P −
2s2p<SUP>3</SUP><SUP>3</SUP>S (359 Å) lines appear to be blended,
possibly with transitions in Fex and FeXI/FeXIII, respectively. We note
that the intensity ratio I(365.6 Å)/I(416.2 Å) should be a valuable
calibration check for a high-resolution extreme ultraviolet instrument
in the spectral range 360-420 Å.
---------------------------------------------------------
Title: A Comparison of Theoretical OIII Line Strengths with Extreme
Ultraviolet Solar Observations from the S082A Instrument of Board
SKYLAB
Authors: Keenan, F. P.; McCann, S. M.; Aggarwal, K. M.; Widing, K. G.
1989SoPh..122....7K Altcode:
Relative level populations in OIII, determined using R-matrix
calculations of electron impact excitation rates, are used to
derive the theoretical emission line ratios R<SUB>1</SUB> =
I(525.80 Å)/I(599.62 Å), R<SUB>2</SUB> = I(507.41 Å)/I(599.62
Å), R<SUB>3</SUB> = I(507.71 Å)/I(599.62 Å), and R<SUB>4</SUB>
= I(508.18 Å)/I(599.62 Å). Electron temperatures deduced from the
observed values of these ratios for several solar features obtained
with the NRL S082A slitless spectrograph on board Skylab are in good
agreement, and also compare favourably with that of maximum OIII
fractional abundance in ionisation equilibrium, logT<SUB>max</SUB> =
4.96. These results provide experimental support for the accuracy of
the atomic data adopted in the line ratio calculations.
---------------------------------------------------------
Title: Si III electron temperature diagnostics for the solar
transition region
Authors: Keenan, F. P.; Dufton, P. L.; Kingston, A. E.
1989SoPh..123...33K Altcode:
R-matrix calculations of electron impact excitation rates for
transitions in Si III are used to derive the electron-density-sensitive
emission line ratios R<SUB>1</SUB> = I(1113.2 Å)/I(1206.3 Å),
R<SUB>2</SUB> = I(1298.9 Å)/I(1206.3 Å), and R<SUB>3</SUB> = I(1296.7
Å)/I(1206.3 Å). A comparison of these with observational data for
several solar features obtained with the Harvard S-055 spectrometer
on board Skylab reveals that theory and experiment are compatible if
the electron temperature of the Si III emitting region of the solar
atmosphere is log T<SUB>e</SUB>= 4.5, but not if log T<SUB>e</SUB>=
4.7. The implication of the choice of a lower temperature on the
electron energy distribution function is also briefly discussed.
---------------------------------------------------------
Title: Argon XV Line Ratios in the Sun
Authors: Keenan, F. P.; Widing, K. G.; McCann, S. M.
1989ApJ...338..563K Altcode:
Theoretical Ar XV emission-line ratios are presented for R1 = I(2s2p
1P-2s2 1S)/I(2s2p 3P1-2s2 1S) = I(221.12 A)/I(423.98 A) and R2 =
I(2s2p 1P-2s2 1S)/I(2p2 3P2-2s2p 3P2) = I(221.12 A)/I(266.23 A),
which are electron temperature and density sensitive, respectively. A
comparison of these with observational data for solar flares obtained
with the NRL S082A slitless spectrograph on board Skylab reveals
that there is good agreement between theory and observation for R1,
which provides experimental support for the accuracy of the atomic
data adopted in the analysis. However the observed values of R2 all
lie below the theoretical high-density limit, which may be due to
blending of the 266.23 A transition with an unidentified line.
---------------------------------------------------------
Title: Low Resolution Observations of Faint Early-Type Halo Stars
Authors: Keenan, F.
1989iue..prop.3616K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: B star 18 kpc above the Galactic plane.
Authors: Keenan, F.; Dufton, P.; Brown, P.
1989Gemin..23....1K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A Search for Beta Cephei
Authors: Keenan, F.
1989iue..prop.3611K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Flare activity on UV Ceti : visible and IUE observations.
Authors: Phillips, K. J. H.; Bromage, G. E.; Dufton, P. L.; Keenan,
F. P.; Kingston, A. E.
1988MNRAS.235..573P Altcode:
Simultaneous far-ultraviolet (IUE) spectroscopy and optical photometry
and spectrophotometry of a flare on UV Ceti are reported. The flare
reached ΔU = 2 mag but showed only modest enhancements in the IUE
spectra. The optical spectrophotometry indicated broadened Balmer line
profiles during the flare, with Hβ and Hγ clearly showing red wings
(≡100 km s<SUP>-1</SUP>). The results are compared with other IUE
and optical observations of UV Ceti, and their solar analogues.
---------------------------------------------------------
Title: The O III 52mu.m/88mu.m emission-line ratio in planetary
nebulae.
Authors: Keenan, F. P.; Aggarwal, K. M.
1988JApA....9..237K Altcode:
R-matrix calculations of electron impact excitation rates in O III are
used to derive the electron-density-sensitive emission-line ratio R
for a range of electron temperatures (T<SUB>e</SUB> = 5000 - 20,000K)
and densities (N<SUB>e</SUB> = 10 - 10<SUP>5</SUP>cm<SUP>-3</SUP>)
applicable to planetary nebulae. Electron densities deduced from the
observed values of R in several planetary nebulae are in excellent
agreement with those deduced from Cl III and Ar IV, which provides
support for the accuracy of the atomic data adopted in the calculations.
---------------------------------------------------------
Title: Population Ratios for the Fine-Structure Ground State of O
i Applicable to the Interstellar Medium
Authors: Keenan, F. P.; Berrington, K. A.
1988ApJ...333..806K Altcode:
Recent R-matrix calculations of electron excitation rates among the
2s<SUP>2</SUP>2p<SUP>4</SUP> <SUP>3</SUP>P fine-structure levels
in O I are used to derive density-sensitive population ratios
n(<SUP>3</SUP>P<SUB>1</SUB>)/n(<SUP>3</SUP>P<SUB>2</SUB>) and
n(<SUP>3</SUP>P<SUB>0</SUB>)/n(<SUP>3</SUP>P<SUB>2</SUB>) for the
ranges of electron and neutral hydrogen densities (n<SUB>e</SUB> =
10<SUP>-2</SUP> - 10<SUP>3</SUP>cm<SUP>-3</SUP>; n<SUB>H</SUB> = 0 -
1000 cm<SUP>-3</SUP>) applicable to H I and H II regions. The results
differ significantly from those of Smeding and Pottasch and will lead
to electron density estimates between 30% and a factor of 2 smaller.
---------------------------------------------------------
Title: Fine-Structure Populations for the 6D Ground State of Fe II
Authors: Keenan, F. P.; Hibbert, A.; Burke, P. G.; Berrington, K. A.
1988ApJ...332..539K Altcode:
In this paper, recent R-matrix calculations of electron impact
excitation rates in Fe II are used to estimate relative level
populations for the 3d6 4s 6D ground state applicable to astrophysical
plasmas. The results are found to be up to a factor of two different
from the earlier calculations of Nussbaumer and Story (1980). Effective
collision strengths for transitions among the 3d6 4s 6D and 3d7 4F
levels in Fe II are also given.
---------------------------------------------------------
Title: Theoretical Si iv line ratios compared to extreme ultraviolet
solar observations
Authors: Keenan, F. P.; Doyle, J. G.
1988SoPh..115..229K Altcode:
New theoretical electron temperature sensitive emission line
ratios in SiIV involving the 3d<SUP>2</SUP>D − 3p<SUP>2</SUP>P and
4s<SUP>2</SUP>S − 3p<SUP>2</SUP>P multiplets at ∼1125 and 816 Å,
respectively, are derived using recent R-matrix electron excitation
rate calculations. A comparison of these with observational data
for a solar active region at the limb obtained with the Harvard
S-055 spectrometer on board Skylab reveals that there is good
agreement between theory and observation for ratios that include
the <SUP>2</SUP>D<SUB>3/2, 5/2</SUB> − <SUP>2</SUP>P<SUB>3/2</SUB>
transition at 1128.3 Å. This is in contrast to the findings of Keenan,
Dufton, and Kingston (1986) and provides support for the atomic data
adopted in the calculations. However, the <SUP>2</SUP>D<SUB>3/2</SUB>
− <SUP>2</SUP>P<SUB>1/2</SUB> line at 1122.5 Å appears to be
severely blended, as suggested previously by Burton and Ridgeley (1970)
and Feldman and Doschek (1977), as it leads to electron temperature
estimates that differ significantly from that expected in ionisation
equilibrium. The fact that the I(1122.5 Å)/I(1128.3 Å) intensity
ratios determined from several flare spectra are closer to theory than
that for the active region indicates that the blending is probably due
to species with relatively low ionization potentials, as noted by Flower
and Nussbaumer (1975). Electron temperatures deduced for a sunspot are
much lower than that predicted from ionisation balance calculations,
in agreement with earlier results, and imply that a cooling flow may
be present.
---------------------------------------------------------
Title: S vi line ratios in the Sun
Authors: Keenan, F. P.
