Author name code: jordan-carole
ADS astronomy entries on 2022-09-14
author:"Jordan, Carole" NOT =author:"Jordan, C.H."
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Title: Long-term rotational and emission variability of 17 radio
pulsars
Authors: Shaw, B.; Stappers, B. W.; Weltevrede, P.; Brook, P. R.;
Karastergiou, A.; Jordan, C. A.; Keith, M. J.; Kramer, M.; Lyne, A. G.
Bibcode: 2022MNRAS.513.5861S
Altcode: 2022MNRAS.tmp.1132S; 2022arXiv220410767S
With the ever-increasing sensitivity and timing baselines of modern
radio telescopes, a growing number of pulsars are being shown to exhibit
transitions in their rotational and radio emission properties. In many
of these cases, the two are correlated with pulsars assuming a unique
spin-down rate ($\dot{\nu }$) for each of their specific emission
states. In this work, we revisit 17 radio pulsars previously shown to
exhibit spin-down rate variations. Using a Gaussian process regression
(GPR) method to model the timing residuals and the evolution of the
profile shape, we confirm the transitions already observed and reveal
new transitions in 8 yr of extended monitoring with greater time
resolution and enhanced observing bandwidth. We confirm that seven
of these sources show emission-correlated $\dot{\nu }$ transitions
($\Delta \dot{\nu }$), and we characterize this correlation for one
additional pulsar, PSR B1642-03. We demonstrate that GPR is able
to reveal extremely subtle profile variations given sufficient data
quality. We also corroborate the dependence of $\Delta \dot{\nu }$
amplitude on $\dot{\nu }$ and pulsar characteristic age. Linking $\Delta
\dot{\nu }$ to changes in the global magnetospheric charge density Δρ,
we speculate that $\dot{\nu }$ transitions associated with large Δρ
values may be exhibiting detectable profile changes with improved data
quality, in cases where they have not previously been observed.
Title: The Jodrell bank glitch catalogue: 106 new rotational glitches
in 70 pulsars
Authors: Basu, A.; Shaw, B.; Antonopoulou, D.; Keith, M. J.; Lyne,
A. G.; Mickaliger, M. B.; Stappers, B. W.; Weltevrede, P.; Jordan,
C. A.
Bibcode: 2022MNRAS.510.4049B
Altcode: 2021arXiv211106835B; 2021MNRAS.tmp.3056B
Pulsar glitches are rapid spin-up events that occur in the rotation
of neutron stars, providing a valuable probe into the physics of the
interiors of these objects. Long-term monitoring of a large number
of pulsars facilitates the detection of glitches and the robust
measurements of their parameters. The Jodrell Bank pulsar timing
programme regularly monitors more than 800 radio pulsars and has
accrued, in some cases, over 50 yr of timing history on individual
objects. In this paper, we present 106 new glitches in 70 radio pulsars
as observed up to the end of 2018. For 70 per cent of these pulsars,
the event we report is its only known glitch. For each new glitch, we
provide measurements of its epoch, amplitude, and any detected changes
to the spin-down rate of the star. Combining these new glitches with
those listed in the Jodrell Bank glitch catalogue, we analyse a total
sample of 543 glitches in 178 pulsars. We model the distribution of
glitch amplitudes and spin-down rate changes using a mixture of two
Gaussian components. We corroborate the known dependence of glitch
rate and activity on pulsar spin-down rates and characteristic ages,
and show that younger pulsars tend to exhibit larger glitches. Pulsars
with spin-down rates between 10-14 and 10-10.5 Hz
s-1 show a mean reversal of 1.8 per cent of their spin-down
as a consequence of glitches. Our results are qualitatively consistent
with the superfluid vortex unpinning models of pulsar glitches.
Title: 4MOST: Project overview and information for the First Call
for Proposals
Authors: de Jong, R. S.; Agertz, O.; Berbel, A. A.; Aird, J.;
Alexander, D. A.; Amarsi, A.; Anders, F.; Andrae, R.; Ansarinejad,
B.; Ansorge, W.; Antilogus, P.; Anwand-Heerwart, H.; Arentsen, A.;
Arnadottir, A.; Asplund, M.; Auger, M.; Azais, N.; Baade, D.; Baker,
G.; Baker, S.; Balbinot, E.; Baldry, I. K.; Banerji, M.; Barden,
S.; Barklem, P.; Barthélémy-Mazot, E.; Battistini, C.; Bauer, S.;
Bell, C. P. M.; Bellido-Tirado, O.; Bellstedt, S.; Belokurov, V.;
Bensby, T.; Bergemann, M.; Bestenlehner, J. M.; Bielby, R.; Bilicki,
M.; Blake, C.; Bland-Hawthorn, J.; Boeche, C.; Boland, W.; Boller,
T.; Bongard, S.; Bongiorno, A.; Bonifacio, P.; Boudon, D.; Brooks,
D.; Brown, M. J. I.; Brown, R.; Brüggen, M.; Brynnel, J.; Brzeski,
J.; Buchert, T.; Buschkamp, P.; Caffau, E.; Caillier, P.; Carrick,
J.; Casagrande, L.; Case, S.; Casey, A.; Cesarini, I.; Cescutti, G.;
Chapuis, D.; Chiappini, C.; Childress, M.; Christlieb, N.; Church, R.;
Cioni, M. -R. L.; Cluver, M.; Colless, M.; Collett, T.; Comparat, J.;
Cooper, A.; Couch, W.; Courbin, F.; Croom, S.; Croton, D.; Daguisé,
E.; Dalton, G.; Davies, L. J. M.; Davis, T.; de Laverny, P.; Deason,
A.; Dionies, F.; Disseau, K.; Doel, P.; Döscher, D.; Driver, S. P.;
Dwelly, T.; Eckert, D.; Edge, A.; Edvardsson, B.; Youssoufi, D. E.;
Elhaddad, A.; Enke, H.; Erfanianfar, G.; Farrell, T.; Fechner, T.;
Feiz, C.; Feltzing, S.; Ferreras, I.; Feuerstein, D.; Feuillet, D.;
Finoguenov, A.; Ford, D.; Fotopoulou, S.; Fouesneau, M.; Frenk, C.;
Frey, S.; Gaessler, W.; Geier, S.; Gentile Fusillo, N.; Gerhard,
O.; Giannantonio, T.; Giannone, D.; Gibson, B.; Gillingham, P.;
González-Fernández, C.; Gonzalez-Solares, E.; Gottloeber, S.; Gould,
A.; Grebel, E. K.; Gueguen, A.; Guiglion, G.; Haehnelt, M.; Hahn, T.;
Hansen, C. J.; Hartman, H.; Hauptner, K.; Hawkins, K.; Haynes, D.;
Haynes, R.; Heiter, U.; Helmi, A.; Aguayo, C. H.; Hewett, P.; Hinton,
S.; Hobbs, D.; Hoenig, S.; Hofman, D.; Hook, I.; Hopgood, J.; Hopkins,
A.; Hourihane, A.; Howes, L.; Howlett, C.; Huet, T.; Irwin, M.; Iwert,
O.; Jablonka, P.; Jahn, T.; Jahnke, K.; Jarno, A.; Jin, S.; Jofre,
P.; Johl, D.; Jones, D.; Jönsson, H.; Jordan, C.; Karovicova, I.;
Khalatyan, A.; Kelz, A.; Kennicutt, R.; King, D.; Kitaura, F.; Klar,
J.; Klauser, U.; Kneib, J. -P.; Koch, A.; Koposov, S.; Kordopatis, G.;
Korn, A.; Kosmalski, J.; Kotak, R.; Kovalev, M.; Kreckel, K.; Kripak,
Y.; Krumpe, M.; Kuijken, K.; Kunder, A.; Kushniruk, I.; Lam, M. I.;
Lamer, G.; Laurent, F.; Lawrence, J.; Lehmitz, M.; Lemasle, B.; Lewis,
J.; Li, B.; Lidman, C.; Lind, K.; Liske, J.; Lizon, J. -L.; Loveday,
J.; Ludwig, H. -G.; McDermid, R. M.; Maguire, K.; Mainieri, V.; Mali,
S.; Mandel, H.; Mandel, K.; Mannering, L.; Martell, S.; Martinez
Delgado, D.; Matijevic, G.; McGregor, H.; McMahon, R.; McMillan,
P.; Mena, O.; Merloni, A.; Meyer, M. J.; Michel, C.; Micheva, G.;
Migniau, J. -E.; Minchev, I.; Monari, G.; Muller, R.; Murphy, D.;
Muthukrishna, D.; Nandra, K.; Navarro, R.; Ness, M.; Nichani, V.;
Nichol, R.; Nicklas, H.; Niederhofer, F.; Norberg, P.; Obreschkow, D.;
Oliver, S.; Owers, M.; Pai, N.; Pankratow, S.; Parkinson, D.; Paschke,
J.; Paterson, R.; Pecontal, A.; Parry, I.; Phillips, D.; Pillepich,
A.; Pinard, L.; Pirard, J.; Piskunov, N.; Plank, V.; Plüschke, D.;
Pons, E.; Popesso, P.; Power, C.; Pragt, J.; Pramskiy, A.; Pryer,
D.; Quattri, M.; Queiroz, A. B. d. A.; Quirrenbach, A.; Rahurkar,
S.; Raichoor, A.; Ramstedt, S.; Rau, A.; Recio-Blanco, A.; Reiss, R.;
Renaud, F.; Revaz, Y.; Rhode, P.; Richard, J.; Richter, A. D.; Rix,
H. -W.; Robotham, A. S. G.; Roelfsema, R.; Romaniello, M.; Rosario, D.;
Rothmaier, F.; Roukema, B.; Ruchti, G.; Rupprecht, G.; Rybizki, J.;
Ryde, N.; Saar, A.; Sadler, E.; Sahlén, M.; Salvato, M.; Sassolas,
B.; Saunders, W.; Saviauk, A.; Sbordone, L.; Schmidt, T.; Schnurr,
O.; Scholz, R. -D.; Schwope, A.; Seifert, W.; Shanks, T.; Sheinis,
A.; Sivov, T.; Skúladóttir, Á.; Smartt, S.; Smedley, S.; Smith,
G.; Smith, R.; Sorce, J.; Spitler, L.; Starkenburg, E.; Steinmetz,
M.; Stilz, I.; Storm, J.; Sullivan, M.; Sutherland, W.; Swann, E.;
Tamone, A.; Taylor, E. N.; Teillon, J.; Tempel, E.; ter Horst, R.;
Thi, W. -F.; Tolstoy, E.; Trager, S.; Traven, G.; Tremblay, P. -E.;
Tresse, L.; Valentini, M.; van de Weygaert, R.; van den Ancker, M.;
Veljanoski, J.; Venkatesan, S.; Wagner, L.; Wagner, K.; Walcher,
C. J.; Waller, L.; Walton, N.; Wang, L.; Winkler, R.; Wisotzki, L.;
Worley, C. C.; Worseck, G.; Xiang, M.; Xu, W.; Yong, D.; Zhao, C.;
Zheng, J.; Zscheyge, F.; Zucker, D.
Bibcode: 2019Msngr.175....3D
Altcode: 2019arXiv190302464D
We introduce the 4-metre Multi-Object Spectroscopic Telescope (4MOST),
a new high-multiplex, wide-field spectroscopic survey facility under
development for the four-metre-class Visible and Infrared Survey
Telescope for Astronomy (VISTA) at Paranal. Its key specifications
are: a large field of view (FoV) of 4.2 square degrees and a high
multiplex capability, with 1624 fibres feeding two low-resolution
spectrographs (R = λ/Δλ 6500), and 812 fibres transferring light
to the high-resolution spectrograph (R 20 000). After a description of
the instrument and its expected performance, a short overview is given
of its operational scheme and planned 4MOST Consortium science; these
aspects are covered in more detail in other articles in this edition
of The Messenger. Finally, the processes, schedules, and policies
concerning the selection of ESO Community Surveys are presented,
commencing with a singular opportunity to submit Letters of Intent
for Public Surveys during the first five years of 4MOST operations.
Title: The Age of Syrtis Major Planum and Implications for the
Circum-Isidis Region
Authors: Fawdon, P.; Balme, M. R.; Vye-Brown, C.; Jordan, C. J.;
Rothery, D. A.
Bibcode: 2019LPI....50.2362F
Altcode:
Syrtis Major Planum is a good stratigraphic marker and is useful
differentiating when regional processes occurred.
Title: Probing the Epoch or Reionisation with the MWA
Authors: Jordan, C.; Trott, C.; Lynch, C.; Line, J. L. B.
Bibcode: 2019qopu.confE..18J
Altcode: 2019PoS...356E..18J
No abstract at ADS
Title: Tests of gravitational symmetries with pulsar binary J1713+0747
Authors: Zhu, W. W.; Desvignes, G.; Wex, N.; Caballero, R. N.;
Champion, D. J.; Demorest, P. B.; Ellis, J. A.; Janssen, G. H.;
Kramer, M.; Krieger, A.; Lentati, L.; Nice, D. J.; Ransom, S. M.;
Stairs, I. H.; Stappers, B. W.; Verbiest, J. P. W.; Arzoumanian,
Z.; Bassa, C. G.; Burgay, M.; Cognard, I.; Crowter, K.; Dolch, T.;
Ferdman, R. D.; Fonseca, E.; Gonzalez, M. E.; Graikou, E.; Guillemot,
L.; Hessels, J. W. T.; Jessner, A.; Jones, G.; Jones, M. L.; Jordan,
C.; Karuppusamy, R.; Lam, M. T.; Lazaridis, K.; Lazarus, P.; Lee,
K. J.; Levin, L.; Liu, K.; Lyne, A. G.; McKee, J. W.; McLaughlin,
M. A.; Osłowski, S.; Pennucci, T.; Perrodin, D.; Possenti, A.;
Sanidas, S.; Shaifullah, G.; Smits, R.; Stovall, K.; Swiggum, J.;
Theureau, G.; Tiburzi, C.
Bibcode: 2019MNRAS.482.3249Z
Altcode: 2018arXiv180209206Z; 2018MNRAS.tmp.2776Z
Symmetries play a fundamental role in modern theories of gravity. The
strong equivalence principle (SEP) constitutes a collection of
gravitational symmetries which are all implemented by general
relativity. Alternative theories, however, are generally expected
to violate some aspects of SEP. We test three aspects of SEP using
observed change rates in the orbital period and eccentricity of binary
pulsar J1713+0747: (1) the gravitational constant's constancy as part of
locational invariance of gravitation; (2) the universality of free fall
(UFF) for strongly self-gravitating bodies; (3) the post-Newtonian
parameter \hat{α }_3 in gravitational Lorentz invariance. Based
on the pulsar timing result of the combined data set from the North
American Nanohertz Gravitational Observatory and the European Pulsar
Timing Array, we find \dot{G}/G = (-0.1 ± 0.9) × 10^{-12} yr^{-1},
which is weaker than Solar system limits, but applies for strongly
self-gravitating objects. Furthermore, we obtain an improved test
for a UFF violation by a strongly self-gravitating mass falling in
the gravitational field of our Galaxy, with a limit of |Δ| <
0.002 (95 per cent C.L.). Finally, we derive an improved limit on
the self-acceleration of a gravitationally bound rotating body,
to a preferred reference frame in the Universe, with -3× 10^{-20}
< \hat{α }_3 < 4× 10^{-20} (95 per cent C.L.). These results
are based on direct UFF and \hat{α }_3 tests using pulsar binaries,
and they overcome various limitations of previous tests of this kind.
Title: Temporal variations in scattering and dispersion measure in
the Crab Pulsar and their effect on timing precision
Authors: McKee, J. W.; Lyne, A. G.; Stappers, B. W.; Bassa, C. G.;
Jordan, C. A.
Bibcode: 2018MNRAS.479.4216M
Altcode: 2018MNRAS.tmp.1658M; 2018arXiv180610486M
We have measured variations in scattering time-scales in the Crab
Pulsar over a 30-yr period, using observations made at 610 MHz with
the 42-ft telescope at Jodrell Bank Observatory. Over more recent
years, where regular Lovell Telescope observations at frequencies
around 1400 MHz were available, we have also determined the dispersion
measure variations, after disentangling the scattering delay from the
dispersive delay. We demonstrate a relationship between scattering
and dispersion measure variations, with a correlation coefficient
of 0.56 ± 0.01. The short time-scales over which these quantities
vary, the size of the variations, and the close correlation between
scattering and dispersion measure all suggest that the effects are due
to discrete structures within the Crab Nebula, with size scales of ∼6
au (corresponding to an angular size of ∼2 mas at an assumed distance
of 2200 pc). We mitigate the effects of scattering on the observed
pulse shape by using the measured scattering information to modify the
template used for generating the pulse arrival times, thus improving
the precision to which the pulsar can be timed. We test this on timing
data taken during periods of high scattering, and obtain a factor of
two improvements in the root mean square of the timing residuals.
Title: Long-term observations of pulsars in the globular clusters
47 Tucanae and M15
Authors: Ridolfi, A.; Freire, P. C. C.; Kramer, M.; Bassa, C. G.;
Camilo, F.; D'Amico, N.; Desvignes, G.; Heinke, C. O.; Jordan, C.;
Lorimer, D. R.; Lyne, A.; Manchester, R. N.; Pan, Z.; Sarkissian,
J.; Torne, P.; van den Berg, M.; Venkataraman, A.; Wex, N.
Bibcode: 2018IAUS..337..251R
Altcode: 2017arXiv171106086R
Multi-decade observing campaigns of the globular clusters 47 Tucanae and
M15 have led to an outstanding number of discoveries. Here, we report on
the latest results of the long-term observations of the pulsars in these
two clusters. For most of the pulsars in 47 Tucanae we have measured,
among other things, their higher-order spin period derivatives, which
have in turn provided stringent constraints on the physical parameters
of the cluster, such as its distance and gravitational potential. For
M15, we have studied the relativistic spin precession effect in PSR
B2127+11C. We have used full-Stokes observations to model the precession
effect, and to constrain the system geometry. We find that the visible
beam of the pulsar is swiftly moving away from our line of sight and
may very soon become undetectable. On the other hand, we expect to
see the opposite emission beam sometime between 2041 and 2053.
Title: The largest glitch observed in the Crab pulsar
Authors: Shaw, B.; Lyne, A. G.; Stappers, B. W.; Weltevrede, P.;
Bassa, C. G.; Lien, A. Y.; Mickaliger, M. B.; Breton, R. P.; Jordan,
C. A.; Keith, M. J.; Krimm, H. A.
Bibcode: 2018MNRAS.478.3832S
Altcode: 2018arXiv180505110S; 2018MNRAS.tmp.1227S
We have observed a large glitch in the Crab pulsar (PSR B0531+21). The
glitch occurred around MJD 58064 (2017 November 8) when the pulsar
underwent an increase in the rotation rate of Δν = 1.530 ×
10-5 Hz, corresponding to a fractional increase of Δν/ν
= 0.516 × 10-6, making this event the largest glitch ever
observed in this source. Due to our high-cadence and long-dwell time
observations of the Crab pulsar, we are able to partially resolve
a fraction of the total spin-up of the star. This delayed spin-up
occurred over a time-scale of ∼1.7 d and is similar to the behaviour
seen in the 1989 and 1996 large Crab pulsar glitches. The spin-down
rate also increased at the glitch epoch by Δ \dot{ν } / \dot{ν }
= 7 × 10^{-3}. In addition to being the largest such event observed
in the Crab, the glitch occurred after the longest period of glitch
inactivity since at least 1984 and we discuss a possible relationship
between glitch size and waiting time. No changes to the shape of the
pulse profile were observed near the glitch epoch at 610 or 1520 MHz,
nor did we identify any changes in the X-ray flux from the pulsar. The
long-term recovery from the glitch continues to progress as \dot{ν }
slowly rises towards pre-glitch values. In line with other large Crab
glitches, we expect there to be a persistent change to \dot{ν }. We
continue to monitor the long-term recovery with frequent, high-quality
observations.
Title: Comparing Redundant and Sky-model-based Interferometric
Calibration: A First Look with Phase II of the MWA
Authors: Li, W.; Pober, J. C.; Hazelton, B. J.; Barry, N.; Morales,
M. F.; Sullivan, I.; Parsons, A. R.; Ali, Z. S.; Dillon, J. S.;
Beardsley, A. P.; Bowman, J. D.; Briggs, F.; Byrne, R.; Carroll, P.;
Crosse, B.; Emrich, D.; Ewall-Wice, A.; Feng, L.; Franzen, T. M. O.;
Hewitt, J. N.; Horsley, L.; Jacobs, D. C.; Johnston-Hollitt, M.;
Jordan, C.; Joseph, R. C.; Kaplan, D. L.; Kenney, D.; Kim, H.;
Kittiwisit, P.; Lanman, A.; Line, J.; McKinley, B.; Mitchell, D. A.;
Murray, S.; Neben, A.; Offringa, A. R.; Pallot, D.; Paul, S.; Pindor,
B.; Procopio, P.; Rahimi, M.; Riding, J.; Sethi, S. K.; Udaya Shankar,
N.; Steele, K.; Subrahmanian, R.; Tegmark, M.; Thyagarajan, N.; Tingay,
S. J.; Trott, C.; Walker, M.; Wayth, R. B.; Webster, R. L.; Williams,
A.; Wu, C.; Wyithe, S.
Bibcode: 2018ApJ...863..170L
Altcode: 2018arXiv180705312L
Interferometric arrays seeking to measure the 21 cm signal from the
epoch of reionization (EOR) must contend with overwhelmingly bright
emission from foreground sources. Accurate recovery of the 21 cm
signal will require precise calibration of the array, and several
new avenues for calibration have been pursued in recent years,
including methods using redundancy in the antenna configuration. The
newly upgraded Phase II of Murchison Widefield Array (MWA) is the
first interferometer that has large numbers of redundant baselines
while retaining good instantaneous UV coverage. This array therefore
provides a unique opportunity to compare redundant calibration with
sky-model-based algorithms. In this paper, we present the first
results from comparing both calibration approaches with MWA Phase II
observations. For redundant calibration, we use the package OMNICAL
and produce sky-based calibration solutions with the analysis package
Fast Holographic Deconvolution (FHD). There are three principal
results: (1) We report the success of OMNICAL on observations of
ORBComm satellites, showing substantial agreement between redundant
visibility measurements after calibration. (2) We directly compare
OMNICAL calibration solutions with those from FHD and demonstrate
that these two different calibration schemes give extremely similar
results. (3) We explore improved calibration by combining OMNICAL and
FHD. We evaluate these combined methods using power spectrum techniques
developed for EOR analysis and find evidence for marginal improvements
mitigating artifacts in the power spectrum. These results are likely
limited by the signal-to-noise ratio in the 6 hr of data used, but they
suggest future directions for combining these two calibration schemes.
Title: A long-term study of three rotating radio transients
Authors: Bhattacharyya, B.; Lyne, A. G.; Stappers, B. W.; Weltevrede,
P.; Keane, E. F.; McLaughlin, M. A.; Kramer, M.; Jordan, C.; Bassa, C.
Bibcode: 2018MNRAS.477.4090B
Altcode: 2018MNRAS.tmp..880B; 2018arXiv180310277B
We present the longest term timing study so far of three rotating
radio transients (RRATs) - J1819-1458, J1840-1419, and J1913+1330 -
performed using the Lovell, Parkes, and Green Bank telescopes over
the past decade. We study long-term and short-term variations of the
pulse emission rate from these RRATs and report a marginal indication
of a long-term increase in pulse detection rate over time for PSR
J1819-1458 and J1913+1330. For PSR J1913+1330, we also observe a two
orders of magnitude variation in the observed pulse detection rates
across individual epochs, which may constrain the models explaining
the origin of RRAT pulses. PSR J1913+1330 is also observed to exhibit
a weak persistent emission mode. We investigate the post-glitch
timing properties of J1819-1458 (the only RRAT for which glitches are
observed) and discuss the implications for possible glitch models. Its
post-glitch over-recovery of the frequency derivative is magnetar-like
and similar behaviour is only observed for two other pulsars, both of
which have relatively high magnetic field strengths. Following the
over-recovery, we also observe that some fraction of the pre-glitch
frequency derivative is gradually recovered.
Title: VizieR Online Data Catalog: Southern H II Region Discovery
Survey: pilot survey (Brown+, 2017)
Authors: Brown, C.; Jordan, C.; Dickey, J. M.; Anderson, L. D.;
Armentrout, W. P.; Balser, D. S.; Bania, T. M.; Dawson, J. R.; Mc
Clure-Griffiths, N. M.; Wenger, T. V.
Bibcode: 2018yCat..51540023B
Altcode:
The Southern H II Region Discovery Survey (SHRDS) is a multi-year
project using the Australia Telescope Compact Array (ATCA) to complement
the GBT and Arecibo HRDS by extending the survey area into the southern
sky (δ<-45°). This area includes the Southern end of the Galactic
Bar, the Near and Far 3 kpc Arms, the Norma/Cygnus Arm, the Scutum/Crux
Arm, the Sagitttarius/Carina Arm, and outside the solar circle, the
Perseus Arm, and the Outer Arm. All pilot SHRDS observations used the
ATCA in the five antenna H75 array configuration, giving a nominal
maximum baseline of 75 m and a beam size of FWHM ~65" at 7.8 GHz
depending on the declination and hour angles of the observations. The
SHRDS pilot observations were done in two sessions. Epoch I, observed
2013 June 30, focused on candidates that were expected to show bright
radio recombination line (RRL) detections, which they did. Epoch II,
observed 2014 June 26 and 27, used a list of candidates with expected
flux densities typical of the SHRDS catalog as a whole. The two epochs
also used different longitude ranges in order to generate samples of
H II regions with different Galactic radii. (3 data files).
Title: Stellar Parameters, Chemical composition and Models of
chemical evolution
Authors: Mishenina, T.; Pignatari, M.; Côté, B.; Thielemann, F. -K.;
Soubiran, C.; Basak, N.; Gorbaneva, T.; Korotin, S. A.; Kovtyukh,
V. V.; Wehmeyer, B.; Bisterzo, S.; Travaglio, C.; Gibson, B. K.;
Jordan, C.; Paul, A.; Ritter, C.; Herwig, F.
Bibcode: 2018IAUS..330..331M
Altcode:
We present an in-depth study of metal-poor stars, based high resolution
spectra combined with newly released astrometric data from Gaia,
with special attention to observational uncertainties. The results
are compared to those of other studies, including Gaia benchmark
stars. Chemical evolution models are discussed, highlighting few puzzles
that are still affecting our understanding of stellar nucleosynthesis
and of the evolution of our Galaxy.
Title: Evolved and Explosive Volcanism in Meroe Patera and Syrtis
Major Central Caldera Complex
Authors: Fawdon, P.; Rogers, D.; Skok, J. R.; Balme, M.; Vye-Brown,
C.; Jordan, C.; Rothery, D.
Bibcode: 2018LPI....49.2865F
Altcode:
Thermally-distinct materials in the Syrtis Major caldera complex are
an extrusive high silica lava and possible further outcrops associated
with an ignimbrite.
Title: A Study of the Interstellar Medium Towards the Unidentified
Dark TeV γ-Ray Sources HESS J1614-518 and HESS J1616-508
Authors: Lau, J. C.; Rowell, G.; Voisin, F.; Braiding, C.; Burton,
M.; Fukui, Y.; Pointon, S.; Ashley, M.; Jordan, C.; Walsh, A.
Bibcode: 2017PASA...34...64L
Altcode: 2017arXiv171101687L
HESS J1614-518 and HESS J1616-508 are two tera-electron volt γ-ray
sources that are not firmly associated with any known counterparts
at other wavelengths. We investigate the distribution of interstellar
medium towards the tera-electron volt γ-ray sources using results from
a 7-mm-wavelength Mopra study, the Mopra Southern Galactic Plane CO
Survey, the Millimetre Astronomer's Legacy Team-45 GHz survey and [C
i] data from the HEAT telescope. Data in the CO(1-0) transition lines
reveal diffuse gas overlapping the two tera-electron volt sources
at several velocities along the line of sight, while observations
in the CS(1-0) transition line reveal several interesting dense gas
features. To account for the diffuse atomic gas, archival H i data
was taken from the Southern Galactic Plane Survey. The observations
reveal gas components with masses 103 to 105
M⊙ and with densities 102 to 103
cm-3 overlapping the two tera-electron volt sources. Several
origin scenarios potentially associated with the tera-electron volt
γ-ray sources are discussed in light of the distribution of the local
interstellar medium. We find no strong convincing evidence linking
any counterpart with HESS J1614-518 or HESS J1616-508.
Title: Long-term observations of the pulsars in 47 Tucanae -
II. Proper motions, accelerations and jerks
Authors: Freire, P. C. C.; Ridolfi, A.; Kramer, M.; Jordan, C.;
Manchester, R. N.; Torne, P.; Sarkissian, J.; Heinke, C. O.; D'Amico,
N.; Camilo, F.; Lorimer, D. R.; Lyne, A. G.
Bibcode: 2017MNRAS.471..857F
Altcode: 2017arXiv170604908F
This paper is the second in a series where we report the results of the
long-term timing of the millisecond pulsars (MSPs) in 47 Tucanae with
the Parkes 64-m radio telescope. We obtain improved timing parameters
that provide additional information for studies of the cluster dynamics:
(a) the pulsar proper motions yield an estimate of the proper motion
of the cluster as a whole (μα = 5.00 ± 0.14 mas yr
- 1, μδ = - 2.84 ± 0.12 mas yr - 1)
and the motion of the pulsars relative to each other. (b) We measure
the second spin-period derivatives caused by the change of the
pulsar line-of-sight accelerations; 47 Tuc H, U and possibly J are
being affected by nearby objects. (c) For 10 binary systems, we now
measure changes in the orbital period caused by their acceleration in
the gravitational field of the cluster. From all these measurements,
we derive a cluster distance no smaller than ∼4.69 kpc and show that
the characteristics of these MSPs are very similar to their counterparts
in the Galactic disc. We find no evidence in favour of an intermediate
mass black hole at the centre of the cluster. Finally, we describe
the orbital behaviour of four 'black widow' systems. Two of them,
47 Tuc J and O, exhibit orbital variability similar to that observed
in other such systems, while for 47 Tuc I and R the orbits seem to be
remarkably stable. It appears therefore that not all 'black widows'
have unpredictable orbital behaviour.
Title: Observing the metal-poor solar neighbourhood: a comparison
of galactic chemical evolution predictions*†
Authors: Mishenina, T.; Pignatari, M.; Côté, B.; Thielemann, F. -K.;
Soubiran, C.; Basak, N.; Gorbaneva, T.; Korotin, S. A.; Kovtyukh,
V. V.; Wehmeyer, B.; Bisterzo, S.; Travaglio, C.; Gibson, B. K.;
Jordan, C.; Paul, A.; Ritter, C.; Herwig, F.; NuGrid Collaboration
Bibcode: 2017MNRAS.469.4378M
Altcode: 2017arXiv170503642M
Atmospheric parameters and chemical compositions for 10 stars with
metallicities in the region of -2.2 < [Fe/H] < -0.6 were precisely
determined using high-resolution, high signal-to-noise, spectra. For
each star, the abundances, for 14-27 elements, were derived using both
local thermodynamic equilibrium (LTE) and non-LTE (NLTE) approaches. In
particular, differences by assuming LTE or NLTE are about 0.10 dex;
depending on [Fe/H], Teff, gravity and element lines used
in the analysis. We find that the O abundance has the largest error,
ranging from 0.10 and 0.2 dex. The best measured elements are Cr, Fe,
and Mn; with errors between 0.03 and 0.11 dex. The stars in our sample
were included in previous different observational work. We provide
a consistent data analysis. The data dispersion introduced in the
literature by different techniques and assumptions used by the different
authors is within the observational errors, excepting for HD103095. We
compare these results with stellar observations from different data
sets and a number of theoretical galactic chemical evolution (GCE)
simulations. We find a large scatter in the GCE results, used to study
the origin of the elements. Within this scatter as found in previous
GCE simulations, we cannot reproduce the evolution of the elemental
ratios [Sc/Fe], [Ti/Fe], and [V/Fe] at different metallicities. The
stellar yields from core-collapse supernovae are likely primarily
responsible for this discrepancy. Possible solutions and open problems
are discussed.
Title: The Southern H II Region Discovery Survey (SHRDS): Pilot Survey
Authors: Brown, C.; Jordan, C.; Dickey, John M.; Anderson, L. D.;
Armentrout, W. P.; Balser, Dana S.; Bania, T. M.; Dawson, J. R.;
McClure-Griffiths, N. M.; Wenger, Trey V.
Bibcode: 2017AJ....154...23B
Altcode: 2017arXiv170508610B
The Southern H II Region Discovery Survey is a survey of the third
and fourth quadrants of the Galactic plane that will detect radio
recombination line (RRL) and continuum emission at cm-wavelengths from
several hundred H II region candidates using the Australia Telescope
Compact Array. The targets for this survey come from the WISE Catalog
of Galactic H II Regions and were identified based on mid-infrared
and radio continuum emission. In this pilot project, two different
configurations of the Compact Array Broad Band receiver and spectrometer
system were used for short test observations. The pilot surveys
detected RRL emission from 36 of 53 H II region candidates, as well
as seven known H II regions that were included for calibration. These
36 recombination line detections confirm that the candidates are true
H II regions and allow us to estimate their distances.
Title: Syrtis Major Planum (Mars): A Type Example or a Special Case
of a Large Igneous Province
Authors: Fawdon, P.; Balme, M. R.; Vye-Brown, C.; Rothery, D. A.;
Jordan, C. J.
Bibcode: 2017LPI....48.2138F
Altcode:
We present the geological history of Syrtis Major Planum (Mars),
which provides an example of how large igneous provinces develop on
terrestrial planets.
Title: VizieR Online Data Catalog: 42 millisecond pulsars
high-precision timing (Desvignes+, 2016)
Authors: Desvignes, G.; Caballero, R. N.; Lentati, L.; Verbiest,
J. P. W.; Champion, D. J.; Stappers, B. W.; Janssen, G. H.; Lazarus,
P.; Oslowski, S.; Babak, S.; Bassa, C. G.; Brem, P.; Burgay, M.;
Cognard, I.; Gair, J. R.; Graikou, E.; Guillemot, L.; Hessels,
J. W. T.; Jessner, A.; Jordan, C.; Karuppusamy, R.; Kramer, M.;
Lassus, A.; Lazaridis, K.; Lee, K. J.; Liu, K.; Lyne, A. G.; McKee,
J.; Mingarelli, C. M. F.; Perrodin, D.; Petiteau, A.; Possenti, A.;
Purver, M. B.; Rosado, P. A.; Sanidas, S.; Sesana, A.; Shaifullah, G.;
Smits, R.; Taylor, S. R.; Theureau, G.; Tiburzi, C.; van Haasteren,
R.; Vecchio, A.
Bibcode: 2017yCat..74583341D
Altcode:
This paper presents the EPTA data set, up to mid-2014, that was
gathered from the 'historical' pulsar instrumentations at EFF, JBO,
NRT and WSRT with, respectively, the EBPP (Effelsberg-Berkeley Pulsar
Processor), DFB (Digital FilterBank), BON (Berkeley-Orleans-Nancay)
and PuMa (Pulsar Machine) backends. The data recorded with the newest
generation of instrumentations, e.g. PSRIX at EFF (Lazarus et al.,
2016MNRAS.458..868L) and PuMaII at WSRT (Karuppusamy, Stappers &
van Straten 2008PASP..120..191K), will be part of a future EPTA data
release. (8 data files).
Title: Epoch of Reionisation
Authors: Barry, N.; Beardsley, A.; Bowman, J.; Briggs, F.; Byrne,
R.; Carroll, P.; Hazelton, B.; Jacobs, D.; Jordan, C.; Kittiwisit,
P.; Lanman, A.; Lenc, E.; Li, W.; Line, J.; McKinley, B.; Mitchell,
D.; Morales, M.; Murray, S.; Paul, S.; Pindor, B.; Pober, J.; Rahimi,
M.; Riding, J.; Sethi, S.; Shankar, U.; Subrahmanyan, R.; Sullivan,
I.; Takahashi, K.; Thyagarajan, N.; Tingay, S.; Trott, C.; Wayth,
R.; Webster, R.; Wyithe, S.