1988SoPh..116..279K Altcode:
R-matrix calculations of electron impact excitation rates in S VI are
used to determine the theoretical temperature sensitive emission line
ratios and which are found to be up to 30% larger than the earlier
results of Flower and Nussbaumer. A comparison of the present data
with solar observations from the Harvard S-055 spectrometer on board
Skylab implies that the 944.5 Å transition may be blended with lines
from species with relatively low ionization potentials, in contrast
to the findings of Flower and Nussbaumer. The 712.8 Å transition may
also be similarly blended.
---------------------------------------------------------
Title: Comparison of Theoretical AR XV Line Strengths with SKYLAB
XUV Observations of Solar Flares
Authors: McCann, S. M.; Keenan, F. P.; Widing, K. G.
1988IrAJ...18..267M Altcode:
The UV emission of the six energetically lowest LS states of AR XV
has been observed in high-temperature laboratory and astrophysical
plasmas. The Skylab-observed line intensity ratio I(212.12)/I(423.98)
for the solar flare of August 9, 1973 is found to be within 25 percent
of the theoretical value of 47.5 at the temperature of the maximum Ar
XV fractional abundance in ionization equilibrium. Observational data
for the ratio I(221.12)/I(266.23) are found to be inconsistent with
the value of N(e) = 10 to the 11th/cu cm derived from the Ca XVII line
strengths in the same flare by Keenan et al. (1988).
---------------------------------------------------------
Title: Studies of the Gas and Dust Distribution in the Local
Interstellar Medium
Authors: Catney, M.; Bates, B.; Keenan, F. P.
1988IrAJ...18..255C Altcode:
Previous results on the gas and dust distribution in the local
interstellar medium are discussed, with special attention given to
the search for possible dust concentrations in regions of the sky
containing high velocity gas components. High-resolution maps of the 4
Lac region reveal an emission feature which contains much structure,
extends from the galactic plane, and is inclined at an angle of
about 45 deg to the plane. An IR emission known as galactic cirrus,
noted at high galactic latitudes, is suggested by Low et al. (1984)
to be due to the presence of dust.
---------------------------------------------------------
Title: AR III in planetary nebulae.
Authors: Keenan, F. P.; Johnson, C. T.; Kingston, A. E.
1988A&A...202..253K Altcode:
Recent R-matrix calculations of electron impact excitation rates in Ar
III are used to derive the theoretical temperature sensitive ratio R =
I(<SUP>3</SUP>P<SUB>1,2</SUB>-<SUP>1</SUP>D<SUB>2</SUB>)/I(<SUP>1</SUP>D<SUB>2</SUB>-<SUP>1</SUP>S<SUB>0</SUB>)
= I(7135 Å+7751 Å)/I(5192 Å). Electron temperatures estimated from
the observed values of R in planetary nebulae are in good agreement with
those deduced from O III. In addition, Ar III abundances determined
from the <SUP>3</SUP>P<SUB>2</SUB>-<SUP>1</SUP>D<SUB>2</SUB> and
<SUP>3</SUP>P<SUB>2</SUB>-<SUP>3</SUP>P<SUB>1</SUB> transitions at
7135 Å and 9 μm respectively are consistent, in contrast to results
found using the excitation rates of Krueger and Czyzak.
---------------------------------------------------------
Title: An abundance and kinematical analysis of four early-type high
latitude stars.
Authors: Conlon, E. S.; Brown, P. J. F.; Dufton, P. L.; Keenan, F. P.
1988A&A...200..168C Altcode:
Stellar absorption line profiles and equivalent widths are measured
from high resolution INT and AAT optical spectra of four high galactic
latitude targets and used in conjunction with model atmosphere codes to
determine their atmospheric parameters and chemical compositions. Normal
Population I abundances are derived, with typical errors of ±0.2 dex,
implying z-distances in the range 1 - 2 kpc. Various explanations
for the existence of such stars so far from the galactic plane are
discussed, the most likely mechanism being cluster ejection.
---------------------------------------------------------
Title: Iras maps for a region of sky containing nearby high-velocity
gas, identified from IUE spectra
Authors: Bates, B.; Catney, M. G.; Keenan, F. P.
1988Ap&SS.146..195B Altcode:
Detailed IRAS contour maps in the 60 and 100 μm wavebands are
presented for a small region of sky towards which ‘high-velocity
gas components’ (HVC) have been clearly identified in spectra
of background stars obtained with the IUE satellite. There is a
coincidence in direction on the sky between the strongest regions
of absorption produced by HVC gas and compact regions of brightest IR
emission. However, there is no clear evidence at present for identifying
the HVC directly with the IR emission due to insufficient spatial
informatin along the lines-of-sight examined. A comparison of Hi column
densities obtained from both the 100 μm emission and colour excess
data indicates that dust emission, rather than atomic line emission,
is the dominant contribution to the IRAS observations in the sightlines
considered. The angular sizes of the brightest IR emitting regions
are small and are of approximate dimensions ∼0.5×0.3 pc<SUP>2</SUP>
if located at a distance ∼220 pc estimated for the HVC gas.
---------------------------------------------------------
Title: Chromospheric mass motions during a flare on UV Ceti
Authors: Phillips, K. J. H.; Bromage, G. E.; Dufton, P. L.; Keenan,
F. P.; Kingston, A. E.
1988ESASP.281a.311P Altcode: 1988uvai....1..311P; 1988IUES....1..315P; 1988IUE88...1..311P
Simultaneous optical and IUE observations of a flare on UV Ceti in 1980
are reported. The IUE spectra show only slight increase of C IV line
emission. The optical spectrophotometric observations show, from Balmer
line profiles, turbulent broadening in quiescent and flare spectra, and
downward-directed flow (of 100 km/sec) during the flare. The latter is
particularly reminiscent of solar flares, and probably arises from the
formation of a chromospheric condensation, as modeled for solar flares.
---------------------------------------------------------
Title: S XV Emission-Line Ratios in the Sun
Authors: McCann, S. M.; Keenan, F. P.
1988ApJ...328..344M Altcode:
Recently calculated electron impact collision rates for S xv are used
to derive the electron temperature sensitive emission-line ratio G =
x + y + z/w, where z is the forbidden 1s21S-1s2s 3S, w is the resonance
1s2 1S-1s2p 1P and x and y, the intercombination 1s2 1S-1s2p 3P2 and
1s2 1S-1s2p 3P1 transitions, respectively. The value of R = z/x +
y, the electron density sensitive ratio, was also calculated in its
low-density limit (Ro), and both are plotted as functions of the
electron temperature. These are found to be in much better agreement
with the observed values of Ro and G obtained by the Flat Crystal
Spectrometer on the Solar Maximum Mission satellite for the 1980
November 5 flare than are the previous results of Pradhan and Shull
(1981). This improvement provides support for the methods and the
atomic data adopted in our calculations.
---------------------------------------------------------
Title: CA XV Line Ratios in Solar Flares
Authors: Keenan, F. P.; Aggarwal, K. M.; Berrington, K. A.; Widing,
K. G.
1988ApJ...327..473K Altcode:
Recent R-matrix calculations of electron impact excitation rates
for Ca XV have been used to obtain theoretical density-sensitive
emission line ratios which are applicable to solar flares. Results for
electron densities derived from the I(208.71 A)/I(200.95 A), I(181.90
A)/I(200.95 A), and I(215.37 A)/I(200.95 A) values for solar flares
obtained by the Skylab NRL S082A slitless spectrograph are in excellant
agreement. Ca XV electron densities are found to compare favorably
with those determined from the line ratios of ions formed at similar
electron temperatures. The results provide support for the accuracy
of the adopted atomic data and for the line ratio calculation method.
---------------------------------------------------------
Title: EUV emission line ratios for Si IV in the solar transition
region.
Authors: Keenan, F. P.; Doyle, J. G.
1988JPhys..49..227K Altcode: 1988IAUCo.102..227K
Theoretical electron temperature sensitive emission line ratios in Si IV
involving the 3d <SUP>2</SUP>D - 3p <SUP>2</SUP>P and 4s <SUP>2</SUP>S
- 3p <SUP>2</SUP>P multiplets at ≡1125 Å and 816 Å respectively
are derived using R-matrix electron excitation rate calculations. A
comparison of these with observational data for a solar active
region obtained with the Harvard S-055 spectrometer on board Skylab
reveals that there is good agreement between theory and observation
for the ratio that includes the <SUP>2</SUP>D<SUB>3/2,5/2</SUB> -
<SUP>2</SUP>P<SUB>3/2</SUB> transition at 1128.3 Å.
---------------------------------------------------------
Title: The comparison of helium-like ion emission line ratios with
solar X-ray spectral data.
Authors: McCann, S. M.; Keenan, F. P.
1988JPhys..49..331M Altcode: 1988IAUCo.102..331M
Electron impact excitation rates recently calculated by Keenan, McCann
and Kingston for transitions in the He-like ions Al XII, Si XIII and S
XV are used to derive the electron temperature sensitive emission line
ratio G and the density sensitive ratio R in its low density limit
(R<SUB>0</SUB>). These ratios are compared with those calculated by
other authors and with the values obtained for solar flares using
instruments on board the P78-1 and Solar Maximum Mission satellites.