Bibcode: 2017mwa..prop..A12W
Altcode:
The Murchison Widefield Array is designed to measure the fluctuations
in the 21cm emission from neutral hydrogen during the Epoch of
Reionisation. The new hex configuration is explicitly designed to test
the predicted increase in sensitivity of redundant baselines. However
the challenge of the new array is to understand calibration with the
new configuration. We have developed two new pipelines to reduce the
hex data, and will compare the results with previous datasets from
the Phase 1 array. We have now processed 80 hours of data refining
the data analysis through our two established Phase 1 pipelines. This
proposal requests as much observing time as possible in semester 2017-A
to (1) obtain a comparable hex dataset to test the sensitivity and
systematic limits with redundant arrays, (2) establish the optimal
observing strategy for an EoR detection, and (3) continue to explore
observational strategies in the three EoR fields to advise the design
of SKA-low experiments. Due to the proposed changes in the array during
the upcoming semester, we have not requested a specific number of hours,
but will optimise our observing program as availability of the telescope
becomes clear. We note that this observing proposal implements the
key scientific program that can benefit from the new hex configuration.
Title: Long-term observations of the pulsars in 47 Tucanae - I. A
study of four elusive binary systems
Authors: Ridolfi, A.; Freire, P. C. C.; Torne, P.; Heinke, C. O.;
van den Berg, M.; Jordan, C.; Kramer, M.; Bassa, C. G.; Sarkissian,
J.; D'Amico, N.; Lorimer, D.; Camilo, F.; Manchester, R. N.; Lyne, A.
Bibcode: 2016MNRAS.462.2918R
Altcode: 2016arXiv160707248R
For the past couple of decades, the Parkes radio telescope has
been regularly observing the millisecond pulsars in 47 Tucanae
(47 Tuc). This long-term timing programme was designed to address
a wide range of scientific issues related to these pulsars and the
globular cluster where they are located. In this paper, the first of
a series, we address one of these objectives: the characterization
of four previously known binary pulsars for which no precise orbital
parameters were known, namely 47 Tuc P, V, W and X (pulsars 47 Tuc R
and Y are discussed elsewhere). We determined the previously unknown
orbital parameters of 47 Tuc V and X and greatly improved those of 47
Tuc P and W. For pulsars W and X we obtained, for the first time, full
coherent timing solutions across the whole data span, which allowed
a much more detailed characterization of these systems. 47 Tuc W,
a well-known tight eclipsing binary pulsar, exhibits a large orbital
period variability, as expected for a system of its class. 47 Tuc
X turns out to be in a wide, extremely circular, 10.9-d long binary
orbit and its position is ∼3.8 arcmin away from the cluster centre,
more than three times the distance of any other pulsar in 47 Tuc. These
characteristics make 47 Tuc X a very different object with respect to
the other pulsars of the cluster.
Title: 21 year timing of the black-widow pulsar J2051-0827
Authors: Shaifullah, G.; Verbiest, J. P. W.; Freire, P. C. C.;
Tauris, T. M.; Wex, N.; Osłowski, S.; Stappers, B. W.; Bassa,
C. G.; Caballero, R. N.; Champion, D. J.; Cognard, I.; Desvignes, G.;
Graikou, E.; Guillemot, L.; Janssen, G. H.; Jessner, A.; Jordan, C.;
Karuppusamy, R.; Kramer, M.; Lazaridis, K.; Lazarus, P.; Lyne, A. G.;
McKee, J. W.; Perrodin, D.; Possenti, A.; Tiburzi, C.
Bibcode: 2016MNRAS.462.1029S
Altcode: 2016arXiv160704167S
Timing results for the black-widow pulsar J2051-0827 are presented,
using a 21 year data set from four European Pulsar Timing Array
telescopes and the Parkes radio telescope. This data set, which is
the longest published to date for a black-widow system, allows for
an improved analysis that addresses previously unknown biases. While
secular variations, as identified in previous analyses, are recovered,
short-term variations are detected for the first time. Concurrently,
a significant decrease of ∼ 2.5 × 10- 3 cm- 3
pc in the dispersion measure associated with PSR J2051-0827 is measured
for the first time and improvements are also made to estimates of
the proper motion. Finally, PSR J2051-0827 is shown to have entered
a relatively stable state suggesting the possibility of its eventual
inclusion in pulsar timing arrays.
Title: A glitch in the millisecond pulsar J0613-0200
Authors: McKee, J. W.; Janssen, G. H.; Stappers, B. W.; Lyne, A. G.;
Caballero, R. N.; Lentati, L.; Desvignes, G.; Jessner, A.; Jordan,
C. A.; Karuppusamy, R.; Kramer, M.; Cognard, I.; Champion, D. J.;
Graikou, E.; Lazarus, P.; Osłowski, S.; Perrodin, D.; Shaifullah,
G.; Tiburzi, C.; Verbiest, J. P. W.
Bibcode: 2016MNRAS.461.2809M
Altcode: 2016arXiv160604098M
We present evidence for a small glitch in the spin evolution of
the millisecond pulsar J0613-0200, using the EPTA Data Release 1.0,
combined with Jodrell Bank analogue filterbank times of arrival (TOAs)
recorded with the Lovell telescope and Effelsberg Pulsar Observing
System TOAs. A spin frequency step of 0.82(3) nHz and frequency
derivative step of -1.6(39) × 10-19 Hz s-1 are
measured at the epoch of MJD 50888(30). After PSR B1821-24A, this is
only the second glitch ever observed in a millisecond pulsar, with a
fractional size in frequency of Δν/ν = 2.5(1) × 10-12,
which is several times smaller than the previous smallest glitch. PSR
J0613-0200 is used in gravitational wave searches with pulsar timing
arrays, and is to date only the second such pulsar to have experienced
a glitch in a combined 886 pulsar-years of observations. We find that
accurately modelling the glitch does not impact the timing precision
for pulsar timing array applications. We estimate that for the current
set of millisecond pulsars included in the International Pulsar Timing
Array, there is a probability of ∼50 per cent that another glitch
will be observed in a timing array pulsar within 10 years.
Title: A millisecond pulsar in an extremely wide binary system
Authors: Bassa, C. G.; Janssen, G. H.; Stappers, B. W.; Tauris,
T. M.; Wevers, T.; Jonker, P. G.; Lentati, L.; Verbiest, J. P. W.;
Desvignes, G.; Graikou, E.; Guillemot, L.; Freire, P. C. C.; Lazarus,
P.; Caballero, R. N.; Champion, D. J.; Cognard, I.; Jessner, A.;
Jordan, C.; Karuppusamy, R.; Kramer, M.; Lazaridis, K.; Lee, K. J.;
Liu, K.; Lyne, A. G.; McKee, J.; Osłowski, S.; Perrodin, D.; Sanidas,
S.; Shaifullah, G.; Smits, R.; Theureau, G.; Tiburzi, C.; Zhu, W. W.
Bibcode: 2016MNRAS.460.2207B
Altcode: 2016arXiv160400129B
We report on 22 yr of radio timing observations of the millisecond
pulsar J1024-0719 by the telescopes participating in the European Pulsar
Timing Array (EPTA). These observations reveal a significant second
derivative of the pulsar spin frequency and confirm the discrepancy
between the parallax and Shklovskii distances that has been reported
earlier. We also present optical astrometry, photometry and spectroscopy
of 2MASS J10243869-0719190. We find that it is a low-metallicity
main-sequence star (K7V spectral type, [M/H] = -1.0, Teff
= 4050 ± 50 K) and that its position, proper motion and distance
are consistent with those of PSR J1024-0719. We conclude that PSR
J1024-0719 and 2MASS J10243869-0719190 form a common proper motion pair
and are gravitationally bound. The gravitational interaction between
the main-sequence star and the pulsar accounts for the spin frequency
derivatives, which in turn resolves the distance discrepancy. Our
observations suggest that the pulsar and main-sequence star are in
an extremely wide (Pb > 200 yr) orbit. Combining the
radial velocity of the companion and proper motion of the pulsar,
we find that the binary system has a high spatial velocity of 384
± 45 km s-1 with respect to the local standard of rest
and has a Galactic orbit consistent with halo objects. Since the
observed main-sequence companion star cannot have recycled the
pulsar to millisecond spin periods, an exotic formation scenario
is required. We demonstrate that this extremely wide-orbit binary
could have evolved from a triple system that underwent an asymmetric
supernova explosion, though find that significant fine-tuning during
the explosion is required. Finally, we discuss the implications of the
long period orbit on the timing stability of PSR J1024-0719 in light
of its inclusion in pulsar timing arrays.
Title: Epoch of Reionisation
Authors: Barry, N.; Beardsley, A.; Bowman, J.; Briggs, F.; Byrne, R.;
Carroll, P.; Hazelton, B.; Jacobs, D.; Jordan, C.; Kittiwisit, P.;
Lanman, A.; Lenc, E.; Li, W.; Line, J.; McKinley, B.; Mitchell, D.;
Morales, M.; Murray, S.; Paul, S.; Pindor, B.; Pober, J.; Procopio,
P.; Rahimi, M.; Riding, J.; Sethi, S.; Shankar, U.; Subrahmanyan, R.;
Sullivan, I.; Takahashi, K.; Thyagarajan, N.; Tingay, S.; Trott, C.;
Wayth, R.; Webster, R.; Wyithe, S.
Bibcode: 2016mwa..prop..B04W
Altcode:
The Murchison Widefield Array is designed to measure the fluctuations
in the 21cm emission from neutral hydrogen during the Epoch of
Reionisation. The new hex configuration is explicitly designed to test
the predicted increase in sensitivity of redundant baselines. However
the challenge of the new array is to understand calibration with the
new configuration. We have developed two new pipelines to reduce the
hex data, and will compare the results with previous datasets from
the Phase 1 array. We have now processed 80 hours of data refining
the data analysis through our two established Phase 1 pipelines. This
proposal requests a total of 730 hours of observing time in semester
2016-B to (1) obtain a comparable hex dataset to test the sensitivity
and systematic limits with redundant arrays, (2) establish the optimal
observing strategy for an EoR detection, and (3) continue to explore
observational strategies in the three EoR fields to advise the design of
SKA-low experiments. We note that this observing proposal implements the
key scientific program that can benefit from the new hex configuration.
Title: Single-Source Gravitational Wave Limits From the J1713+0747
24-hr Global Campaign
Authors: Dolch, T.; NANOGrav Collaboration; Ellis, J. A.; Chatterjee,
S.; Cordes, J. M.; Lam, M. T.; Bassa, C.; Bhattacharyya, B.; Champion,
D. J.; Cognard, I.; Crowter, K.; Demorest, P. B.; Hessels, J. W. T.;
Janssen, G.; Jenet, F. A.; Jones, G.; Jordan, C.; Karuppusamy, R.;
Keith, M.; Kondratiev, V. I.; Kramer, M.; Lazarus, P.; Lazio, T. J. W.;
Lorimer, D. R.; Madison, D. R.; McLaughlin, M. A.; Palliyaguru,
N.; Perrodin, D.; Ransom, S. M.; Roy, J.; Shannon, R. M.; Smits,
R.; Stairs, I. H.; Stappers, B. W.; Stinebring, D. R.; Stovall, K.;
Verbiest, J. P. W.; Zhu, W. W.
Bibcode: 2016JPhCS.716a2014D
Altcode: 2015arXiv150905446D
Dense, continuous pulsar timing observations over a 24-hr period
provide a method for probing intermediate gravitational wave (GW)
frequencies from 10 microhertz to 20 millihertz. The European Pulsar
Timing Array (EPTA), the North American Nanohertz Observatory for
Gravitational Waves (NANOGrav), the Parkes Pulsar Timing Array (PPTA),
and the combined International Pulsar Timing Array (IPTA) all use
millisecond pulsar observations to detect or constrain GWs typically
at nanohertz frequencies. In the case of the IPTA's nine-telescope
24-Hour Global Campaign on millisecond pulsar J1713+0747, GW limits
in the intermediate frequency regime can be produced. The negligible
change in dispersion measure during the observation minimizes red noise
in the timing residuals, constraining any contributions from GWs due
to individual sources. At 10-5 Hz, the 95% upper limit on
strain is 10-11 for GW sources in the pulsar's direction.
Title: High-precision timing of 42 millisecond pulsars with the
European Pulsar Timing Array
Authors: Desvignes, G.; Caballero, R. N.; Lentati, L.; Verbiest,
J. P. W.; Champion, D. J.; Stappers, B. W.; Janssen, G. H.; Lazarus,
P.; Osłowski, S.; Babak, S.; Bassa, C. G.; Brem, P.; Burgay, M.;
Cognard, I.; Gair, J. R.; Graikou, E.; Guillemot, L.; Hessels,
J. W. T.; Jessner, A.; Jordan, C.; Karuppusamy, R.; Kramer, M.;
Lassus, A.; Lazaridis, K.; Lee, K. J.; Liu, K.; Lyne, A. G.; McKee,
J.; Mingarelli, C. M. F.; Perrodin, D.; Petiteau, A.; Possenti, A.;
Purver, M. B.; Rosado, P. A.; Sanidas, S.; Sesana, A.; Shaifullah, G.;
Smits, R.; Taylor, S. R.; Theureau, G.; Tiburzi, C.; van Haasteren,
R.; Vecchio, A.
Bibcode: 2016MNRAS.458.3341D
Altcode: 2016arXiv160208511D; 2016MNRAS.tmp..265D
We report on the high-precision timing of 42 radio millisecond pulsars
(MSPs) observed by the European Pulsar Timing Array (EPTA). This EPTA
Data Release 1.0 extends up to mid-2014 and baselines range from
7-18 yr. It forms the basis for the stochastic gravitational-wave
background, anisotropic background, and continuous-wave limits
recently presented by the EPTA elsewhere. The Bayesian timing analysis
performed with TEMPONEST yields the detection of several new parameters:
seven parallaxes, nine proper motions and, in the case of six binary
pulsars, an apparent change of the semimajor axis. We find the NE2001
Galactic electron density model to be a better match to our parallax
distances (after correction from the Lutz-Kelker bias) than the M2 and
M3 models by Schnitzeler. However, we measure an average uncertainty
of 80 per cent (fractional) for NE2001, three times larger than what
is typically assumed in the literature. We revisit the transverse
velocity distribution for a set of 19 isolated and 57 binary MSPs and
find no statistical difference between these two populations. We detect
Shapiro delay in the timing residuals of PSRs J1600-3053 and J1918-0642,
implying pulsar and companion masses m_p=1.22_{-0.35}^{+0.5} M_{⊙},
m_c = 0.21_{-0.04}^{+0.06} M_{⊙} and m_p=1.25_{-0.4}^{+0.6} M_{⊙},
m_c = 0.23_{-0.05}^{+0.07} M_{⊙}, respectively. Finally, we use
the measurement of the orbital period derivative to set a stringent
constraint on the distance to PSRs J1012+5307 and J1909-3744, and set
limits on the longitude of ascending node through the search of the
annual-orbital parallax for PSRs J1600-3053 and J1909-3744.
Title: The Red Radio Ring: a gravitationally lensed hyperluminous
infrared radio galaxy at z = 2.553 discovered through the citizen
science project SPACE WARPS
Authors: Geach, J. E.; More, A.; Verma, A.; Marshall, P. J.; Jackson,
N.; Belles, P. -E.; Beswick, R.; Baeten, E.; Chavez, M.; Cornen, C.;
Cox, B. E.; Erben, T.; Erickson, N. J.; Garrington, S.; Harrison,
P. A.; Harrington, K.; Hughes, D. H.; Ivison, R. J.; Jordan, C.; Lin,
Y. -T.; Leauthaud, A.; Lintott, C.; Lynn, S.; Kapadia, A.; Kneib,
J. -P.; Macmillan, C.; Makler, M.; Miller, G.; Montaña, A.; Mujica,
R.; Muxlow, T.; Narayanan, G.; O'Briain, D.; O'Brien, T.; Oguri,
M.; Paget, E.; Parrish, M.; Ross, N. P.; Rozo, E.; Rusu, Cristian
E.; Rykoff, E. S.; Sanchez-Argüelles, D.; Simpson, R.; Snyder, C.;
Schloerb, F. P.; Tecza, M.; Wang, W. -H.; Van Waerbeke, L.; Wilcox,
J.; Viero, M.; Wilson, G. W.; Yun, M. S.; Zeballos, M.
Bibcode: 2015MNRAS.452..502G
Altcode: 2015arXiv150305824G
We report the discovery of a gravitationally lensed hyperluminous
infrared galaxy (intrinsic LIR ≈ 1013
L⊙) with strong radio emission (intrinsic L1.4
GHz ≈ 1025 W Hz-1) at z = 2.553. The
source was identified in the citizen science project SPACE WARPS
through the visual inspection of tens of thousands of iJKs
colour composite images of luminous red galaxies (LRGs), groups and
clusters of galaxies and quasars. Appearing as a partial Einstein
ring (re ≈ 3 arcsec) around an LRG at z = 0.2, the
galaxy is extremely bright in the sub-millimetre for a cosmological
source, with the thermal dust emission approaching 1 Jy at peak. The
redshift of the lensed galaxy is determined through the detection of the
CO(3→2) molecular emission line with the Large Millimetre Telescope's
Redshift Search Receiver and through [O III] and Hα line detections
in the near-infrared from Subaru/Infrared Camera and Spectrograph. We
have resolved the radio emission with high-resolution (300-400 mas)
eMERLIN L-band and Very Large Array C-band imaging. These observations
are used in combination with the near-infrared imaging to construct a
lens model, which indicates a lensing magnification of μ ≈ 10. The
source reconstruction appears to support a radio morphology comprised
of a compact (<250 pc) core and more extended component, perhaps
indicative of an active nucleus and jet or lobe.
Title: Carbon-rich Presolar Grains from Massive Stars: Subsolar
12C/13C and 14N/15N
Ratios and the Mystery of 15N
Authors: Pignatari, M.; Zinner, E.; Hoppe, P.; Jordan, C. J.; Gibson,
B. K.; Trappitsch, R.; Herwig, F.; Fryer, C.; Hirschi, R.; Timmes,
F. X.
Bibcode: 2015ApJ...808L..43P
Altcode: 2015arXiv150609056P
Carbon-rich grains with isotopic anomalies compared to the Sun are
found in primitive meteorites. They were made by stars, and carry the
original stellar nucleosynthesis signature. Silicon carbide grains
of Type X and C and low-density (LD) graphites condensed in the
ejecta of core-collapse supernovae. We present a new set of models
for the explosive He shell and compare them with the grains showing
12C/13C and 14N/15N ratios
lower than solar. In the stellar progenitor H was ingested into the He
shell and not fully destroyed before the explosion. Different explosion
energies and H concentrations are considered. If the supernova shock
hits the He-shell region with some H still present, the models can
reproduce the C and N isotopic signatures in C-rich grains. Hot-CNO
cycle isotopic signatures are obtained, including a large production
of 13C and 15N. The short-lived radionuclides
22Na and 26Al are increased by orders of
magnitude. The production of radiogenic 22Ne from the decay
of 22Na in the He shell might solve the puzzle of the Ne-E(L)
component in LD graphite grains. This scenario is attractive for the SiC
grains of type AB with 14N/15N ratios lower than
solar, and provides an alternative solution for SiC grains originally
classified as nova grains. Finally, this process may contribute to the
production of 14N and 15N in the Galaxy, helping
to produce the 14N/15N ratio in the solar system.
Title: The geological history of Nili Patera, Mars
Authors: Fawdon, P.; Skok, J. R.; Balme, M. R.; Vye-Brown, C. L.;
Rothery, D. A.; Jordan, C. J.
Bibcode: 2015JGRE..120..951F
Altcode:
Nili Patera is a 50 km diameter caldera at the center of the Syrtis
Major Planum volcanic province. The caldera is unique among Martian
volcanic terrains in hosting: (i) evidence of both effusive and
explosive volcanism, (ii) hydrothermal silica, and (iii) compositional
diversity from olivine-rich basalts to silica-enriched units. We have
produced a new geological map using three mosaicked 18 m/pixel Context
Camera digital elevation models, supplemented by Compact Remote Imaging
Spectrometer for Mars Hyperspectral data. The map contextualizes these
discoveries, formulating a stratigraphy in which Nili Patera formed by
trapdoor collapse into a volcanotectonic depression. The distinctive
bright floor of Nili Patera formed either as part of a felsic pluton,
exposed during caldera formation, or as remnants of welded ignimbrite(s)
associated with caldera formation—both scenarios deriving from
melting in the Noachian highland basement. After caldera collapse,
there were five magmatic episodes: (1) a basaltic unit in the caldera's
north, (2) a silica-enriched unit and the associated Nili Tholus cone,
(3) an intrusive event, forming a ~300 m high elliptical dome; (4) an
extrusive basaltic unit, emplaced from small cones in the east; and (5)
an extreme olivine-bearing unit, formed on the western caldera ring
fault. The mapping, together with evidence for hydrated materials,
implies magmatic interaction with subsurface volatiles. This, in an
area of elevated geothermal gradient, presents a possible habitable
environment (sampled by the hydrothermal deposits). Additionally,
similarities to other highland volcanoes imply similar mechanisms and
thus astrobiological potential within those edifices.
Title: Evolving Magmas, Explosive Eruptions and Hydrothermal Deposits
at Nili Patea Caldera, Syrtis Major, Mars
Authors: Fawdon, P.; Skok, J. R.; Balme, M. R.; Vye-Brown, C.; Rothery,
D. A.; Jordan, C. J.
Bibcode: 2015LPI....46.1783F
Altcode: 2015LPICo1832.1783F
Nili Patera: ignimbrites, caldera collapse, intrusive and extrusive
magmatism, and implications for habitability.
Title: 45 years of rotation of the Crab pulsar
Authors: Lyne, A. G.; Jordan, C. A.; Graham-Smith, F.; Espinoza,
C. M.; Stappers, B. W.; Weltevrede, P.
Bibcode: 2015MNRAS.446..857L
Altcode: 2014arXiv1410.0886L
The 30-Hz rotation rate of the Crab pulsar has been monitored at
Jodrell Bank Observatory since 1984 and by other observatories before
then. Since 1968, the rotation rate has decreased by about 0.5 Hz,
interrupted only by sporadic and small spin-up events (glitches). 24 of
these events have been observed, including a significant concentration
of 15 occurring over an interval of 11 yr following MJD 50000. The
monotonic decrease of the slowdown rate is partially reversed at
glitches. This reversal comprises a step and an asymptotic exponential
with a 320-d time constant, as determined in the three best-isolated
glitches. The cumulative effect of all glitches is to reduce the
decrease in slowdown rate by about 6 per cent. Overall, a low mean
braking index of 2.342(1) is measured for the whole period, compared
with values close to 2.5 in intervals between glitches. Removing
the effects of individual glitches reveals an underlying power-law
slowdown with the same braking index of 2.5. We interpret this
value in terms of a braking torque due to a dipolar magnetic field
in which the inclination angle between the dipole and rotation axes
is increasing. There may also be further effects due to a monopolar
particle wind or infalling supernova debris.
Title: A 24 Hr Global Campaign to Assess Precision Timing of the
Millisecond Pulsar J1713+0747
Authors: Dolch, T.; Lam, M. T.; Cordes, J.; Chatterjee, S.; Bassa,
C.; Bhattacharyya, B.; Champion, D. J.; Cognard, I.; Crowter, K.;
Demorest, P. B.; Hessels, J. W. T.; Janssen, G.; Jenet, F. A.; Jones,
G.; Jordan, C.; Karuppusamy, R.; Keith, M.; Kondratiev, V.; Kramer,
M.; Lazarus, P.; Lazio, T. J. W.; Lee, K. J.; McLaughlin, M. A.;
Roy, J.; Shannon, R. M.; Stairs, I.; Stovall, K.; Verbiest, J. P. W.;
Madison, D. R.; Palliyaguru, N.; Perrodin, D.; Ransom, S.; Stappers,
B.; Zhu, W. W.; Dai, S.; Desvignes, G.; Guillemot, L.; Liu, K.; Lyne,
A.; Perera, B. B. P.; Petroff, E.; Rankin, J. M.; Smits, R.
Bibcode: 2014ApJ...794...21D
Altcode: 2014arXiv1408.1694D
The radio millisecond pulsar J1713+0747 is regarded as one of the
highest-precision clocks in the sky and is regularly timed for the
purpose of detecting gravitational waves. The International Pulsar
Timing Array Collaboration undertook a 24 hr global observation of
PSR J1713+0747 in an effort to better quantify sources of timing
noise in this pulsar, particularly on intermediate (1-24 hr)
timescales. We observed the pulsar continuously over 24 hr with
the Arecibo, Effelsberg, GMRT, Green Bank, LOFAR, Lovell, Nançay,
Parkes, and WSRT radio telescopes. The combined pulse times-of-arrival
presented here provide an estimate of what sources of timing noise,
excluding DM variations, would be present as compared to an idealized
\sqrt{N} improvement in timing precision, where N is the number of
pulses analyzed. In the case of this particular pulsar, we find that
intrinsic pulse phase jitter dominates arrival time precision when the
signal-to-noise ratio of single pulses exceeds unity, as measured using
the eight telescopes that observed at L band/1.4 GHz. We present first
results of specific phenomena probed on the unusually long timescale
(for a single continuous observing session) of tens of hours, in
particular interstellar scintillation, and discuss the degree to which
scintillation and profile evolution affect precision timing. This
paper presents the data set as a basis for future, deeper studies.
Title: The Nili Patea Caldera; Evolving Magmas, Explosive Eruptions
and Hydrothermal Deposits on Mars
Authors: Fawdon, P.; Skok, J. R.; Balme, M. R.; Vye-Brown, C. L.;
Rothery, D. A.; Jordan, C. J.
Bibcode: 2014LPI....45.1967F
Altcode:
A geological history connecting: Caldera formation, with an ignimbrite
or pluton base. Post-caldera dacite flows, resurgent dome, and mafic
ring fault volcanism.
Title: A Day in the Life of Millisecond Pulsar J1713+0747: Limits
on Timing Precision Over 24 Hours and Implications for Gravitational
Wave Detection
Authors: Dolch, Timothy; Bailes, M.; Bassa, C.; Bhat, R.;
Bhattacharyya, B.; Champion, D.; Chatterjee, S.; Cognard, I.; Cordes,
J. M.; Crowter, K.; Demorest, P.; Finn, L. S.; Fonseca, E.; Hessels,
J.; Hobbs, G.; Janssen, G.; Jones, G.; Jordan, C.; Karuppusamy, R.;
Keith, M.; Kramer, M.; Kraus, A.; Lam, M. T.; Lazarus, P.; Lazio,
J.; Lee, K.; Levin, L.; Liu, K.; Lorimer, D.; Manchester, R. N.;
McLaughlin, M.; Palliyaguru, N.; Perrodin, D.; Petroff, E.; Rajwade,
K.; Rankin, J. M.; Ransom, S. M.; Rosenblum, J.; Roy, J.; Shannon, R.;
Stappers, B.; Stinebring, D.; Stovall, K.; Teixeira, M.; van Leeuwen,
J.; van Straten, W.; Verbiest, J.; Zhu, W.
Bibcode: 2014AAS...22311404D
Altcode:
A 24-hour global observation of millisecond radio pulsar J1713+0747 was
undertaken by the International Pulsar Timing Array (IPTA) collaboration
as an effort to better quantify sources of noise in this object,
which is regularly timed for the purpose of detecting gravitational
waves (GWs). Given an 8-year timing RMS of 30ns, it is regarded as one
of the best precision clocks in the PTA. However, sources of timing
noise visible on timescales longer than the usual 20-30min biweekly
observation may nonetheless be present. Data from the campaign were
taken contiguously with the Parkes, Arecibo, Green Bank, GMRT, LOFAR,
Effelsberg, WSRT, Lovell, and Nancay radio telescopes. The combined
pulse times-of-arrival provide an estimate of the absolute noise floor,
in other words, what unaccounted sources of timing noise impede an
otherwise simple sqrt(N) improvement in timing precision, where N
is the number of pulses in a single observing session. We present
first results of specific phenomena probed on the unusual timescale
of tens of hours, in particular interstellar scattering (ISS), and
discuss the degree to which ISS affects precision timing. Finally,
we examine single pulse information during selected portions of the
observation and determine the degree to which the pulse jitter of
J1713+0747 varies throughout the course of the day-long dataset.
Title: VizieR Online Data Catalog: HIJASS HI survey in the Ursa
Major region (Wolfinger+, 2013)
Authors: Wolfinger, K.; Kilborn, V. A.; Koribalski, B. S.; Minchin,
R. F.; Boyce, P. J.; Disney, M. J.; Lang, R. H.; Jordan, C. A.
Bibcode: 2014yCat..74281790W
Altcode:
The HI data cubes analysed in this paper were obtained in 2001-2002
as part of the HIJASS (Lang et al., 2003, Cat. J/MNRAS/342/738). The
blind HI survey was conducted using the four-beam receiver mounted on
the 76.2-m Lovell telescope at Jodrell Bank Observatory, UK. (3
data files).
Title: InSAR Monitoring OF Landslides In Britain: BGS' Feasibility
Map And First ISBAS Studies Over The South Wales Coalfield
Authors: Cigna, F.; Bateson, L.; Dashwood, C.; Jordan, C. J.; Sowter,
A.; Boon, D.
Bibcode: 2013ESASP.722E.286C
Altcode:
InSAR is an accepted method for monitoring ground motion, however its
applicability in non-urban areas is generally limited except for rocky
terrains. This paper investigates a new method for deriving improved
results outside the urban environment. Topographic distortions to
the ERS-1/2 and ENVISAT SAR acquisition modes are simulated based on
high resolution DTMs of the landmass of Britain. Persistent Scatterers
(PS) densities are predicted by calibrating the CORINE Land Cover 2006
dataset using PS data available via the ESA Terrafirma and EC FP7 PanGeo
projects. The InSAR feasibility to monitor land motions is discussed for
the South Wales Coalfield, and the Intermittent Small Baseline Subset
(ISBAS) technique is tested over the Coalfield using 55 ERS-1/2 images
(1992-1999). With unprecedented target coverage, ISBAS reveals up to
1cm/yr uplift in areas of former coal mining, likely associated with
groundwater rebound following cessation of mine water pumping.
Title: The volcanic and tectonic evolution of Syrtis Major
Authors: Fawdon, P.; Balme, M. R.; Vye-Brown, C. L.; Rothery, D. A.;
Jordan, C. J.
Bibcode: 2013EPSC....8..204F
Altcode:
The Syrtis Major Planum, originally mapped as unit Hs in the Greely
and Guest 1987 map [1], is a low-angle basaltic shield volcano
(Figure 1). Greeley and Guest suggested it is Hesperian (3.7 - 3.0
Ga) age, but recent work suggests a wider range of formation ages
[2]. The edifice is a 1500 km by 1100 km (~1 % of the martian surface)
basaltic lava plain with a total lava thickness of ~500 m.. At
the center of the edifice there is a 1500 m depression containing
two distinct central calderas believed to contain evolved volcanic
products [3]. Additionally, extensional and compressional fault systems,
orientated concentrically and radially from the central caldera complex,
dissect the flanks. Syrtis Major has not been holistically investigated
since a summary of MGS data in 2004 [4]. Other works have focused on
different aspects of its evolution.
Title: Searches for Dispersed Radio Pulsar Emission from the Sag
A* SGR
Authors: Bassa, C. G.; Jordan, C. A.; Keane, E. F.; Lyne, A. G.;
Stappers, B. W.; Weltevrede, P.
Bibcode: 2013ATel.5033....1B
Altcode:
We report on a search for radio pulsations at the 3.76-s period found
by Mori et al. (ATEL #5020) of the magnetar towards Sgr A*. The 76-m
Lovell radio telescope at Jodrell Bank observed the XRT position
(Kennea et al. ATEL #5009) from 03:30UT to 04:30UT on April 27,
2013. Raw voltages of two orthogonal polarisations over 400 MHz of
bandwidth at L-band (1332 to 1732MHz) were Nyquist sampled, digitised
at 8 bits and recorded to disk.
Title: The Evolution of Volcanism in Syrtis Major Planum (Mars):
Drawing Insight from Terrestrial Analogues
Authors: Fawdon, P.; Balme, M. R.; Vye-Brown, C. L.; Rothery, D. A.;
Jordan, C. J.
Bibcode: 2013LPI....44.2232F
Altcode: 2013LPICo1719.2232F
Using two rheological models we calculate eruption parameters and
rheological properties for lava flows on Syrtis Major Planum.
Title: A blind HI survey in the Ursa Major region
Authors: Wolfinger, K.; Kilborn, V. A.; Koribalski, B. S.; Minchin,
R. F.; Boyce, P. J.; Disney, M. J.; Lang, R. H.; Jordan, C. A.
Bibcode: 2013MNRAS.428.1790W
Altcode: 2012MNRAS.tmp..163W; 2012arXiv1210.2727W
We have conducted the first blind HI survey covering 480 deg2
and a heliocentric velocity range from 300 to 1900 km s-1
to investigate the HI content of the nearby spiral-rich Ursa Major
region and to look for previously uncatalogued gas-rich objects. Here
we present the catalogue of HI sources. The HI data were obtained with
the four-beam receiver mounted on the 76.2-m Lovell telescope [full
width at half-maximum (FWHM) 12 arcmin] at the Jodrell Bank Observatory
(UK) as part of the HI Jodrell All Sky Survey (HIJASS). We use the
automated source finder duchamp and identify 166 H i sources in the data
cubes with HI masses in the range of 107-1010.5
M⊙. Our Ursa Major HI catalogue includes 10 first-time
detections in the 21-cm emission line. We identify optical
counterparts for 165 HI sources (99 per cent). For 54 HI sources
(∼33 per cent) we find numerous optical counterparts in the
HIJASS beam, indicating a high density of galaxies and likely tidal
interactions. Four of these HI systems are discussed in detail. We find only one HI source (1 per cent) without a visible optical
counterpart out of the 166 HI detections. Green Bank Telescope (FWHM
9 arcmin) follow-up observations confirmed this HI source and its HI
properties. The nature of this detection is discussed and compared to
similar sources in other HI surveys.
Title: Analytical approximations to numerical solutions of theoretical
emission measure distributions
Authors: Jordan, C.; Ness, J. -U.; Sim, S. A.
Bibcode: 2012MNRAS.419.2987J
Altcode: 2011arXiv1110.2342J; 2011MNRAS.tmp.2007J
Emission line fluxes from cool stars are widely used
to establish an apparent emission measure distribution,
Emdapp(Te), between temperatures characteristic
of the low transition region and the low corona. The true emission
measure distribution, Emdt(Te), is determined
by the energy balance and geometry adopted and, with a numerical
model, can be used to predict Emdapp(Te),
to guide further modelling. The scaling laws that exist between
coronal parameters arise from the dimensions of the terms in the
energy balance equation. Here, analytical approximations to numerical
solutions for Emdt(Te) are presented, which show
how the constants in the coronal scaling laws are determined. The
apparent emission measure distributions show a minimum value at
some To and a maximum at the mean coronal temperature
Tc (although in some stars, emission from active regions
can contribute). It is shown that, for the energy balance and
geometry adopted, the analytical values of the emission measure
and electron pressure at To and Tc depend on
only three parameters: the stellar surface gravity and the values of
To and Tc. The results are tested against full
numerical solutions for ɛ Eri (K2 V) and are applied to Procyon (α
CMi, F5 IV/V). The analytical approximations can be used to restrict
the required range of full numerical solutions, to check the assumed
geometry and to show where the adopted energy balance may not be
appropriate.
Title: Third largest Glitch observed in the rotation of the Crab
pulsar
Authors: Espinoza, C. M.; Jordan, C.; Bassa, C.; Janssen, G.; Lyne,
A. G.; Smith, F. G.; Stappers, B. W.; Weltevrede, P.
Bibcode: 2011ATel.3777....1E
Altcode:
The normal spindown of the Crab pulsar was suddenly interrupted by
an increase in its rotation rate at around 12:30 GTM on the 10th
of November 2011. Using the almost daily observations performed by
the 42-ft (at 608 MHz) and Lovell (at 1520 MHz) radiotelescopes at
Jodrell Bank Observatory, we measure a difference of dNu=1.4 +- 0.1
uHz between the projected spin frequency using pre-glitch ephemerides
(http://www.jb.man.ac.uk/pulsar/crab.html) and the current observations.
Title: A search for optical bursts from the rotating radio transient
J1819-1458 with ULTRACAM - II. Simultaneous ULTRACAM-Lovell Telescope
observations
Authors: Dhillon, V. S.; Keane, E. F.; Marsh, T. R.; Stappers, B. W.;
Copperwheat, C. M.; Hickman, R. D. G.; Jordan, C. A.; Kerry, P.;
Kramer, M.; Littlefair, S. P.; Lyne, A. G.; Mignani, R. P.; Shearer, A.
Bibcode: 2011MNRAS.414.3627D
Altcode: 2011MNRAS.tmp..709D; 2011arXiv1103.1304D
The rotating radio transient (RRAT) J1819-1458 exhibits ∼3 ms bursts
in the radio every ∼3 min, implying that it is visible for only ∼1
s per day. Assuming that the optical light behaves in a similar manner,
long exposures of the field would be relatively insensitive due to the
accumulation of sky photons. A much better way of detecting optical
emission from J1819-1458 would then be to observe with a high-speed
optical camera simultaneously with radio observations, and co-add only
those optical frames coincident with the dispersion-corrected radio
bursts. We present the results of such a search, using simultaneous
ULTRACAM and Lovell Telescope observations. We find no evidence for
optical bursts in J1819-1458 at magnitudes brighter than i'= 19.3 (5σ
limit). This is nearly 3 mag fainter than the previous burst limit,
which had no simultaneous radio observations.
Title: The emission line near 1319 Å in solar and stellar spectra
Authors: Jordan, C.
Bibcode: 2011MNRAS.414..634J
Altcode: 2011MNRAS.tmp..392J; 2011arXiv1102.0476J
An emission line at ≃1319Å is one of the strongest unidentified
lines in the ultraviolet spectra of cool dwarf stars. In most lists
of solar and stellar lines it is identified as a transition in N I,
although its intensity would then be anomalous and the wavelength does
not precisely fit that expected for N I. The line is also observed
in giant stars but becomes very weak in supergiants, relative to
photoexcited lines of neutral atoms. The measured wavelength of
the line in stellar spectra is 1318.94 ± 0.01 Å. Observations
of giant stars provide further information that shows that this
line is not due to N I. It is proposed that the line is due
to a decay from the 3p3(2Do)3d
1Do2 level of S I, above the first
ionization limit. The previous tentative assignment of this upper
level to an S I line at ≃1309.3Å then needs to be revised. The
1309.3-Å line is identified here for the first time in an astrophysical
source. The 3d 1Do2 level could, in
principle, be populated by collisions from nearby autoionizing levels
that are shown to have large number densities, through population
by low-temperature dielectronic capture. Spin-orbit interaction
with the autoionizing 3d 3Do2
level might also lead to dielectronic capture into the 3d
1Do2 level. A line at 1309.87 Å
observed in cool giant stars is identified as a transition in P II,
pumped by the O I resonance lines.
Title: The 1997 event in the Crab pulsar revisited
Authors: Graham Smith, F.; Lyne, A. G.; Jordan, C.
Bibcode: 2011MNRAS.410..499G
Altcode: 2010MNRAS.tmp.1372G; 2010arXiv1008.4494S
A complex event observed in the radio pulses from the Crab pulsar
in 1997 included echoes, a dispersive delay and large changes in
intensity. It is shown that these phenomena were due to refraction
at the edge of a plasma cloud in the outer region of the Crab
nebula. Several similar events have been observed, although in less
detail. It is suggested that the plasma cloud is in the form of
filaments with diameter around 3 × 1011 m and electron
density of the order of 104 cm-3.
Title: Radio Timing of the Crab Pulsar during Recent Gamma-Ray Flare
Authors: Espinoza, C. M.; Jordan, C.; Stappers, B. W.; Lyne, A. G.;
Weltevrede, P.; Cognard, I.; Theureau, G.
Bibcode: 2010ATel.2889....1E
Altcode:
We report radio timing observations of the Crab pulsar during the
recent enhancement in gamma-ray emission from the Crab Nebula region,
reported by AGILE on Sept. 22 (ATel #2855) and confirmed and more
recently followed up by Fermi (ATel #2861). Daily monitoring at 608
MHz with the 13-m telescope at Jodrell Bank Observatory combined with
higher-frequency (between 1.4 and 2.0 GHz) monitoring with the Nancay
and Lovell radio telescopes shows no evidence for a glitch within the
last 60 days.
Title: The International Pulsar Timing Array project: using pulsars
as a gravitational wave detector
Authors: Hobbs, G.; Archibald, A.; Arzoumanian, Z.; Backer, D.;
Bailes, M.; Bhat, N. D. R.; Burgay, M.; Burke-Spolaor, S.; Champion,
D.; Cognard, I.; Coles, W.; Cordes, J.; Demorest, P.; Desvignes,
G.; Ferdman, R. D.; Finn, L.; Freire, P.; Gonzalez, M.; Hessels, J.;
Hotan, A.; Janssen, G.; Jenet, F.; Jessner, A.; Jordan, C.; Kaspi,
V.; Kramer, M.; Kondratiev, V.; Lazio, J.; Lazaridis, K.; Lee, K. J.;
Levin, Y.; Lommen, A.; Lorimer, D.; Lynch, R.; Lyne, A.; Manchester,
R.; McLaughlin, M.; Nice, D.; Oslowski, S.; Pilia, M.; Possenti,
A.; Purver, M.; Ransom, S.; Reynolds, J.; Sanidas, S.; Sarkissian,
J.; Sesana, A.; Shannon, R.; Siemens, X.; Stairs, I.; Stappers, B.;
Stinebring, D.; Theureau, G.; van Haasteren, R.; van Straten, W.;
Verbiest, J. P. W.; Yardley, D. R. B.; You, X. P.
Bibcode: 2010CQGra..27h4013H
Altcode: 2009arXiv0911.5206H
The International Pulsar Timing Array project combines
observations of pulsars from both northern and southern hemisphere
observatories with the main aim of detecting ultra-low frequency
(~ 10-9-10-8 Hz) gravitational waves. Here
we introduce the project, review the methods used to search for
gravitational waves emitted from coalescing supermassive binary
black-hole systems in the centres of merging galaxies and discuss the
status of the project.
Title: The European Pulsar Timing Array: current efforts and a LEAP
toward the future
Authors: Ferdman, R. D.; van Haasteren, R.; Bassa, C. G.; Burgay,
M.; Cognard, I.; Corongiu, A.; D'Amico, N.; Desvignes, G.; Hessels,
J. W. T.; Janssen, G. H.; Jessner, A.; Jordan, C.; Karuppusamy, R.;
Keane, E. F.; Kramer, M.; Lazaridis, K.; Levin, Y.; Lyne, A. G.; Pilia,
M.; Possenti, A.; Purver, M.; Stappers, B.; Sanidas, S.; Smits, R.;
Theureau, G.
Bibcode: 2010CQGra..27h4014F
Altcode: 2010arXiv1003.3405F
The European Pulsar Timing Array (EPTA) is a multi-institutional,
multi-telescope collaboration, with the goal of using high-precision
pulsar timing to directly detect gravitational waves. In this paper we
discuss the EPTA member telescopes, current achieved timing precision
and near-future goals. We report a preliminary upper limit to the
amplitude of a gravitational wave background. We also discuss the Large
European Array for Pulsars, in which the five major European telescopes
involved in pulsar timing will be combined to provide a coherent array
that will give similar sensitivity to the Arecibo radio telescope,
and larger sky coverage.
Title: New Stars Within 33 parsecs of the Sun from the SUPERBLINK
Survey
Authors: Stone, Jacqueline; Lepine, S.; Cruz, B.; Jordan, C.
Bibcode: 2010AAS...21542409S
Altcode: 2010BAAS...42..332S
Numerous star systems within 33 parsecs of our Sun remain to be
identified, in particular low-mass stars with relatively small proper
motions. We present the identification of 1412 new stars within 33
parsecs of the Sun, including 7 new stars within just 12 parsecs,
from the SUPERBLINK proper motion survey. We searched the database
of 1.6 million SUPERBLINK stars with proper motions between 0.04
and 0.15 seconds of arc per year, covering the entire northern
sky. Photometric distances were calculated from infrared and optical
colors and magnitudes (from the 2MASS and USNO-B catalogs). Infrared
color cuts were used to eliminate background giants. A list of the
nearest new stars is presented.
Title: New Binary Systems in the Northern Sky from the SUPERBLINK
Survey
Authors: Cruz, Bryndis; Lepine, S.; Stone, J.; Jordan, C.
Bibcode: 2010AAS...21541925C
Altcode: 2010BAAS...42..280C
More than half of all stars are believe to a part of a binary or
multi-star system. Our search of proper motion objects from the
SUPERBLINK survey has uncovered numerous pairs of co-moving stars, a
significant fraction of which are revealed to be resolved, wide binaries
within 100pc of the Sun. The pairs were identified from the SUPERBLINK
database of northern stars with proper motions of 0.04 seconds of arc
per year or larger. Wide binaries were found by looking for pairs of
stars within 2 minutes of arc from each other and with proper motions
comparable to within the measurement errors. For pairs in which one
of the stars has an accurate distance measurement, this provides an
instant determination of the companion's distance from the Sun. Some
interesting new binaries are presented.
Title: Generic tests of the existence of the gravitational dipole
radiation and the variation of the gravitational constant
Authors: Lazaridis, K.; Wex, N.; Jessner, A.; Kramer, M.; Stappers,
B. W.; Janssen, G. H.; Desvignes, G.; Purver, M. B.; Cognard, I.;
Theureau, G.; Lyne, A. G.; Jordan, C. A.; Zensus, J. A.
Bibcode: 2009MNRAS.400..805L
Altcode: 2009arXiv0908.0285L; 2009MNRAS.tmp.1335L
We present results from the high-precision timing analysis of the
pulsar-white dwarf (WD) binary PSR J1012+5307 using 15 years of
multitelescope data. Observations were performed regularly by the
European Pulsar Timing Array (EPTA) network, consisting of Effelsberg,
Jodrell Bank, Westerbork and Nançay. All the timing parameters have
been improved from the previously published values, most by an order
of magnitude. In addition, a parallax measurement of π = 1.2(3)mas is
obtained for the first time for PSR J1012+5307, being consistent with
the optical estimation from the WD companion. Combining improved 3D
velocity information and models for the Galactic potential, the complete
evolutionary Galactic path of the system is obtained. A new intrinsic
eccentricity upper limit of e < 8.4 × 10-7 is acquired,
one of the smallest calculated for a binary system and a measurement
of the variation of the projected semimajor axis also constrains the
system's orbital orientation for the first time. It is shown that PSR
J1012+5307 is an ideal laboratory for testing alternative theories of
gravity. The measurement of the change of the orbital period of the
system of is used to set an upper limit on the dipole gravitational
wave emission that is valid for a wide class of alternative theories of
gravity. Moreover, it is shown that in combination with other binary
pulsars PSR J1012+5307 is an ideal system to provide self-consistent,
generic limits, based only on millisecond pulsar data, for the dipole
radiation and the variation of the gravitational constant .
Title: Stellar and galactic environment survey (SAGE)
Authors: Barstow, M. A.; Burleigh, M. R.; Bannister, N. J.; Lapington,
J. S.; Kowalski, M. P.; Cruddace, R. G.; Wood, K. S.; Auchere,
F.; Bode, M. F.; Bromage, G. E.; Gibson, B.; Collier Cameron, A.;
Cassatella, A.; Delmotte, F.; Ravet, M. -F.; Doyle, J. G.; Jeffery,
C. S.; Gaensicke, B.; Jordan, C.; Kappelmann, N.; Werner, K.;
Lallement, R.; de Martino, D.; Matthews, S. A.; Phillips, K. J. H.;
Del Zanna, G.; Orio, M.; Pace, E.; Pagano, I.; Schmitt, J. H. M. M.;
Welsh, B. Y.
Bibcode: 2009Ap&SS.320..231B
Altcode: 2008Ap&SS.tmp..161B
This paper describes a proposed high resolution soft X-ray and
Extreme Ultraviolet (EUV) spectroscopy mission to carry out a survey
of Stellar and Galactic Environments (SAGE). The payload is based on
novel diffraction grating technology which has already been proven in
a sub-orbital space mission and which is ready to fly on a satellite
platform with minimal development. Much of the technical detail of
the instrumentation has been reported elsewhere and we concentrate
our discussion here on the scientific goals of a SAGE base-line
mission, demonstrating the scientific importance of high resolution
spectroscopy in the Extreme Ultraviolet for the study of stars and
the local interstellar medium.
Title: Simultaneous multifrequency single-pulse properties of AXP
XTE J1810-197
Authors: Serylak, M.; Stappers, B. W.; Weltevrede, P.; Kramer, M.;
Jessner, A.; Lyne, A. G.; Jordan, C. A.; Lazaridis, K.; Zensus, J. A.
Bibcode: 2009MNRAS.394..295S
Altcode: 2009MNRAS.tmp..176S; 2008arXiv0811.3829S
We have used the 76-m Lovell, 94-m equivalent Westerbork Synthesis
Radio Telescope (WSRT) and 100-m Effelsberg radio telescopes to
investigate the simultaneous single-pulse properties of the radio
emitting magnetar Anomalous X-ray Pulsar (AXP) XTE J1810-197 at
frequencies of 1.4, 4.8 and 8.35GHz during 2006 May and July. We study
the magnetar's pulse-energy distributions which are found to be very
peculiar as they are changing on time-scales of days and cannot be
fit by a single statistical model. The magnetar exhibits strong spiky
single giant-pulse-like subpulses, but they do not fit the definition
of the giant pulse or giant micropulse phenomena. Measurements of the
longitude-resolved modulation index reveal a high degree of intensity
fluctuations on day-to-day time-scales and dramatic changes across pulse
phase. We find the frequency evolution of the modulation index values
differs significantly from what is observed in normal radio pulsars. We
find that no regular drifting subpulse phenomenon is present at any
of the observed frequencies at any observing epoch. However, we find
a quasi-periodicity of the subpulses present in the majority of the
observing sessions. A correlation analysis indicates a relationship
between components from different frequencies. We discuss the results
of our analysis in light of the emission properties of normal radio
pulsars and a recently proposed model which takes radio emission from
magnetars into consideration.
Title: Stellar And Galactic Environment survey (SAGE)
Authors: Barstow, M. A.; Kowalski, M. P.; Cruddace, R. G.; Wood, K. S.;
Auchere, F.; Bannister, N. J.; Bode, M. F.; Bromage, G. E.; Burleigh,
M. R.; Collier Cameron, A.; Cassatella, A.; Delmotte, F.; Doyle, J. G.;
Gaensicke, B.; Gibson, B.; Jeffery, C. S.; Jordan, C.; Kappelmann,
N.; Lallement, R.; Lapington, J. S.; de Martino, D.; Matthews, S. A.;
Orio, M.; Pace, E.; Pagano, I.; Phillips, K. J. H.; Ravet, M. -F.;
Schmitt, J. H. M. M.; Welsh, B. Y.; Werner, K.; Del Zanna, G.
Bibcode: 2009ExA....23..169B
Altcode: 2008ExA...tmp...25B
This paper describes a proposed high resolution soft X-ray and Extreme
Ultraviolet spectroscopy mission to carry out a survey of Stellar
and Galactic Environments (SAGE). The payload is based on novel
diffraction grating technology which has already been proven in a
sub-orbital space mission and which is ready to fly on a satellite
platform with minimal development. We discuss the goals of a SAGE
base-line mission and demonstrate the scientific importance of high
resolution spectroscopy in the Extreme Ultraviolet for the study of
stars and the local interstellar medium.
Title: Radio spectrum of the AXP J1810-197 and of its profile
components
Authors: Lazaridis, K.; Jessner, A.; Kramer, M.; Stappers, B. W.;
Lyne, A. G.; Jordan, C. A.; Serylak, M.; Zensus, J. A.
Bibcode: 2008MNRAS.390..839L
Altcode: 2008MNRAS.tmp.1070L; 2008arXiv0808.0244L
As part of a European Pulsar Network (EPN) multitelescope observing
campaign, we performed simultaneous multifrequency observations at 1.4,
4.9 and 8.4 GHz during 2006 July and quasi-simultaneous multifrequency
observations from 2006 December until 2007 July at 2.7, 4.9, 8.4,
14.6 and 32 GHz, in order to obtain flux density measurements and
spectral features of the 5.5s radio-emitting magnetar AXPJ1810-197. We
monitored the spectral evolution of its pulse shape which consists
of a main pulse (MP) and an interpulse (IP). We present the flux
density spectrum of the average profile and of the separate pulse
components of this first-known radio-emitting transient anomalous
X-ray pulsar. We observe a decrease in the flux density by a factor
of 10 within 8 m and follow the disappearance of one of the two main
components. Although the spectrum is generally flat, we observe large
fluctuations of the spectral index with time. For that reason, we have
made some measurements of modulation indices for individual pulses in
order to investigate the origin of these fluctuations.
Title: Correlation of the scattering and dispersion events in the
Crab Nebula pulsar
Authors: Kuzmin, A.; Losovsky, B. Ya.; Jordan, C. A.; Smith, F. G.
Bibcode: 2008A&A...483...13K
Altcode: 2008arXiv0802.4424K
In separate series of observations of the Crab pulsar, pulse broadening
due to scattering was measured at 111 MHz, and variations of dispersion
due to pulse delay were measured at higher radio frequencies. In a
remarkable event lasting 200 days a large increase occurred in both
parameters and with similar time signatures. The increases in scattering
and dispersion measure observed over the 200 days MJD 53 950-54 150 are
attributable to the effects of an ionised cloud or filament crossing the
line of sight. The cloud would be 1011{-}1012 m
across, with electron density 10^3{-}104 cm-3. The
increased scattering might originate within the cloud itself, or the
moving filament might induce turbulence in a separate higher density
cloud in the line of sight.
Title: The corona and upper transition region of epsilon Eridani
Authors: Ness, J. -U.; Jordan, C.
Bibcode: 2008MNRAS.385.1691N
Altcode: 2008MNRAS.tmp..360N; 2007arXiv0711.3805N
We present analyses of observations of epsilon Eridani (K2 V) made with
the Low Energy Transmission Grating Spectrometer onboard Chandra and the
Extreme Ultraviolet Explorer, supplemented by observations made with the
Space Telescope Imaging Spectrograph, the Far Ultraviolet Spectroscopic
Explorer and the Reflection Grating Spectrometer onboard XMM-Newton. The
observed emission lines are used to find relative element abundances, to
place limits on the electron densities and pressures and to determine
the mean apparent emission measure distribution. As in a previous
paper by Sim & Jordan, the mean emitting area as a function of
the electron temperature is derived by comparisons with a theoretical
emission measure distribution found from energy balance arguments. The
final model has a coronal temperature of 3.4 × 106 K,
an electron pressure of 1.3 × 1016cm-3K at
Te = 2 × 105K and an area filling factor of 0.14
at 3.2 × 105K. We discuss a number of issues concerning
the atomic data currently available. Our analyses are based mainly
on the latest version of CHIANTI (v5.2). We conclude that the Ne/O
relative abundance is 0.30, larger than that recommended from solar
studies, and that there is no convincing evidence for enhanced coronal
abundances of elements with low first ionization potentials.
Title: Slow Neighbors: A Search for Nearby Stars With Small Proper
Motions
Authors: Lepine, Sebastien; Bongiorno, B.; Corin, E.; Halmo, M.;
Jordan, C.; Moffett, A. J.; Patton, K.; Shara, M. M.; Wittenberg,
A.; Zaiats, M.
Bibcode: 2007AAS...211.7306L
Altcode: 2007BAAS...39Q.864L
We present the results of a search for nearby low mass stars and white
dwarfs among proper motion stars identified in the full SUPERBLINK
all-sky survey. Over 1 million stars with low proper motions (40 mas/yr
< μ < 150 mas/yr), are being sifted through in search of nearby
objects with relatively small transverse velocities, which have been
much overlooked in the past. We show that our survey will considerably
extend the census of low-mass stars and white dwarfs within 100 parsecs
of the Sun. In particular, this survey will identify most of the still
elusive, slow-moving stars in the Solar Neighborhood (d<33; pc),
bringing the local stellar census to near completion. This research
has been supported by NSF grant AST 0607757, and by the NSF Research
Experience for Undergraduates program.
Title: New Low-mass Stars With Small Proper Motions In The Solar
Neighborhood From The Superblink Database.
Authors: Zaiats, Marina; Lepine, S.; Corin, E.; Patton, K.; Jordan, C.
Bibcode: 2007AAS...21110320Z
Altcode: 2007BAAS...39..922Z
We present a search for nearby faint dwarfs with small motions within
the Solar neighborhood (25 parsecs from Sun). We have assembled
a database of stars with proper motions between 0.04 and 0.15
seconds of arc per year identified in the Digitized Sky Surveys
with SUPERBLINK. Photometric distances are estimated using the
V-J color absolute magnitude relationship. We used the V-J versus
J-K color-color diagram to eliminate distant giants, and the V-J
versus J-K diagram to remove other background contaminates. Out of
the 231 stars identified within 15 parsecs, 176 had no counterparts
in the astronomical literature (SIMBAD) and are thus entirely new
discoveries. These stars contribute to completing the census of stars
in the solar neighborhood from which the number of stars in the galaxy
as a whole can be inferred.
Title: Kinematics Of Low-mass Stars In The Vicinity Of The Sun From
The SUPERBLINK Survey
Authors: Corin, Elysa; Lepine, S.; Jordan, C.; Patton, K.; Zaiats, M.
Bibcode: 2007AAS...21110409C
Altcode: 2007BAAS...39R.925C
We investigate the kinematics of low-mass red dwarfs in the vicinity of
the Sun using a new database of Northern Hemisphere stars with proper
motions between ."04-."15/yr, identified in the SUPERBLINK survey. We
have isolated stars at high Galactic northern latitudes and analyzed
their projected motions in the UV velocity plane. Groups and streams
of stars that are moving together in the Galaxy are qualitatively
identified. It is demonstrated that low-mass stars have motions largely
consistent with those of higher-mass (Sun-like) stars in the Solar
vicinity. We investigate possible evidence of metallicity variations
between stars associated with the Hercules, Hyades, and Sirius streams,
using infrared photometry from 2MASS.
Title: Polarized radio emission from a magnetar
Authors: Kramer, M.; Stappers, B. W.; Jessner, A.; Lyne, A. G.;
Jordan, C. A.
Bibcode: 2007MNRAS.377..107K
Altcode: 2007astro.ph..2365K
We present polarization observations of the radio emitting magnetar
AXPJ1810-197. Using simultaneous multifrequency observations performed
at 1.4, 4.9 and 8.4 GHz, we obtained polarization information for single
pulses and the average pulse profile at several epochs. We find that in
several respects this magnetar source shows similarities to the emission
properties of normal radio pulsars while simultaneously showing striking
differences. The emission is nearly 80-95 per cent polarized, often with
a low but significant degree of circular polarization at all frequencies
which can be much greater in selected single pulses. The position
angle swing has a low average slope of only 1 deg deg-1,
deviating significantly from an S-like swing as often seen in radio
pulsars which is usually interpreted in terms of a rotating vector model
and a dipolar magnetic field. The observed position angle is consistent
at all frequencies while showing significant secular variations. On
average, the interpulse is less linearly polarized but shows a higher
degree of circular polarization. Some epochs reveal the existence
of non-orthogonal emission modes in the main pulse and systematic
wiggles in the PA swing, while the interpulse shows a large variety of
position angle values. We interpret many of the emission properties
as propagation effects in a non-dipolar magnetic field configuration
where emission from different multipole components is observed.
Title: OI line emission in cool stars: calculations using partial
redistribution
Authors: Koncewicz, R.; Jordan, C.
Bibcode: 2007MNRAS.374..220K
Altcode: 2006MNRAS.tmp.1337K
Radiative transfer calculations have been performed for five cool
stars: α Tau, β Gem, Procyon, ɛ Eri and the Sun, for the purpose
of investigating the behaviour of the OI emission over a wide range of
stellar types, and its dependence on coherent photon scattering. These
stars span a range of spectral types from F5 IV-V to K5 III and surface
gravities 1.25 < logg* < 4.75. Particular attention has been
paid to the calculation of the flux in the resonance triplet around
1305 Å which is pumped by H Lyβ, including the effects of partial
redistribution (PRD) and cross-redistribution of photons. These are the
first calculations for the resonance triplet in giant stars using a full
PRD treatment. Calculations of the predominantly collisionally excited
intersystem doublet at 1355, 1358 Å are included, and it is found
that the ratio of these fluxes shows the effects of opacity. The flux
in the forbidden line at 1641 Å is calculated for the giant stars and
the effects of coherent scattering on this line are investigated. The
discrepancy between the calculated and observed fluxes in the OI lines
is used to infer the inadequacy of single-component chromospheric
models.
Title: a Dark Galaxy in the Virgo Cluster Imaged at 21-CM
Authors: Minchin, R.; Disney, M. J.; Davies, J. I.; Marble, A. R.;
Impey, C. D.; Boyce, P. J.; Garcia, D. A.; Grossi, M.; Jordan, C. A.;
Lang, R. H.; Roberts, S.; Sabatini, S.; van Driel, W.
Bibcode: 2007ASSP....3..101M
Altcode: 2007iuse.book..101M; 2005astro.ph..8153M
Dark Matter supposedly dominates the extragalactic Universe (Peebles
1993; Peacock 1998; Moore et al. 1999; D'Onghi & Lake 2004), yet
no dark structure of galactic proportions has ever been convincingly
identified. Earlier (Minchin et al. 2005) we suggested that VIRGOHI 21,
a 21-cm source we found in the Virgo Cluster at Jodrell Bank using
single-dish observations (Davies et al. 2004), was probably such a
dark galaxy because of its broad line-width (~200 km s-1)
unaccompanied by any visible gravitational source to account for
it. We have now imaged VIRGOHI 21 in the neutral-hydrogen line, and
have found what appears to be a dark, edge-on, spinning disc with the
mass and diameter of a typical spiral galaxy. Moreover the disc has
unquestionably interacted with NGC 4254, a luminous spiral with an
odd one-armed morphology, but lacking the massive interactor normally
linked with such a feature. Published numerical models (Vollmer et
al. 2005) of NGC 4254 call for a close interaction ~108 years ago
with a perturber of ~1011 solar masses. This we take as further,
independent evidence for the massive nature of VIRGOHI 21.
Title: Off-radial flow of the solar wind from EISCAT and MERLIN
IPS observations
Authors: Bisi, M. M.; Breen, A. R.; Fallows, R. A.; Dorrian, G. D.;
Jones, R. A.; Wannberg, G.; Thomasson, P.; Jordan, C.
Bibcode: 2006AGUFMSH33A0399B
Altcode:
No abstract at ADS
Title: Sometimes a Pulsar!
Authors: O'Brien, J. T.; Kramer, M.; Lyne, A. G.; Lorimer, D. R.;
Jordan, C. A.
Bibcode: 2006ChJAS...6b...4O
Altcode:
This paper reports on the discovery of a new population of transient
neutron stars. This new class of pulsars is characterized by
quasi-periodic bursting with a non-radiating or `switched off' state,
the duration of which exceeds the radiating `on' state. There are
currently four such objects known, the prototype being the isolated
pulsar B1931+24 (J1933+2421). This pulsar emits radio radiation for
approximately 4-10 days before switching off completely for between
30-40 days, hence it is only visible for ∼ 10%-20% of the time. It
is therefore concluded from simple calculations, that many more of
these objects must exist and this will have large consequences for
the population estimates of neutron stars in our Galaxy. Further
studies will provide information about the conditions necessary for
radio emission.
Title: Extremely long baseline interplanetary scintillation
measurements of solar wind velocity
Authors: Breen, A. R.; Fallows, R. A.; Bisi, M. M.; Thomasson, P.;
Jordan, C. A.; Wannberg, G.; Jones, R. A.
Bibcode: 2006JGRA..111.8104B
Altcode: 2006JGRA..11108104B
We present results of observations of interplanetary scintillation
(IPS) made using the telescopes of the MERLIN and EISCAT networks in
which the beam separation approached 2000 km, much larger than in
any previous IPS experiments. Significant correlation between the
scintillation patterns was observed at time lags of up to 8 s and
fast and slow streams of solar wind were very clearly resolved. One
observation showed clear evidence of two discrete modes of fast
solar wind, which we interpret as originating in the crown of the
northern polar coronal hole and in an equatorward extension of the
polar hole. We suggest that experiments of this type will provide a
new and important source of information on the temporal and spatial
variation of small-scale turbulence in the solar wind. The improved
velocity resolution available from extremely long baseline measurements
also provides new information on the development of the large-scale
velocity structure of the solar wind in interplanetary space.
Title: A Periodically Active Pulsar Giving Insight into Magnetospheric
Physics
Authors: Kramer, M.; Lyne, A. G.; O'Brien, J. T.; Jordan, C. A.;
Lorimer, D. R.
Bibcode: 2006Sci...312..549K
Altcode: 2006astro.ph..4605K
PSR B1931+24 (J1933+2421) behaves as an ordinary isolated radio pulsar
during active phases that are 5 to 10 days long. However, when the radio
emission ceases, it switches off in less than 10 seconds and remains
undetectable for the next 25 to 35 days, then switches on again. This
pattern repeats quasi-periodically. The origin of this behavior is
unclear. Even more remarkably, the pulsar rotation slows down 50% faster
when it is on than when it is off. This indicates a massive increase
in magnetospheric currents when the pulsar switches on, proving that
pulsar wind plays a substantial role in pulsar spin-down. This allows
us, for the first time, to estimate the magnetospheric currents in a
pulsar magnetosphere during the occurrence of radio emission.
Title: VizieR Online Data Catalog: Spectrum of {epsilon} Eri (Sim+,
2005)
Authors: Sim, S. A.; Jordan, C.
Bibcode: 2006yCat..73611102S
Altcode:
Measurements of ultraviolet line fluxes from Space Telescope Imaging
Spectrograph and Far-Ultraviolet Spectroscopic Explorer spectra of the
K2-dwarf eps Eri are reported. These are used to develop new emission
measure distributions and semi-empirical atmospheric models for the
chromosphere and lower transition region of the star. These models
are the most detailed constructed to date for a main-sequence star
other than the Sun. New ionization balance calculations, which account
for the effect of finite density on dielectronic recombination rates,
are presented for carbon, nitrogen, oxygen and silicon. The results of
these calculations are significantly different from the standard Arnaud
& Rothenflug ion balance, particularly for alkali-like ions. The
new atmospheric models are used to place constraints on possible first
ionization potential (FIP)-related abundance variations in the lower
atmosphere and to discuss limitations of single-component models for
the interpretation of certain optically thick line fluxes. (4
data files).
Title: High resolution H i imaging of VIRGOHI 21 - a dark galaxy in
the Virgo Cluster
Authors: Minchin, R. F.; Davies, J. I.; Disney, M. J.; Marble, A. R.;
Impey, C. D.; Boyce, P. J.; Garcia, D. A.; Grossi, M.; Jordan, C. A.;
Lang, R. H.; Roberts, S.; Sabatini, S.; van Driel, W.
Bibcode: 2005AAS...20718813M
Altcode: 2005BAAS...37.1483M
Dark Matter supposedly dominates the extragalactic Universe, yet
no totally dark structure of galactic proportions has ever been
convincingly identified. Minchin et al. (2005) suggested that VIRGOHI
21, a 21-cm source found in the Virgo Cluster by Davies et al. (2004),
was probably such a dark galaxy because of its broad line-width
( ∼ 200 km s-1) unaccompanied by any visible massive
object to account for it. We have now imaged VIRGOHI 21 in the neutral
hydrogen line, and indeed we find what appears to be a dark, edge-on,
spinning disk with the mass and diameter of a typical spiral galaxy. We
also find that there is an indubitable interaction with NGC 4254, a
luminous spiral with an odd one-armed morphology but lacking the massive
interactor normally linked with such a feature. Published numerical
models of NGC 4254 call for a close interaction ∼ 108 years
ago with a perturber of ∼ 1011 M⊙. This we
take as further, independent evidence for the massive nature of VIRGOHI
21. The Arecibo Observatory is part of the National Astronomy
and Ionosphere Center, which is operated by Cornell University under
a cooperative agreement with the National Science Foundation
Title: An X-ray emission-line spectrum of Nova V382Velorum 1999
Authors: Ness, J. -U.; Starrfield, S.; Jordan, C.; Krautter, J.;
Schmitt, J. H. M. M.
Bibcode: 2005MNRAS.364.1015N
Altcode: 2005astro.ph.10039N; 2005MNRAS.tmp..988N
We report on the analysis of an X-ray grating spectrum of the Classical
Nova V382Vel (1999), obtained with the Low Energy Transmission Grating
(LETG)+HRC-S instrument onboard Chandra, which shows emission lines
dominating over any continuum. Lines of Si, Mg, Ne, O, N and C are
identified, but no Fe lines are detected. The total luminosity in
the lines is ~4 × 1027ergs-1 (corrected for
NH= 1.2 × 1021cm-2). The lines have
broad profiles with full width at half-maximum corresponding to a
velocity ~2900 +/-200kms-1. Some structure is identified
in the profiles, but for different elements we find different
profile structures. While lines of O show a broadened Gaussian
profile, those of Ne are double-peaked, suggesting a fragmented
emitting plasma. Using the emission measure distribution, we derive
relative element abundances and find abundances of Ne and N that
are significantly enhanced relative to that of O, while Fe is not
overabundant. The lack of any source emission longwards of 50Åand
the OVIII Lyα/Lyβ line ratio supports previous
values of the hydrogen column density. We find weak continuum emission
from the white dwarf, consistent with a blackbody spectrum with an
upper limit to the temperature of T= 3 × 105K, assuming a
source radius of 6000km. The upper limit for the integrated blackbody
luminosity is 2 × 1036ergs-1. The BeppoSAX and
Chandra ACIS observations of V382Vel show that the nova was bright
and in the Super-Soft phase as late as 1999 December 30. Our LETG
observation obtained 6 weeks later, as well as all subsequent X-ray
observations, showed a remarkable fading to a nearly pure emission
line phase which suggests that nuclear burning on the white dwarf
had turned off by February. In the absence of a photoionizing source,
the emission lines were formed in a collisionally ionized and excited
expanding shell.
Title: Photon scattering in the solar ultraviolet lines of HeI
and HeII
Authors: Jordan, C.; Smith, G. R.; Houdebine, E. R.
Bibcode: 2005MNRAS.362..411J
Altcode: 2005MNRAS.tmp..702J
Observations made with the Coronal Diagnostic Spectrometer (CDS) onboard
the Solar and Heliospheric Observatory (SOHO) are used to investigate
the behaviour of the intensities of the emission lines of HeI, HeII
and OIII at the quiet Sun-centre and at θ= 60° towards the equatorial
limb. The aim is to examine the possible effects of photon scattering
on the spatial variation of the optically thick helium lines. At the
quiet Sun-centre, we find that, in agreement with previous work, the
ratios of the intensities of the HeI 584-Åand HeII 304-Ålines to
those of the OIII 600-Åline decrease systematically as the intensity
of the OIII line increases. However, we find that the dependence of
these ratios on the OIII intensity is not unique, but differs between
the individual regions studied. Similar results are found at θ=
60°. We have also used line intensities and intensity ratios to
investigate limb-to-disc effects and variations across a sample of
supergranulation cell boundaries and adjacent cell interiors at both
locations. The results do not exclude photon scattering as the cause of
the larger observed ratios in cell interiors. The differences between
the apparent widths of boundaries in OIII at Sun-centre and 60° show
that the emitting material is extended in height, which will aid the
process of scattering into cell interiors. Photon scattering could
also account for the lack of oscillations in the HeI intensities in
a cell interior studied by Pietarila & Judge. Three-dimensional
radiative transfer calculations in chosen geometries are now needed
to account for the observations in detail.
Title: Modelling the chromosphere and transition region of ɛ Eri
(K2 V)
Authors: Sim, S. A.; Jordan, C.