---------------------------------------------------------
Title: High-Resolution Spectroscopy of Astronomical Objects
Authors: Keenan, F. P.
1988IrAJ...18..161K Altcode:
This paper reviews recent advancements in the main astrophysics research
interest of the Physics Department at QUB, that of high-resolution
spectroscopy of astronomical objects. The major areas of study are
early-type stars, the interstellar medium and emission-line regions of
Seyfert galaxies and planetary nebulae. These are discussed separately
in detail.
---------------------------------------------------------
Title: Theoretical Emission Line Strengths for the Beryllium-Like
Ion Sxiii Compared to Extreme Ultraviolet Observations of Solar Flares
Authors: Keenan, F. P.; McCann, S. M.; Widding, K. G.
1988SoPh..117...69K Altcode:
A comparison of Skylab S082A observations for several solar
flares with calculations of the electron temperature sensitive
emission line ratio R<SUB>1</SUB> = I(2s2p<SUP>1</SUP>P −
2s<SUP>2</SUP><SUP>1</SUP>S)/I(2s2p<SUP>3</SUP>P<SUB>1</SUB>
- 2s<SUP>2</SUP><SUP>1</SUP>S) = = I(256.68 Å)/I(491.45 Å) in
Be-like SXIII reveals good agreement between theory and experiment,
which provides observational support for the accuracy of the
adopted atomic data. However, observed values of the electron
density sensitive ratio R<SUB>2</SUB> = I(2s2p<SUP>1</SUP>P −
2s<SUP>2</SUP><SUP>1</SUP>S)/I(2p<SUP>2</SUP><SUP>3</SUP>P<SUB>2</SUB>
- 2s2p<SUP>3</SUP>P<SUB>2</SUB>) = = I(256.68 Å)/I(308.96 Å) all
lie below the theoretical high density limit, which is probably due
to blending in the 308.96 Å line.
---------------------------------------------------------
Title: Interstellar CA II absorption towards early-type stars at
high galactic latitudes.
Authors: Keenan, F. P.; Conlon, E. S.; Brown, P. J. F.; Dufton, P. L.
1988A&A...192..295K Altcode:
New high resolution AAT and INT observations of the Ca II 3933 Å
interstellar line towards nine early-type stars at high galactic
latitudes are presented. These are combined with the authors' earlier
AAT data to investigate the distribution of Ca II in the galactic
halo. A comparison of these results with Ca II equivalent widths for
extragalactic sightlines implies that there is a significant amount
of this ion out to z ≅ 1 kpc, but not much beyond z ≅ 2 kpc. No
coincident high velocity Ca II absorption is detected in the spectra of
stars near known high velocity clouds (HVC). Although this may indicate
that the HVCs are either at greater distances than the stars or have
angular extents smaller than the separations of the stellar and HVC
sightlines, it is also possible that they are nearby but contain too
little Ca II to produce an observable absorption line.
---------------------------------------------------------
Title: Electron Density Diagnostics for Late-Type Stellar Atmospheres
Authors: Keenan, F. P.; Dufton, P. L.; Aggarwal, K. M.; Kingston, A. E.
1988ApJ...324.1068K Altcode:
R-matrix calculations of electron excitation rates in C III, O III,
and Si IV have been used to obtain several theoretical emission-line
ratios for a range of electron temperatures and densities applicable
to late-type stellar atmospheres. Data are derived for the ratios I(C
III 1908 A)/I(O III 1666 A), I(O III 1666 A)/I(Si IV 1402 A), and I(C
III 1908 A)/I(Si IV 1402 A). It is suggested that differences found
between the results and those of Doschek et al. (1978) are due to the
present adoption of improved atomic data.
---------------------------------------------------------
Title: Electron impact excitation rates for transitions in
beryllium-like P XII, S XIII, Cl XIV, Ar XV and K XVI
Authors: Keenan, F. P.
1988PhyS...37...57K Altcode:
The R-matrix electron excitation rates determined by Berrington et
al. (1985) for C III, O V, Ne VII, and Si XI and by Dufton et al. (1983)
for Ca XVII are used to interpolate the rates for Be-like P XII, S XIII,
Cl XIV, Ar XV, and K XVI. The results are presented in a series of
tables and briefly characterized. The accuracy of the present findings
is estimated as + or - 10 percent within 0.8 dex of log Tmax, where
Tmax is the temperature of maximum fractional abundance for ionization
equilibrium. The applicability of the results to the diagnostics of
astrophysical and laboratory plasmas is indicated.
---------------------------------------------------------
Title: High Resolution Observations of Early-Type Halo Stars PHL 1580
Authors: Keenan, F.
1988iue..prop.3215K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Emission-Line Ratios for O III in Gaseous Nebulae and a
Comparison between Theory and Observation
Authors: Keenan, F. P.; Aggarwal, K. M.
1987ApJ...319..403K Altcode:
Recent R-matrix calculations of electron excitation rates in O III are
used to derive electron temperature and density-sensitive emission-line
ratios R1 = I(2322 A)/I(1661 A + 1667 A), R2 = I(1661 A + 1667 A)/I(4960
A + 5009 A), and R3 = I(4363 A)/I(4960 A + 5009 A) for a range of Te
(7500-40,000 K) and Ne 10 to the 2nd to 10 to the 7th/cu cm applicable
to gaseous nebulae. Electron temperatures and densities deduced from
these and observed values of R1, R2, and R3 for several planetary
nebulae and a Seyfert galaxy in general show good internal agreement
and also compare favorably with results deduced from the line ratios
of other species, thereby providing support for the atomic data adopted
in the calculations.
---------------------------------------------------------
Title: NE IX Emission-Line Ratios in Solar Active Regions
Authors: Keenan, F. P.; McKenzie, D. L.; McCann, S. M.; Kingston, A. E.
1987ApJ...318..926K Altcode:
Emission-line ratios for Ne IX are derived and compared with
observational data for solar active regions obtained with the SOLEX B
spectrometer on the P78-1 satellite. Excellent agreement is obtained,
providing support for the atomic data adopted in the calculations and
resolving discrepancies between existing theoretical calculations and
solar data. The calculated R-ratio for the low-density limit agrees
well with the SOLEX observations.
---------------------------------------------------------
Title: Relative emission line strengths for Fe VII in astrophysical
plasmas.
Authors: Keenan, F. P.; Norrington, P. H.
1987A&A...181..370K Altcode:
Recent R-matrix calculations of electron impact excitation rates in Fe
VII are used to derive relative emission line strengths for a range of
electron temperatures (Te of between 8000 and 120,000 K, inclusively)
and densities (Ne of between 10 to the 4th/cu cm and 10 to the 10th/cu
cm, inclusively) applicable to gaseous nebulae. The results are found
to be significantly different from those of Nussbaumer and Storey
(1982), especially at low temperatures.
---------------------------------------------------------
Title: A search for far-infrared (IRAS) emission from early-type
stars at high galactic latitudes.
Authors: Keenan, F. P.; Conlon, E. S.; Brown, P. J. F.
1987A&A...178..317K Altcode:
Recently Lamers et al. (1986) have found that HR 4049 (B supergiant
at z = 1300 pc) is surrounded by a dust cloud which produces a large
IR excess, from which it is inferred that the star may be a much less
luminous low mass object close to the Galactic plane. Here, the results
of a search for strong FIR (IRAS) emission from a sample of early-type
high-Galactic-latitude stars, estimated to be at z-distances of up to
9000 pc from optical spectral analyses, are reported. No IR emission was
detected for any of the stars investigated, which would not be expected
if they were nearby objects with dust clouds. It is therefore concluded
that they are normal stars at the large distances previously estimated.
---------------------------------------------------------
Title: Non-LTE abundance analysis of the early-type high galactic
latitude star HD 100340.
Authors: Keenan, F. P.; Brown, P. J. F.; Conlon, E. S.; Dufton, P. L.;
Lennon, D. J.
1987A&A...178..194K Altcode:
Stellar equivalent widths and line profiles, measured from high
resolution AAT and IUE spectra, are used in conjunction with non-LTE
and LTE model atmosphere calculations to estimate the atmospheric
parameters and chemical composition of the early-type high galactic
latitude star HD 100340. The effective temperature (T<SUB>eff</SUB>=
25000K), surface gravity (log g = 3.8) and abundances of He, C, O, Al,
Si, and Fe are similar to those of Population I OB stars, from which
it is concluded that HD 100340 is a normal star at a distance from the
galactic plane of z = 4.6±0.8 kpc. Several possible explanations for
the existence of this star at such a large z-distance are discussed,
including ejection from the galactic plane and formation in the halo.
---------------------------------------------------------
Title: The SI III 1892 A/C III 1908 A emission-line ratio in
late-type stars
Authors: Keenan, F. P.; Kingston, A. E.; Dufton, P. L.