Bibcode: 2005MNRAS.361.1102S
Altcode: 2005MNRAS.tmp..621S; 2005astro.ph..6060S
Measurements of ultraviolet line fluxes from Space Telescope Imaging
Spectrograph and Far-Ultraviolet Spectroscopic Explorer spectra of the
K2-dwarf ɛ Eri are reported. These are used to develop new emission
measure distributions and semi-empirical atmospheric models for the
chromosphere and lower transition region of the star. These models
are the most detailed constructed to date for a main-sequence star
other than the Sun. New ionization balance calculations, which account
for the effect of finite density on dielectronic recombination rates,
are presented for carbon, nitrogen, oxygen and silicon. The results of
these calculations are significantly different from the standard Arnaud
& Rothenflug ion balance, particularly for alkali-like ions. The
new atmospheric models are used to place constraints on possible first
ionization potential (FIP)-related abundance variations in the lower
atmosphere and to discuss limitations of single-component models for
the interpretation of certain optically thick line fluxes.
Title: Benchmark Exercises for stellar X-ray Spectroscopy Testing
(BEXST)
Authors: Maggio, A.; Drake, J. J.; Favata, F.; Güdel, M.; Jordan, C.
Bibcode: 2005AIPC..774..401M
Altcode:
No abstract at ADS
Title: The value of density measurements in stellar coronae
Authors: Ness, Jan-Uwe; Jordan, Carole
Bibcode: 2005AIPC..774..187N
Altcode: 2005astro.ph..4146N
The grating instruments on board Chandra and XMM-Newton now allow
measurements of electron densities. These rely on the ratios of fluxes
in emission lines, where one line depends on both collisional and
radiative decay rates. The electron density is required to constrain
the physical extent of the emitting region, and large samples of
measurements are of interest in the context of trends in coronal
activity. Here we discuss the important He {\sc i}-like ions and the
differences in densities that result when different current data bases
are used.
Title: Emission measures for the single giant β Ceti
Authors: Sägesser, S. N.; Jordan, C.
Bibcode: 2005ESASP.560..931S
Altcode: 2005csss...13..931S
No abstract at ADS
Title: VizieR Online Data Catalog: Long-term timing observations of
374 pulsars (Hobbs+, 2004)
Authors: Hobbs, G.; Lyne, A. G.; Kramer, M.; Martin, C. E.; Jordan, C.
Bibcode: 2005yCat..73531311H
Altcode:
The majority of pulse times of arrival (TOAs) were obtained using the
76-m Lovell Radio Telescope at Jodrell Bank Observatory. Results are
also included, for the brighter pulsars, from the 30-m MkII telescope
also situated at Jodrell Bank. The earliest TOAs for 18 pulsars (between
the years 1968 and 1981) were obtained from observations using the
NASA Deep Space Network (Downs & Reichley, 1983ApJS...53..169D). (4 data files).
Title: Solar and stellar physics - I
Authors: Jordan, C.
Bibcode: 2004Obs...124..346J
Altcode:
No abstract at ADS
Title: Long-term timing observations of 374 pulsars
Authors: Hobbs, G.; Lyne, A. G.; Kramer, M.; Martin, C. E.; Jordan, C.
Bibcode: 2004MNRAS.353.1311H
Altcode:
We present pulsar timing solutions for 374 pulsars. Each ephemeris
was obtained by analysing archival data stored at Jodrell Bank
Observatory. This data archive contains over 5600 yr of pulsar
rotational history with individual data-spans of up to 34 yr. A new
method has been developed to mitigate the effects of timing noise by
whitening the pulsar timing residuals. This whitening is applied before
standard fitting procedures are followed to measure the astrometric and
dispersion measure (DM) parameters of a pulsar. We show that the values
obtained using this new technique are consistent with other methods,
and that the new timing solutions are, in general, significantly more
precise than those in earlier publications. We consider the second
derivative of the frequency ν of pulsars, , and the DM gradient,
d(DM)/dt, in detail. The values are obtained by fitting to timing
residuals that have not been whitened and are found to be orders of
magnitude larger than those expected from magnetic dipole radiation;
the measured values are dominated by the effects of timing noise,
and therefore lead to braking indices that are not consistent with
magnetic dipole radiation. We find a dependence between |d(DM)/dt| and
DM of pc yr-1, which allows DM variations to be estimated
for any radio pulsar.
Title: The Structure and Dynamics of the Outer Atmosphere of
&epsil Eri
Authors: Sim, S. A.; Jordan, C.
Bibcode: 2004IAUS..219..254S
Altcode: 2003IAUS..219E..85S
Analyses of the fluxes widths and shifts of lines in the ultraviolet
spectrum of the active dwarf Epsilon Eri (K2 V) are presented. The
spectra were recorded with the STIS and FUSE instruments and provide
detailed new information on the star's chromosphere transition region
and inner corona. A combination of simple theoretical arguments and
observational constraints are used to deduce new information about the
structure of the upper transition region/corona. The area filling factor
of emitting material is determined in the upper atmosphere as a function
of temperature. This provides new constraints on how the magnetic field
might expand between the transition region and corona of an active
main sequence star. The results are compared with similar studies of
the Sun. The line widths are used together with a new semi-empirical
model of the atmosphere to compute the non-thermal energy density
as a function of temperature. Limits on the energy fluxes carried by
acoustic and Alfven waves are derived and compared with estimates of
the energy input required to support the combined radiative/conductive
losses in the upper atmosphere. It is found that in principle Alfven
waves could provide sufficient energy to heat the corona.
Title: Proposed mission concept for the Astrophysical Plasmadynamic
Explorer (APEX): an EUV high-resolution spectroscopic SMEX
Authors: Kowalski, Michael P.; Cruddace, Raymond G.; Wood, Kent S.;
Yentis, Daryl J.; Wolff, Michael T.; Laming, J. M.; Gursky, Herbert;
Carruthers, George R.; Barbee, Troy W., Jr.; Kordas, Joseph F.; Mauche,
Chris W.; Fritz, Gilbert G.; Varlese, Steve J.; Barstow, Martin A.;
Fraser, George W.; Siegmund, Oswald H. W.; Welsh, Barry Y.; Brickhouse,
Nancy S.; Dupree, Andrea K.; Brown, Alex; Bruhweiler, Frederick C.;
Cameron, Andrew C.; Holberg, Jay B.; Howell, Steven B.; Jordan, Carole;
Linsky, Jeffrey L.; Matthews, Sarah A.; Sion, Edward M.; Werner, Klaus
Bibcode: 2003SPIE.5164....1K
Altcode:
APEX is a proposed mission for a Small Explorer (SMEX) satellite. APEX
will investigate the density, temperature, composition, magnetic field,
structure, and dynamics of hot astrophysical plasmas (log T = ~5-7),
which emit the bulk of their radiation at EUV wavelengths and produce
critical spectral diagnostics not found at other wavelengths. APEX
addresses basic questions of stellar evolution and galactic structure
through high-resolution spectroscopy of white dwarf stars, cataclysmic
variables, the local interstellar medium, and stellar coronae. Thus
APEX complements the Chandra, Newton-XMM, FUSE, and CHIPS missions. The
instrument is a suite of 8 near-normal incidence spectrometers (~90-275
Angstroms, resolving power ~10,000, effective area 30-50 cm2)
each of which employs a multilayer-coated ion-etched blazed diffraction
grating and a microchannel plate detector of high quantum efficiency
and high spatial resolution. The instrument is mounted on a 3-axis
stabilized commercial spacecraft bus with a precision pointing
system. The spacecraft is launched by a Taurus vehicle, and payload
size and weight fit comfortably within limits for the 2210 fairing. Of
order 100 targets will be observed over the baseline mission of 2
years. These are selected carefully to maximize scientific return,
and all were detected in the EUVE and the ROSAT WFC surveys.
Title: On the filling factor of emitting material in the upper
atmosphere of ɛ Eri (K2 V)
Authors: Sim, S. A.; Jordan, C.
Bibcode: 2003MNRAS.346..846S
Altcode: 2003astro.ph..8502S
The emission measure distribution in the upper transition region
and corona of ɛ Eri is derived from observed emission-line
fluxes. Theoretical emission measure distributions are calculated
assuming that the radiation losses are balanced by the net conductive
flux. We discuss how the area factor of the emitting regions as
a function of temperature can be derived from a comparison between
these emission measure distributions. It is found that the filling
factor varies from ~0.2 in the mid-transition region to ~1.0 in the
inner corona. The sensitivity of these results to the adopted ion
fractions, the iron abundance and other parameters is discussed. The
area factors found are qualitatively similar to the observed structure
of the solar atmosphere, and can be used to constrain two-component
models of the chromosphere. Given further observations, the method
could be applied to investigate the trends in filling factors with
indicators of stellar activity.
Title: The Structure and Energy Balance of the Chromosphere,
Transition Region and Corona of ɛ Eri (K2 V)
Authors: Jordan, C.; Sim, S. A.; McMurry, A. D.
Bibcode: 2003csss...12..840J
Altcode:
Observations of ɛ Eri have been made with the Space Telescope
Imaging Spectrograph (STIS) on the Hubble Space Telescope (HST). The
magnetic dipole lines of ion{Fe}{12} at 1242.20 and 1349.38 Å have
been observed. Using lines of ion{Si}{3} and ion{O}{4}, the mean
electron pressure is 4.8 × 1015 cm-3 K. We
discuss how comparisons between theoretical and observed emission
measure distributions can be used to investigate the inhomogeneity
of the corona and lower transition region. The observed line widths
can be used to investigate the non-thermal heating. Evidence of two
components to some line profiles is found.
Title: VizieR Online Data Catalog: HI Jodrell All Sky Survey
(Lang+, 2003)
Authors: Lang, R. H.; Boyce, P. J.; Kilborn, V. A.; Minchin, R. F.;
Disney, M. J.; Jordan, C. A.; Grossi, M.; Garcia, D. A.; Freeman,
K. C.; Phillipps, S.; Wright, A. E.
Bibcode: 2003yCat..73420738L
Altcode:
Details are presented of the H I Jodrell All Sky Survey (HIJASS). HIJASS
is a blind neutral hydrogen (H I) survey of the northern sky
({delta}>22{deg}), being conducted using the multibeam receiver on
the Lovell Telescope (full width at half-maximum beamwidth 12-arcmin)
at Jodrell Bank. HIJASS covers the velocity range -3500 to 10000
km/s, with a velocity resolution of 18.1km/s and spatial positional
accuracy of ~2.5arcmin. Thus far about 1115 deg2 of sky
have been surveyed. The average rms noise during the early part of the
survey was around 16mJy/beam Following the first phase of the Lovell
Telescope upgrade (in 2001), the rms noise is now around 13mJy/beam. We
describe the methods of detecting galaxies within the HIJASS data and
of measuring their H I parameters. The properties of the resulting H
I-selected sample of galaxies are described. Of the 222 sources so far
confirmed, 170 (77 per cent) are clearly associated with a previously
catalogued galaxy. A further 23 sources (10 per cent) lie close (within
6 arcmin) to a previously catalogued galaxy for which no previous
redshift exists. A further 29 sources (13 per cent) do not appear to
be associated with any previously catalogued galaxy. (1 data file).
Title: The Proper Motion, Age, and Initial Spin Period of PSR
J0538+2817 in S147
Authors: Kramer, M.; Lyne, A. G.; Hobbs, G.; Löhmer, O.; Carr, P.;
Jordan, C.; Wolszczan, A.
Bibcode: 2003ApJ...593L..31K
Altcode: 2003astro.ph..6628K
We present results of the timing observations of the 143 ms pulsar PSR
J0538+2817 that provide a proper-motion measurement clearly showing an
association of the pulsar with the supernova remnant S147. We measure
a proper motion of 67+48-22 mas yr-1,
implying a transverse velocity of v=385+260-130
km s-1. We derive an age of the pulsar and S147 of only
30+/-4 kyr, which is a factor of 20 times less than the pulsar's
characteristic age of τc=620 kyr. This age implies an
initial spin period of P0=139 ms, close to the present pulse
period and a factor of several larger than what is usually inferred
for birth periods. Implications for recent X-ray detections of this
pulsar are discussed.
Title: A study of velocity fields in the transition region of ɛ Eri
(K2 V)
Authors: Sim, S. A.; Jordan, C.
Bibcode: 2003MNRAS.341..517S
Altcode: 2003astro.ph..1396S
Analyses of the widths and shifts of optically thin emission lines
in the ultraviolet spectrum of the active dwarf ɛ Eri (K2 V) are
presented. The spectra were obtained using the Space Telescope Imaging
Spectrograph on the Hubble Space Telescope and the Far Ultraviolet
Spectroscopic Explorer. The linewidths are used to find the non-thermal
energy density and its variation with temperature from the chromosphere
to the upper transition region. The energy fluxes that could be
carried by Alfvén and acoustic waves are investigated, to test their
possible roles in coronal heating. Acoustic waves do not appear to be
a viable means of coronal heating. There is, in principle, ample flux
in Alfvén waves, but detailed calculations of wave propagation are
required before definite conclusions can be drawn concerning their
viability. The high sensitivity and spectral resolution of the above
instruments have allowed two-component Gaussian fits to be made to the
profiles of the stronger transition region lines. The broad and narrow
components that result share some similarities with those observed in
the Sun, but in ɛ Eri the broad component is redshifted relative to
the narrow component and contributes more to the total line flux. The
possible origins of the two components and the energy fluxes implied
are discussed. On balance our results support the conclusion of Wood,
Linsky & Ayres, that the narrow component is related to Alfvén
waves reaching to the corona, but the origin of the broad component
is not clear.
Title: A transient event in lines of Ne V, VI and VII
Authors: Houdebine, E. R.; Jordan, C.
Bibcode: 2003A&A...401.1131H
Altcode:
We report observations of a transition region brightening made with
the Coronal Diagnostic Spectrometer onboard the Solar and Heliospheric
Observatory. We observed a region of the quiet Sun in 12 spectral
lines with temperatures of formation from =~ 3 x 104
K to 1.1 x 106 K. The transient event occured in a
network boundary region and was most pronounced in the Ne VI 562.8-Å
line. Although the Ne V 572.3-Å and Ne VII 561.7-Å lines also show
increases in intensity, the changes in the lines of helium, oxygen and
magnesium, formed at lower or higher temperatures, are smaller or not
significant. Thus the event is most significant in the relatively narrow
temperature range of =~ 3 x 105 K to =~ 5 x 105
K. The event lasted at least 53 min. In the many data sets we have
obtained, only one other region shows an obviously high Ne VI to O IV
intensity ratio, so the observed event is clearly unusual. Previous
studies of blinkers have not included the lines of Ne V, Ne VI or Ne
VII; the highest temperature transition region line used has been the O
V 627.9-Å line. Future studies of blinkers should include these higher
temperature lines. We derive volume emission measures in the event
from the various line intensities, estimate the electron densities
and discuss the energy budget and possible origins of the event.
Title: "Curious About Astronomy?": Cornell University's Ask an
Astronomer Website
Authors: Carruba, V.; Carter, L. M.; Cuk, M.; Jackson, M. A.; Jordan,
C. E.; Krco, M.; Masters, K. L.; Pandian, J. D.; Rothstein, D. M.;
Saintonge, A.; Scharringhausen, B. R.; Spekkens, K.; Springob, C. M.;
Kornreich, D. A.; Curious Team
Bibcode: 2003LPI....34.1893C
Altcode:
"Curious About Astronomy? Ask an Astronomer" is a website
(http://curious.astro.cornell.edu) run by graduate and undergraduate
student volunteers at Cornell University. Questions from the general
public are submitted by email and answered by members of the Curious
Team.
Title: New constraints on the formation of the helium lines
Authors: Houdebine, E. R.; Smith, G. R.; Jordan, C.
Bibcode: 2003EAS.....9..365H
Altcode:
We analyse observations of the helium lines obtained with CDS onboard
SOHO. The He i 584.3 Å/O iii intensity ratio shows a lower limit and
an upper limit that decrease with increasing O iii intensity. At low
O iii intensities this ratio increases significantly. An upper limit
arises naturally if the enhancement mechanism involves turbulent motions
transporting the helium atoms and ions through the steep transition
region temperature gradient. The He i 537.0-Å/He i 584.3-Å and He
ii 303.8-Å/He i 584.3-Å intensity ratios both decrease as the He
i 584.3-Å line intensity increases. The values of the line ratios
support the enhancement of the helium lines by turbulent motions, but
appear to rule out the enhancement due to excitation by non-thermal
coronal electrons.
Title: Coherent On-line Baseband Receiver for Astronomy
Authors: Joshi, B. C.; Lyne, A. G.; Kramer, M.; Lorimer, D. R.;
Jordan, C.; Holloway, A.; Ikin, T.; Stairs, I. H.
Bibcode: 2003ASPC..302..321J
Altcode: 2003rapu.conf..321J
No abstract at ADS
Title: The Crab Glitches: Incidence and Cumulative Effect
Authors: Smith, F. Graham; Jordan, C.
Bibcode: 2003ASPC..302..231S
Altcode: 2003astro.ph..1174S; 2003rapu.conf..231S
The fourteen glitches observed during 33 years do not show the simple
pattern expected from a relaxation oscillator. They may however be
regarded as three major events separated by about 12 years, the third
being a group of smaller glitches. There is a step increase in slowdown
rate at each glitch, whose cumulative effect makes a significant
contribution to the second differential nu-ddot. The braking index
"n" has previously been evaluated only between glitches: the effect
of the glitches is to reduce "n" from 2.51 to 2.45. This extra effect
due to the glitches would be explained by an increase in dipole field
at the fractional rate of 1.5x10^-5 per annum.
Title: The corona and upper transition region of ∈ Eri
Authors: Sim, S. A.; Jordan, C.
Bibcode: 2002ASPC..277..231S
Altcode: 2002sccx.conf..231S
No abstract at ADS
Title: Conference Summary
Authors: Jordan, C.
Bibcode: 2002ASPC..277..621J
Altcode: 2002sccx.conf..621J
No abstract at ADS
Title: Enhancement of the helium resonance lines in the solar
atmosphere by suprathermal electron excitation - I. Non-thermal
transport of helium ions
Authors: Smith, G. R.; Jordan, C.
Bibcode: 2002MNRAS.337..666S
Altcode: 2002astro.ph..8314S
Models of the solar transition region made from lines other than those
of helium cannot account for the strength of the helium lines. However,
the collisional excitation rates of the helium resonance lines are
unusually sensitive to the energy of the exciting electrons. Non-thermal
motions in the transition region could drive slowly ionizing helium
ions rapidly through the steep temperature gradient, exposing them to
excitation by electrons characteristic of higher temperatures than
those describing their ionization state. We present the results of
calculations which use a more physical representation of the lifetimes
of the ground states of HeI and HeII than was adopted in earlier
work on this process. New emission measure distributions are used
to calculate the temperature variation with height. The results show
that non-thermal motions can lead to enhancements of the HeI and HeII
resonance line intensities by factors that are comparable to those
required. Excitation by non-Maxwellian electron distributions would
reduce the effects of non-thermal transport. The effects of non-thermal
motions are more consistent with the observed spatial distribution
of helium emission than are those of excitation by non-Maxwellian
electron distributions alone. In particular, they account better for
the observed line intensity ratio I(537.0 Å)/I(584.3 Å), and its
variation with location.
Title: ``Curious About Astronomy?": Cornell University's Ask an
Astronomer Website
Authors: Carruba, V.; Carter, L. M.; Cuk, M.; Jackson, M. A.; Jordan,
C. E.; Krco, M.; Masters, K. L.; Pandian, J. D.; Rothstein, D. M.;
Saintonge, A.; Scharringhausen, B. R.; Spekkens, K.; Springob, C. M.;
Kornreich, D. A.; Curious Team
Bibcode: 2002AAS...201.5310C
Altcode: 2002BAAS...34Q1197C
``Curious About Astronomy? Ask an Astronomer" is a website
(http://curious.astro.cornell.edu) run by graduate and undergraduate
student volunteers at Cornell University. Questions from the general
public, submitted either by email or using a convenient web form, are
answered by members of the Curious Team, and particularly interesting
questions are posted on the website for visitors to browse. We receive
and answer a few hundred questions each month from people of diverse
backgrounds, including K-12 and post-secondary students and instructors,
amateur astronomers, parents, scientists in various fields and others
around the world with an interest in astronomy. We have recently
upgraded the website, creating 22 different sections about specific
topics in astronomy, a searchable index of hundreds of cross-listed
questions and a page of suggestions and guidelines for teachers. The
Curious Page has already become a source of useful information for
the public. Questions and answers about the so-called ``Moon Hoax"
and a recent news article about the Sun going supernova have received
thousands of hits. By offering individual responses about any aspect of
astronomy to anyone who has Internet access and by continually updating
our archive of answered questions, we hope to provide a unique, growing
astronomy resource for students, educators and the general public---as
well as a valuable opportunity for the Curious Team to participate in
educational outreach and improve its communication skills in a setting
that requires no formal budget or faculty supervision.
Title: Observations of rotational instabilities in radio pulsars.
Authors: Joshi, B. C.; Lyne, A. G.; Jordan, C.; Krawczyk, A.; Gil,
J. A.
Bibcode: 2002BASI...30..691J
Altcode:
No abstract at ADS
Title: Slow and fast solar wind acceleration near solar maximum
Authors: Breen, A. R.; Thomasson, P.; Jordan, C. A.; Tappin, S. J.;
Fallows, R. A.; Canals, A.; Moran, P. J.
Bibcode: 2002AdSpR..30..433B
Altcode:
2-site measurements of interplanetary scintillation (IPS) provide
measurements of solar wind speed in regions of the heliosphere which
are otherwise inaccessible. We present results from co-ordinated
observations made with the EISCAT and MERLIN facilities during 1999
and 2000, covering heliocentric distances from 7 to 80 solar radii (R)
predominantly in the slow solar wind. The 1999 results are compared
with optical measurements from LASCO covering 4-30 R. Most slow
acceleration appears to take place between 5 and 10 R, but the slow
wind continues to accelerate out to 25-35 R. Some of the observations
included identifiable fast flow, and in these regions acceleration
began lower down and was much more rapid, with 50% of cruising speed
reached by 4-5 R and acceleration complete inside 10 R — results
which are similar to those from solar minimum.
Title: The anomalous intensities of helium lines in a coronal hole
Authors: Jordan, C.; Macpherson, K. P.; Smith, G. R.
Bibcode: 2001MNRAS.328.1098J
Altcode:
Observations made at the quiet Sun-centre with the Coronal Diagnostic
Spectrometer (CDS) and Solar Ultraviolet Measurements of Emitted
Radiation (SUMER) instruments on the Solar and Heliospheric Observatory
(SOHO) have shown that the intensities of the resonance lines of HeI
and HeII are significantly larger than predicted by emission measure
distributions found from other transition region lines. The intensities
of the helium lines are observed to be lower in coronal holes than in
the quiet Sun. Any theory proposed to account for the behaviour of the
helium lines must explain the observations of both the quiet Sun and
coronal holes. We use observations made with SOHO to find the physical
conditions in a polar coronal hole. The electron pressure is found
using the CIII 1175-Å and NIII 991.5-Å lines, as the CIII line at
977.0Å becomes optically thick in some regions at high latitudes. The
mean electron pressure is a factor of ~=2 lower than that at the
quiet Sun-centre. The mean coronal electron temperature is <=
9.4×105K. The helium lines are enhanced with respect to
other transition region lines but by factors which are ~=30 per cent
smaller than at the quiet Sun-centre. The mean ratios of the intensities
of the HeI 537.0- and 584.3-Å lines and of the HeI and HeII 303.8-Å
lines vary little with the type of region studied. These ratios are
compared with those predicted by models of the transition region, taking
into account the radiative transfer in the helium lines. No significant
variation is found in the relative abundances of carbon and silicon.
Title: Simultaneous single-pulse observations of radio pulsars. I. The
polarization characteristics of PSR B0329+54
Authors: Karastergiou, A.; von Hoensbroech, A.; Kramer, M.; Lorimer,
D. R.; Lyne, A. G.; Doroshenko, O.; Jessner, A.; Jordan, C.;
Wielebinski, R.
Bibcode: 2001A&A...379..270K
Altcode: 2001astro.ph..9507K
We present the first results from a programme of multi-frequency
simultaneous single pulse observations carried out as part of the
European Pulsar Network. We detail the main data analysis methods
and apply them to simultaneous observations of the strong pulsar
B0329+54 at 1.4 and 2.7 GHz using the Jodrell Bank and Effelsberg
radio telescopes respectively. The pulses at different frequencies
are highly correlated in their total intensity, as seen in previous
experiments, and generally show consistent position angles of the
linearly polarized component. In contrast, the circularly polarized
emission sometimes shows clear differences between pulses received
at different frequencies. These results are unexpected and warrant
further follow-up studies to interpret them in the context of the
intrinsic bandwidth of pulsar radiation.
Title: A Blind H I Survey of the M81 Group
Authors: Boyce, P. J.; Minchin, R. F.; Kilborn, V. A.; Disney, M. J.;
Lang, R. H.; Jordan, C. A.; Grossi, M.; Lyne, A. G.; Cohen, R. J.;
Morison, I. M.; Phillipps, S.
Bibcode: 2001ApJ...560L.127B
Altcode: 2001astro.ph..9086B
Results are presented of the first blind H I survey of the M81 Group
of galaxies. The data were taken as part of the H I Jodrell All-Sky
Survey (HIJASS). The survey reveals several new aspects to the complex
morphology of the H I distribution in the group. All four of the known
dwarf irregular (dIrr) galaxies close to M81 can be unambiguously seen
in the HIJASS data. Each forms part of the complex tidal structure in
the area. We suggest that at least three of these galaxies may have
formed recently from the tidal debris in which they are embedded. The
structure connecting M81 to NGC 2976 is revealed as a single tidal
bridge of mass ~=2.1×108 Msolar and projected
spatial extent ~=80 kpc. Two ``spurs'' of H I projecting from the
M81 complex to lower declinations are traced over a considerably
larger spatial and velocity extent than by previous surveys. The dwarf
elliptical (dE) galaxies BK5N and Kar 64 lie at the spatial extremity of
one of these features and appear to be associated with it. We suggest
that these may be the remnants of dIrr's that have been stripped of
gas and transmuted into dE's by close gravitational encounters with
NGC 3077. The nucleated dE galaxy Kar 61 is unambiguously detected
in H I for the first time and has an H I mass of ~108
Msolar, further confirming it as a dE/dIrr transitional
object. HIJASS has revealed one new possible group member, HIJASS
J1021+6842. This object contains ~=2×107 Msolar
of H I and lies ~=105' from IC 2574. It has no optical counterpart on
the Digital Sky Survey.
Title: The electron pressure in the outer atmosphere of ɛ Eri (K2 V)
Authors: Jordan, C.; Sim, S. A.; McMurry, A. D.; Aruvel, M.
Bibcode: 2001MNRAS.326..303J
Altcode:
Observations of ɛ Eri (K2 V) have been made with the Space Telescope
Imaging Spectrograph on the Hubble Space Telescope. The spectra obtained
show a number of emission lines which can be used to determine, or
place limits on, the electron density and pressure. Values of the
electron pressure are required in order to make quantitative models
of the transition region and inner corona from absolute line fluxes,
and to constrain semi-empirical models of the chromosphere. Using
line flux ratios in Siiii and Oiv a mean electron pressure of
Pe=NeTe=4.8×1015cm-3K
is derived. This value is compatible with the lower and upper limits
to Pe found from flux ratios in Ciii, Ov and Fexii. Some
inconsistencies which may be because of small uncertainties in the
atomic data used are discussed.
Title: Identification of Fe II Emission Lines in FUSE Stellar Spectra
Authors: Harper, Graham M.; Wilkinson, Erik; Brown, Alexander; Jordan,
Carole; Linsky, Jeffrey L.
Bibcode: 2001ApJ...551..486H
Altcode:
We identify two complexes of Fe II emission lines in far-ultraviolet
spectra of the stars α TrA and HD 104237. Using spectra from both the
Far Ultraviolet Spectroscopic Explorer (FUSE) and the Space Telescope
Imaging Spectrograph (STIS) on board the Hubble Space Telescope (HST),
we show that these emission lines, which represent the majority of
previously unidentifed emission features in cool star spectra between
912 and 1180 Å, are fluorescent decays in Fe II following excitation
by H Lyα. Specifically, following photoexcitation from the third term
(4s a 4D) of Fe II, subsequent decays are observed to the
two lowest terms (4s a 6D and 3d7 a 4F)
which are observed near 1100 and 1135 Å, respectively. Decays to higher
terms, and hence longer wavelengths, also are clearly seen in the STIS
spectra. Differences in the fluorescent Fe II spectra of α TrA and HD
104237 are tentatively identified as resulting from differences in the
intrinsic width of the density-weighted H Lyα radiation fields. The
additional Fe II lines observed in α TrA result from a broadened H
Lyα profile. Two features near 1060 Å appear to be fluorescent lines
of Cr II, also excited by H Lyα.
Title: Detection of magnetic dipole lines of Fexii in the ultraviolet
spectrum of the dwarf star ɛ Eri
Authors: Jordan, C.; McMurry, A. D.; Sim, S. A.; Arulvel, M.
Bibcode: 2001MNRAS.322L...5J
Altcode: 2001astro.ph..1290J
We report observations of the dwarf star ɛ Eri (K2V) made with
the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space
Telescope. The high sensitivity of the STIS instrument has allowed
us to detect the magnetic dipole transitions of Fexii at 1242.00
and 1349.38Å for the first time in a star other than the Sun. The
width of the stronger line at 1242.00Å has also been measured; such
measurements are not possible for the permitted lines of Fexii in
the extreme-ultraviolet. To within the accuracy of the measurements,
the Nv and the Fexii lines occur at their rest wavelengths. Electron
densities and linewidths have been measured from other transition
region lines. Together, these can be used to investigate the non-thermal
energy flux in the lower and upper transition regions, which is useful
in constraining possible heating processes. The Fexii lines are also
present in archival STIS spectra of other G/K-type dwarfs.
Title: Studies of Cool Giant Stars using GHRS Spectra (CD-ROM
Directory: contribs/jordan)
Authors: Jordan, C.; McMurry, A. D.
Bibcode: 2001ASPC..223..351J
Altcode: 2001csss...11..351J
No abstract at ADS
Title: Cool CO and Shocks in K Giants (CD-ROM Directory:
contribs/mcmurry)
Authors: McMurry, A. D.; Jordan, C.
Bibcode: 2001ASPC..223..832M
Altcode: 2001csss...11..832M
No abstract at ADS
Title: Origins, Structure, and Evolution of Magnetic Activity in
the Cool Half of the H--R Diagram: Progress Report on a Major HST
STIS Stellar Survey
Authors: Ayres, T. R.; Brown, A.; Drake, S. A.; Dupree, A. K.; Guedel,
M.; Guinan, E.; Harper, G. M.; Jordan, C.; Linsky, J. L.; Reimers,
D.; Schmitt, J. H. M. M.; Simon, T.
Bibcode: 2000AAS...197.4407A
Altcode: 2000BAAS...32.1472A
In early October 2000, HST completed a year and a half long ultraviolet
spectral survey of late-type stars with its Space Telescope Imaging
Spectrograph (STIS). Thirteen stars were observed, ranging over
spectral types F7--K0 on the main sequence, F8--G8 in the giant branch,
and G0--G8 in the supergiants. A total of 72 observation sequences
were executed, some consisting of several independent exposures
(up to 13: in the case of HR 1099, recorded during a long grating
observation by Chandra ). Spectra were taken in the medium resolution
echelle modes (E140M, E230M: R ~ 30--40,000) below about 2500 Å,
and in the high-resolution echelle mode (E230H: R ~ 105)
between 2500--3000 Å. For each target, about 70% of the exposure
time was devoted to the key E140M interval (1150--1700 Å). Although
the observations were collected primarily to study the magnetically
disturbed outer atmospheres of late-type stars, they also are valuable
for investigating the local interstellar medium through UV absorptions
in H 1, O 1, Fe 2, and Mg 2, and for measuring the cosmologically
significant D/H ratio. We present examples of the superb spectra
resulting from the program, and discuss some of the new insights we
have gained concerning plasma dynamics in the 105 K layers
of the stellar ``transition zone;'' the super-rotational broadening
of the Si 4, C 4, and N 5 emissions in Hertzsprung gap giants; and the
spectral peculiarities of the ``hybrid chromosphere'' supergiants. This
work was supported by grant GO-08280.01-97A from STScI. Observations
were from the NASA/ESA HST, collected at the STScI, operated by AURA,
under contract NAS5-26555.
Title: Washington Color Magnitude Diagrams of Galactic Globular
Clusters
Authors: Gillam, S. D.; Asbury, D.; Jordan, C.; Patton, J.;
Rodriguez, J.
Bibcode: 2000AAS...196.6201G
Altcode: 2000BAAS...32Q1284G
Washington System color magnitude diagrmas (CMDs) of the galactic
globular clusters M92 and NGC4147 are presented. The photometry was
carried out using the Table Mountain Observatory 0.6-m telescope. These
CMDs are part of an effort to estimate the age of the universe using
old galactic globular clusters. Much of this work was carried out by
undergraduates in the Cal. State U.L.A./JPL Consortium for Undergraduate
Research (CURE) program. Their work was funded by an REU grant from
the National Science Foundation and a NASA Faculty Award for Research
(FAR) grant.
Title: Simultaneous interplanetary scintillation and optical
measurements of the acceleration of the slow solar wind
Authors: Breen, A. R.; Tappin, S. J.; Jordan, C. A.; Thomasson, P.;
Moran, P. J.; Fallows, R. A.; Canals, A.; Williams, P. J. S.
Bibcode: 2000AnGeo..18..995B
Altcode:
Simultaneous observations of the slow solar wind off the southeast
limb of the Sun were made in May 1999 using optical measurements
from the C2 and C3 LASCO coronagraphs on board the SOHO spacecraft and
radio-scattering measurements from the MERLIN and EISCAT facilities. The
observations show the slow solar wind accelerating outwards from 4.5
solar radii (R), reaching a final velocity of 200-300 km s-1 by 25-30
R. The acceleration profile indicated by these results is more gentle
than the average profile seen in earlier LASCO observations of larger
scale features, but is within the variation seen in these studies.
Title: Stellar Activity and Outer Atmospheric Structure of Yellow
Supergiants from HST STIS and GHRS Spectroscopy
Authors: Brown, A.; Ayres, T. R.; Harper, G. M.; Osten, R. A.; Linsky,
J. L.; Dupree, A. K.; Jordan, C.
Bibcode: 2000AAS...196.4013B
Altcode: 2000BAAS...32..739B
Yellow supergiants with spectral types F-G show a complex pattern of
outer atmospheric structure with stellar wind and activity indicators
varying significantly for stars with similar positions in the H-R
diagram. The efficiency of the processes driving their stellar winds and
heating their atmospheres is critically dependent on the evolutionary
position and surface gravity of each star. We present high-resolution
ultraviolet HST/STIS and HST/GHRS spectra for a range of intermediate
mass F and G supergiants, including Alpha Car (F0 Ib), Beta Cam (G0 Ib),
Beta Dra (G2 Ib), and Epsilon Gem (G8 Ib), and compare the atmospheric
properties of these stars with lower luminosity giants and bright
giants. We provide a systematic overview of the supergiant atmospheric
properties dealing particularly with activity levels, the presence
of hot ``transition region'' plasma, signatures of wind outflow, and
the role of overlying cool absorbing plasma that becomes increasingly
prominent for the cooler stars like Epsilon Gem. This work is supported
by HST grants for program GO-08280 and by NASA grant NAG5-3226.
Title: Current understanding of the heating of the solar corona
Authors: Jordan, C.
Bibcode: 2000PPCF...42..415J
Altcode:
The heating of the solar corona is thought to occur through the
dissipation of magnetohydrodynamic (MHD) wave energy and/or through
energy released during the reconnection of magnetic fields. Observations
of emission line fluxes and widths provide constraints that must be
satisfied by the proposed heating and dissipation processes. Although
observations of the Sun provide the most detailed information,
observations of other main-sequence stars lead to trends in coronal
parameters with simple indicators of stellar magnetic activity that
must also be explained by any successful theory. Observations of the
quiet (average) solar transition region and inner corona are broadly
consistent with coronal heating by high frequency Alfvén waves,
which might be generated by magnetic reconnection.
Title: The outer atmosphere of α Tau - III. Inhomogeneities deduced
from cold CO fluorescence
Authors: McMurry, A. D.; Jordan, C.