1987MNRAS.225..859K Altcode:
Theoretical values of the density-sensitive emission-line ratio R =
I(Si III 3s<SUP>21</SUP>S-3s3p<SUP>3</SUP>P<SUB>1</SUB>)/I(C III
2s<SUP>21</SUP>S-2s2p<SUP>3</SUP>P<SUB>1</SUB> = I(1892 Å)/I(1908
Å) are presented for a range of electron densities (10<SUP>8</SUP>
≤ N<SUB>e</SUB> ≤ 10<SUP>13</SUP>cm<SUP>-3</SUP>) applicable to
late-type stellar atmospheres. These results differ from the earlier
calculations of Doschek et al. and Cook & Nicolas, mainly due
to the improved electron excitation rates for Si III adopted in the
present analysis.
---------------------------------------------------------
Title: Theoretical emission line ratios for Si XIII compared to
solar observations
Authors: McCann, S. M.; Keenan, F. P.
1987SoPh..112...83M Altcode:
The electron collision excitation rates recently calculated for
transitions in Si XIII by Keenan et al. (1987) are used to derive
the electron temperature sensitive ratio G(=(f + i)/r and the density
sensitive ratio R(=f/i), where i, f, and r are the intercombination
(1s<SUP>2</SUP><SUP>1</SUP>S − 1s2p<SUP>3</SUP>P<SUB>1, 2</SUB>)
forbidden (1s<SUP>2</SUP><SUP>1</SUP>S − 1s2s<SUP>3</SUP>S),
and resonance (1s<SUP>2</SUP><SUP>1</SUP>S − 1s2p<SUP>1</SUP>P),
transitions respectively. Also estimated are the values of R in
the low-density limit (R<SUB>0</SUB>) as a function of electron
temperature. The theoretical G ratio at the temperature of maximum
emissivity for Si XIII, G(T<SUB>m</SUB>) = 0.70, is in much better
agreement with the observed G for the 1985, May 5 flare determined by
McKenzie et al. (G = 0.60 ± 0.07) than is the earlier calculation
of Pradhan, who derived G(T<SUB>m</SUB>) = 0.85. The error in the
observed R<SUB>0</SUB> ratio is so large that both our result and
Pradhan's fall within the acceptable limits of uncertainty and hence
one cannot estimate which of the two is the more accurate.
---------------------------------------------------------
Title: Al XII line ratios in the Sun
Authors: Keenan, F. P.; McCann, S. M.
1987SoPh..109...31K Altcode:
Recent calculations of electron impact excitation rates in He-like
AlXII are used to derive the theoretical electron temperature and
density sensitive emission line ratios G ( = (f + i)/r and R ( =
f/i, where f, i, and r are the forbidden 1s<SUP>2</SUP><SUP>1</SUP>S
− 1s2s<SUP>3</SUP>S, intercombination 1s<SUP>2</SUP><SUP>1</SUP>S
− 1s2p<SUP>3</SUP>P and resonance 1s<SUP>2</SUP><SUP>1</SUP>S −
1s2p<SUP>1</SUP>P transitions, respectively. These ratios are found
to be significantly different from earlier calculations, and are in
much better agreement with X-ray spectral data for two solar flares
obtained with the SMM and P78-1 satellites.
---------------------------------------------------------
Title: Relative emission line strengths for the sodium-like ions AL
III and SI IV in the sun
Authors: Keenan, F. P.; Dufton, P. L.; Kingston, A. E.
1986A&A...169..319K Altcode:
Recent R-matrix calculations of electron excitation rates for the
Na-sequence ions Al III and Si IV are used to determine theoretical
emission line ratios applicable to the solar transition region. A
comparison of the Al III results with high resolution (≅0.06 Å)
solar data obtained with the NRL S082-B spectrograph on board Skylab
shows reasonable agreement between theory and observations. However
a similar analysis for Si IV using low resolution (≅2 Å) EUV
satellite spectra for the quiet sun and an active region reveals that
the calculations and observational data are incompatible. It is shown
that this is probably due to the Si IV 3d<SUP>2</SUP>D<SUB>3/2</SUB>
- 3p<SUP>2</SUP>P<SUB>1/2</SUB> and 3d<SUP>2</SUP>D<SUB>3/2,5/2</SUB>
- 3p<SUP>2</SUP>P<SUB>3/2</SUB> transitions at 1122.5 Å and 1128.3 Å
respectively being blended with lines arising from ions with relatively
low ionization potentials.
---------------------------------------------------------
Title: The variation of interstellar element abundances with hydrogen
density
Authors: Keenan, F. P.; Dufton, P. L.; Hibbert, A.; Murray, M. J.
1986MNRAS.222..143K Altcode:
The variation of the interstellar nitrogen, oxygen and magnesium
abundances with mean line-of-sight density >n<SUB>H</SUB>< is
analysed in terms of a two-component model first employed by Jenkins,
Savage and Spitzer (1986), which consists of warm, low-density
neutral gas and cold clouds. In all cases the gas-phase abundances
have been deduced using reliable oscillator strengths specifically
calculated for this purpose. Depletions in the warm and cold gas,
denoted D<SUB>w</SUB> and D<SUB>c</SUB> respectively, are derived from
non-linear least-squares fits to the data. Values of D<SUB>w</SUB> for
the species considered are found to be small (≅0.1 dex), consistent
with the low reddening and hence grain content in such sight-lines.
---------------------------------------------------------
Title: Evidence for Recent Star Formation in the Galactic halo
Authors: Keenan, F. P.
1986IrAJ...17..483K Altcode:
Observational data for PHL 346 obtained with the 2.5 m Issac Newton
telescope on August 1985 are studied. Measured stellar Stromgren colors,
hydrogen-line profiles, and helium and metal-line equivalent widths
are compared with those predicted by local thermodynamic equilibrium
model-atmosphere calculations. Effective temperature, surface gravity,
microturbulent velocity, and helium and metal abundances for the star
are derived. A mass of 13 + or - 2 solar masses, a lifetime of 11 x
10 to the 6th yr, a distance from the galactic plane of 8.7 + or -
1.5 kpc, and a velocity in the z direction of +56 + or - 10 km/s are
calculated for the star. The data reveal that the star was not ejected
from the galactic plane, but that it formed out of galactic fountain
gas at about 6 kpc from the disc.
---------------------------------------------------------
Title: IUE and optical studies of nearby interstellar gas
Authors: Keenan, F. P.; Bates, B.; Catney, M. G.
1986ESASP.263..565K Altcode: 1986NIA86......565K; 1986niia.conf..565K
Red-shifted high velocity interstellar gas components with velocities
up to ≅100 km s<SUP>-1</SUP> have been detected in the IUE spectra of
several stars in the Galactic direction l ≅ 100°, b ≅ -7°. These
are compared with complementary high resolution optical observations of
the NaD interstellar lines, which allow the distribution of the gas to
be mapped more extensively than in earlier surveys. New calculations
of the temperature sensitive N(Mg I)/N(Na I) ratio are presented, and
used in conjunction with the UV results to partially derive physical
conditions within several of the high velocity clouds.
---------------------------------------------------------
Title: The abundance of phosphorus in the interstellar medium.
Authors: Dufton, P. L.; Keenan, F. P.; Hibbert, A.
1986A&A...164..179D Altcode:
New oscillator strengths for P II resonance transitions are used in
conjunction with published Copernicus observations to derive P II
column densities toward 51 stars. It is found that phosphorus is: (a)
undepleted along sightlines containing predominantly low density neutral
gas and (b) depleted by approximately 0.5 dex in cold clouds. These
results differ from the recent analysis of Jenkins et al., principally
due to changes in the atomic data but also due to a consequential
decrease in estimated b-values. The reliability of other atomic data
currently adopted in analyses of interstellar observations is also
briefly discussed.
---------------------------------------------------------
Title: A Model Atmosphere Analysis of the Faint Early-Type Halo Star
PHL 346
Authors: Keenan, F. P.; Lennon, D. J.; Brown, P. J. F.; Dufton, P. L.
1986ApJ...307..694K Altcode:
Stellar equivalent widths and hydrogen line profiles, measured from
high-resolution optical spectra obtained with the 2.5 m Issac Newton
Telescope, are used in conjunction with model atmosphere calculations
to determine the atmospheric parameters and chemical composition of the
faint, high galactic latitude early-type star PHL 346. The effective
temperature (Teff = 22,600 + or - 1000 K) and surface gravity (log g =
3.6 + or - 0.2), as well as the chemical composition, are found to be
similar to those of normal OB stars. Therefore, it is concluded that
PHL 346 is an ordinary Population I object, at a z distance of 8.7 +
or - 1.5 kpc. The relatively small stellar velocity in the z-direction
(Vz = +56 + or - 10 km/s) then implies that PHL 346 must have been
formed in the halo, possibly from galactic fountain material at a z
distance of about 6 kpc.
---------------------------------------------------------
Title: The chemical composition of six southern clusters and
associations.
Authors: Brown, P. J. F.; Dufton, P. L.; Lennon, D. J.; Keenan, F. P.