Bibcode: 2000MNRAS.313..423M
Altcode:
Ultraviolet spectra of α Tau obtained with the Goddard High Resolution
Spectrograph (GHRS) on the Hubble Space Telescope show clusters of
CO emission lines which are excited by the Oi (uv2) multiplet near
1304Å. Identifications of these fluorescent lines and their pumping
routes are presented. The absolute intensities of the CO lines and their
ratios cannot be explained by the one-dimensional chromospheric model
based on collisionally excited lines. The excitation temperature of the
CO is found to be only ~=2000K, lower than that of the minimum value in
the chromospheric model. The CO line intensities are used to deduce the
Oi radiation field, linewidths and opacity where the CO is pumped. The
low opacity deduced implies that the Oi radiation and CO molecules must
be in close proximity, implying a two-component atmosphere. Although
a combination of regions of traditional `chromosphere' within a cool
radiative equilibrium atmosphere cannot yet be excluded, the uv spectrum
could instead be accounted for, in principle, by shocks within such
a cool atmosphere.
Title: Origins, Structure, and Evolution of Magnetic Activity in
the Cool Half of the H--R Diagram: an HST STIS Survey
Authors: Ayres, T. R.; Brown, A.; Drake, S. A.; Dupree, A. K.; Guedel,
M.; Guinan, E.; Harper, G. M.; Jordan, C.; Linsky, J. L.; Reimers,
D.; Schmitt, J. H. M. M.; Simon, T.
Bibcode: 1999AAS...195.5013A
Altcode: 1999BAAS...31Q1449A
In HST's cycle 8, we are carrying out a major ultraviolet spectral
survey of late-type stars using the powerful capabilities of the
Space Telescope Imaging Spectrograph (STIS). The origin of the hot
UV emissions of otherwise cool stars is a fundamental puzzle in
astrophysics. Magnetic phenomena---at the heart of chromospheric and
coronal activity, and perhaps wind driving as well---play a central
role in many cosmic settings. Our objective is to obtain high-quality
ultraviolet spectra of a diverse collection of F--K stars, of all
luminosity classes. Such a major project was unthinkable before
STIS, but now is practical given the high resolution, broad spectral
coverage, and sensitivity of the second generation spectrograph. Here,
we discuss our choice of the thirteen targets; the observing strategy
(which captures the entire UV spectrum between 1150--3000 Angstroms
at resolutions λ /δ λ 30--100*E3 with good S/N); and
preliminary results for the several targets observed to date (ζ Dor, F7
V, 1 May 1999, 2 CVZ orbits; V711 Tau, K1 IV+G5 IV, 15 September 1999, 5
orbits; β Cam, G0 I, 19 September 1999, 4 CVZ orbits). The observation
of V711 Tau (HR 1099) was carried out during a long transmission grating
pointing by the Chandra X-ray Observatory, in support of its ``Emission
Line Project.'' This work was supported by grant GO-08280.01-97A from
STScI. Observations were from the NASA/ESA HST, collected at the STScI,
operated by AURA, under contract NAS5-26555.
Title: Dynamical Behaviour Of Helium Lines In The Quiet Solar
Transition Region
Authors: MacPherson, K. P.; Jordan, C.; Smith, G.
Bibcode: 1999ESASP.446..461M
Altcode: 1999soho....8..461M
The dynamic behaviour of the resonance lines of He I and He II in
the quiet solar transition region is examined. Previous observations
have suggested that the intensities of these lines are anomalously
strong in the quiet solar transition region compared with other
transition region lines formed at the same temperature. These results
have now been confirmed using the latest data from the SOHO CDS and
SUMER spectrometers (Macpherson &Jordan 1997, 1999). One of the
interesting results from SOHO concerns the variations with time of
transition region lines in the supergranulation network (Harrison
1997). He found that the O IV line at 554-A varied by factors of 2-3
over a few minutes, while the He I line at 537-A and the Mg IX line at
368-A varied far less. New observations using high-rate telemetry have
been made using CDS, including the lines of He I, He II and of other
transition region and coronal lines. The observations give several
hours of repeated 25-s exposures of the quiet Sun to allow studies
of the dynamical properties of the He I and He II lines in comparison
with the other lines observed. These complement our previous studies of
the spatial variation of the He I and He II lines and are an important
part of understanding the helium line formation. We report the results
of analyses of these data.
Title: The anomalous intensities of helium lines in the quiet solar
transition region
Authors: MacPherson, K. P.; Jordan, C.
Bibcode: 1999MNRAS.308..510M
Altcode:
Previous studies using observations made at low spatial and
spectral resolution showed that the resonance lines of Hei and
Heii are anomalously strong in the quiet Sun when compared with
other transition region lines formed at similar temperatures. Here,
the higher spatial and spectral resolution provided by the Coronal
Diagnostic Spectrometer (cds) instrument on board the Solar and
Heliospheric Observatory (SOHO) is used to re-examine the behaviour
of the Hei and Heii lines and other transition region lines, in quiet
regions near Sun centre. Supergranulation cell boundaries and cell
interiors are examined separately. Near-simultaneous observations
with the sumer instrument provide information on the lower transition
region and the electron pressure. While the lines of Hei and Heii
have a common behaviour, as do the other transition region lines, the
behaviour of the helium lines relative to the other transition region
lines is significantly different. The emission measure distributions
that account for all transition region lines, except those of helium,
fail to produce sufficient emission in the Hei and Heii resonance
lines by around an order of magnitude, in both supergranulation cell
boundary and cell interior regions. The electron pressure appears to
be higher in the cell interiors than in the average cell boundaries,
although the uncertainties are large. While the VAL-D model gives
a closer match to the Hei 584.3-Å line, it does not successfully
reproduce other transition region lines.
Title: Is SiO observed in the uv spectrum of Beta Gem?
Authors: Jordan, Carole
Bibcode: 1999hst..prop.8294J
Altcode: 1999hst..prop.4628J
Beta Gem {HD 62509} is a K0 III star with relatively low ultraviolet
{uv} emission line fluxes and X-ray emission, and is thought to be
a helium core- burning `clump' giant. However, since it lies at a
distance of only about 10 parsecs the fluxes at the Earth are sufficient
for detailed spectral studies in the uv. Although our main interest
in the star has been in modelling for the purposes of establishing
and understanding the energy balance requirements, this proposal is
concerned with a specific aspect of its spectrum around 2320 Angstrom to
2365 Angstrom. In Beta Gem {HD 62509} and cooler giants the strongest
lines in this region are those of C II, Si II and Fe II. The spectrum
of Beta Gem {HD 62509} is so far unique in that it also shows a number
of narrow emission features that are not observed in the cooler stars,
with an overall structure that suggests the presence of a molecular
band. We wish to investigate the possibility that this is the A^1Pi -
X^1Sigma {0 - 0} b an d of SiO, which has never been identified in an
astrophysical spectrum. This requires the high spectral resolution of
STIS. Other bands in the above system would then also be expected in
the region from about 2300 Angstrom to 2500 Angstrom. Chromospheric
models would be used to understand the presence of the SiO band system
in Beta Gem {HD 62509} and its absence in cooler giants.
Title: Lines of OIV and SIV in the Goddard High-Resolution
Spectrograph spectrum of RR Tel: constraints on atomic data
Authors: Harper, G. M.; Jordan, C.; Judge, P. G.; Robinson, R. D.;
Carpenter, K. G.; Brage, T.
Bibcode: 1999MNRAS.303L..41H
Altcode:
High signal-to-noise ratio spectra of RR Tel obtained at medium
resolution with the Goddard High-Resolution Spectrograph (GHRS) on the
Hubble Space Telescope (HST) are used to test available atomic data for
the OIV 2s^22p ^2P-2s2p^2 ^4P multiplet (UV 0.01). The fine-structure
intervals of the 2s2p^2 ^4P term given by Moore (1983) appear to need
revision. The flux ratios of lines within multiplet UV (0.01), which
have a common upper level, depend only on transition probabilities. The
observed flux ratio of lines from the ^4P_3/2 level differs from that
predicted by theory, but this difference cannot be attributed to a
blend with a line of SIV]. At the electron densities in the RR Tel
nebula, other flux ratios give information on the relative electron
excitation rates between the ^2P and ^4P fine-structure levels. Using
the collision strengths calculated by Zhang, Graziani & Pradhan,
the rate to the ^4P_5/2 level, relative to the rates to the other J
states, appears to be underestimated by ~ 10 per cent, which is within
the expected uncertainty of 20 per cent. We also discuss the SIV 3s^23p
^2P-3s3p^2 ^4P multiplet.
Title: The outer atmosphere of Tau - II. Fluorescent lines
Authors: McMurry, A. D.; Jordan, C.; Carpenter, K. G.
Bibcode: 1999MNRAS.302...48M
Altcode:
The Goddard High Resolution Spectrograph (GHRS) on the Hubble Space
Telescope has been used to observe α Tau (K5 III). The resulting
spectra contain many sharp fluorescent lines. Most of these have been
identified as lines of Fe ii, Ca ii and H2, radiatively
excited by H Lyα. The chromospheric model developed in an accompanying
paper has been used to calculate the fluxes in these lines. The Ca ii
lines have been modelled with a full radiative transfer calculation,
but the Fe ii and H2 systems are more complex and, for
these, a simpler calculation has been made. Overall, the trend in the
Fe ii line fluxes provides evidence for a multicomponent model of the
atmosphere, a chromosphere with intrusions of hotter material or vice
versa. The hotter material could be in shocks propagating through
the chromosphere. Comparisons of the observed and calculated fluxes
of individual lines of Fe ii show that some atomic data need to be
improved. The analysis of the H2 lines is restricted by
a lack of suitable molecular data. The two observed Ca ii lines are
reproduced to within a factor of 2.
Title: Coronal and Transition Region Structure in the RS Canum
Venaticorum Binaries V711 Tauri, AR Lacertae, and II Pegasi. I. Data
Analysis and Emission Measure Distributions
Authors: Griffiths, N. W.; Jordan, C.
Bibcode: 1998ApJ...497..883G
Altcode:
We present a study of the transition regions and coronae of the
RS CVn binaries V711 Tau, AR Lac, and II Peg. Archival data from
the Extreme Ultraviolet Explorer (EUVE), International Ultraviolet
Explorer (IUE), Goddard High-Resolution Spectrograph (GHRS), and a
variety of X-ray telescopes have been analyzed and modeled. Emission
measure distributions have been determined for the transition region of
each system. The upper transition region (6.1 < log Te
< 7.4) has been studied using line fluxes from the EUVE. Emission
measure distributions for the lower transition region (3.8 <
log Te < 5.3) have been found using emission-line
fluxes obtained with IUE and the GHRS. Electron densities of ~1.6
× 1011 and ~5 × 1011 cm-3 have
been determined at log Te = 7.0 and log Te
= 4.7 respectively, using the density-sensitive Fe XXI λ128.7
and Si III] λ1892 lines. The total pressure (gas + turbulent)
is smaller at the lower temperature, indicating that the high-
and low-temperature material originates in physically unconnected
regions. The emission measure distributions derived from the EUVE line
spectra are compared with emission measures found from spectral fits
to a variety of low-resolution X-ray spectra, including our reanalysis
of archival EXOSAT spectra. Although the emission measure distribution
is continuous, both types of analysis lead to two distinct peaks in
the high-temperature emission measure distribution, suggesting that
there may be two classes of structure in the upper transition region
and corona, e.g., two families of loops.
Title: Fluorescence in the Chromosphere of alpha Tau (K5 III)
Authors: McMurry, A. D.; Jordan, C.; Carpenter, K. G.; Robinson, R. D.
Bibcode: 1998ASPC..154.1293M
Altcode: 1998csss...10.1293M
The Goddard High Resolution Spectrograph (GHRS) on the Hubble Space
Telescope has been used to obtain spectra of alpha Tau covering many
parts of the uv spectrum between 1200AA and 2000AA. Here we concentrate
on the region between 1320AA and 1390AA, which is covered by 2 medium
resolution exposures. Most of the lines appearing in these spectra have
been identified, including 2 bands of fluorescent CO lines. Preliminary
modelling of these CO lines has been carried out, and the results are
compared with the observations.
Title: Identifications of Emission Lines in GHRS Spectra of RR Tel
Authors: Jordan, C.; Harper, G. M.
Bibcode: 1998ASPC..154.1277J
Altcode: 1998csss...10.1277J
Spectra of the symbiotic nova RR Tel, obtained with the Goddard High
Resolution Telescope on the Hubble Space Telescope, have been used
to make identifications of the emission lines observed. The 2p^4
^3P2 - ^1D2 transition in Al 6, at 2429.50 AA
(lambdaair) has been identified for the first time. The He 2
Paschen series has been extended from the n = 3 to n = 16 transition at
2124.61 AA. Further primary and secondary decays from Fe 2 levels pumped
by H Lyman alpha and O 6 have been identified. Lines from levels pumped
by Si 3 (1206.51 \AA) and He 2 (1084.98 AA), have also been identified.
Title: Coronal Abundances: What are They?
Authors: Jordan, C.; Doschek, G. A.; Drake, J. J.; Galvin, A. B.;
Raymond, J. C.
Bibcode: 1998ASPC..154...91J
Altcode: 1998csss...10...91J
Derivation of coronal abundances in the Sun and cool stars has led
to conflicting results. In some stars, the coronal abundances appear
metal deficient (MAD: a metal abundance deficiency), in others the
abundance seems dependent on the ionization potential of the first ion
(FIP-effect: First Ionization potential). Additionally, in the Sun
there may be evidence for abundance variations from one feature to
another. If abundance differences are real, they could give valuable
insight to the physical processes of heating and mass transport in
the chromospheres and coronas of cool stars.
Title: Cool giants and supergiants: chromospheres and winds
Authors: Jordan, Carole
Bibcode: 1997A&G....38f..21J
Altcode:
No abstract at ADS
Title: Epsilon Eri: Structure and Non-Thermal Heating
Authors: Jordan, Carole
Bibcode: 1997hst..prop.7479J
Altcode:
Epsilon Eri {K2 V} is the most active single K dwarf within 10 pc of the
Sun, and its proximity {3.3 pc} allows studies of emission line profiles
as well as fluxes. We have observed Epsilon Eri with IUE, at Lo and Hi
resolution, and with ROSAT {PSPC and WFC}, and have used these spectra
to make models of the structure of the transition region and corona,
and to establish the non-thermal energy requirements. The accuracy
of the current models is limited by the available line widths and the
electron density {Ne} derived from the Si III line at 1892 Angstrom. The
aim of the observations with STIS is to measure the profiles and fluxes
of lines formed in the chromosphere and transition region, including
several lines which can yield Ne. Significantly improved models from
the photosphere to the corona could then be obtained, to investigate
the non-thermal heating. With Ne determined from line ratios there are
sufficient lines of C and Si ions to find the C/Si abundance ratio,
for co mparison with photospheric values. Epsilon Eri has a measured
magnetic field and area filling factor, and together with xi Boo A
{G8 V} {our Cycle 5 observations} and the Sun {G2 V}, the observations
will aid our understanding of the observed correlations between line
fluxes, magnetic fluxes and activity indicators such as the rotation
period and the Rossby number.
Title: Magnetic activity in late-type stars
Authors: Jordan, Carole
Bibcode: 1997A&G....38b..10J
Altcode:
No abstract at ADS
Title: An exceptional X-ray flare on the dMe star EQ1839.6+8002
Authors: Pan, H. C.; Jordan, C.; Makishima, K.; Stern, R. A.;
Hayashida, K.; Inda-Koide, M.
Bibcode: 1997MNRAS.285..735P
Altcode:
A large impulsive flare was detected serendipitously during observations
of the radio galaxy 3C390.3 made with the Ginga satellite on 1991
February 14, between 22:30 and 23:00 (UT). The dMe star EQ1839.6+8002
is the most likely source of this flare. The rise of the flare was
observed and the spectra obtained are of sufficient quality to determine
the temperature and emission measure as a function of time. The flare
is exceptional in its high peak temperature (T_e~10^8K) and emission
measure (~9x10^53 cm^-3), the largest recorded for a flare on a dMe
star, and comparable with those for flares in RS CVn systems. The
normalized X-ray luminosity is also very large (L_X/L_bol~0.25). The
flare geometry and plasma parameters are derived by making various
assumptions concerning the dominant terms in the internal energy
equation, which takes account of a varying mass and volume. The initial
heating appears to be proportional to the gas pressure. At the peak
T_e the electron density is ~1.7x10^12 cm^-3, and the hot plasma has a
length ~10^10 cm. The flare plasma then cools initially by `evaporative
conduction'. Two alternative simple models are made of the flare decay
beyond this time (cooling with constant mass or constant volume). Both
require continued heating, and the latter gives results similar to
those expected in quasi-static conditions. The evolution of the flare
temperature and density broadly resembles that predicted by numerical
simulations. Observations with the Einstein IPC, the EXOSAT LE and the
ROSAT PSPC instruments show flaring and quiescent properties similar
to those of the flare stars discussed by Pallavicini et al.
Title: Helium Line Studies Using CDS and SUMER
Authors: MacPherson, K. P.; Jordan, C.
Bibcode: 1997ESASP.404..533M
Altcode: 1997cswn.conf..533M
No abstract at ADS
Title: Address of the President (Dr. C. Jordan) on the presentation
of the Jackson-Gwilt Medal to Dr. J. A. Mattei on Friday 1996 March 8.
Authors: Jordan, C.
Bibcode: 1996QJRAS..37..279J
Altcode:
The Jackson-Gwilt Medal and Gift for 1995 is awarded to J. A. Mattei for
her contributions as Director of the American Association of Variable
Star Observers (AAVSO).
Title: Address of the President (Dr. C. Jordan) on the presentation of
the Herschel Medal to Professor G. R. Isaak on Friday 1995 December 8.
Authors: Jordan, C.
Bibcode: 1996QJRAS..37..275J
Altcode:
The Herschel Medal for 1995 is awarded to G. R. Isaak for his
pioneering work in measuring global solar oscillations, of which he
was a discoverer.
Title: Address of the President (Dr. C. Jordan) on the presentation
of the Gold Medal to Sir John Houghton on Friday 1995 October 13.
Authors: Jordan, C.
Bibcode: 1996QJRAS..37...99J
Altcode:
The Gold Medal of the Royal Astronomical Society is awarded to
J. Houghton for his distinguished and inspiring work in atmospheric
physics.
Title: The Chromosphere-Corona Transition Region in Late-Type Stars
Authors: Jordan, C.
Bibcode: 1996Ap&SS.237...13J
Altcode:
Observations of the Sun show that the chromosphere-corona transition
region has a complex geometry and dynamic nature. In spite of this,
observations of stellar transition regions show common behaviour as
well as systematic trends. The basic methods used in making models
of the transition region are set out. Observations relating to
inhomogeneities in the solar transition region are summarized. The
structure and energy balance of stellar transition regions and the
trends emerging are discussed.
Title: Tomography of the solar atmosphere
Authors: Sarro, L. M.; Montesinos, B.; Jordan, C.
Bibcode: 1996ASPC..109..159S
Altcode: 1996csss....9..159S
No abstract at ADS
Title: Coronal and transition region structure in RS CVn binaries
Authors: Griffiths, N. W.; Jordan, C.
Bibcode: 1996ASPC..109..647G
Altcode: 1996csss....9..647G
No abstract at ADS
Title: Identification and analysis of UV emission lines observed near
1550 Angstroms in the spectrum of alpha Tau obtained with the GHRS
Authors: McMurry, A. D.; Jordan, C.; Rowe, A. K.; Carpenter, K. G.;
Robinson, R. D.
Bibcode: 1996ASPC..109..271M
Altcode: 1996csss....9..271M
No abstract at ADS
Title: EUVE Spectra of Coronae and Flares
Authors: Jordan, Carole
Bibcode: 1996aeu..conf...81J
Altcode: 1996IAUCo.152...81J
No abstract at ADS
Title: The Astrophysical Laboratory RR Tel: Observations
Authors: Harper, G. M.; Brown, A.; Robinson, R. D.; Jordan, C.;
Carpenter, K. G.; Shore, S. N.
Bibcode: 1995AAS...187.1910H
Altcode: 1995BAAS...27.1313H
The rich emission line spectrum of the bright symbiotic nova RR
Tel provides one of the best laboratories for determining empirical
values of atomic parameters, including branching ratios, Einstein
A-values and electron collision strengths. In addition to providing
atomic parameters not measurable in the laboratory, the observations
also test recent theoretical calculations of these parameters. In July
1995 we obtained high quality low and medium resolution, large aperture
spectra of RR Tel using the Goddard High Resolution Spectrograph (GHRS)
on board the Hubble Space Telescope. These spectra sample wavelengths
from 1100 Angstroms to 2680 Angstroms and contain numerous lines of
astrophysical interest which will be used to derive empirical atomic
data (e.g. branching ratios in C II], N III], O III] and O IV])
as well as lines from which the local temperature and density can
be determined. The GHRS spectra have greater dynamic range and lower
background noise than available high resolution IUE data, permitting
detailed evaluation of spectral diagnostics even for the weak emission
features from some intercombination and forbidden transitions. In this
paper we show examples of the spectra, discuss the atomic transitions
for which atomic data will be derived and describe the methods used in
determining these parameters. RR Tel and AG Peg, both of which have been
observed with the GHRS, are fundamental for studying time variability
of spectra of a symbiotic nova and the GHRS observations will be
compared with previous IUE results to investigate this variability. We
will also discuss the observed flows and turbulence found from the
line profiles as well as the shape of the UV continuum. Support for
this work was provided by NASA through grant number GO-05863.01-94A
from the Space Telescope Science Institute, which is operated by the
Association of Universities for research in Astronomy, Inc., under
NASA contract NAS5-26555.
Title: Xi Boo a: Structure and Non-Thermal Heating
Authors: Jordan, Carole
Bibcode: 1995hst..prop.6076J
Altcode: 1995hst..prop.2549J
Xi Boo A is a G8 V star which is substantially more active than the
Sun.It is an ideal target for the GHRS instrument which can make
observationsof density sensitive emission line ratios and line widths
that areimpossible with IUE. We have used our existing observations
of xi Boo A,made with IUE, the PSPC and WFC instruments on ROSAT,
and EUVE, to makemodels of the atmosphere from the photosphere
to the corona, using theMULTI radiative transfer code to model
the chromosphere. Discriminationbetween these requires an improved
measurement of the electron density.Comparisons of transition region
and coronal pressures provide constraintson the geometry, including
non-homogeneity. Line widths enter theturbulent pressure and non-thermal
energy density, and are required forcomparisons between empirical energy
losses and specific heatingmechanisms. Xi Boo A has a measured magnetic
field and follows a varietyof field, rotation and line flux correlations
found from wider studies ofmain-sequence stars.These can be understood
only by elucidating thephysics within a given stellar atmosphere. Xi
Boo B can be observedseparately to aid the interpretation of X-ray and
EUVE fluxes. We willalso apply for observing time with the HRI on ROSAT.
Title: Address of the President (Dr. C. Jordan) on the presentation
of the Gold Medal to Professor T. R. Kaiser on Monday 1994 July 11.
Authors: Jordan, C.
Bibcode: 1995QJRAS..36...81J
Altcode: 1995QJRAS..36...81.
The Gold Medal for Geophysics and Planetary Science for 1994 is
awarded to T. R. Kaiser for his fundamental work and leadership in
space geophysics.
Title: Book Review: Cosmical magnetism / Kluwer, 1994
Authors: Jordan, C.
Bibcode: 1995Obs...115...47B
Altcode:
No abstract at ADS
Title: Chromospheric and Coronal Spectra
Authors: Jordan, C.
Bibcode: 1995ASPC...78..371J
Altcode: 1995aapn.conf..371J
No abstract at ADS
Title: The RIASS Coronathon: Joint X-Ray and Ultraviolet Observations
of Normal F--K Stars
Authors: Ayres, Thomas R.; Fleming, T. A.; Simon, T.; Haisch, B. M.;
Brown, A.; Lenz, D.; Wamsteker, W.; de Martino, D.; Gonzalez, C.;
Bonnell, J.; Mas-Hesse, J. M.; Rosso, C.; Schmitt, J. H. M. M.;
Truemper, J.; Voges, W.; Pye, J.; Dempsey, R. C.; Linsky, J. L.;
Guinan, E. F.; Harper, G. M.; Jordan, C.; Montesinos, B. M.; Pagano,
I.; Rodono, M.
Bibcode: 1995ApJS...96..223A
Altcode:
Between 1990 August and 1991 January the ROSAT/IUE All Sky Survey
(RIASS) coordinated pointings by the International Ultraviolet Explorer
(IUE) with the continuous X-ray/EUV mapping by the Roentgensatellit
(ROSAT). The campaign provided an unprecedented multiwavelength
view of a wide variety of cosmic sources. We report findings for
F-K stars, a large proportion of the RIASS targets. Forty-eight of
our 91 'Coronathon' candidates were observed by the IUE during the
campaign. For stars missed by the IUE, we supplemented the ROSAT survey
fluxes with archival UV spectra and/or follow-on observations.
Title: ROSAT observations of the flare star CC ERI
Authors: Pan, H. C.; Jordan, C.
Bibcode: 1995MNRAS.272...11P
Altcode: 1994astro.ph..9044P
The flare/spotted spectroscopic binary star CC Eri was observed with
the Position Sensitive Proportional Counter (PSPC) on the X-ray
satellite ROSAT on 1990 July 9-11 and 1992 January 26-27. During
the observations, the source was variable on time-scales from a few
minutes to several hours, with the X-ray (0.2-2 keV) luminosity in
the range ~(2.5-6.8)x10^29 erg s^-1. An X-ray flare-like event,
which has a 1-h characteristic rise time and a 2-h decay time,
was observed from CC Eri on 1990 July 10, 16:14-21:34 (UT). The
X-ray spectrum of the source can be described by current thermal
plasma codes with two temperature components or with a continuous
temperature distribution. The spectral results show that plasma
at T_e~10^7K exists in the corona of CC Eri. The variations in
the observed source flux and spectra can be reproduced by a flare,
adopting a magnetic reconnection model. Comparisons with an unheated
model, late in the flare, suggest that the area and volume of the flare
are substantially larger than in a solar two-ribbon flare, while the
electron pressure is similar. The emission measure and temperature of
the non-flaring emission, interpreted as the average corona, lead to
an electron pressure similar to that in a well-developed solar active
region. Rotational modulation of a spot-related active region requires
an unphysically large X-ray flux in a concentration area.
Title: X-ray Variability of the Flare Star CC ERI
Authors: Pan, H. C.; Jordan, C.
Bibcode: 1995LNP...454..170P
Altcode: 1995flfl.conf..170P; 1995IAUCo.151..170P
No abstract at ADS
Title: Chromospheric and coronal spectra
Authors: Jordan, C.
Bibcode: 1995HiA....10..580J
Altcode:
No abstract at ADS
Title: X-ray observations of the dMe star EQ1839.6+8002 in 1980 1993
Authors: Pan, H. C.; Jordan, C.; Makishima, K.; Stern, R. A.;
Hayashida, K.; Inda-Koide, M.
Bibcode: 1995LNP...454..171P
Altcode: 1995flfl.conf..171P; 1995IAUCo.151..171P
No abstract at ADS
Title: Book Review: UV and X-ray spectroscopy of laboratory and
astrophysical plasmas / Cambridge U Press, 1993
Authors: Jordan, C.; Harper, G.
Bibcode: 1994Obs...114..196J
Altcode: 1994Obs...114..196S
No abstract at ADS
Title: Empirical models of the magnetospheric magnetic field.
Authors: Jordan, C. E.
Bibcode: 1994RvGeo..32..139J
Altcode:
Space scientists have a wide variety of models to choose from for
their studies of the Earth's auroral phenomenon, radiation belts,
magnetotail, magnetopause, etc. Different types of models are suited
for different purposes. At this time, there is no one model to suit
everyone's needs. In this paper a general overview of magnetospheric
modeling is given, along with a more detailed discussion of several
empirical models which are widely used.
Title: Book-Review - the Solar Transition Region
Authors: Mariska, J. T.; Harper, G.; Jordan, C.
Bibcode: 1994Obs...114...58M
Altcode:
No abstract at ADS
Title: Modelling the X-Ray Light Curve of CC ERI
Authors: Pan, H. C.; Jordan, C.
Bibcode: 1994ASPC...64..119P
Altcode: 1994csss....8..119P
No abstract at ADS
Title: Coronal Heating in Late-Type Stars
Authors: Jordan, C.; Montesinos, B.
Bibcode: 1994emsp.conf..137J
Altcode:
No abstract at ADS
Title: Advances in solar physics: Conference summary.
Authors: Jordan, C.
Bibcode: 1994LNP...432..321J
Altcode: 1994LNPM...11..321J
No abstract at ADS
Title: On magnetic fields, rossby numbers and dynamo action in
late-type stars
Authors: Montesinos, B.; Jordan, C.
Bibcode: 1994LNP...432..101M
Altcode: 1994LNPM...11..101M
In this paper we give a brief account of our comparisons of predicted
and observed trends in the dependence of the magnetic flux, B s f s,
and the filling factor, f s on the Rossby number, Ro, in main-sequence
late-type stars. A sample of stars with reliable measurements of B s
and f s has been selected. The surface average magnetic field, B s f s,
and the fraction of the star covered by this field, the filling factor,
f s, were computed by using a simple dynamo model plus some assumptions
on how the field generated at the bottom of the convection zone emerges
at the photosphere. The best fits between B s f s and f s with Ro are
shown and a possible theoretical basis for the saturation observed at
small values of Ro, both in B s f s and fs is discussed. Full details of
the work summarised here can be found in Montesinos and Jordan (1993).
Title: On magnetic fields, stellar coronae and dynamo action in
late-type dwarfs.
Authors: Montesinos, B.; Jordan, C.
Bibcode: 1993MNRAS.264..900M
Altcode:
The chromospheric and coronal emission from late-type dwarf stars is
thought to depend on the stellar magnetic fields. The observed relations
between the average surface magnetic fields Bsfs,
the filling factors fs and the Rossby numbers RO
are discussed and compared with the predictions of simple dynamo
theory. The Ca II excess flux density ΔFHK as a fraction
of the bolometric flux is found to correlate most closely with RO, a
conclusion similar to that drawn by Noyes et al. Coronal scaling laws,
based on the minimum energy loss hypothesis of Hearn, are compared
with observed coronal parameters, and on average can account for the
observed trends. The total coronal heating flux required is found
to scale approximately as RO-1. If magnetic reconnection
provides this flux, a combination of the plasma parameters required
to match the empirical heating flux can be found. The scalings of
the implied coronal field and surface magnetic flux with RO cannot be
reconciled with magnetic flux conservation, suggesting that not all the
surface flux extends to the corona. The dependence of chromospheric and
coronal parameters on RO is not yet understood. However, the correlation
between the Ca II excess flux density ΔFHK and the X-ray
flux (more strictly, the coronal emission measure) can be accounted
for by relating these quantities through the electron pressure.
Title: The Coronae of F-K Dwarfs: Factors Controlling Their Properties
Authors: Jordan, C.
Bibcode: 1993AAS...182.3806J
Altcode: 1993BAAS...25..856J
X-ray observations of late-type stars can be used to determine average
coronal emission measures, Em(T_c), and temperature, T_c, provided the
spectra can be fitted adequately by single temperatures. Em(T_c) and T_c
can be correlated with stellar properties, such as the rotation period,
or with convection zone parameters, such as the Rossby number (Ro =
P(rot)/turnover time at the base of the convection zone). Including
F to K dwarfs, the closest correlations are found between Em(T_c) g*
((1)/(2)) and Ro, and T_c g* ((1)/(2)) and Ro. The total energy losses
from the coronae (radiation plus thermal conduction) can, with some
assumptions, also be expressed in terms of Em(T_c) and T_c. These
total losses, and hence the non-thermal energy required to heat the
corona, scale approximately as Ro(-1) . The coronal magnetic field can
also be expressed in terms of Em(T_c) and T_c, through the pressure
and plasma Beta, and comparisons can be made with specific heating
mechanisms. Some recent results will be presented, including the
relation between these implied coronal fields and surface magnetic
fields and filling factors. The contribution from new observations
with ROSAT, and expected from EUVE, will be discussed. This work has
been supported by the SERC through grant GR/H25539.
Title: Book Review: The cosmic water hole / MIT Press, 1991
Authors: Jordan, C.
Bibcode: 1993Ap&SS.201..161J
Altcode: 1993Ap&SS.201..161D
No abstract at ADS
Title: Cool Stars with Measured Surface Magnetic Fields
Authors: Jordan, C.
Bibcode: 1993iue..prop.4611J
Altcode:
No abstract at ADS
Title: Magnetic Fields and Coronae in Late-Type Stars
Authors: Montesinos, B.; Jordan, C.
Bibcode: 1993ASSL..183..579M
Altcode: 1993pssc.symp..579M
No abstract at ADS
Title: Comparison of magnetospheric magnetic field models with CRRES
observations during the August 26, 1990, storm
Authors: Jordan, C. E.; Bass, J. N.; Gussenhoven, M. S.; Singer,
H. J.; Hilmer, R. V.
Bibcode: 1992JGR....9716907J
Altcode:
Four magnetospheric magnetic field models are compared on the
basis of the current systems they represent, their agreement with
observations, and their computational performance. These models are
the Olson-Pfitzer dynamic (1988), Tsyganenko 1989, Hilmer-Voigt,
and Olson-Pfitzer tilt-dependent (1977). The models are summarized
in terms of their components: the main field, the ring currents, the
tail currents, and the magnetopause. Differences among the models
must be considered when determining which is best for a specific
application. The models are evaluated using data from CRRES during
both quiet and storm time conditions on August 26, 1990. CRRES is in
a geosynchronous transfer orbit with perigree at 360 km and apogee
at 33000 km. Thus, the focus of our comparisons is on the inner
magnetosphere out to about 6.3 RE (distant tail properties
will not be discussed). Tsyganenko 1989 is a good average model of the
magnetospheric magnetic field for various Kp levels. Olson-Pfitzer
dynamic and Hilmer-Voigt both clearly show changes in the magnetic
field due to the compression of the magnetopause as determined from the
standoff distance. Hilmer-Voigt is the most flexible model as it has
a parameter to specify the position of the inner edge of the plasma
sheet, but it is also the slowest to execute. Olson-Pfitzer dynamic
showed the best agreement with the data presented here.
Title: Solar physics
Authors: Jordan, C.
Bibcode: 1992ConPh..33..329J
Altcode:
No abstract at ADS
Title: Book Review: The Yohkoh (Solar-A) mission / Kluwer
Authors: Jordan, C.
Bibcode: 1992Ap&SS.192..164J
Altcode: 1992Ap&SS.192..164S
No abstract at ADS
Title: Book reviews
Authors: Leitner, R.; Hartquist, T. W.; Dyson, John; Williams, D. A.;
Jordan, C.
Bibcode: 1992Ap&SS.192..157L
Altcode:
No abstract at ADS
Title: Fe II Emission Lines. II. Excitation Mechanisms in Cool Stars
Authors: Judge, P. G.; Jordan, C.; Feldman, U.
Bibcode: 1992ApJ...384..613J
Altcode:
Excitation mechanisms are discussed for the 'resonance' transitions
(between the 3d(6)4s, 3d7, and 3d(6)4p configurations) of Fe II observed
in emission in the near-UV spectra of cool stars. The analysis is
based upon: (1) emission measure analysis of previously measured
lines in IUE spectra of cool giants; (2) discussion of the behavior
of Fe II lines observed above the solar limb from Skylab spectra; (3)
approximate radiative-transfer calculations in a 59 level Fe-II model
atom using mean escape probabilities and a parameterization of optical
radiation fields; and (4) accurate radiative transfer calculations in
a smaller atomic model. The solar spectra show unambiguous evidence
that electron collisions are responsible for most of the Fe-II emission
observed above the white-light limb. The terms leading to UV multiplets
3-6, 34-36, and 61-64 are excited by electron excitation of metastable
quartet terms below about 4 eV, followed by photoexcitation in lines at
optical wavelengths by photospheric radiation. A 'cool-star' diagnostic
diagram is constructed showing the regimes in which electron collisions
and continuum photoexcitation are important in the chromospheres of
cool stars.
Title: Modelling of solar coronal loops
Authors: Jordan, C.
Bibcode: 1992MmSAI..63..605J
Altcode:
Solar active regions are observed to be composed of loop structures,
with a wide range of maximum temperatures and lengths. There has,
over the past fifteen years or so, been considerable interest in
understanding these structures in terms of the possible energy input
processes, and in terms of their MHD and thermal stability. This review
concentrates on what is known about the observable parameters, and how
these are related to the theoretical energy balance equation. Although
it is difficult to derive the form of the heating function, because
of the uncertainties inherent in the observations, very few sets
of observations exist in which all the useful parameters have been
measured simultaneously. In order to investigate heating processes
other observations are also required, i.e. of nonthermal velocities
and magnetic fields in the photosphere and in loops (through microwave
data). The pressure variation across loops is still poorly known,
and is also important for studies of loop stability.
Title: Stellar coronae and their relation to convection zones and
rotation rates
Authors: Jordan, C.; Montesinos, B.
Bibcode: 1992MmSAI..63..735J
Altcode:
Correlations between stellar coronal properties and convection zone
properties are derived using simple scaling laws and available data. It
is shown that the use of term g* in the basic realtionship
between the coronal emission measure Em(Tc) and coronal pressure,
explains why the Em(Tc) or the Einstein X-ray fluxes should scale with
the Rossby number Ro.
Title: Modelling of solar coronal loops
Authors: Jordan, C.
Bibcode: 1992HiA.....9..661J
Altcode:
No abstract at ADS
Title: The first EUV survey: white dwarfs and cool stars
Authors: Jordan, C.; Pounds, K. A.
Bibcode: 1992HiA.....9..241J
Altcode:
No abstract at ADS
Title: A Magnitude-Limited Survey of Single, Non-Variable G
Supergiants
Authors: Jordan, C.
Bibcode: 1992iue..prop.4366J
Altcode:
No abstract at ADS
Title: A Magnitude-limited Survey of Single, Non-variable G
Supergiants
Authors: Jordan, C.
Bibcode: 1992iue..prop.4427J
Altcode:
No abstract at ADS
Title: Preliminary comparison of dose measurements on CRRES to NASA
model predictions
Authors: Gussenhoven, M. S.; Mullen, E. G.; Brautigam, D. H.; Holeman,
E.; Jordan, C.; Hanser, F.; Dichter, B.
Bibcode: 1991ITNS...38.1655G
Altcode:
Measurements of proton and electron dose from the space radiation
dosimeter on the CRRES satellite, in a 18.1 deg, 350 km by 33,000 km
orbit, are compared to the NASA models for solar maximum conditions. Up
to the time of the large, solar-initiated particle events near the end
of March 1991, the results are similar to those previously reported for
solar minimum at low altitudes. That is, prior to the March event, there
is excellent agreement between model and measured values for protons
and poor agreement for electrons. During the event period a second
proton belt was formed at higher altitudes which is not contained
in the proton models, and the electrons increased over an order
of magnitude for the CRRES orbit. This resulted in poorer agreement
between model and measured values for protons during and after the solar
proton event and better agreement for electrons during the electron
enhancement period. What the data show is that, depending on orbit,
both the existing proton and electron models can give large errors in
dose that can compromise space system performance and lifetime.
Title: The dependence of coronal temperatures on Rossby numbers.
Authors: Jordan, C.; Montesinos, B.
Bibcode: 1991MNRAS.252P..21J
Altcode:
Previous observations have shown that although correlations exist
between chromospheric, transition region and coronal emission fluxes,
the correlations between these fluxes and stellar rotational periods
depend on the spectral type and luminosity class. The measured
coronal temperatures (Tc) also depend on the type of star, with clear
distinctions between F and G/K dwarf stars and between dwarf and giant
stars. Others have argued that these emission fluxes, or luminosities,
normalized to the stellar bolometric values can be related more closely
to the Rossby number, Ro. Assuming that the coronal gas energy density
depends only on the magnetic energy density a correlation is derived
between the parameters Em(Tc) (the coronal emission measure), Tc,
the surface gravity, and the required coronal magnetic field. This
correlates well with the Rossby number for the dwarf stars. It is
discussed how evolved stars might be included by also considering
correlations with the dynamo number. Coronal temperatures and emission
measures therefore provide an empirical way of investigating convection
zone properties.
Title: Fe II Emission Lines. I. Chromospheric Spectra of Red Giants
Authors: Judge, P. G.; Jordan, C.
Bibcode: 1991ApJS...77...75J
Altcode:
A 'difference filtering' algorithm developed by Ayers (1979) is used
to construct high-quality high-dispersion long-wavelength IUE spectra
of three giant stars. Measurements of all the emission lines seen
between 2230 and 3100 A are tabulated. The emission spectrum of Fe II is
discussed in comparison with other lines whose formation mechanisms are
well understood. Systematic changes in the Fe II spectrum are related
to the different physical conditions in the three stars, and examples
are given of line profiles and ratios which can be used to determine
conditions in the outer atomspheres of giants. It is concluded that
most of the Fe II emission results from collisional excitation and/or
absorption of photospheric photons at optical wavelengths, but some
lines are formed by fluorescence, being photoexcited by other strong
chromospheric lines. Between 10 and 20 percent of the radiative losses
of Fe II arise from 10 eV levels radiatively excited by the strong
chromospheric H Ly-alpha line.
Title: Empirical Constraints on Coronal Heating Processes (With
5 Figures)
Authors: Jordan, C.
Bibcode: 1991mcch.conf..300J
Altcode:
No abstract at ADS
Title: Observations Relating to Stellar Activity Magnetism and Dynamos
Authors: Jordan, C.
Bibcode: 1991LNP...380..509J
Altcode: 1991IAUCo.130..509J; 1991sacs.coll..509J; 1991LNP...380..507J
Dynamo theory can in principle be tested by comparing its predictions
with a variety of types of solar and stellar observations. The progress
apparent from papers presented at this Colloquium is summarized,
and areas where further observations would be of particular value
are stressed.
Title: Extreme Ultraviolet Emission from Cool Star Coronae - a Review
Authors: Jordan, C.
Bibcode: 1991eua..coll...80J
Altcode:
No abstract at ADS
Title: Magnetic Fields and Filling Factors in Late-Type Stars -
Predictions from Dynamo Theory
Authors: Montesinos, B.; Fernández-Villacañas, J. L.; Jordan, C.
Bibcode: 1991LNP...380..430M
Altcode: 1991IAUCo.130..430M; 1991sacs.coll..430M
In this paper we examine the link between observed magnetic fields
and filling factors in main-sequence stars of types G and K, and the
results obtained for these parameters from a simple dynamo model. We
explore how the predicted magnetic fluxes, fB, for a selected sample
of stars, vary with rotation, adopting two theoretical approaches to
estimate the filling factor, and considering different expressions
for the variation of the stellar angular velocity, w, with depth.
Title: The physics of solar flares. Proceedings.
Authors: Culhane, J. L.; Jordan, C.
Bibcode: 1991psf..conf.....C
Altcode:
First published in Philos. Trans. R. Soc. London, Ser A, Vol. 336,
No. 1643, p. 321 - 495 (1991). The purpose of this volume is to review
the contribution of the three spacecraft (P78-1, SMM, and Hinotori)
to the study of solar flares. It also includes discussions of the
current theoretical basis of some aspects of solar flares (including
magnetic energy conversion).
Title: Chromospheres of Two Red Giants in NGC 6752
Authors: Dupree, A. K.; Harper, G. M.; Hartmann, L.; Jordan, Carole;
Rodgers, A. W.; Smith, Graeme H.
Bibcode: 1990ApJ...361L...9D
Altcode:
Two red giant stars, A31 and A59, in the globular cluster NGC 6752
exhibit Mg II (2800 A) emission with surface fluxes comparable to
those observed among metal-deficient halo field giants, and among
low-activity Population I giants. Optical echelle spectra of these
cluster giants reveal emission in the core of the Ca II K (3933.7 A)
line, and in the wing of the H-alpha (6562.8 A) profile. Asymmetries
exist both in the emission profiles and the line cores. These
observations demonstrate unequivocally the existence of chromospheres
among old halo population giants, and the presence of mass outflow
in their atmospheres. Maintenance of a relatively constant level of
chromospheric activity on the red giant branch contrasts with the
decay of magnetic dynamo activity exhibited by dwarf stars and younger
giants. A purely hydrodynamic phenomenon may be responsible for heating
the outer atmospheres of these stars, enhancing chromospheric emission,
thus extending the atmospheres and facilitating mass loss.
Title: On the disappearance of OI in some high-luminosity cool stars
Authors: Carpenter, K. G.; Norman, D.; Robinson, R.;
Fernandez-Villacanas, J. L.; Jordan, C.; Judge, P.
Bibcode: 1990ESASP.310..307C
Altcode: 1990eaia.conf..307C
No abstract at ADS
Title: Fe II Emission Lines: Chromospheric Spectra of Red Giants
Authors: Judge, P. G.; Jordan, C.
Bibcode: 1990BAAS...22..848J
Altcode:
No abstract at ADS
Title: The spectra of cool stars in the ultraviolet region
Authors: Jordan, C.
Bibcode: 1990asos.conf...61J
Altcode:
No abstract at ADS
Title: Ultraviolet Observations of the New, Very Hot DA White Dwarf
HS 1 234+4811
Authors: Jordan, C.
Bibcode: 1990iue..prop.3877J
Altcode:
No abstract at ADS
Title: Book Review: Circumstellar matter. (IAU Symposium no. 122)
/ Reidel, 1987.
Authors: Jordan, C.; Dimitrov, D. L.
Bibcode: 1989SoPh..119..419J
Altcode: 1989SoPh..119..419A
No abstract at ADS
Title: Book Review: Astrophysics of the sun. / CUP, 1988
Authors: Jordan, C.
Bibcode: 1989Obs...109..170J
Altcode: 1989Obs...109..170Z
No abstract at ADS
Title: Book-Review - the Atmosphere of the Sun
Authors: Durrant, C. J.; Jordan, C.
Bibcode: 1989Obs...109..122D
Altcode:
No abstract at ADS
Title: Integrated analytical evaluation and optimization of model
parameters against preprocessed measurement data
Authors: Bass, J. N.; Phavnani, K. H.; Bonito, N. A.; Bounar, K.;
Hein, C. A.; Jordan, C. J.; McNeil, W. J.; Pratt, M. M.; Reynolds,
D. S.; Roberts, F. R.
Bibcode: 1989radi.rept.....B
Altcode:
This contract supported investigations for integrated applications
of ephemerides, physics, and mathematics of the atmosphere and near
space. Projects undertaken and reported on included satellite, rocket,
and astronomical circumstances; data based studies of atmospheric
density and structure; spacecraft interactions leading to charging
and contamination; auroral ion and electric field modeling; trapped
particle, magnetic field, and instrumentation studies for CRRES;
shuttle simulation and mission support; POLAR BEAR imaging and attitude
determination; scintillation and spaced receivers; GE (Group Encoded)
OTHB Radar processing system; lightning detection; file generating
systems for ephemeris and attitude; study of common data formats;
and software for interactive graphics.
Title: Book-Review - Circumstellar Matter - I.A.U. SYMP.122
Authors: Appenzeller, I.; Jordan, C.; Henning, T.
Bibcode: 1989SSRv...49..444A
Altcode:
No abstract at ADS
Title: A new window on the Universe
Authors: Gondhalekar, P.; Jordan, C.
Bibcode: 1989Natur.338..378G
Altcode:
No abstract at ADS
Title: Book Review: Solar and stellar physics. / Springer-Verlag, 1987
Authors: Jordan, C.
Bibcode: 1989Obs...109...31J
Altcode: 1989Obs...109...31S
No abstract at ADS
Title: Far-UV Low Resolution Spectroscopy of High Luminosity K and
M Stars
Authors: Jordan, C.
Bibcode: 1989iue..prop.3597J
Altcode:
No abstract at ADS
Title: Variability and Inhomogeneity of T Tauri Stars
Authors: Jordan, C.
Bibcode: 1989iue..prop.3580J
Altcode:
No abstract at ADS
Title: Chromospheric explosions.
Authors: Doschek, G. A.; Antiochos, S. K.; Antonucci, E.; Cheng,
C. -C.; Culhane, J. L.; Fisher, G. H.; Jordan, C.; Leibacher, J. W.;
MacNiece, P.; McWhirter, R. W. P.; Moore, R. L.; Rabin, D. M.; Rust,
D. M.; Shine, R. A.
Bibcode: 1989epos.conf..303D
Altcode:
The work of this team addressed the question of the response and
relationship of the flare chromosphere and transition region to the
hot coronal loops that reach temperatures of about 107K
and higher. Flare related phenomena such as surges and sprays were
also discussed. The team members debate three main topics: 1) whether
the blue-shifted components of X-ray spectral lines are signatures of
"chromospheric evaporation"; 2) whether the excess line broadening of UV
and X-ray lines is accounted for by "convective velocity distribution"
in evaporation; and 3) whether most chromospheric heating is driven by
electron beams. These debates illustrated the strengths and weaknesses
of our current observations and theories.
Title: High Dispersion of Ru Lupi
Authors: Jordan, C.
Bibcode: 1989iue..prop.3579J
Altcode:
No abstract at ADS
Title: CDS: The Coronal Diagnostic Spectrometer
Authors: Patchett, B. E.; Harrison, R. A.; Sawyer, E. C.; Aschenbach,
B.; Culhane, J. L.; Doschek, G. A.; Gabriel, A. H.; Huber, M. C. E.;
Jordan, C.; Kjeldseth-Moe, O.
Bibcode: 1988sohi.rept...39P
Altcode:
The prime objective of the Coronal Diagnostic Spectrometer (CDS) is to
obtain intensity ratios of selected extreme-ultraviolet line pairs, with
spatial and temporal scales appropriate to the fine-scale features of
the solar atmosphere. This will be done simultaneously across a large
portion of the solar atmosphere. From this, density and temperature
information will be derived which coupled with a modest capability for
the detection of flows will be used to study the energy and mass balance
of the atmosphere. Understanding the heating of the solar corona and the
acceleration of the solar wind are the ultimate goals of this research.
Title: Ultraviolet spectroscopy of cool stars.
Authors: Jordan, C.
Bibcode: 1988JOSAB...5.2252J
Altcode: 1988OSAJB...5.2252J
A review is given of some developments in the study of UV
emission-line spectra of cool stars, including the Sun, in recent
years. Observations of cool low-gravity stars (giants and supergiants)
with the International Ultraviolet Explorer have led to the discovery
of a variety of fluorescent excitation processes, some resulting
in the determination of further energy levels. Some examples of
line-identification problems and excitation processes are discussed.
Title: Chromospheric Emission from the Red Giant A59 in NGC 6752
Authors: Dupree, A. K.; Hartmann, L.; Jordan, C.; Rodgers, A. W.;
Smith, G. H.
Bibcode: 1988BAAS...20..996D
Altcode:
No abstract at ADS
Title: The outer atmospheres and winds of T Tau and RU Lupi
Authors: Jordan, C.; Kuin, N. P. M.
Bibcode: 1988ESASP.281b..97J
Altcode: 1988uvai....2...97J; 1988IUE88...2...97J
Emission line fluxes were used to establish the emission measure
distribution for T Tau and RU Lupi. Intersystem lines are used to
constrain the electron density in the emitting regions. These are
compared with the results of Alfven wave driven wind models. Observed
emission line widths and absorption components formed in the stellar
winds are also compared with the theoretical predictions. It is
concluded that the transition region lines are not formed in the
wind and that the large widths of these emission lines are caused by
nonthermal turbulent motions. However, the intersystem lines formed
at Te less than or = 10,000 K indicate the presence of a lower density
region, identified with the wind. Alfven-wave driven winds, with T max
= 10,000 K long damping lengths, and high initial wave amplitudes may
be able to account for the observed characteristics.
Title: On the flux-period and flux-flux correlations in late-type
stars
Authors: Montesinos, B.; Jordan, C.
Bibcode: 1988ESASP.281a.283M
Altcode: 1988duvb.conf..283M; 1988uvai....1..283M
The analysis of a wide sample of stars including both main-sequence and
evolved stars shows that while flux-flux correlations are the same for
the whole sample, the flux-period relations show a lower dependence
on period for evolved stars. A gravity dependence also enters the
flux-period relation for evolved stars. The flux-flux and flux-period
relations are combined with coronal parameters to express Pc, Tc,
and Bc in terms of the period. All increase with decreasing period,
as expected if dynamo action controls activity. Specific relations
between observable quantities are found which could be tested from
further observations. Calculations of the convective zone fields
in mildly evolved stars suggest that a larger convective zone field
results which could explain the greater emission from evolved stars
for a given period.
Title: Book-Review - Circumstellar Matter - I.A.U. SYMP.122
Authors: Appenzeller, I.; Jordan, C.
Bibcode: 1988S&T....75Q.387A
Altcode:
No abstract at ADS
Title: Book-Review - Circumstellar Matter - I.A.U.SYMP.122
Authors: Appenzeller, I.; Jordan, C.; Wynn-Williams, G.
Bibcode: 1988JBAA...98..118A
Altcode:
No abstract at ADS
Title: Book Review: Circumstellar matter. (IAU Symposium no. 122)
/ Reidel, 1987.
Authors: Jordan, C.; Dyson, J.
Bibcode: 1988Ap&SS.141..187J
Altcode: 1988Ap&SS.141..187A
No abstract at ADS
Title: Book-Review - Circumstellar Matter
Authors: Appenzeller, I.; Jordan, C.
Bibcode: 1988ApL&C..27..287A
Altcode: 1988ApL....27..287A
No abstract at ADS
Title: Book-Review - Circumstellar Matter - I.A.U. SYMP.122
Authors: Appenzeller, I.; Jordan, C.; Smith, L. J.
Bibcode: 1988Obs...108Q.103A
Altcode:
No abstract at ADS
Title: A High Dispersion Study of Chromospheric Lines in G/K Dwarfs
Authors: Jordan, C.
Bibcode: 1988iue..prop.3290J
Altcode:
No abstract at ADS
Title: The interpretation of solar EUV and X-ray variability
Authors: Jordan, C.
Bibcode: 1988AdSpR...8g..95J
Altcode: 1988AdSpR...8...95J
Variations in the EUV and X-ray emission from solar active regions
are observed which are associated both with the long-term evolution
of the regions and the short-term fluctuations in individual loop
structures. The typical distribution of temperature and density within
an active region is known. Also, correlations between the fluxes of
lines formed in the chromosphere, transition region and `coronal' parts
of active regions seem to exist. Correlations with photospheric magnetic
fields are less secure. Simple models of active region loop structure
and energy balance can be made. However, in order to obtain a full
understanding of active region structure and evolution the mechanisms
heating the loops need to be identified. Specific mechanisms can lead
to scaling laws against which observations might be tested. Further
data sets, including measurements of underlying magnetic fields,
are required.
Title: Ultraviolet Fe II emission from cool star chromospheres
Authors: Jordan, C.
Bibcode: 1988ASSL..138..223J
Altcode: 1988IAUCo..94..223J; 1988pffl.proc..223J
A review is given of the presence and excitation of ultraviolet Fe
II emission lines from the chromopsheres of cool stars, including
the sun. The requirements for further atomic data, particularly
collision cross-sections, are stressed. Some unresolved issues of line
identification and excitation mechanisms are discussed.
Title: The Intrinsic Hydrogen Lyman Alpha Line Profile of a High
Radial Velocity G Giant
Authors: Jordan, C.
Bibcode: 1988iue..prop.3267J
Altcode:
No abstract at ADS
Title: Multiwavelength observations of magnetic fields and related
activity on Xi Bootis A.
Authors: Saar, S. H.; Huovelin, J.; Giampapa, M. S.; Linsky, J. L.;
Jordan, C.
Bibcode: 1988ASSL..143...45S
Altcode: 1988acse.conf...45S
The authors present preliminary results of coordinated observations
of magnetic fields and related activity on the active dwarf, ξ Boo
A. Combining the magnetic fluxes with the linear polarization data,
a simple map of the stellar active regions has been constructed.
Title: Chromospheres of Red Giants in Globular Clusters
Authors: Jordan, C.
Bibcode: 1988iue..prop.3291J
Altcode:
No abstract at ADS
Title: Ultraviolet Stellar Spectroscopy
Authors: Jordan, C.
Bibcode: 1988ASIC..249...97J
Altcode: 1988htpa.conf...97J
No abstract at ADS
Title: Understanding the ultraviolet spectra of cool stars.
Authors: Jordan, C.; Judge, P. G.
Bibcode: 1988CoAMP..21...97J
Altcode:
No abstract at ADS
Title: Book-Review - Circumstellar Matter - I.A.U. SYMP.122
Authors: Appenzeller, I.; Jordan, C.
Bibcode: 1987JBAA...98...47A
Altcode:
No abstract at ADS
Title: Book-Review - Circumstellar Matter
Authors: Appenzeller, I.; Jordan, C.
Bibcode: 1987Sci...238..238A
Altcode:
No abstract at ADS
Title: Book-Review - Progress in Solar Physics
Authors: de Jager, C.; Svestka, Z.; Jordan, C.
Bibcode: 1987Obs...107..130D
Altcode:
No abstract at ADS
Title: The chromospheres and coronae of five G-K main-sequence stars.
Authors: Jordan, C.; Ayres, T. R.; Brown, A.; Linsky, J. L.; Simon, T.
Bibcode: 1987MNRAS.225..903J
Altcode:
Five main-sequence stars, χ1 Ori (G0 V), α Cen A (G2
V), ξ Boo A (G8 V), α Cen B (K0 V) and ɛ Eri (K2 V) have been
observed at low and high dispersion with the International Ultraviolet
Explorer (IUE) satellite. The data obtained and X-ray observations
reported in the literature are used to make models of the structure
of the atmospheres of these stars, from the high chromosphere to the
corona. The electron pressures and coronal temperatures in these stars
range from being similar to those in the quiet solar atmosphere (α Cen
A) to the higher values found more typically in solar active regions
(e.g. χ1 Ori, ξ Boo A). The models are used to examine
the energy lost by radiation and transferred by thermal conduction,
in order to establish the heating requirements. The results are similar
to those found for the solar atmosphere.
Title: New spectral line identifications in high-temperature flares
Authors: Fawcett, B. C.; Phillips, K. J. H.; Jordan, C.; Lemen, J. R.
Bibcode: 1987MNRAS.225.1013F
Altcode:
A solar flare spectrum in the wavelength region between 7.8 and 10.0
Å, recorded by the Flat Crystal Spectrometer on Solar Maximum Mission
during a flare on 1985 July 2, is presented. It includes several
spectral emission lines not hitherto reported. Most are identified
through comparison with wavelengths either measured in laser-produced
spectra or calculated ab initio. It is found that they are mainly
due to n = 2-4, 5 transitions in Fe XIX to Fe XXIII. In a few cases,
previous identifications are corrected. The more intense lines appear
in second order in another channel of the spectrometer. The potential
of line-intensity ratios for temperature and density diagnostics
is discussed.
Title: Relations Between Chromospheric and Coronal Structure,
Flux-Flux Correlations and Convective Zone Properties
Authors: Jordan, C.; Montesinos, B.
Bibcode: 1987LNP...291..146J
Altcode: 1987LNP87.291..146J; 1987csss....5..146J
No abstract at ADS
Title: Delta Andromedae (K3III) : an IRAS source with an unusual
ultraviolet spectrum.
Authors: Judge, P. G.; Jordan, C.; Rowan-Robinson, M.
Bibcode: 1987MNRAS.224...93J
Altcode:
The IRAS survey has revealed anomalous cool infrared emission from
a number of otherwise apparently normal K stars. IUE spectra of the
brightest of these stars, Delta And, which is a spectroscopic binary
and optical standard K3 III star, is obtained. The IUE spectra show the
unexpected presence of C IV in emission, implying hot material (about
100,000 K), and evidence for a strong, high-velocity wind. It is argued
that the unusual ultraviolet spectrum arises solely from the primary
star and that it is another example of a 'hybrid' K star. The infrared
excess appears to be caused by a primordial dust shell extending
from about 1 to 30 arcsec from the primary. One of the companions of
Delta And lies close to the inner edge of the shell and another one
(possibly two) lies close to the outer edge, so that interesting
dynamical interactions between the companions and the dust shell may
be expected. The dust shell may be analogous to the Oort cometary
cloud in the Solar System or to a scaled-up version of Saturn's rings.
Title: Circumstellar matter: proceedings of the 122nd Symposium of
the International Astronomical Union held in Heidelberg, F.R.G.,
June 23- 27, 1986.
Authors: Appenzeller, I.; Jordan, C.
Bibcode: 1987IAUS..122.....A
Altcode:
The physics and chemistry of circumstellar matter are discussed
in reviews and reports of recent observational and theoretical
investigations. Topics addressed include bipolar flows, jets, and
protostars; Herbig-Haro objects; circumstellar shells and envelopes;
and mass loss from cool stars. Consideration is given to stellar
coronae and the chromospheres of cool stars, mass loss from hot stars,
symbiotic stars, planetary nebulae, circumstellar dust and chemistry,
and NASA plans relevant to the study of circumstellar matter.
Title: δ Andromedae (K3 III): a hybrid giant in an extended dust
shell.
Authors: Jordan, C.; Judge, P. G.; Rowan-Robinson, M.
Bibcode: 1987IAUS..122..321J
Altcode:
Spectra of δ And have been obtained with the International Ultraviolet
Explorer in both the long and short wavelength regions. These spectra
show several features unusual in a K giant as cool as δ And, in
particular. The IRAS observations are interpreted in terms of a cool
(≡100 K) dust cloud surrounding δ And - a spectroscopic binary
system - and a third component at 1200 A.U.
Title: A High Dispersion Study of Alpha Hya, K3 II-III
Authors: Jordan, C.
Bibcode: 1987iue..prop.3003J
Altcode:
No abstract at ADS
Title: The ultraviolet spectra of cool star chromospheres; excitation
processes and plasma diagnostics.
Authors: Jordan, C.
Bibcode: 1987PhST...17..104J
Altcode: 1987PhyS...17..104J
The advent of ultraviolet observations from space has led to rapid
advances in our knowledge of the conditions in the chromospheres
which surround cool stars. In contrast to the solar chromosphere
and corona, where electron temperatures reach Te >
106K, observations with IUE have shown that stars with
low surface gravities have only cool chromospheres with Te
⪉ 2×104K. The gas density regime is also lower and the
excitation of many of the ultraviolet lines is by radiative processes
rather than by ion/electron collisions as in the sun. In particular,
higher opacities lead to multiple photon scattering and line leakage
in semi-forbidden transitions. Quantitative analyses of such spectra
are at an early stage and a wide variety of atomic rate coefficients
need to be known more accurately.
Title: Song of Alpha Ori (Reigning Cool Star of the Year)
Authors: Jordan, C.
Bibcode: 1987LNP...291..535J
Altcode: 1987csss....5..535J
No abstract at ADS
Title: Circumstellar matter. Proceedings of the 122nd Symposium of the
International Astronomical Union, held in Heidelberg, F.R. Germany,
23 - 27 June 1986.
Authors: Appenzeller, I.; Jordan, C.
Bibcode: 1987cmp..book.....A
Altcode:
No abstract at ADS
Title: Chromospheres and Transition Regions
Authors: Jordan, Carole; Linsky, Jeffrey L.
Bibcode: 1987ASSL..129..259J
Altcode: 1987euwi.book..259J
The properties of stellar chromospheres are examined, summarizing the
results of observations obtained with the IUE satellite since its launch
in 1978. Numerous sample spectra, graphs, and diagrams are presented and
analyzed in detail. Consideration is given to 120-320-nm spectroscopy of
main-sequence stars, giants, and supergiants; the global properties of
main-sequence and post-main-sequence chromospheres; dynamic phenomena
and structures (systematic flows, atmospheric inhomogeneities, and
intrinsic variability); and structural and energy-balance modeling. A
number of outstanding problems are listed, and the potential value of
data from the Hubble Space Telescope and the Lyman FUV Spectroscopic
Explorer in solving them is indicated.
Title: High-Dispersion Observations of Alpha Bootis (K1 III) with
the International Ultraviolet Explorer
Authors: Ayres, T. R.; Judge, P.; Jordan, C.; Brown, A.; Linsky, J. L.
Bibcode: 1986ApJ...311..947A
Altcode:
The authors have obtained very deeply exposed IUE echelle spectrograms
of the bright, early-K giant Arcturus. They did not detect significant
flux in the most prominent high-excitation species of a solar-like
transition zone, C IV λ1548.2. The presence of a weak feature of
Si III] λ1892.0, and possibly also Si IV λ1393.8, indicates the
existence of a small amount of plasma at temperatures as hot as
6×104K. Measurements of C II] multiplet UV0.01 near 2325
Å provide a lower limit of about 5×109cm-3 for
the electron density in the chromospheric layers. C II UV1 (1335 Å)
emission is very weak. These results confirm that the "coronal" activity
of the old red giants is considerably diminished from that of even the
"quietest" of their main-sequence predecessors, stars like the Sun.
Title: Identification of [Fe III] in the solar ultraviolet spectrum
Authors: Jordan, C.; Bartoe, J. -D. F.; Brueckner, G. E.; Dere, K. P.
Bibcode: 1986Natur.324..444J
Altcode:
Solar ultraviolet spectra have been obtained with high spectral and
spatial resolution using the Naval Research Laboratory's high-resolution
telescope and spectrograph1 (HRTS) flown on rockets since
1975 and most recently on the Spacelab 2 Shuttle flight. Because the
solar spectrum between ~1,170 and 1,719 Å has been well observed for
some years, few lines of substantial intensity remain unidentified. (See
for example the recent compilation by Sandlin et al.2). The
longest exposures during the first rocket flight of the HRTS, which
obtained spectra with a spatial resolution of ~ 1 arc s along the slit,
of length ~ 1 solar radius, and a spectral resolution of ~0.05 Å,
showed a number of weak emission lines at the solar limb, in particular
between 1,570 and 1,600 Å (see Plates 16 and 17 in ref. 3), that could
not readily be identified. Improved observations of these lines were
obtained during the flight of HRTS on the Spacelab 2 Shuttle flight in
July-August 1985, by making longer exposures (60,100 and 250 s). The
scope of the data obtained has been described4. We have
now identified the emission lines concerned as forbidden (electric
quadrupole and magnetic dipole) transitions in Fe III, the first
detection of these particular transitions in any source. They must now
be considered potential candidates for previously unidentified lines in
other low-density (Ne <~ 1010 cm-3)
astrophysical sources.
Title: Chromospheric explosions
Authors: Doschek, G. A.; Antiochos, S. K.; Antonucci, E.; Cheng,
C. -C.; Culhane, J. L.; Fisher, G. H.; Jordan, C.; Leibacher, J. W.;
MacNeice, P.; McWhirter, R. W. P.
Bibcode: 1986epos.conf..4.1D
Altcode: 1986epos.confD...1D
Three issues relative to chromospheric explosions were debated. (1)
Resolved: The blue-shifted components of x-ray spectral lines are
signatures of chromospheric evaporation. It was concluded that
the plasma rising with the corona is indeed the primary source of
thermal plasma observed in the corona during flares. (2) Resolved:
The excess line broading of UV and X-ray lines is accounted for by a
convective velocity distribution in evaporation. It is concluded that
the hypothesis that convective evaporation produces the observed
X-ray line widths in flares is no more than a hypothesis. It is
not supported by any self-consistent physical theory. (3) Resolved:
Most chromospheric heating is driven by electron beams. Although it
is possible to cast doubt on many lines of evidence for electron
beams in the chromosphere, a balanced view that debaters on both
sides of the question might agree to is that electron beams probably
heat the low corona and upper chromosphere, but their direct impact
on evaporating the chromosphere is energetically unimportant when
compared to conduction. This represents a major departure from the
thick-target flare models that were popular before the Workshop.
Title: Chromospheres of cool stars
Authors: Jordan, C.
Bibcode: 1986ESASP.263...17J
Altcode: 1986NIA86.......17J; 1986niia.conf...17J
Progress in understanding the nature and origin of cool star
chromospheres and transition regions since the launch of IUE is
reviewed. While previous observations in the visible and UV regions laid
the foundations for present work, the nature of the IUE instruments and
long operating lifetime led to substantial advances. The broad sample
of objects obtainable with IUE at low spectral resolution allowed
insights into the properties of chromospheres and coronae across the
H-R diagram. High resolution spectra are used to model the structure
and energy balance in a variety of stars. Trends in line fluxes are
being understood in a quantitative manner allowing further insight
into heating processes. Insights into the basic spectroscopy and atomic
physics of cool giant and supergiant chromospheres are obtained.
Title: X-ray and optical observations of a dMe flare star in the T
Tauri field.
Authors: Smale, A. P.; Charles, P. A.; Corbet, R. H. D.; Jordan, C.;
Brown, A.; Walter, F.
Bibcode: 1986MNRAS.221...77S
Altcode:
The authors present observations of a newly discovered dMe flare
star within 20 pc of the Sun. An EXOSAT observation of this source
shows an almost complete X-ray flare light curve with rise time
≡600 s, decay time ≡1500 s, and peak luminosity Lx =
6.1×1029erg s-1, a 40-fold increase in brightness
over the quiescent level (1.5×1028erg s-1). The
total energy in the flare is 2.7×1032 < Ex
< 3.3×1033erg. The authors also present results of two
Einstein IPC observations. They identify the source with a hitherto
unstudied nearby star with magnitude V ≡ 13 and spectral type
≡dM5e, at a distance of ≡13 pc. A loop model for the quiescent
corona gives physically unrealistic values for the size of the loop
structure; however, considering the quiescent corona to be uniform
and symmetrical gives acceptable values for the mean pressure and
density. For the flare, the authors explore a variety of different
physical assumptions about the cooling mechanism and derive possible
values for loop lengths and electron densities.
Title: Wave-driven Winds from Cool Stars: Progress and Problems
Authors: Jordan, C.
Bibcode: 1986IrAJ...17..227J
Altcode:
When the ab initio, constant damping length approach to the solution of
cool star momentum, mass and energy equations is applied to specific
stars, fundamental difficulties arise in simultaneously matching data
for emission line fluxes, widths, and the constraints implied by the
absorption lines. The adoption of a semiempirical approach allows both
hydrostatic and wind models to be made on the basis of emission measure
distribution and boundary conditions on pressure and mass loss rate;
the energy balance, however, requires a severely nonradial magnetic
field, and no self-consistent model has yet been produced. Attention is
presently given to alternative solutions for these difficulties. Further
observations are needed to distinguish between these alternatives.
Title: The outer atmosphere of Procyon (alpha CMi F5IV-V) : evidence
of supergranulation or active regions.
Authors: Jordan, C.; Brown, A.; Walter, F. M.; Linsky, J. L.
Bibcode: 1986MNRAS.218..465J
Altcode:
Observations made with the Einstein X-ray observatory and Exosat have
shown Procyon (Alpha CMi) to have a measurable X-ray flux. The flux
observed is similar to the upper limits previously reported. The
interpretation of the X-ray data in the context of models made
previously by Brown and Jordan (1981) based on spectra obtained with
the IUE satellite. The X-ray data lead to a higher electron pressure
than does the UV spectrum. These results support the conclusion by Brown
and Jordan that the UV data cannot be reconciled with a hot corona in a
spherically symmetric uniform model. Two types of models are explored;
one in which the X-ray emission originates from an isothermal corona
but the UV emission is restricted to limited regions of the disk,
analogous to solar supergranulation structure; the other in which
hot loop structures are embedded in a cool (T(e) of about 300,000 K)
corona. Monitoring of Procyon to search for variability is urgently
required to distinguish between these models. Some comparisons with
the predictions of scaling laws are made. This hot isothermal coronal
model agrees quite well with the predictions of Hearn's (1977) minimum
flux model.
Title: Chromospheric explosions.