1986MNRAS.220.1003B Altcode:
Seventy-one early-type main-sequence stars have been observed
spectroscopically in five southern galactic clusters and a loose
association. Hydrogen-line profiles and helium-diffuse-line equivalent
widths have been measured for all stars, together with line strengths
for metal and helium nondiffuse lines in 27 stars with small projected
rotational velocities. Stromgren photometry has been obtained for
stars where previous results do not exist, and effective temperatures
have been determined from the index. Surface gravities have been
estimated primarily from theoretical profiles fitted to the H-delta
absorption line, and also from H-beta photometry. Abundances, deduced
from comparison with LTE and non-LTE model-atmosphere calculations,
are generally found to be consistent with a normal early-type stellar
composition.
---------------------------------------------------------
Title: An approximate calculation of the effect of opacity on SI
III emission line ratios near the solar limb
Authors: Keenan, F. P.; Kingston, A. E.
1986MNRAS.220..493K Altcode:
The present analysis of the Si III spectrum obtained by the Skylab
spectrograph as the slit was stepped across the solar disk, and out
above the limb, interprets the ratio between a pair of these lines to be
due to the effect of opacity; its variation is consistent with a simple
model for the atmosphere, allowing the calculation of optical depths
for several of the Si III transitions at the limb and solar center. The
results obtained are noted to compare well with those estimated on the
basis of the solar model D or Gabriel (1976). An effective thickness
for the Si III-emitting region of the solar atmosphere is calculated
to be 26 km, in excellent agreement with the 22-km value deduced from
Gabriel's solar transition region model D.
---------------------------------------------------------
Title: Fine-structure population ratios for the 2P ground state of
C II
Authors: Keenan, F. P.; Lennon, D. J.; Johnson, C. T.; Kingston, A. E.
1986MNRAS.220..571K Altcode:
Results of R-matrix calculations of electron excitation rates for the
2s<SUP>2</SUP>2p<SUP>2</SUP>P<SUB>1/2</SUB>-2s<SUP>2</SUP>2p<SUP>2</SUP>P<SUB>3/2</SUB>
fine-structure transition in C II are
used to derive density sensitive population ratios
n(2s<SUP>2</SUP>2p<SUP>2</SUP>P<SUB>3/2</SUB>)/n(2s<SUP>2</SUP>2p<SUP>2</SUP>P<SUB>1/2</SUB>)
for the ranges of electron and neutral hydrogen densities
(n<SUB>e</SUB>= 10<SUP>-3</SUP> - 10<SUP>3</SUP>cm<SUP>-3</SUP>;
n<SUB>H</SUB>= 0 - 1000 cm<SUP>-3</SUP>) applicable to H I and H II
regions. These are found to differ significantly from the earlier
calculations of Smeding & Pottasch, and lead to electron density
estimates between 40 and 60 per cent smaller.
---------------------------------------------------------
Title: Theoretical Ne v emission line ratios compared to solar
observations
Authors: Keenan, F. P.; Aggarwal, K. M.; Widing, K. G.
1986SoPh..105...47K Altcode:
The recent level population calculations for Ne v by
Aggarwal are used to determine the theoretical emission line
ratios R<SUB>1</SUB> = I(2s2p<SUP>3</SUP><SUP>1</SUP>D<SUP>o</SUP> -
2s<SUP>2</SUP>2p<SUP>2</SUP><SUP>1</SUP>D<SUP>e</SUP>)/I(2s2p<SUP>3</SUP><SUP>3</SUP>D<SUB>2</SUB><SUP>0</SUP>-
2s<SUP>2</SUP>2p<SUP>2</SUP><SUP>3</SUP>P<SUB>1</SUB><SUP>e</SUP>)
and R<SUB>2</SUB> =
I(2s2p<SUP>3</SUP><SUP>1</SUP>D<SUP>o</SUP>-2s<SUP>2</SUP>2p<SUP>2</SUP><SUP>1</SUP>D<SUP>e</SUP>)/I(2s2p<SUP>3</SUP><SUP>3</SUP>D<SUB>3</SUB><SUP>0</SUP>-2s<SUP>2</SUP>2p<SUP>2</SUP><SUP>3</SUP>P<SUB>2</SUB><SUP>e</SUP>).
A comparison of these with observational data for a solar flare and
erupting prominence obtained with the NRL XUV spectrograph on board
Skylab reveals that R<SUB>1</SUB> and R<SUB>2</SUB> are in their
predicted high density limits. Although the ratios cannot be used as
density diagnostics for values of n<SUB>e</SUB> typical of the solar
transition region, it is shown that they are temperature sensitive
and hence may be employed to determine the electron temperatures of
Ne v line emitting regions.
---------------------------------------------------------
Title: The Derivation of Solar Coronal Electron Temperature from
the 1 1S--n 1P/1 1S--2 1P Emission-Line Ratios in MG XI
Authors: Keenan, F. P.; Kingston, A. E.; McKenzie, D. L.
1986ApJ...303..486K Altcode:
Recent R-matrix calculations of electron excitation rates for
transitions in Mg XI are used to determine the theoretical emission-line
ratios as a function of electron temperature. These are found to be more
temperature sensitive than the normal diagnostic for He-like ions, by
factors of approximately 2.6 and 5.9 respectively, between T<SUB>e</SUB>
= 1 × 10<SUP>6</SUP> K and 1 × 1O<SUP>7</SUP> K. Electron temperatures
deduced from R<SUB>1</SUB>, and R<SUB>2</SUB> ratios observed by the
P78-1 satellite for solar flares and active regions are in excellent
agreement with those previously determined by other methods.
---------------------------------------------------------
Title: Plasma densities from the He-like ion NE IX
Authors: Doyle, J. G.; Keenan, F. P.
1986A&A...157..116D Altcode:
The authors present line emissivity data for the three principal lines
of the He-like ion Ne IX. This data is compared with high resolution
solar flare observations from the Solar Maximum Mission. During the
rise phase of flares it is shown that the forbidden line is blended
with a high temperature line, as opposed to the intercombination line
suggested by McKenzie (1985). It is suggested that the electron density
during the rise phase of flares be determined from the intercombination
to resonance line ratio which the authors have integrated over a
multi-thermal plasma and is shown to be only slightly dependent on
the assumed differential emission measure distribution. Scattering
of resonance line photons from the line-of-sight is shown to be
unimportant.
---------------------------------------------------------
Title: Mg vii and Si ix line ratios in the sun
Authors: Keenan, F. P.; Kingston, A. E.; Aggarwal, K. M.; Widing, K. G.
1986SoPh..103..225K Altcode:
Recent R-matrix calculations of electron excitation rates for Mg VII and
Si IX are used to determine the theoretical density sensitive emission
line ratios R<SUB>1</SUB>= I(2s2p<SUP>3</SUP><SUP>1</SUP>D<SUP>0</SUP> -
2s<SUP>2</SUP>2p<SUP>2</SUP><SUP>1</SUP>D<SUP>e</SUP>)/I(2s2p<SUP>3</SUP><SUP>3</SUP>S<SUP>0</SUP>
- 2s<SUP>2</SUP>2p<SUP>2</SUP><SUP>3</SUP>P<SUB>2</SUB><SUP>e</SUP>)
and R<SUB>2</SUB>= I(2s2p<SUP>3</SUP><SUP>1</SUP>P<SUP>0</SUP> -
2s<SUP>2</SUP>2p<SUP>2</SUP><SUP>1</SUP>D<SUP>e</SUP>)/I(2s2p<SUP>3</SUP><SUP>3</SUP>S<SUP>0</SUP>
- 2s<SUP>2</SUP>2p<SUP>2</SUP><SUP>3</SUP>P<SUB>2</SUB><SUP>e</SUP>).
These are found to be quite similar to the earlier results of Mason
and Bhatia. Electron densities derived using observed R<SUB>1</SUB>
and R<SUB>2</SUB> ratios from Skylab NRL XUV spectra of solar flares
and active regions are in good agreement, and compare favourably with
those deduced from ions formed at similar electron temperatures to Mg
VII and Si IX.
---------------------------------------------------------
Title: Observations of early-type stars at high galactic latitudes.
Authors: Keenan, F. P.; Brown, P. J. F.; Lennon, D. J.
1986A&A...155..333K Altcode:
Using equivalent widths and line profiles measured from high resolution
AAT spectra in conjunction with model atmosphere calculations, it is
shown that a sample of eleven high galactic latitude early-type stars
are normal, distant objects. Stellar velocities in the z-direction
determined from the spectra, coupled with the galactic gravitational
field g(z), allow the times the stars would have taken to reach their
present positions if they were ejected from the disc to be derived. A
comparison of these times with the evolutionary ages indicate that
at least four of the stars have been formed in situ, possibly from
galactic fountain material.
---------------------------------------------------------
Title: S V Line Ratios in the Sun
Authors: Dufton, P. L.; Hibbert, A.; Keenan, F. P.; Kingston, A. E.;
Doschek, G. A.