Authors: Doschek, G. A.; Antiochos, S. K.; Antonucci, E.; Cheng,
C. -C.; Culhane, J. L.; Fisher, G. H.; Jordan, C.; Leibacher, J. W.;
MacNiece, P.; McWhirter, R. W. P.; Moore, R. L.; Rabin, D. M.; Rust,
D. M.; Shine, R. A.
Bibcode: 1986NASCP2439....4D
Altcode:
The work of this team addressed the question of the response and
relationship of the flare chromosphere and transition region to the
hot coronal loops that reach temperatures of about 107K
and higher. Flare related phenomena such as surges and sprays are
also discussed. The team members debated three main topics: 1. whether
the blue-shifted components of X-ray spectral lines are signatures of
"chromospheric evaporation"; 2. whether the excess line broadening of UV
and X-ray lines is accounted for by "convective velocity distribution"
in evaporation; and 3. whether most chromospheric heating is driven
by electron beams.
Title: The Chromosphere, Corona and Wind of Alpha TRA (k 4 ii)
Authors: Jordan, C.
Bibcode: 1986iue..prop.2605J
Altcode:
No abstract at ADS
Title: Structure of Main Sequence Star Transition Tegions and Coronae
Authors: Jordan, C.
Bibcode: 1986iue..prop.2686J
Altcode:
No abstract at ADS
Title: Ultraviolet Observations of Young Stars in the Chameleon
1 Association
Authors: Brown, A.; Linsky, J. L.; Walter, F.; Jordan, C.; Judge,
P.; Gahm, G.; Feigelson, E. D.
Bibcode: 1985BAAS...17R.837B
Altcode: 1985BAAS...17..837B
No abstract at ADS
Title: On the outer atmospheres of hybrid stars.
Authors: Hartmann, L.; Dupree, A. K.; Jordan, C.; Brown, A.
Bibcode: 1985ApJ...296..576H
Altcode:
The authors discuss a variety of ultraviolet observations of four
hybrid atmosphere stars, objects which exhibit both cold winds and
high-temperature (transition-region) emission. New IUE data confirm
that the K3 II stars ι Aur and θ Her are hybrid stars. In addition γ
Aql (K3 II) is found to be another hybrid object. The analysis of the
emission lines indicates that at ≡105K, the pressure is
between 10-2 and 10-3 that in the solar atmosphere
at the same temperature. A corona with average temperature up to
≡5×105K could be accommodated. The observed line widths
indicate that turbulent pressure is important. Very deep exposures of
the Mg II emission lines in α TrA show that wind absorption is visible
at velocities up to 180 km s-1 relative to the photosphere.
Title: Multiwavelength Analysis of a Well Observed Flare from Solar
Maximum Mission
Authors: MacNeice, P.; Pallavicini, R.; Mason, H. E.; Simnett, G. M.;
Antonucci, E.; Shine, R. A.; Rust, D. M.; Jordan, C.; Dennis, B. R.
Bibcode: 1985SoPh...99..167M
Altcode:
We describe and analyse observations of an M1.4 flare which began at 17:
00 UT on 12 November, 1980. Ground based Hα and magnetogram data have
been combined with EUV, soft and hard X-ray observations made with
instruments on-board the Solar Maximum Mission (SMM) satellite. The
preflare phase was marked by a gradual brightening of the flare site
in Ov and the disappearance of an Hα filament. Filament ejecta were
seen in Ov moving southward at a speed of about 60 km s−1,
before the impulsive phase. The flare loop footpoints brightened in Hα
and the CaXIX resonance line broadened dramatically 2 min before the
impulsive phase. Non-thermal hard X-ray emission was detected from the
loop footpoints during the impulsive phase while during the same period
blue-shifts corresponding to upflows of 200-250 km s−1
were seen in Ca XIX. Evidence was found for energy deposition in both
the chromosphere and corona at a number of stages during the flare. We
consider two widely studied mechanisms for the production of the high
temperature soft X-ray flare plasma in the corona, i.e. chromospheric
evaporation, and a model in which the heating and transfer of material
occurs between flux tubes during reconnection.
Title: Rare Transit across Sun 1984MAY30
Authors: O'Sullivan, T.; Jordan, C.; Bailey, M.
Bibcode: 1985S&T....70..197O
Altcode:
No abstract at ADS
Title: High-Resolution Observations of Magnetic Structures
Authors: Jordan, C.
Bibcode: 1985ESASP.235..161J
Altcode: 1985shpp.rept..161J; 1985fmsh.work..161J
High resolution observations in the ultra-violet spectral region are
required in order to study the structure and energy balance of the
solar atmosphere. Previous observations made with high spatial and
spectral resolution show structure in the quiet and active atmosphere
on the 1 arc sec scale. In addition to all pervasive non-thermal line
broadening such observations show small regions where unusually large
line widths and line shifts exist. The observations still required to
investigate even the existence of wave heating modes are discussed,
emphasising the importance of simultaneous measurements of line fluxes,
electron densities and line profiles. The SOHO mission provides an
excellent opportunity to resolve the issue of coronal heating.
Title: Derivation of atmospheric structure from emission-line fluxes
Authors: Jordan, C.
Bibcode: 1985MNRAS.214P...1J
Altcode:
In the present consideration of the way in which the pressure and
temperature gradient in a stellar chromosphere and corona are related
to the emission temperature distribution, the conditions under which a
simple approximation for the temperature vs height suggested by Lago,
Penston and Johnstone (1985) is appropriate are critically discussed. It
is concluded that such approximations are not generally appropriate,
and are an insufficient basis on which to construct atmospheric models.
Title: Gas dynamics in the impulsive phase of solar flares. III
Energy transport in a flaring loop
Authors: Nagai, F.; Jordan, C.
Bibcode: 1985A&A...146...25N
Altcode:
In the present investigation of the relation between the dynamical
behavior of a flare plasma and the evolution of various energy terms,
using an electron beam enhancement model in the impulsive phase of
solar flares, the energy input or output rates integrated along the
entire loop are evaluated and the distribution of the flare energy
among various energy terms is demonstrated through the integration of
those rates over time. A one-fluid, two-temperature model is adopted,
and nonthermal electrons with power law spectra are assumed to be
isotropically injected from the loop apex. The spatial distribution
of thermal conduction shows that thermal energy is removed from the
high temperature region and is primarily deposited in the thermal
conduction front.
Title: Emission Line Variability of RY Tau, DR Tau and SU Aur
Authors: Brown, A.; Walter, F. M.; Carpenter, K. G.; Jordan, C.;
Judge, P.
Bibcode: 1985BAAS...17..556B
Altcode:
No abstract at ADS
Title: The Mild BA Star Beta UMI (k 4iii)
Authors: Jordan, C.
Bibcode: 1985iue..prop.2279J
Altcode:
No abstract at ADS
Title: Ultraviolet Observations of Infra-Red Sources in the Iras
Mini-Survey
Authors: Jordan, C.
Bibcode: 1985iue..prop.2318J
Altcode:
No abstract at ADS
Title: High Resolution Spectroscopy of the PMS Star T Tauri
Authors: Jordan, C.
Bibcode: 1985iue..prop.2319J
Altcode:
No abstract at ADS
Title: Atmospheric properties of RU Lupi derived from high- and
low-resolution IUE spectra.
Authors: Brown, A.; Penston, M. V.; Johnstone, R.; Jordan, C.; Kuin,
N. P. M.; Lago, M. T. V. T.; Gross, B.; Linsky, J. L.
Bibcode: 1984NASCP2349..338B
Altcode: 1984fiue.rept..338B; 1984IUE84......338B
High and low-dispersion IUE spectra of the premain sequence star, RU
Lupi, were obtained using both the short wave prime (SWP) and long wave
redundant (LWR) cameras. Strong P Cygni line profiles are seen in Mg II
and Fe II emission lines, indicating that the lines are formed in the
stellar wind of RU Lupi. An increase in transition region line widths is
seen with increasing temperature, which cannot be due solely to opacity
broadening, thus indicating that kinematic broadening mechanisms are
dominant. The transition region density is approx. 3 x 10 to the 10th
power cubic cm derived from the Si III lambda1892/C III lambda1909 line
ratio. The status of the atmospheric modeling of RU Lupi is discussed.
Title: A progress report on the analysis of long exposure SWP high
resolution spectra of cool stars.
Authors: Linsky, J. L.; Ayres, T. R.; Brown, A.; Carpenter, K.;
Jordan, C.; Judge, P.; Gustafsson, B.; Eriksson, K.; Saxner, M.;
Engvold, O.; Jensen, E.; Moe, O. K.; Simon, T.
Bibcode: 1984NASCP2349..445L
Altcode: 1984fiue.rept..445L; 1984IUE84......445L
The IUE is the first experiment with sufficient sensitivity to obtain
high resolution spectra (lambda/delta lambda is approximately 10,000)
of many cool stars in the vitally important 1200 to 2000 A spectral
region. These data provide qualitatively new information with
which to understand the properties of and structures in the outer
atmospheres of these stars. Also, these cool star spectra will be
extremely useful in planning for the Space Telescope High Resolution
Spectrograph, which will be 1000 times more sensitive than IUE but will
be hampered by limited observing time and limited spectral bandwidth
in each exposure. Very long exposure, high disperson SWP spectra of
many stars located throughout the cool half of the HR diagram were
obtained. These 12 to 21 hour exposures were obtained by combining
NASA and Vilspa shifts so as to obtain the longest possible exposures
at times of low background. Included are dwarf stars of spectral type
G0 V to M2 V, G9.5 III to M5 II giants, G2 Ib to M2 Iab supergiants,
a number of RS CVn-type systems, and Barium stars.
Title: Precise measurements of radial velocities of emission lines
in the far-ultraviolet spectra of late-type stars.
Authors: Ayres, T. R.; Engvold, O.; Moe, D. K.; Simon, T.; Jordan,
C.; Judge, P.; Brown, A.; Linsky, J. L.
Bibcode: 1984NASCP2349..468A
Altcode: 1984fiue.rept..468A; 1984IUE84......468A
The radial velocities of emission lines in deep short wave prime camera
echelle exposures of several late-type dwarf and giant stars were
measured. The goal was to search for absolute and differential Doppler
shifts of emission lines formed at different temperatures in the stellar
outer atmospheres analogous to the redshifts of C IV lambda 1548 (10
to the 5th power K) which occur in the solar transition zone. Existing
images, taken without the precise radial velocity precautions, of five
dwarf stars, four giant stars, and three supergiants are reanalyzed.
Title: Observational constraints on heating processes.
Authors: Jordan, C.; Mendoza, B.; Gill, R. S.
Bibcode: 1984ESASP.220..133J
Altcode: 1984ESPM....4..133J
A brief account is given of how spectroscopic measurements of emission
line fluxes and widths relate to the plasma parameters relevant to wave
heating processes, e.g. the magnetic field strength and its fluctuation,
the damping length and plasma β. The need for further measurements
of line profiles and of flux and profile periodicities in the inner
corona is stressed and it is shown how systematic studies across
coronal holes might elucidate the solar coronal heating mechanism.
Title: Selective excitation of Fe II in the laboratory and late-type
stellaratmospheres.
Authors: Johansson, S.; Jordan, C.
Bibcode: 1984MNRAS.210..239J
Altcode:
Low resolution spectra of cool giants and supergiants observed with the
International Ultraviolet Explorer (IUE) satellite contain emission
features for which it has been difficult to establish unambiguous
identifications. High resolution spectra of RR Tel and Beta Gru
(M 3 II) show lines which can be definitely attributed to Fe II. The
presence of particular transitions and absence of others suggests that
the source of excitation for levels with excitation energy around 10
eV is emission in the H Ly alpha line which is strong and broad in
the cool giants and supergiants. New laboratory spectra confirm the
excitation route for Ly alpha pumping to a further 4G0 level at about
13 eV, which decays to give the strong feature at 1870 A observed at
low spectral resolution in several cool stars.
Title: The development and cooling of a solar limb-flare
Authors: Veck, N. J.; Strong, K. T.; Jordan, C.; Simnett, G. M.;
Cargill, P. J.; Priest, E. R.
Bibcode: 1984MNRAS.210..443V
Altcode:
Observations of a flare that began in soft X-rays at 20:37 UT on 1980
April 12, at the west limb of the Sun are discussed. The Solar Maximum
Mission (SMM) satellite was used to obtain X-ray images before the flare
and for a period during the decay phase. Hα photographs and the soft
X-ray flux measured by the GOES-3 satellite are available throughout
the flare. Some alternative models are discussed but insufficient
data are available for a full treatment. Overall, the observations are
best fitted qualitatively by a model where pre-existing magnetic loop
structures are perturbed by the intrusion of new magnetic flux.
Title: High-resolution, far-ultraviolet study of beta Draconis
(G2 Ib-II) : transition region structure and energy balance.
Authors: Brown, A.; Jordan, C.; Stencel, R. E.; Linsky, J. L.; Ayres,
T. R.
Bibcode: 1984ApJ...283..731B
Altcode:
High-resolution far ultraviolet spectra of the star Beta Draconis have
been obtained with the IUE satellite. The observations and emission
line data from the spectra are presented, the interpretation of the
emission line widths and shifts is discussed, and the implications
are given in terms of atmospheric properties. The emission measure
distribution is derived, and density diagnostics involving both line
ratios and line opacity arguments is investigated. The methods for
calculating spherically symmetric models of the atmospheric structure
are outlined, and several such models are presented. The extension of
these models to log T(e) greater than 5.3 using the observed X-ray flux
is addressed, the energy balance of an 'optimum' model is investigated,
and possible models of energy transport and deposition are discussed.
Title: The Chromospheres, Coronae and Winds of Hybrid Bright Giants
Authors: Jordan, C.
Bibcode: 1984iue..prop.2034J
Altcode:
No abstract at ADS
Title: Derivation of ionization balance for calcium XVIII/XIX using
XRP solar X-ray data
Authors: Antonucci, E.; Gabriel, A. H.; Doyle, J. G.; Dubau, J.;
Faucher, P.; Jordan, C.; Veck, N.
Bibcode: 1984A&A...133..239A
Altcode:
Spectra of calcium from solar flares are used in an attempt to derive
an ionization balance for Ca XVIII/Ca XIX. The isothermal assumption
inherent in this derivation is shown not to introduce errors, by
modelling a number of hypothetical nonisothermal plasmas. The unresolved
blend of calcium and argon lines prevents a definitive determination of
the results, owing to uncertainties in the ratio of abundances of these
elements. The resulting ionization balance curves are presented as a
function of the solar argon/calcium abundance ratio. The theoretical
ionization balance of Doyle and Raymond is consistent with the data. To
within the expected accuracy of the atomic theories, there is no reason
to assume that the flare plasma is other than close to steady-state
ionization balance.
Title: The chromosphere and corona of T Tauri.
Authors: Brown, A.; de M. Ferraz, M. C.; Jordan, C.
Bibcode: 1984MNRAS.207..831B
Altcode:
Observations of the ultraviolet spectrum of the pre-main-sequence star T
Tauri have been made using the International Ultraviolet Explorer (IUE)
satellite. The fluxes of the emission lines are used to make models of
the temperature and density structure of the chromosphere and transition
region to the corona. Several models are discussed to cover the range of
possible gas and electron pressures. Various spectroscopic techniques
are used to limit the range of acceptable electron pressures. Previous
observations in the X-ray flux measured with the Einstein satellite
by Feigelson and De Campli (1981) are used to extend the models to a
corona at Te about 5,000,000 K. It is difficult to avoid the
conclusion that a two-component atmosphere is required - one having a
high electron pressure extending to high temperatures to produce the
X-ray emission and the other a region of lower density where the mass
loss, indicated by blueshifted absorption, originates. In addition to
hydrostatic models a simple Alfven wave-driven dynamic model is made
using the same aproximations as adopted by Hartmann et al. (1980, 1982).
Title: Book-Review - Solar Magnetohydrodynamics
Authors: Priest, E. R.; Jordan, C.
Bibcode: 1984Obs...104...32P
Altcode:
No abstract at ADS
Title: Ultraviolet Spectroscopy of Cool Stars from IUE (invited Paper)
Authors: Jordan, C.; Judge, P.; Johansson, S.
Bibcode: 1984uxsa.coll...51J
Altcode: 1984IAUCo..86...51J; 1984uxsa.conf...51J
No abstract at ADS
Title: Preliminary Results from Studies of High Resolution Line
Spectra in Late-type Giant and Supergiant Stars
Authors: Engvold, O.; Kjeldseth Moe, O.; Jensen, E.; Jordan, C.;
Stencel, R.; Linsky, J.
Bibcode: 1984LNP...193..359E
Altcode: 1984csss....3..359E
No abstract at ADS
Title: Radiative processes in cool star chromospheres.
Authors: Jordan, C.; Judge, P.
Bibcode: 1984PhST....8...43J
Altcode: 1984PhyS....8...43J
Observations made with the IUE satellite between 1200 Å and 3000 Å
have shown that the spectra of giant and supergiant stars later than
about K0 are dominated by emission from neutral atoms and singly charged
ions. The cool star spectra show many examples of photo-excitation,
line-leaking and fluorescent processes, some of which are discussed
here. There is evidence that the H Ly α and H Ly β lines play an
important role in the production of emission from O I, S I and Fe
II. Some lines which remain without satisfactory explanations in both
the stellar and solar spectra are discussed.
Title: Electron densities in active galaxies
Authors: Jordan, C.
Bibcode: 1983Natur.306..503J
Altcode:
No abstract at ADS
Title: Outer atmospheres of cool stars. XV. High-dispersion
ultraviolet studies of active chromospheric G-K dwarfs.
Authors: Ayres, T. R.; Linsky, J. L.; Simon, T.; Jordan, C.; Brown, A.
Bibcode: 1983ApJ...274..784A
Altcode:
The authors have obtained IUE ultraviolet echelle spectra of the three
late-type active-chromosphere dwarf stars χ1 Ori, ξ Boo A
and ɛ Eri. These are compared with previously published observations
of the quiet chromosphere dwarfs α Cen A and α Cen B. The spectra
indicate a gross strengthening of chromospheric and transition-region
line fluxes from quiet to active dwarf stars without a fundamental
change in the line shapes. Qualitatively the same spectroscopic behavior
is seen in detail on the solar surface between regions of strong and
weak magnetic fields. They believe that the correspondence between
the stellar and solar behavior is not accidental, but instead affirms
that enhanced chromospheric and coronal emission on late-type main
sequence stars is a result of increased surface coverage of magnetic
active regions.
Title: Redshifts of high-temperature emission lines in the
far-ultraviolet spectra of late-type stars.
Authors: Ayres, T. R.; Stencel, R. E.; Linsky, J. L.; Simon, T.;
Jordan, C.; Brown, A.; Engvold, O.
Bibcode: 1983ApJ...274..801A
Altcode:
High-dispersion IUE spectra of six late-type stars exhibit small but
statistically significant differential redshifts of high-temperature
emission lines, like Si IV and C IV, with respect to low-temperature
lines like S I and O I. A well-exposed, small-aperture spectrum of
the active chromosphere binary Capella (Alpha Aurigae A: G6 II+F9
III) establishes that the high-temperature lines are redshifted in an
absolute sense with respect to the accurately determined photospheric
velocity of the system at single-line phase 0.50. Several possible
explanations for the stellar redshifts are discused, including a warm
wind (100,000 K) in which aparent redshifts are produced in optically
thick lines by an accelerating outfow, and the downflowing component
of a vertical circulation system for which the up-leg portion of the
flow is too cool, too hot, or too tenuous to be visible in Si IV and C
IV. If the second scenario is true, the stellar redshifts may provide
an important phenomenological link to the downflows observed in 100,000
K species over magnetic active regions in the sun.
Title: Book-Review - Solar and Interplanetary Dynamics -
I.A.U. SYMP.91
Authors: Dryer, M.; Tandberg-Hanssen, E.; Jordan, C.
Bibcode: 1983Obs...103..262D
Altcode:
No abstract at ADS
Title: Models of T-Tauri from EUV and X-Ray Observations
Authors: Jordan, C.
Bibcode: 1983Obs...103..129J
Altcode:
No abstract at ADS
Title: Summaries of Papers Presented at the R.A.S. Specialist
Discussion on Pre-Main Stars and Their Environment
Authors: Jordan, C.
Bibcode: 1983Obs...103..126J
Altcode:
No abstract at ADS
Title: The Decay of a Large Limb Flare
Authors: Cargill, P. J.; Veck, N. J.; Jordan, C.; Strong, K. T.;
Simnett, G. M.; Priest, E. R.
Bibcode: 1983BAAS...15..712C
Altcode:
No abstract at ADS
Title: IUE and other new observations of the slow nova RR Tel.
Authors: Penston, M. V.; Benvenuti, P.; Cassatella, A.; Heck, A.;
Selvelli, P.; Macchetto, F.; Ponz, D.; Jordan, C.; Cramer, N.; Rufener,
F.; Manfroid, J.
Bibcode: 1983MNRAS.202..833P
Altcode:
IUE satellite UV spectra of RR Tel covering 1150-3200 A at high and
low dispersion through both large and small apertures are reported,
and a list of 431 lines is presented which gives measured wavelength,
intensity, and full width at half maximum. Over three-quarters of the
lines are identified, and a correlation is noted between line width and
ionization energy. The lines identified, which include common species
ionized from one to four times, are generally resonance, forbidden or
semiforbidden lines but also include the recombination lines for C,
O and Ne. Many Fe II lines are present. Forbidden line wavelengths
are used to define intersystem separations of energy levels in some
species. The continuum energy distribution yielded by low dispersion
data is not due to a simple recombination of gaseous emission processes
and a hot star or accretion disk, but the very high ratio of the
energy in the lines to that in the continuum of 2.4 indicates that a
high temperature source must be present.
Title: Chromospheric Properties of T-Tauri Stars Determined from
EUV Spectra
Authors: Brown, A.; Jordan, C.
Bibcode: 1983ards.proc..509B
Altcode: 1983IAUCo..71..509B
IUE spectra of six pre-main-sequence (PMS) stars are analysed and the
resultant emission measure distributions compared with that of T Tau
for which a chromospheric model has been calculated. Evidence for the
influence of large scale motions and/or stellar winds on the transition
region and coronal emission measures is found.
Title: Chromospheric Properties of T Tauri Stars Determined from
EUV Spectra
Authors: Brown, A.; Jordan, C.
Bibcode: 1983ASSL..102..509B
Altcode:
IUE spectra of six pre-main-sequence [PMS) stars are analysed and the
resultant emission measure distributions compared with that of T Tau for
which a chromospheric model has been calculated. The general shape and
absolute level of the mean emission measure distributions are remarkably
similar, indicating the relevance of the T Tau chromospheric model to
other PMS stars. Evidence for the influence of large scale motions
and/or stellar winds on the transition region and coronal emission
measures is found. The relative importance of different energy balance
terms is discussed.
Title: The UV Variability and Rotational Modulation of T Tauri Stars
Authors: Jordan, C.
Bibcode: 1983iue..prop.1679J
Altcode:
No abstract at ADS
Title: The structure and energy balance in main sequence stars
Authors: Jordan, C.; Ayres, T. R.; Brown, A.
Bibcode: 1983ASSL..102...61J
Altcode: 1983ards.proc...61J; 1983IAUCo..71...61J
High-resolution spectra obtained with the IUE satellite have been
used to study the structure and energy balance in the main sequence
stars ξ Boo A, α Cen A, α Cen B and ɛ Eri. The EUV observations
are combined with X-ray fluxes to predict the coronal temperatures,
the electron pressures and energy lost or transferred by radiation
and thermal conduction.
Title: An analysis of the ultraviolet spectrum of T Tauri.
Authors: Jordan, C.; Ferraz, M. C. D. M.; Brown, A.
Bibcode: 1982ESASP.176...83J
Altcode: 1982IUE3r.......83J; 1982iue..conf...83J
The IUE T Tauri data are considered. Significant changes are seen
in the Mg II line profiles at different epochs. An emission measure
distribution is derived and chromospheric models are computed. There
is evidence from lower temperature lines of two different density
components in the chromosphere. A two-component model is deduced,
involving a low density region with Ne = 1 billion per cu cm, possibly
associated with the observed stellar wind, and a high density region
with Ne = 100 billion per cu cm. The high density region is the
source of the high temperature emission, such as C IV, N V and the
X-rays. The chromospheric radiation losses are a significant fraction
of the stellar luminosity.
Title: Outer atmospheric properties of beta Draconis (G2 Ib-II)
Authors: Brown, A.; Jordan, C.; Ayres, T. R.; Linsky, J. L.; Stencel,
R. E.
Bibcode: 1982ESASP.176..142B
Altcode: 1982IUE3r......142B; 1982iue..conf..142B
Observations of the supergiant Beta Draconis made by IUE are
discussed. Electron pressure is comparable with that found in the quiet
solar atmosphere. The X-ray fluxes from previous observations suggest
T = 10 to 20 million k, when combined with the analysis of the IUE
spectra; this would be greater than the proton escape velocity. The
radiation losses between 10,000 and 100,000 K exceed those from the
Sun by an order of magnitude, but in the absence of a stellar wind the
energy losses from the corona would be lower than in the Sun. The line
profile widths indicate substantial (M=2) nonthermal broadening. If
interpreted as energy associated with a wave flux, they would imply
more coronal energy than required by radiation and conduction losses,
suggesting an energetic mass loss. However, line asymmetries can also
be interpreted as motions within the atmosphere.
Title: High resolution EUV spectroscopy of 56 Pegasi (K0II P + wd).
Authors: Jordan, C.; Brown, A.; Ayres, T. R.; Linsky, J. L.; Stencel,
R. E.
Bibcode: 1982ESASP.176..161J
Altcode: 1982iue..conf..161J; 1982IUE3r......161J
The hypothesis that X-ray and UV emission by 56 Pegasi (K0II p + wd)
originates in a conventional chromosphere, transition region and corona,
as opposed to Schindler's hypothesis of accretion of the cool stellar
wind onto the white dwarf companion, is discussed. Analysis of IUE data
indicates that within the uncertainties associated with determining the
stellar radius and abundances, the chromosphere, transition region, and
corona of 56 Peg are similar to that of Beta Draconis both in structure
and energy balance. The accretion hypothesis is not a unique explanation
of the observed spectral properties and the white dwarf companion may
not play a direct role. Furthermore, 56 Peg, according to current
values of V-R and luminosity class, is on the nonsolar side of the
Linsky-Haisch dividing line whereas Beta Draconis is on the solar side.
Title: Comparison of observed Ca xix and Ca xviii relative line
intensities with current theory
Authors: Jordan, C.; Veck, N. J.
Bibcode: 1982SoPh...78..125J
Altcode:
A comparison is made between Ca XIX and Ca XVIII line ratios observed
in solar flares with the Bent Crystal Spectrometer (BCS) on the
Solar Maximum Mission (SMM) satellite and currently available atomic
data. Close agreement is found with the excitation rates recently
published by Pradhan et al. (1981). The observations show little
dependence of line ratios on electron temperature, supporting a
further conclusion that cascade contributions to the 23P
and 23S levels are not significant.
Title: High dispersion IUE spectra of active chromosphere G and
K dwarfs.
Authors: Ayres, T. R.; Linsky, J. L.; Brown, A.; Jordan, C.; Simon, T.
Bibcode: 1982NASCP2238..281A
Altcode: 1982auva.nasa..281A; 1982NASCP2338..281A; 1982IUE82......281A
IUE far ultraviolet echelle spectra of three active chromosphere
dwarf stars X1 Orionis (GO V), Bootis A (G8 V), and Eridani (K2 V),
are analyzed utilizing spectra of Alpha Cen A (G2 V) and Alpha Cen B
(K1 V) as quiet chromosphere comparisons.
Title: Chromospheres and Coronae of Stars On or Near the Main Sequence
Authors: Jordan, C.
Bibcode: 1982iue..prop.1368J
Altcode:
No abstract at ADS
Title: The Structure, Energy Balance and Dynamics of Stellar
Chromospheres and Coronae
Authors: Jordan, C.
Bibcode: 1982iue..prop.1332J
Altcode:
No abstract at ADS
Title: High dispersion far ultraviolet spectra of cool stars.
Authors: Stencel, R. E.; Linsky, J. L.; Ayres, T. R.; Jordan, C.;
Brown, A.; Engvold, O.
Bibcode: 1982NASCP2238..259S
Altcode: 1982auva.nasa..259S; 1982IUE82......259S; 1982NASCP2338..259S
Recent far ultraviolet high dispersion spectra of two cool supergiant
stars, Beta Dra (G2 Ib) and Alpha Ori (M2 Iab) are examined in the
context of current questions regarding stellar chromospheres, coronae
and mass loss. These stars show very different outer atmosphere
structure. Beta Dra has a geometrically thin transition region with
bright emission lines of 100,000 K plasma that are red-shifted,
indicating downflow in magnetic flux tubes. By contrast, Alpha Ori
has a cool extended chromosphere and circumstellar envelope with large
mass loss.
Title: The Active Sun
Authors: Jordan, C.
Bibcode: 1981SSRv...29..363J
Altcode:
A brief summary is given of observations which will be required to
investigate further the structure and energy balance of active regions.
Title: The solar atmosphere: From photosphere to corona
Authors: Jordan, C.
Bibcode: 1981ESASP.164...29J
Altcode: 1981sse..conf...29J
Developments in solar physics, emphasizing areas where observations from
space contribute substantially, are reviewed. Progress in establishing
the temperature and density structure of the outer solar layers is
made through measurements of emission line fluxes in the extreme UV
and X-ray wavelengths combined with spatial information from imaging
instruments. The processes by which the corona and other hot plasma are
heated remain elusive. Although the source of the heating is considered
to be the interaction between gas motions and the magnetic fields
in the subphotospheric convective zone, the means by which energy is
transported and dissipated are unknown. Observations required to limit
the range of possible mechanisms are discussed.
Title: Chromospheres and Coronae of Late-Type Stars
Authors: Jordan, C.
Bibcode: 1981IrAJ...15..110J
Altcode:
No abstract at ADS
Title: Detailed observations of NGC 4151 with the IUE. I. Low
dispersion data up to 1979 january.
Authors: Penston, M. V.; Boksenberg, A.; Bromage, G. E.; Clavel, J.;
Elvius, A.; Gondhalekar, P. M.; Jordan, C.; Lind, J.; Lindegren,
L.; Perola, G. C.; Pettini, M.; Snijders, M. A. J.; Tanzi, E. G.;
Tarenghi, M.; Ulrich, M. H.
Bibcode: 1981MNRAS.196..857P
Altcode: 1981STIN...8227202P
Low resolution ultraviolet spectroscopic monitoring of NGC 4151, the
brightest Type 1 Seyfert galaxy, with the IUE from February, 1978
to January, 1979, is presented. Data acquisition and reduction are
described. Observations were made at seven different epochs. Optimum
exposure times, when the object is bright, were found to be 25-30 min
and 50-60 min in large and small apertures respectively. When the object
was faint or when a better signal-to-noise ratio in the continuum was
required, a large-aperture exposure of 40-50 min was added. After the
wavelength scale was determined for each spectrum, data obtained on the
same day were averaged and regions affected by saturation, fiducials,
geocoronal Lyman alpha emission and particle events were excluded from
the mean spectra. Fifteen absorption features (most of which arise in
the nucleus of NGC 4151) are identified and their equivalent widths
measured. Velocity variations in the absorption region are indicated
by changing V/R ratios in the overall C IV feature. The Si IV lines
are unsaturated and must therefore be broad. The strong emission lines
include those seen in quasars. The intensities of the high-ionization
emission lines are variable, as are the linewidths of C IV.
Title: The chromosphere and corona of Procyon (Alf CMi,F5IV-V).
Authors: Brown, A.; Jordan, C.
Bibcode: 1981MNRAS.196..757B
Altcode:
Observations are reported of Procyon (alpha CMi), an F5 IV-V star,
obtained with the IUE satellite at low and high spectral resolutions as
part of a program to study the chromospheres and coronae in late-type
stars. Methods for analyzing the fluxes and linewidths of alpha CMi
and other near main sequence stars are presented, and applied to alpha
CMi to give the emission measure distribution, the electron pressure,
and hence a model of the density and temperature as a function of
height. Models are made for several boundary values of the electron
pressure. The maximum temperature for a model with uniform emission
is deduced to be 300,000 K. Higher temperature and pressure models
are allowed only if the EUV emission originates from limited areas
of the stellar disk. The terms of the energy balance equation are
calculated, and the profiles of several lines are analyzed to give the
non-thermal motions. A comparison is made between the empirical energy
input function and that expected from the dissipation of acoustic and
Alfven waves.
Title: Density sensitive C II lines in cool stars of low gravity.
Authors: Stencel, R. E.; Linsky, J. L.; Brown, A.; Jordan, C.;
Carpenter, K. G.; Wing, R. F.; Czyzak, S.
Bibcode: 1981MNRAS.196P..47S
Altcode:
It is shown that the relative intensities of emission lines within the
multiplet UV 0.01 of C II, around 2325 A, are sensitive to electron
density in the range 10 to the 9th to 10 to the 7th per cu cm. The lines
therefore offer a valuable method for measuring electron densities in
the chromospheres of late-type giants and supergiants. Calculated line
ratios are compared with those observed in a range of objects.
Title: Solar physics at Oxford
Authors: Roxburgh, I. W.; Jordan, C.
Bibcode: 1981Natur.292..194R
Altcode:
No abstract at ADS
Title: The chromospheres of late-type giants.
Authors: Jordan, C.
Bibcode: 1981Obs...101...42J
Altcode:
No abstract at ADS
Title: H2 emission in the EUV spectrum of T Tauri and
Burnham's nebula
Authors: Brown, A.; Jordan, C.; Millar, T. J.; Gondhalekar, P.;
Wilson, R.
Bibcode: 1981Natur.290...34B
Altcode:
Emission in the Lyman bands of H2 has been detected in an
extreme ultraviolet (EUV) spectrum of T Tauri and its adjacent nebula,
obtained with the international UV explorer (IUE) satellite. We report
here that the emission is in a progression which can be excited through
fluorescence with the red wing of the H Lyα line, as found also in
the solar atmosphere1. The observed EUV fluxes, absence of
other progressions and the flux in the previously observed2
1-0 S(1) IR line support a model where collisional rather than radiative
excitation leads to an excitation temperature of ≳ 2,000 K.
Title: Observations of the limb solar flare on 1980 April 30 with
the SMM X-ray polychromator
Authors: Gabriel, A. H.; Phillips, K. J. H.; Acton, L. W.; Wolfson,
C. J.; Culhane, J. L.; Rapley, C. G.; Bentley, R. D.; Kayat, M. A.;
Jordan, C.; Antonucci, E.
Bibcode: 1981ApJ...244L.147G
Altcode:
No abstract at ADS
Title: IUE Echelle Mode Observations Contrasting Coronal and
Non-Coronal Late Type Giant and Supergiant Stars
Authors: Brown, A.; Stencel, R. E.; Linsky, J. L.; Jordan, C.;
Engvold, O.
Bibcode: 1981BAAS...13..885B
Altcode:
No abstract at ADS
Title: X-ray spectra of solar flares obtained with a high-resolution
bent crystal spectrometer
Authors: Culhane, J. L.; Rapley, C. G.; Bentley, R. D.; Gabriel,
A. H.; Phillips, K. J.; Acton, L. W.; Wolfson, C. J.; Catura, R. C.;
Jordan, C.; Antonucci, E.
Bibcode: 1981ApJ...244L.141C
Altcode:
Preliminary results obtained for three solar flares with the bent
crystal spectrometer on the SMM are presented. Resonance and satellite
lines of Ca XIX and XVIII and Fe XXV and XXIV are observed together
with the Fe XXVI Lyman-alpha line. Plasma properties are deduced from
line ratios and evidence is presented for changes of line widths
coincident with the occurrence of a hard X-ray impulsive burst. Fe
K-alpha spectra from a disk center and a limb flare agree with the
predictions of a fluorescence excitation model. However, a transient
Fe K-alpha burst observed in a third flare may be explained by the
collisional ionization of cool iron by energetic electrons.
Title: Solar maximum mission experiment: Early results from the soft
X-ray polychromator experiment
Authors: Gabriel, A. H.; Antonucci, E.; Phillips, K. J. H.; Culhane,
J. L.; Bentley, R. D.; Parmar, A. N.; Rapley, C. G.; Acton, L. W.;
Leibacher, J. W.; Wolfson, C. J.; Strong, K. T.; Jordan, C.
Bibcode: 1981AdSpR...1m.267G
Altcode: 1981AdSpR...1Q.267G
The X-Ray Polychromator experiment has been in operation on the
SMM satellite for over three months. It is observing flares and
active regions in the wavelength range 1Å to 23Å using a number
of different modes. These include polychromatic imaging, high
resolution line profiles, high dispersion spectra, and light curves
with high time-resolution. Data are described together with some of
the preliminary analysis and interpretation.