1986ApJ...300..448D Altcode:
In the present prediction of level populations and emission line
intensity ratios for electron densities and temperatures appropriate to
the sun, on the basis of new atomic data for S V, the electron impact
collision rates for spin-forbidden transitions, and the intercombination
transition spontaneous radiative rate, are noted to be substantially
larger than previously ascertained. The S V intensity ratio is shown
to be a useful electron density diagnostic for log N(e) greater than
11.5 ratios deduced from observations obtained with a slit spectrograph
aboard Skylab generally agree with the theoretical values presented.
---------------------------------------------------------
Title: Possible effects of organelle charge and density on cell
metabolism
Authors: Bates, B.; Catney, M. G.; Keenan, F. P.
1986AdSpR...6b..47B Altcode: 1986AdSpR...6...47B
To respond to gravity a biological system must: First, perceive the
stimulus; and, second transduce the stimulus into an appropriate
response. This laboratory has studied a system of perception and
transduction involving the gravity-induced asymmetric distribution
of a plant growth hormone. From these studies we have developed a
working theory which states as its postulates that: a) The perception
of the gravitational stimulus involved a perturbation of the plant's
bio-electric field; and b) that the transduction of the stimulus
involved voltage-gating of hormone movement from the plant's vascular
tissue into the hormone responsive growing tissue. These studies may
provide the simplest system for studing the mechanism whereby the
gravity signal is translated into a biological response. <P />Present
Address: Plant Breeding Institute, 62-095 Morowana Goslina, Przebedowo -
7, woj. Poznan, POLAND
---------------------------------------------------------
Title: The chemical composition of the young open cluster NGC 6611.
Authors: Brown, P. J. F.; Dufton, P. L.; Lennon, D. J.; Keenan, F. P.;
Kilkenny, D.
1986A&A...155..113B Altcode:
Four color photometric and spectroscopic observations for eight
early-type main sequence stars in the cluster NGC 6611 were obtained
at the South African and Anglo-Australian observatories. Equivalent
widths and line profiles were measured for lines of hydrogen, helium and
seven other elements present in the spectra of five stars. Effective
temperatures were derived from ionization equilibria while surface
gravities were estimated from profiles fitted to H-delta and H-epsilon
absorption lines. Abundances, deduced from comparison with LTE and
non-LTE model atmosphere calculations are found to be consistent with
normal early-type stellar abundances. NGC 6611 lies at a distance of
approximately 1 kpc from NGC 6231, whose early-type main sequence stars
possibly exhibit an underabundance in nitrogen. Hence the present study
implies the possibility of abundance variations over relatively small
distance scales.
---------------------------------------------------------
Title: Improved theoretical line ratios for C iii in the Sun
Authors: Keenan, F. P.; Berrington, K. A.
1985SoPh...99...25K Altcode:
The recent twelve-state R-matrix calculations of electron
excitation rates in CIII by Berrington are used to derive
level populations applicable to the solar transition
region. Line ratios R = I(2p<SUP>2 3</SUP>P<SUP>e</SUP> -
2s2p<SUP>3</SUP>P<SUP>°</SUP>)/I(2s2p<SUP>1</SUP>P<SUP>°</SUP>
- 2s<SUP>2 1</SUP>S<SUP>e</SUP>) and R<SUB>2</SUB>=I(2p<SUP>2
1</SUP>S<SUP>e</SUP> - 2s2p<SUP>1</SUP>P<SUP>°</SUP>)/I(2p<SUP>2
3</SUP>P<SUP>e</SUP> - 2s2p<SUP>3</SUP>P<SUP>°</SUP>) deduced from
these data in conjunction with the relevent transition probabilities
are found to be in much better agreement with the observed quiet Sun
values than those determined from the level population calculations
of Keenan et al.
---------------------------------------------------------
Title: Population ratios for the fine structure ground state of SI
II applicable to the interstellar medium
Authors: Keenan, F. P.; Johnson, C. T.; Kingston, A. E.; Dufton, P. L.
1985MNRAS.214P..37K Altcode:
Using recent R-matrix calculations of electron excitation rates for the
3s<SUP>2</SUP>3p<SUP>2</SUP>P<SUB>1/2</SUB>-3s<SUP>2</SUP>3p<SUP>2</SUP>P<SUB>3/2</SUB>
fine structure transition in Si II, the
electron density sensitive population ratio
n(<SUP>2</SUP>P<SUB>3/2</SUB>)/n(<SUP>2</SUP>P<SUB>1/2</SUB>)
has been derived for the ranges of temperature (100 - 20000K) and
hydrogen density (0 - 1000 cm<SUP>-3</SUP>) applicable to H I and H II
regions. The results differ appreciably from those of Smeding &
Pottasch, and lead to electron density estimates approximately 30 to
40 per cent larger.
---------------------------------------------------------
Title: The abundance of oxygen in the interstellar medium.
Authors: Keenan, F. P.; Hibbert, A.; Dufton, P. L.
1985A&A...147...89K Altcode:
O I equivalent widths observed by the Copernicus satellite and Doppler
widths determined from curves-of-growth for weak N I lines are used
to rederive column densities towards 26 early-type stars. Oxygen is
found to have a mean abundance of approximately 50 percent of its solar
value towards both reddened and unreddened stars. In addition, there
appears to be no correlation between depletion and total hydrogen
column density, in contrast to the results of York et al. (1983),
who found a greater depletion for sightlines with a log of the total
hydrogen column density of less than 20.5.
---------------------------------------------------------
Title: Oscillator strengths for transitions in N I and the
interstellar abundance of nitrogen.
Authors: Hibbert, A.; Dufton, P. L.; Keenan, F. P.
1985MNRAS.213..721H Altcode:
Oscillator strengths based on configuration interaction wavefunctions
are presented for both optically allowed and forbidden transitions
in N I. Particular attention is given to the multiplets at 951 Å
(2p<SUP>3</SUP> <SUP>4</SUP>S-2p<SUP>2</SUP>3d<SUP>2</SUP>D), 952 Å
(2p<SUP>3</SUP> <SUP>4</SUP>S-2p<SUP>2</SUP>3d<SUP>4</SUP>D) and 1160
Å (2p<SUP>3</SUP> <SUP>4</SUP>S-2p<SUP>2</SUP>3s<SUP>2</SUP>P) which
have been extensively observed by the COPERNICUS satellite. For these
transitions, the radiative rates are estimated to have an accuracy of
20 per cent or better. A re-analysis of the COPERNICUS observational
data indicates there is no depletion of nitrogen towards reddened
stars. Possible causes of a small depletion (≅0.2 dex) towards
several nearby unreddened stars are discussed.
---------------------------------------------------------
Title: The l(1)S-n(1)P/1(1)S-2(1)P emission-line ratios in O VII as
temperature diagnostics for solar flares and active regions
Authors: Keenan, F. P.; Kingston, A. E.; McKenzie, D. L.
1985ApJ...291..855K Altcode:
Recent R-matrix calculations of O VII electron excitation
rates by Tayal and Kingston are used to determine the
theoretical emission-line ratios R<SUB>1</SUB> = I(1s<SUP>2
1</SUP>S-ls3p<SUP>1</SUP>P)/I(1s<SUP>2 1</SUP>S-ls2p<SUP>1</SUP>P)
and R<SUB>2</SUB> = I(1s<SUP>2 1</SUP>S-ls4p<SUP>1</SUP>P)/
I(1s<SUP>2 1</SUP>S-ls2p<SUP>1</SUP>P). These ratios are found
to vary by factors of 3.3 and 4.9, respectively, between
T<SUB>e</SUB> = 6 x 1O<SUP>5</SUP> and 2 x 10<SUP>6</SUP>
K. However, G = [I(1s<SUP>2 1</SUP>S-1s2s<SUP>3</SUP>S) + I(1s<SUP>2
1</SUP>S-ls2p<SUP>3</SUP>P)]/I(1s<SUP>2 1</SUP>S-ls2p<SUP>1</SUP>P),
a commonly used temperature diagnostic for He-like ions, only varies by
a factor of 1.8. Electron temperatures derived using observed values of
R<SUB>1</SUB> and R<SUB>2</SUB> from P78-1 satellite spectra of solar
flares and active regions are in good agreement and compare favorably
with those deduced from G.
---------------------------------------------------------
Title: The Interstellar Abundance of Nitrogen
Authors: Keenan, F. P.; Hibbert, A.; Dufton, P. L.
1985IrAJ...17...20K Altcode:
Interstellar nitrogen abundances toward 25 stars are determined on
the basis of the N I equivalent widths of Bohlin et al. (1983) and
the oscillator strengths calculated by Hibbert et al. (1985) using
configuration-interaction wavefunctions. The results are presented
in tables and compared to those obtained by York et al. (1983) using
oscillator strengths deduced for the observed curves of growth of
other N I lines. N I is found to be undepleted toward reddened and
moderately reddened stars, in agreement with theoretical models of
nitrogen formation and adhesion into grains or grain surfaces in the
interstellar medium and in disagreement with the finding of depletion
by Ferlet (1981) and York et al. (1983). Toward unreddened stars, a
depletion of 0,2 dex is attributed to contamination of Lyman-alpha lines
by stellar absorption, to systematic errors in the data observations
or the oscillator strengths, or to the presence of N-depleted matter
toward these objects.
---------------------------------------------------------
Title: The masses of early-type stars in the galactic halo determined
from ultraviolet resonance line profiles.
Authors: Keenan, F. P.; Dufton, P. L.
1984A&A...139..227K Altcode:
Terminal velocities for stellar winds in intermediate and high
galactic latitude OB stars have been determined from high resolution
IUE ultraviolet spectra. These velocities, together with previous
estimates, have been used to deduce stellar masses which are found
to be similar to those derived from conservative and non-conservative
evolutionary tracks for Population I stars. It is therefore concluded
that the stars are not subluminous, nearby objects but are normal and
at the large z-distances calculated by previous authors.
---------------------------------------------------------
Title: Mg ix and Si xi line ratios in the sun
Authors: Keenan, F. P.; Kingston, A. E.; Dufton, P. L.; Doyle, J. G.;
Widing, K. G.
1984SoPh...94...91K Altcode:
New theoretical emission line ratios for the Be-sequence ions
MgIX and SiXI are presented. A comparison with observational
data for two solar flares and an active region loop obtained
with the Harvard EUV spectrometer and NRL XUV spectroheliograph
aboard Skylab reveals that these plasmas are in ionization
equilibrium at coronal temperatures. Unfortunately most of the
density diagnostics are not particularly useful under solar plasma
conditions, as they vary only slightly over the electron density
range 10<SUP>8</SUP>-10<SUP>13</SUP>cm<SUP>−3</SUP>. However
the SiXI ratioI(<SUP>3</SUP>P<SUP>e</SUP><SUB>2</SUB>
-<SUP>3</SUP>P<SUP>o</SUP><SUB>2</SUB>)/I(<SUP>3</SUP>P<SUP>o</SUP><SUB>1</SUB>
-<SUP>1</SUP>S<SUP>e</SUP><SUB>0</SUB>) is density sensitive in the
range 10<SUP>8</SUP> to 10<SUP>10</SUP>cm<SUP>−3</SUP>, which is
representative of electron densities found in solar active regions or
small flares.
---------------------------------------------------------
Title: Theoretical Ne ix line ratios compared to solar observations
Authors: Keenan, F. P.; Tayal, S. S.; Kingston, A. E.
1984SoPh...94...85K Altcode:
R-matrix calculations of the 1<SUP>1</SUP>S - 2<SUP>3</SUP>S and
1<SUP>1</SUP>S - 2<SUP>3</SUP>P electron excitation rates in He - like
CV, OVII, and MgXI by Kingston and Tayal are used to interpolate results
for NeIX. Adoption of these in emission line strength calculations
leads to values for the density-sensitiveR ratio very similar to those
of Pradhanet al. and Wolfsonet al., although the temperature-sensitiveG
ratios are approximately 10 to 20 % lower than those deduced by these
authors. However the present theoretical value ofG at the temperature
of maximum NeIX emission,G(T<SUB>m</SUB>) = 0.82, is in excellent
agreement with those observed by the SMM and P78-1 satellites for the
1980, November5 flare (G = 0.83 ± 0.01) and nonflaring active regions
(G = 0.80 ± 0.05), respectively.
---------------------------------------------------------
Title: SI III emission line strengths in low density plasmas.
Authors: Dufton, P. L.; Keenan, F. P.; Kingston, A. E.
1984MNRAS.209P...1D Altcode:
Theoretical emissivity ratios appropriate to homogeneous optically
thin plasmas are presented for the Si III lines at 1883 and 1892
Å. These lines are a useful density diagnostic for N<SUB>e</SUB>
≥ 10<SUP>4</SUP>cm<SUP>-3</SUP>, their use being illustrated for
the planetary nebulae NGC 7662 and V1016 Cygni.
---------------------------------------------------------
Title: Further studies of nearby high velocity interstellar gas.
Authors: Bates, B.; Brown-Kerr, W.; Giaretta, D. L.; Keenan, F. P.
1984ESASP.218..145B Altcode: 1984iue..conf..145B
Red shifted high velocity gas components (HVC) were detected in spectra
of nine out of a survey of 47 stars. The properties of gas density
and thickness of the material responsible for the HVC appear quite
similar to those derived from direct observations of supernova remnants
(SNR). The majority of the survey stars whose spectra show HVC lie close
to the Galactic plane near l = 88 to 110 deg. A distance estimate places
the HVC material within 190 pc. The improved mapping of the sky and
the distance estimate to the HVC material are discussed in terms of an
association with nearby radio loops. The possibility that the material
may be produced by two interacting SNR (Loops 2 and 3) is considered.
---------------------------------------------------------
Title: Observational evidence for non-Maxwellian electron energy
distributions in the solar transition region
Authors: Dufton, P. L.; Kingston, A. E.; Keenan, F. P.
1984ApJ...280L..35D Altcode:
Calculations of Si III emission-line strengths, which incorporate
the non-Maxwellian electron energy distributions given by Shoub,
are compared with Skylab observations for the quiet Sun and a solar
flare. The good agreement provides plausible evidence for the existence
of such electron energy distributions in the lower solar transition
region.
---------------------------------------------------------
Title: Theoretical emission line ratios for O VII in low-density
plasmas.
Authors: Keenan, F. P.; Tayal, S. S.; Kingston, A. E.
1984SoPh...92...75K Altcode:
New electron excitation rates for O VII calculated by Tayal and Kingston
using the R-matrix method are used to determine theoretical emission
line strengths. Values of the electron density sensitive ratio R
(forbidden line to intercombination line) are found to be very similar
to those deduced by other authors. However the temperature sensitive
ratios G (intercombination plus forbidden lines to resonance line)
are approximately 20% lower than the best previous estimates. The
observed value of G for solar active regions (G = 1.0 ± 0.1) predicts
an electron temperature in the range 1.1 × 10<SUP>6</SUP> K <
T<SUB>e</SUB> < 1.8 × 10<SUP>6</SUP> K, which overlaps that of
maximum O VII emissivity, T<SUB>M</SUB> = 1.8 × 10<SUP>6</SUP> K. In
addition, the theoretical G versus T<SUB>e</SUB> curve is in excellent
agreement with that observed for a Tokamak plasma.
---------------------------------------------------------
Title: The nitrogen-deficient cluster NGC 6231.
Authors: Keenan, F. P.; Brown, P. J. F.; Dufton, P. L.; Lennon, D. J.
1984ApJ...279L..11K Altcode:
Spectra of five main-sequence B type stars have been obtained for the
wavelength range from 3900 to 4020 A at a spectral resolution of 0.2
A with the Anglo-Australian Telescope. Analysis of the absorption-line
strengths yields a nitrogen underabundance of 0.5 + or - 0.1 dex with
other element abundances being normal. This composition is believed to
reflect that of the interstellar medium from which the cluster recently
formed, implying that significant galactic abundance variations are
present on distance scales of the order of 1 kpc.
---------------------------------------------------------
Title: MG XI line ratios in the sun
Authors: Keenan, F. P.; Kingston, A. E.; Tayal, S. S.
1984MNRAS.207P..51K Altcode:
The recent R-matrix calculations of the 1(1)S-2(3)S and 1(1)S-2(3)P
electron excitation collision rates in Mg XI by Tayal and Kingston
(1984) are used to determine the ratio R of the forbidden to
the intercombination line and the ratio G of the forbidden plus
intercombination lines to the resonance line. These ratios are
respectively electron density and temperature sensitive. Values for
R very similar to those deduced by Wolfson et al. (1983), Pradhan and
Shull (1981), and Pradhan (1982) are found. The results for G, however,
are 25-30 percent smaller than those calculated by these authors. The
theoretical value of G at the temperature of maximum emission is now
in excellent agreement with that observed for the November 5, 1980
flare by the SMM satellite.
---------------------------------------------------------
Title: Level populations for Be-sequence ions in astrophysical plasmas
Authors: Keenan, F. P.; Berrington, K. A.; Burke, P. G.; Kingston,
A. E.; Dufton, P. L.
1984MNRAS.207..459K Altcode:
Level populations for the 10 n = 2 states of ions in the
Be-sequence from C III to Si XI are presented. The results are for
two ranges of electron density (N<SUB>e</SUB> = 10<SUP>8</SUP> -
10<SUP>13</SUP>cm<SUP>-3</SUP> and N<SUB>e</SUB> = 10<SUP>2</SUP> -
10<SUP>7</SUP>cm<SUP>-3</SUP>), the former applicable to the solar
corona and transition region and the latter to other astrophysical
objects such as quasars and Seyfert galaxies.
---------------------------------------------------------
Title: The Effect of a Non-Maxwellian Electron Velocity Distribution
on Be-Like Ion Diagnostics in the Sun
Authors: Keenan, F. P.
1984SoPh...91...27K Altcode:
Non-Maxwellian collision rates of the Be-sequence ions CIII and OV
in the solar transition region are derived for quiet Sun and flare
conditions using the electron velocity distribution functions of
Shoub. The rates are found to be enhanced relative to the Maxwellian
values but only at low temperatures where the fractional abundances of
these species is very small. This implies that the electron density and
temperature diagnostics used by previous authors for the transition
region will be unchanged by non-Maxwellian effects. It is noted that
such effects will only be important for species that are formed at
low temperatures and have large transition energies such as HeI.
---------------------------------------------------------
Title: Photoionization rates in the interstellar medium
Authors: Keenan, F. P.
1984MNRAS.206..449K Altcode:
The Gondhalekar et al. (1980) determination of the radiation field
from 2740 A down to the Lyman limit at 912 A is the basis of the
present calculation of photoionization rates for several species that
are of importance in the interstellar medium. The results obtained are
compared with previous estimates by De Boer et al. (1973). It is noted
that large radiation field variations will occur in regions of space
near OB associations or within dense dust clouds, with corresponding
effects on the photoionization rates.
---------------------------------------------------------
Title: An LTE analysis of the blue halo star HD 214080.
Authors: Keenan, F. P.; Lennon, D. J.
1984A&A...130..179K Altcode:
Stellar equivalent widths and hydrogen line profiles measured from a
high quality coudé spectrum, are used to determine accurate atmospheric
parameters for the early-type halo star HD 214080. Abundances of helium
plus eleven other species are also derived, and are found to be similar
to those of normal OB stars, from which it is concluded that HD 214080
is an ordinary Population I object. The stellar velocity coupled with
its z-distance imply that HD 214080 cannot have been ejected from
the disc as has been proposed for other halo stars. It is concluded
that the star was probably formed in the halo, possibly as a result
of cloud-cloud collisions at high galactic latitudes.
---------------------------------------------------------
Title: Line ratios for solar ultra-violet lines of O v
Authors: Doyle, J. G.; Dufton, P. L.; Keenan, F. P.; Kingston, A. E.
1983SoPh...89..243D Altcode:
New O V rate coefficients are used to calculate the ratio of the
intensity of the 760 Å multiplet to that of the 630 Å line. Results
are given for a range of electron densities and temperatures. The
theoretical ratios are compared with observed line ratios for different
solar regions.
---------------------------------------------------------
Title: On the nature of early-type stars in the galactic halo.
Authors: Keenan, F. P.; Dufton, P. L.
1983MNRAS.205..435K Altcode:
Effective temperatures and surface gravities of 46 intermediate and high
galactic latitude OB stars have been estimated from Stromgren /C1/ and
H-beta photometry. In addition, helium, calcium and magnesium abundances
relative to hydrogen have been derived for eleven stars. The typical
OB-type stellar parameters indicate that they are normal Population I
stars, several of which require ejection velocities of more than 100
km/s from the plane in order to reach their present z-distances during
their lifetimes. The observed correlation between peculiar velocity
and mass for stars with /z/ not less than 400 pc is compatible with
the Blaauw runaway hypothesis as the acceleration mechanism. A plot of
log N(Na I) versus E(B-V) implies that the gas-to-dust ratio in the
halo is probably similar to that found for material in the galactic
disc. This implies that the sputtering of calcium from grain surfaces
is probably responsible for the observed velocity dependence of the
N(Na I)/N(Ca II) ratio.
---------------------------------------------------------
Title: Early-type Stars at Large Distances from the Galactic Plane
Authors: Keenan, F. P.
1983IrAJ...16..131K Altcode:
Tobin and Kaufmann (1984) have shown that three early-type halo stars
are normal, distant objects, and there appears to be increasing evidence
to support the large distances derived for these stars. The present
investigatiton is concerned with research which provides some insight
into the nature and possible origin of these objects. The nature of the
early-type stars in the Galactic halo is discussed, taking into account
atmospheric parameters and chemical compositions, and distances and
ejection velocities. In connection with a consideration of the origin
of the early-type halo stars, it is pointed out that some mechanism
has to be invoked to accelerate stars to large velocities in order to
explain their presence in the halo. Attention is given to the 'runaway'
hypothesis considered by Zwicky (1957).
---------------------------------------------------------
Title: IUE observations of high velocity interstellar gas tentatively
associated with Radio Loop II.
Authors: Bates, B.; Brown-Kerr, W.; Giaretta, D. L.; Keenan, F. P.
1983A&A...122...64B Altcode:
Red-shifted high velocity gas components (HVC) have been positively
detected in IUE spectra of six out of a sample of eleven selected stars
across a region of sky of some 40°. Properties of the HVC determined
from the spectra of three stars indicate that the material is cool gas
with a density n<SUB>H</SUB> ≈ 100 cm<SUP>-3</SUP> and thickness
≈0.1 pc. The HVC velocities are consistent with a large expanding
spherical shell of gas having the parameters of Radio Loop II, in
which case the expansion velocity deduced for the shell is ≈100 km
s<SUP>-1</SUP>. Whilst the authors tentatively associate the HVC with
Loop II the IUE observations suggest also that they may be smaller
scale features which are connected with the larger loop.
---------------------------------------------------------
Title: Interstellar CA II and NA I line profiles towards halo
OB stars.
Authors: Keenan, F. P.; Dufton, P. L.; McKeith, C. D.; Blades, J. C.
1983MNRAS.203..963K Altcode:
High resolution Ca II and Na I interstellar line profiles towards
several halo OB stars are presented. The profiles have been corrected
where necessary for the presence of stellar features, and analyzed using
multicomponent models to derive information on the radial velocities,
internal velocity dispersions, and column densities of individual
interstellar clouds. A method is described for estimating peculiar
velocities for the clouds, and a significant trend of decreasing R =
N(Na I)/N(Ca II) with increasing peculiar velocity is found. The ratio,
R, is also shown to be generally smaller in the halo than in the plane,
implying that many of the halo clouds may have peculiar velocities. The
data indicate that there are both few clouds and a small Ca II density
beyond the absolute z value of 2 kpc.
---------------------------------------------------------
Title: The Galactic Halo
Authors: Keenan, F. P.
1982IrAJ...15..309K Altcode:
A survey of observations and analyses of phenomena associated with the
theoretical galactic halo (GH) or corona is presented, with a focus
on research performed at Queen's University in Belfast. The origin
and main features of the GH theory are outlined, and the previous
observations supporting it are reviewed, including visible clouds at
high Galactic latitudes (z), UV absorption lines in the GH, absorption
in the haloes of other galaxies, and early-type stars in the GH. The
Queen's University work is based on spectroscopic observations of 18
high-z OB stars obtained at high resolution (lambda/delta lambda =
20,000) in the 389-402 and 576-604-nm bands with the Anglo-Australian
Telescope in September 1979 and 1980. The stars are found to be normal,
with no evidence of subluminosity, and to lie at z distances of about
0.3-3.5 kpc; hence they are considered good tracers of GH gas. A
velocity dependence of the N(Na I)/N(Ca II) ratio is observed and
attributed to Ca sputtering from grain surfaces rather than to the
collisional ionization of Na I.
---------------------------------------------------------
Title: Atmospheric parameters and chemical composition of eighteen
halo OB stars.
Authors: Keenan, F. P.; Dufton, P. L.; McKeith, C. D.
1982MNRAS.200..673K Altcode:
Stellar equivalent widths and He line profiles, measured from 5 and
10 A/mm IPCS spectra obtained at the AAT, are presented for 18 halo OB
stars. Effective temperatures and gravities have been estimated using
Stromgren and H-beta photometry in conjunction with these data. Also
derived are the abundances relative to hydrogen of helium, carbon,
nitrogen, oxygen and calcium. From the normal chemical compositions
and atmospheric parameters obtained, it is concluded that the stars are
not subluminous and show no evidence of any other peculiarities. Using
conservative and nonconservative evolutionary tracks, masses, ages and
distances are deduced for the stars, implying that several of them
have been ejected from the galactic plane with velocities in excess
of 100 km/s.
---------------------------------------------------------
Title: A fine analysis of stellar and interstellar lines towards
four halo Bstars.
Authors: Keenan, F. P.; McKeith, C. D.; Dufton, P. L.; Blades, J. C.
1981MNRAS.197..799K Altcode:
High resolution observations of Ca II and Na I interstellar line
profiles toward four halo B stars are analyzed in terms of multicloud
models. Stellar CNO lines present in the spectra have been used in
conjunction with an LTE model atmosphere program to derive values of
effective temperature and microturbulence. Using these atmospheric
parameters, stellar contributions to the interstellar Ca II and Na I
profiles have been calculated and removed. The subsequent renormalized
interstellar line profiles were analyzed to derive information on the
radial velocities, internal velocity dispersions and column densities
within individual interstellar clouds. The Na I/Ca II ratio decreases
from a value of 2 to 0.02 with increasing radial velocity; this range
is smaller than that found by previous workers using the doublet
ratio method. Additionally, the stellar CNO lines in the halo stars
imply a composition similar to that found for unevolved B stars in
the galactic plane.