Title: IUE and other new observations of the slow nova RR Tel.
Authors: Penston, M. V.; Benvenuti, P.; Cassatella, A.; Heck, A.;
Selvelli, P.; Ponz, D.; Macchetto, F.; Jordan, C.; Cramer, N.; Rufener,
F.; Manfroid, J.
Bibcode: 1981NASCP2171..469P
Altcode: 1981NASCP3171..469P; 1980IUE80......469P
No abstract at ADS
Title: Solar Maximum Mission experiment: early results from the soft
X-ray polychromator experiment.
Authors: Gabriel, A. H.; Culhane, J. L.; Acton, L. W.; Antonucci,
E.; Bentley, R. D.; Jordan, C.; Leibacher, J. W.; Parmar, A. N.;
Phillips, K. J. H.; Rapley, C. G.; Wolfson, C. J.; Strong, K. T.
Bibcode: 1981hea..conf..267G
Altcode:
No abstract at ADS
Title: The outer layers of the Sun.
Authors: Jordan, C.
Bibcode: 1981ScPrD..67....1J
Altcode:
No abstract at ADS
Title: The First three years of IUE
Authors: Gondhalekar, P. M.; Jordan, C.; Meadows, A. J.; Nandy, K.;
Penston, M. V.
Bibcode: 1981ftyi.book.....G
Altcode: 1981QB474.F57......
The report highlights results obtained from the International
Ultraviolet Explorer satellite, a project in which the UK was
involved. These include the observation of the UV spectra of
nearly all primary bodies in the solar system; of a large sample
of quasars, including the detection of faint high redshift objects;
and of chromospheric effects over a wide range of late-type stars. New
evolutionary theories have been required to explain the high mass loss
rates found in the winds of luminous stars. Interaction effects between
primary and compact objects were seen in several X-ray binaries. An
exhaustive analysis of nova Cyg 1978 supported the theory that the
outburst is caused by thermonuclear runway in material accreted onto
a white dwarf.
Title: Energy balance in solar and stellar coronae.
Authors: Jordan, C.; Brown, A.
Bibcode: 1981ASIC...68..199J
Altcode: 1981spss.conf..199J
Methods for determining the energy balances in solar and stellar coronae
are surveyed, and available results of such studies are presented for
a range of late-type stars. The derivation of temperature and density
structures from observed EUV and X-ray line fluxes is examined, and
expressions for the terms in the energy balance equation expressing
radiation losses and the net conductive flux are formulated in terms
of atmospheric modeling parameters. Results of energy balance modeling
are then illustrated for near main sequence stars including the sun
(spectral type G2V) Procyon (F5 IV-V) and Epsilon Eri (K2 V), and
for giants and supergiants including Beta Gem (K0 III) and Alpha Tau
(K5 III). It is noted that the main sequence stars have hot coronae
with thermal conduction important, while the giants and supergiants
have either hot or cool coronae depending on the surface gravity and
the presence of a strong stellar wind.
Title: The structure of chromospheres around late-type giants and
supergiants.
Authors: Brown, A.; Ferraz, M.; Jordan, C.
Bibcode: 1981NASCP2171..297B
Altcode: 1981NASCP3171..297B; 1981uviu.nasa..297B; 1980IUE80......297B
Observations alpha Tau (K5III) and beta Gru (M2II) made at high
resolution are used to confirm line identifications of features
blended at low resolution. The high resolution spectra allow
selected pairs of lines to be used to find the electron density and
the opacity. Methods for determining these factors and the usual
emission measure are presented. The electron density and opacity can
be used together with the emission measure to place constraints on the
structure of the atmosphere. The line formation processes are briefly
discussed. Photo-excitation by strong lines appears to be important
in these late type atmospheres.
Title: Solar Activity
Authors: Jordan, C.
Bibcode: 1981ESPM....3.....J
Altcode:
No abstract at ADS
Title: Stark effect at the SI I series limit
Authors: Jordan, C.; Bartoe, J. -D. F.; Brueckner, G. E.
Bibcode: 1980ApJ...240..702J
Altcode:
Small redshifts and weakenings of high n lines in members of the
Si series observed over a sunspot are interpreted as due to the
Stark effect. Other origins, including Doppler motions, appear to
be excluded. The spectra were obtained with high spatial resolution
using the NRL high-resolution telescope and spectrograph. The origin
of the Stark effect is not yet certain. An interpretation in terms of
a quasi-static quadratic effect would require rather high perturber
densities. An alternative interpretation would be a motional Stark
effect, arising perhaps through the presence of magnetohydrodynamic
waves.
Title: Chromospheric Densities and Geometrical Extensions of Red
Giants and Supergiants using C II Lines as Diagnostics
Authors: Stencel, R. E.; Jordan, C.; Wing, R. F.; Linsky, J. L.;
Carpenter, K. G.; Brown, A.; Czyzak, S. J.
Bibcode: 1980BAAS...12..806S
Altcode:
No abstract at ADS
Title: Helium Line Emission: Its Relation to Atmospheric Structure
Authors: Jordan, C.
Bibcode: 1980RSPTA.297..541J
Altcode: 1980RSLPT.297..541J
A brief review is given of observations of the resonance lines of
He I and He II and their interpretation. As discussed in a previous
paper, the helium lines are anomalously strong in the quiet Sun when
compared with other transition region lines. The enhancement can be
brought about by the transient excitation of the lines by electrons of
higher temperature than that which determines the ion population. The
variation in the intensity of the helium lines relative to those of
other transition region lines appears to be related to variations in
the temperature gradient between different parts of the atmosphere. To
relate the degree of enhancement to other observable parameters,
such as electron pressure and absolute line intensities, and thus to
the structure of the atmosphere, a method for analysing the emission
measure distribution previously developed in the context of the quiet
atmosphere and active region loops is applied also to coronal holes. It
is proposed that the non-thermal ion motions observed in the transition
region can provide the required mechanism for transporting the helium
ions across the steep temperature gradient. By making a simple model,
an expression is developed which relates the helium enhancement to the
non-thermal motions, the transition region temperature gradient and
the electron pressure. The scaling laws implied can be tested against
further observations when they become available.
Title: S I emission in EUV spectra of late-type stars.
Authors: Brown, A.; Jordan, C.
Bibcode: 1980MNRAS.191P..37B
Altcode:
Observations of strong neutral sulfur emission lines in the EUV
spectra of late-type giant and supergiant stars are discussed. Low-
and high-resolution spectra of Alpha Tauri and Beta Gru are presented
which demonstrate the contribution of the S I (UV 9) multiplet to the
observed features at approximately 1296 A as well as the strong O I
multiplet at 1304 A. S I lines which must be taken into consideration
in the analysis of stellar spectra are also found at 1807.34, 1820.36
and 1826.26 A (UV 2) in the vicinity of Si II lines, at 1900.27 and
1914.68 A (UV 1), at 1474.0 and 1474.4 A (UV 3), and possibly near
1640 A (UV 5). Evidence of photoexcitation and high line opacities of
neutral S is pointed out, and it is noted that the opacities together
with absolute fluxes can provide information on atmospheric structure.
Title: The energy balance of the solar transition region
Authors: Jordan, C.
Bibcode: 1980A&A....86..355J
Altcode:
It is shown how the observed distribution of the emission measure
with temperature can be used to limit the range of energy deposition
functions suitable for heating the solar transition region and inner
corona. The minimum energy loss solution is considered in view of the
work by Hearn (1975) in order to establish further scaling laws between
the transition region pressure, the maximum coronal temperature and
the parameter giving the absolute value of the emission measure. Also
discussed is the absence of a static energy balance at the base of
the transition region in terms of measurable atmospheric parameters,
and the condition for a static energy balance is given. In addition,
the possible role of the emission from He II in stabilizing the
atmosphere by providing enhanced radiation loss is considered.
Title: The chromospheric and coronal structure of alf CMi (F5 IV-V)
Authors: Brown, A.; Jordan, C.
Bibcode: 1980ESASP.157...71B
Altcode: 1980IUE2n.......71B
Observations of alpha CMi (Procyon) obtained with the International
Ultraviolet Explorer satellite were analyzed to determine the structure
of the outer atmosphere. This analysis is used to examine the terms
of the energy balance equation. Radiation losses exceed those from
comparable regions of the solar atmosphere and dominate the energy
balance of the atmosphere. The coronal temperature and pressure are
300,000 K and 2 X 10 to the 14th power cu/cm K. Line profiles from
high resolution spectra are used to determine the nonthermal energy
flux. Comparisons made between the required energy input and that
expected from heating by acoustic waves show that, from observations
and models, energy deposition by acoustic waves should be sufficient
to account for the radiative losses.
Title: Observations of NGC 4151 with IUE.
Authors: Boksenberg, A.; Bromage, G.; Clavel, J.; Elvius, A.; Gabriel,
A.; Gondhalekar, P.; Jordan, C.; Lind, J.; Lindegren, L.; Longair,
M.; Penston, M. V.; Perola, G.; Perryman, M.; Pettini, M.; Rees, M.;
Sciama, D.; Snijders, M.; Tanzi, E.; Tarenghi, M.; Ulrich, M. H.;
Wilson, R.
Bibcode: 1980ESASP.157D..67B
Altcode:
No abstract at ADS
Title: Chromospheres, coronae and mass loss in solar and late-type
stars.
Authors: Jordan, C.
Bibcode: 1980HiA.....5..533J
Altcode:
No abstract at ADS
Title: Studies of Stellar Chromsopheres and Coronae
Authors: Jordan, C.
Bibcode: 1980iue..prop..649J
Altcode:
No abstract at ADS
Title: CO emission lines in the solar atmosphere.
Authors: Jordan, C.; Bartoe, J. -D. F.; Brueckner, G. E.; Nicolas,
K. R.; Sandlin, G. D.; Vanhoosier, M. E.
Bibcode: 1979MNRAS.187..473J
Altcode:
New identifications of CO emission lines in the EUV spectrum of a
sunspot are reported. The spectra were obtained with the Naval Research
Laboratory's High Resolution Telescope and Spectrograph. The emission is
from the CO fourth positive system and is excited by the strong lines of
C IV, Si IV and O IV. Transitions in the 0-3 band which lie above 1700
A and other lines at shorter wavelengths have been identified from the
spectrum of the June 15, 1973 flare, obtained with the Naval Research
Laboratory's normal incidence spectrograph on Skylab. The observed
intensities in the sunspot are used to derive the CO column density.
Title: H2 emission in the solar atmosphere.
Authors: Bartoe, J. -D. F.; Brueckner, G. E.; Nicolas, K. R.; Sandlin,
G. D.; Vanhoosier, M. E.; Jordan, C.
Bibcode: 1979MNRAS.187..463B
Altcode:
New identifications of emission lines of molecular hydrogen in the EUV
spectrum of sunspots are reported. The spectra were obtained during
the first and second flights of the Naval Research Laboratory's High
Resolution Telescope and Spectrograph (HRTS). While most of the lines
originate in the Lyman bands, fluorescence from the Werner bands has
been found for the first time in the solar atmosphere. H2 fluorescent
emission has also been identified in the spectra of a solar flare
observed with NRL's normal incidence spectrograph on Skylab. Column
densities for H2 are derived from intensities of lines in the sunspot
spectra.
Title: Observations of late-type stars with IUE
Authors: Brown, A.; Jordan, C.; Wilson, R.
Bibcode: 1979IUE1.symp..232B
Altcode:
Observations of stars with spectral types between F5 and MO and
luminosity classes I to VI have been made with the IUE satellite. The
aim of the program is to establish the late-type stars which possess
chromospheres and coronae, and to determine the temperature,
density structure and energy deposition requirements of these
atmospheres. Preliminary analyses show that F5 to K3 main sequence stars
are likely to possess coronae hotter than 10 to the 5th power K. Late
type giants show no evidence for material hotter than approximately
20,000 K, but instead show a spectrum dominated by fluorescence excited
by a few strong emission lines such as HLy alpha HLy beta.
Title: Observations of the ultraviolet spectrum of the variable
Seyfert galaxy NGC4151
Authors: Baldwin, J.; Boksenberg, A.; Bromage, G.; Carswell, R.;
Elvius, A.; Gabriel, A.; Gondhalekar, P. M.; Jordan, C.; Lind, J.;
Lindegren, L.; Longair, M. S.; Penston, M. V.; Perola, G. C.; Perryman,
M. A. C.; Pettini, M.; Rees, M.; Snijders, M. A. J.; Tanzi, E. G.;
Tarenghi, M.; Ulrich, M. H.; Wilson, R.
Bibcode: 1979IUE1.symp..126B
Altcode:
High-resolution UV spectra of NGC 4151 from the IUE satellite are
presented and discussed. The Lyman-alpha emission line is narrow and
asymmetrical - there are two absorption systems. One is narrow and
probably represents the outer parts of NGC 4151. The other is broad,
primarily from material nearer to the nucleus. C IV 1550 A emission is
broad, with absorption between velocities of -100 and -1100 km/sec. The
absorbing clouds cover at least 80 percent of the emission region. Due
to the doublet nature of the line, alternative explanations are possible
for the details of the C IV absorption profile. Two such alternatives
are discussed.
Title: Chromospheres and Coronae
Authors: Jordan, C.
Bibcode: 1979iue..prop..402J
Altcode:
No abstract at ADS
Title: On the Ultraviolet Spectrum of RR-Tel
Authors: Cassatella, A.; Benvenuti, P.; Clavel, J.; Heck, A.; Jordan,
C.; Macchetto, F.; Penston, M. V.; Selvelli, P. L.
Bibcode: 1979IUE1.symp...78C
Altcode:
No abstract at ADS
Title: Emission lines of H2 in the extreme-ultraviolet
solar spectrum.
Authors: Jordan, C.; Brueckner, G. E.; Bartoe, J. -D. F.; Sandlin,
G. D.; Vanhoosier, M. E.
Bibcode: 1978ApJ...226..687J
Altcode:
A sunspot EUV spectrum covering the wavelength range from 1175 to 1714
A with high spatial and spectral resolution is examined which contains
about 200 lines not previously reported in solar spectra. Many of
the lines are identified as transitions in the Lyman bands of H2. It
is shown that the H2 lines are photoexcited not only by H L-alpha, as
reported previously, but also by the strong transition-region lines of
C II, Si IV, and O IV. The line intensities are analyzed as far as is
possible at present, and differences between the quiet chromosphere
and the sunspot chromosphere are deduced. The polarization of the
observed lines is briefly discussed, the importance of the H L-alpha
fluorescence mechanism for the excitation of the H2 Lyman bands is
demonstrated, and it is concluded that the H2 lines could also be
observable in stars of spectral type later than the sun.
Title: IUE observations of extragalactic objects
Authors: Boksenberg, A.; Snijders, M. A. J.; Wilson, R.; Benvenuti,
P.; Clavell, J.; Macchetto, F.; Penston, M.; Boggess, A.; Gull, T. R.;
Gondhalekar, P.; Lane, A. L.; Turnrose, B.; Wu, C. C.; Burton, W. M.;
Smith, A.; Bertola, F.; Capaccioli, M.; Elvius, A. M.; Fosbury, R.;
Tarenghi, M.; Ulrich, M. H.; Hackney, R. L.; Jordan, C.; Perola,
C. G.; Roeder, R. C.; Schmidt, M.
Bibcode: 1978Natur.275..404B
Altcode:
During the commissioning phase of IUE several extragalactic objects
were observed spectrally at low dispersion in the UV range lambda lambda
1150-3200: the Seyfert galaxies NGC4151 and NGC1068, the QSO 3C273, the
BL Lacertae object B2 1101+38, the giant elliptical galaxy M87 and the
spiral galaxy M81. The results obtained are presented and a preliminary
analysis given for all six objects, discussing the continuous spectrum,
extinction, emission line spectrum and absorption line spectrum, where
possible for each case. Several new or confirmatory astrophysical
results are obtained.
Title: IUE observations of cool stars : alf Aur, HR 1099, lam and
EPS Eri.
Authors: Linsky, J. L.; Ayres, T. R.; Basri, G. S.; Morrison, N. D.;
Boggess, A.; Schiffer, F. H., III; Holm, A.; Cassatella, A.; Heck,
A.; Macchetto, F.; Stickland, D.; Wilson, R.; Blanco, C.; Dupree,
A. K.; Jordan, C.; Wing, R. F.
Bibcode: 1978Natur.275..389L
Altcode:
Initial IUE observations of four cool stars are reported. Observed
fluxes and surface fluxes are given for several UV emission lines in
the spectral range 1175-2000 A, obtained at low and high dispersion with
the short-wavelength spectrograph and camera. These lines are formed in
the outer atmospheres of these stars, in regions presumably analogous to
the solar chromosphere and transition region. The surface fluxes in the
lines increase along the sequence: quiet sun, Epsilon Eri, Lambda And,
Alpha Aur, and HR1099. The 2.8-d RS CVn-type binary HR1099, observed on
1 March 1978 near the end of a major flaring episode, has line surface
fluxes roughly 100 times that of the quiet sun, similar to those seen in
solar flares. Line profiles and flux ratios in multiplets for Capella
are presented, and comments given on the opacity of the lines and on
a tendency of line width to increase with temperature of formation.
Title: CO fluorescence in the extreme-ultraviolet solar spectrum.
Authors: Bartoe, J. -D. F.; Brueckner, G. E.; Sandlin, G. D.;
Vanhooster, M. E.; Jordan, C.
Bibcode: 1978ApJ...223L..51B
Altcode:
Emission lines in the fourth positive system of CO have been identified
in the extreme-ultraviolet solar spectrum 1540-1660 A. These lines
are excited by the C IV transition-zone lines at 1548 and 1551 A. They
are strong in the spectrum of a sunspot and in parts of the adjacent
active region. Some of them appear as weak, broad emission features
in the quiet sun.
Title: A Study of the Nuclei of Seyfert Galaxies by Observing Their
EUV Emission Spectrum
Authors: Jordan, C.
Bibcode: 1978iue..prop...94J
Altcode:
No abstract at ADS
Title: Applications of Atomic Physics to Astrophysical Plasmas
Authors: Jordan, Carole
Bibcode: 1978pas..conf.1453J
Altcode:
No abstract at ADS
Title: Lines of H2 in extreme-ultraviolet solar spectra
Authors: Jordan, C.; Brueckner, G. E.; Bartoe, J. -D. F.; Sandlin,
G. D.; van Hoosier, M. E.
Bibcode: 1977Natur.270..326J
Altcode:
The first detection of molecular hydrogen in the sun is reported. The
observations were made with the aid of a high resolution telescope
and spectrograph flown in a rocket on July 21, 1975. A short stretch
of a spectrum obtained with a 51-sec exposure time is presented in a
graph. It has been found that at least 30 of the new lines are related
to known transitions in the Lyman bands of H2. The H2 molecules in
the sunspot, or pore, can be excited by photons in the red wing of H
L-alpha as they travel down towards the photosphere.
Title: Molecular Hydrogen in the Solar Atmosphere.
Authors: Brueckner, G.; Bartoe, J. -D. F.; Sandlin, G. D.; Vanhoosier,
M. E.; Jordan, C.
Bibcode: 1977BAAS....9..568B
Altcode:
No abstract at ADS
Title: Book Review: The solar chromosphere and corona:
Quiet Sun. R. GRANT ATHAY: Reidel, Dordrecht, 1976. xii +
504. Dfl. 150. U.S.$59.00
Authors: Jordan, Carole
Bibcode: 1977P&SS...25..893J
Altcode:
No abstract at ADS
Title: Transition Region
Authors: Jordan, C.
Bibcode: 1977ASSL...69...35J
Altcode: 1977igss.conf...35J
Transition Region Di-Electronic Recombination Intersystem or
Intercombination Lines Satellite Lines Grazing-Incidence Optics Crystal
Spectrometers
Title: Studies of the Solar Atmosphere Using Density-Sensitive
Line Ratios.
Authors: Jordan, C.
Bibcode: 1977uxsa.coll...16J
Altcode: 1977IAUCo..43...16J
No abstract at ADS
Title: Plasma diagnostic techniques in the ultraviolet: the C III
density-sensitive lines in the sun.
Authors: Dupree, A. K.; Foukal, P. V.; Jordan, C.
Bibcode: 1976ApJ...209..621D
Altcode:
Spectra and spectroheliograms of the C III transitions at 977 and 1176
A are obtained with the Harvard extreme-ultraviolet spectrometer on
Skylab. Analysis of the intensities of these lines, and of their
density-sensitive ratio, indicates a wide range of temperature
gradients and electron densities in the transition region of various
solar features. From values of the observed ratio, we suggest necessary
revisions to the excitation rates, and propose a relationship between
the ratio and density. The significantly higher ratio found in active
regions indicates a density increase of about a factor 2 relative to the
network. In the quiet sun, there is no significant difference in density
between network and cell interiors, but the uncertainty is as large as
a factor 3. The very central 10% of the areas of cell interiors shows
a significantly higher density than the mean value for cell interiors.
Title: The Structure and Energy Balance of Solar Active Regions
Authors: Jordan, C.
Bibcode: 1976RSPTA.281..391J
Altcode: 1976RSLPT.281..391J
The interpretation of the emission measures calculated from e.u.v. and
X-ray line intensities is discussed. A general method for deriving the
temperature and density structure and energy balance in either the quiet
Sun or active regions is given. In particular simple relations are found
between the coronal temperature, the pressure in the chromosphere-corona
transition region, P0, the conductive flux at P0,
the mechanical energy dissipated above P0 and the radiation
losses above P0. A range of models for quiet and active
regions is given. The rate of change of the mechanical energy deposition
as a function of height is used to find empirical damping lengths which
are compared with those expected from either the conduction damping of
sound waves or the viscous damping of Alfven waves. The wave frequencies
and peak amplitude velocities required to satisfy both the empirical and
theoretical damping lengths and energy deposition rates are discussed.
Title: Radiation and structure of the solar atmosphere (Radiation
et structure de l'atmosphère solaire).
Authors: Giovanelli, R. G.; Mein, P.; Bappu, M. K. V.; Jordan, C.;
MacQueen, R. M.
Bibcode: 1976IAUTA..16b..55G
Altcode:
No abstract at ADS
Title: Ultraviolet observations of C III transitions in the sun.
Authors: Dupree, A. K.; Foukal, P.; Jordan, C.
Bibcode: 1976BAAS....8..292D
Altcode:
No abstract at ADS
Title: Analysis of EUV observations of regions of the quiet and
active corona at the time of the 1970 March 7 eclipse.
Authors: Gabriel, A. H.; Jordan, C.
Bibcode: 1975MNRAS.173..397G
Altcode:
A series of EUV spectra were obtained from a rocket flight during
the 1970 March 7 total solar eclipse. The intensities of permitted
and forbidden emission lines in both quiet and active regions have
been analyzed. The densities and temperatures have been derived as a
function of position in the active region. In a given line-of-sight
the density increases with increasing temperature and overall the
central, low, parts of the active region contain more material at
the higher temperatures than do the more extensive loop systems. The
populations of the excited levels of the forbidden lines have been
calculated using currently available atomic data. It appears that
these and known excitation processes significantly underestimate the
excited level populations. The populations used have therefore been
normalized by using a quiet region of the corona as a diagnosed plasma.
Title: Observations of chromospheric and coronal emission lines in
F stars.
Authors: Evans, R. G.; Jordan, C.; Wilson, R.
Bibcode: 1975MNRAS.172..585E
Altcode:
Results are reported for Copernicus satellite observations of the
Ly-alpha, Si III, and O VI chromospheric emission lines of alpha CMi
(Procyon, F5 IV). Mg II h and k emission was also detected in Procyon
as well as in alpha Car (Canopus, FO Ib). A H I column density of
the order of 1.6 by 10 to the 17th power per sq cm is derived from
the Ly-alpha interstellar-absorption component, and a value of 0.015
atoms per cu cm is obtained for the neutral-hydrogen density in the
solar neighborhood. The observed line widths of the Mg II emissions
are used to evaluate the Wilson-Bappu correlation of line width with
luminosity. Two models of Procyon's atmosphere are proposed on the
basis of analysis of the emission-line intensities.
Title: Further measurements of emission line profiles in the solar
ultraviolet spectrum.
Authors: Boland, B. C.; Dyer, E. P.; Firth, J. G.; Gabriel, A. H.;
Jones, B. B.; Jordan, C.; McWhirter, R. W. P.; Monk, P.; Turner, R. F.
Bibcode: 1975MNRAS.171..697B
Altcode:
A further flight of a high resolution echelle spectrograph has been
carried out on a Skylark rocket to measure solar line profiles in
the region 1400-2200 A. Improvements in reflective coatings and better
thermal stability resulted in an increase in both the number and quality
of profiles recorded. Microdensitometer traces for 37 emission lines are
presented. Analysis of the profiles leads to a nonthermal mechanical
velocity component which increases with temperature over the range
6,000 to 100,000 K, always remaining subsonic. Interpretations are
considered in terms of a progressive mechanical energy flux to the
corona. These include acoustic and MHD modes for both spherically
symmetric and network models of the atmosphere.
Title: The intensities of helium lines in the solar EUV spectrum.
Authors: Jordan, C.
Bibcode: 1975MNRAS.170..429J
Altcode:
The present paper points out that the lines of neutral and singly
ionized helium in the solar EUV spectrum have anomalously high
intensities when compared with lines of other ions formed at similar
temperatures. It is suggested that the observed absolute and relative
intensities, and, in addition, the line widths, can be accounted for
if a mechanism which causes the helium atoms and ions to be excited by
electrons with temperatures greater than the ionization equilibrium
value is operating. Further, the observed decrease of helium line
intensities in coronal holes, while other transition-region lines
decrease little if at all, can be accounted for by the reduction
of the enhancement mechanism in coronal holes and/or by the reduced
temperature gradient in these regions. An essential factor that makes
the helium lines so sensitive to the presence of such a mechanism is
the large value of the ratio of the excitation potential of the lines
to the electron temperature.
Title: Ultraviolet emission lines in the spectrum of Procyon
Authors: Evans, R. G.; Jordan, C.
Bibcode: 1975Natur.253..612E
Altcode:
THE Princeton instrumentation1 on the satellite Copernicus
has been used to observe the F5 1V star, αCMi (Procyon). Tn addition
to previously observed2 lines of Mg II, the Lyman-α line
of H I (1,216 Å), and the resonance lines of Si III(1,206 Å) and
O VI (1,032 Å) have been observed for the first time in an F-type
star. Figure 1 shows the observed lines, all of which exceed the two
standard deviation level.
Title: The Structure of Solar Active Regions from EUV and Soft
X-Ray Observations
Authors: Jordan, C.
Bibcode: 1975IAUS...68..109J
Altcode:
The structure of solar active regions derived from EUV and soft X-ray
observations is reviewed. The methods by which the emission measure
as a function of temperature can be interpreted are discussed. The
models of density and temperature which can be made from a variety of
combinations of the emission measure with information on the spatial
distribution of material are broadly consistent. They show that the
plasma at low heights over the central parts of an active region
is hotter and denser than that which extends to greater heights. It
appears that much of the emitting material exists in the form of loop
structures, presumably magnetically controlled flux tubes. Analytical
relationships between the physically important parameters describing
the properties of the active region at Te greater than
200,000 K are developed and discussed.
Title: Solar limb and disk continuum intensities in the wavelength
region 1450-1950 A
Authors: Jordan, C.; Ridgeley, A.
Bibcode: 1974MNRAS.168..533J
Altcode:
Observations of the intensity of the solar continuum in the wavelength
region 1450-1950 A are reported. Measurements of fluxes were made on the
disk and across the limb and have been compared with those predicted by
the Bilderberg Continuum Atmosphere and the arvard Smithsonian Reference
Atmosphere. A large discrepancy between the observed fluxes and those
predicted by the models is found for the region where A> i7ooA,
as reported by other authors. The origin of the continuum (i.e. the
photosphere, region of the temperature minimum or chromosphere) as a
function of wavelength is deduced from the observed limb-brightening
or limbdarkening. There is evidence that continuum emission from
material with brightness temperatures less than about 5000 K extends
further beyond the limb than predicted by the spherically symmetric
homogeneous models.
Title: The Measurement of Electron Densities from Beryllium-like
Ion Line Ratios
Authors: Jordan, C.
Bibcode: 1974A&A....34...69J
Altcode:
Summary. The theoretical dependence of line intensity ratios in the
beryllium-like ions C ii' and 0 V is discussed. Comparison of the line
ratios, calculated using currently available excitation cross-sections
and transition probabilities, with those observed shows that the
theoretical atomic data cannot account for the observed ratios with
electron densities consistent with those given by models derived from
absolute line fluxes. However, changes to the excitation cross-sections
for permitted and spin4orbidden transitions within the quoted error
bars, plus increased mixing of the 2s2p3P levels could account for the
majority of the observed ratios. It is therefore premature to conclude
that the discrepancy between the observed and calculated lines ratios
originates from the existence of solar electron densities, where the C
iii and 0 V lines are formed, which are greatly different from those
derived from current models of the chromosphere-corona transition
region. Key words: sun electron density beryllium-like ions
Title: Are coronal holes M-regions?
Authors: Jordan, C.
Bibcode: 1974Obs....94..141J
Altcode:
No abstract at ADS
Title: Observations of the solar spectrum in the re.-ion 150 A to
870 A emitted from the disk and above the limb
Authors: Firth, J. G.; Freeman, F. F.; Gabriel, A. H.; Jones, B. B.;
Jordan, C.; Negus, C. R.; Shenton, D. B.; Turner, R. F.
Bibcode: 1974MNRAS.166..543F
Altcode:
Photographic spectra have been obtained in the grazing-incidence
region from a position on the quiet solar disk and from a region
just above the visible limb. The payload, which was launched on a
Sun-stabilized Skylark rocket, contained three grazing-incidence
spectrographs, each illuminated by a two-component grazing-incidence
telescope mirror. One of these, which was viewing the limb spectrum,
was fitted with a fine-alignment servo system to stabilize the image. A
careful intensity calibration will enable the data to be analysed in
terms of limbldisk intensity ratios, and absolute intensities. The
present paper presents a full identification of the spectra, which
includes a number of intersystem transitions, notably in iron ions.
Title: Analysis of EUV Observations of a Coronal Active Region Made
during the 7 March 1970 Eclipse (presented by C. Jordan)
Authors: Gabriel, A. H.; Jordan, C.
Bibcode: 1974IAUS...57...93G
Altcode:
No abstract at ADS
Title: Further Observations of the Structure of the
Chromosphere-Corona Transition Region from Limb and Disk Intensities
Authors: Burton, W. M.; Jordan, C.; Ridgeley, A.; Wilson, R.
Bibcode: 1974IAUS...56...89B
Altcode:
No abstract at ADS
Title: The Temperature Dependence of Line Ratios of Helium-Like Ions
Authors: Gabriel, A. H.; Jordan, C.
Bibcode: 1973ApJ...186..327G
Altcode:
In a recent paper Blumenthal et a!. have suggested that the
use of helium-like intercombination to forbidden line ratios to
measure electron densities is complicated by an important electron-
temperature dependence of the ratios. It is shown here that their
theory uses an incorrect treatment of dielectronic recombination and
that the temperature dependence is in fact smaller. It is concluded
that significant observations of ratios which vary by more than I 10
percent can safely be attributed to electron density effects. Recent
observations, in particular those of Acton et a!. of O vii, show
variations of only 15 percent. Although Acton et a!. consider that
their data support the temperature dependence predicted by Blumenthal
et a!., they can equally well agree with a much lower temperature
dependence. However, the accuracy of the observations to date is
not sufficient to show a definite dependence on temperature. Subject
headings: atomic processes - atmospheres, solar
Title: Further Observations of the Structure of the
Chromosphere-corona Transition Region from Limb and Disk Intensities
Authors: Burton, W. M.; Jordan, C.; Ridgeley, A.; Wilson, R.
Bibcode: 1973A&A....27..101B
Altcode:
Summary. Further observations of limb to disk intensity ratios of
emission lines in the EUV solar spectrum were obtained on a Skylark
rocket ffight on 5 August 1971. Analysis of the data has shown that the
observations support the existence of a steep rise in temperature in
the transition region between Te 6 x 10 0K and 3 x tO 0K. A decrease
in temperature gradient above Te 7 x tO 0K is observed. The absolute
height of the transition region above the visible limb has been measured
with a greater accuracy than previously possible and is 1700 km +700
km. An independent method using arc-length measurements of spectrnm
lines gives an absolute height of 2100 km +850 km. The absorption of
lines lying at wavelengths shorter than the head of the Lyman continuum
has been studied, and can be explained by spicular material with Ne=
1.4 x 10" and Te= 1.1 x 1O 0K. The abundance 6f iron has been derived
from the chromospheric emission lines of Fe ii. This value agrees,
within the experimental accuracy of a factor of two, with the value of
N<Fe)/N(H) =4 x 1O- found from previous analyses of photo spheric and
coronal lines. Key words: transition region - spicules - iron abundance
Title: Identification of Emission Lines in the EUV Solar Spectrum
(invited Paper)
Authors: Jordan, Carole
Bibcode: 1972SSRv...13..595J
Altcode: 1972IAUCo..14..595J
No abstract at ADS
Title: The Identification of New Forbidden Coronal Lines in the
Solar EUV Spectrum (Papers presented at the Proceedings of the
International Symposium on the 1970 Solar Eclipse, held in Seattle,
U. S. A. , 18-21 June, 1971.)
Authors: Jordan, Carole
Bibcode: 1971SoPh...21..381J
Altcode:
Identifications are proposed for twenty of the twenty-eight coronal
lines observed in the spectra obtained during a rocket flight
into the path of the 7 March, 1970 solar eclipse. The methods by
which the lines have been identified are discussed. Most of the
lines identified are from forbidden transitions between levels
in the ground 2pn and 3pn configurations
in high ions of magnesium, silicon, sulphur, iron, and nickel. The
temperature range represented is from 6.9 × 105 K to 2.5 ×
106 K. The classification of three lines of FeXII and two
of NiXIV has led to a revised identification for the near ultraviolet
2D3/2-2P1/2 transition
in Fe XII. This transition can be identified with the line at 3072 Å
rather than that at 3021 Å as previously suggested in the literature.
Title: Rocket Observations of the Ultraviolet Solar Spectrum during
the Total Eclipse of 1970 March 7
Authors: Gabriel, A. H.; Garton, W. R. S.; Goldberg, L.; Jones,
T. J. L.; Jordan, Carole; Morgan, F. J.; Nicholls, R. W.; Parkinson,
W. J.; Paxton, H. J. B.; Reeves, E. M.; Shenton, C. B.; Speer, R. J.;
Wilson, R.
Bibcode: 1971ApJ...169..595G
Altcode:
A sequence of thirty-five ultraviolet photographic spectra of the
Sun has been obtained in the wavelength region 850-2190 A, as a
function of time during the eclipse. These cover the range from before
second contact until midtotality, with a spatial resolution of the
order 2 arc sec. A general description of the experiment and data is
given. Twenty-five new coronal lines have been seen, the majority of
which have been identified as new forbidden transitions. The La corona
is observed out to over 1.5 R0, and a quantitative interpretation
is presented. Analyses of other features-e.g., prominences,
quiet-atmosphere structure, and coronal condensations-are continuing.
Title: On the Identffication of the A417 Line in the Solar Extreme
Ultraviolet Spectrum
Authors: Flower, D. R.; Jordan, C.
Bibcode: 1971A&A....14..473F
Altcode:
Collision strengths for transitions between terms of the first four
configurations of Fe xv have been calculated in the distorted wave
approximation and show good agreement with Coulomb-Born results of
Bely and Blaha (1968). The computed ratio of the intensity of the
1S5 - 8p1O transition to that of the 1S5 - 3s3p iP? transition agrees
within a factor of two with the most recent observations by Hall and
Hinteregger(1970) of the intensity ratio of the solar lines at 417 A and
284 A. The possibility of other contributors to the observed line at 417
A is discussed. Key words: Fe xv - solar corona - collision strengths
Title: The Structure of the Chromosphere-Corona Transition Region
from Limb and Disk Intensities
Authors: Burton, W. M.; Jordan, Carole; Ridgeley, A.; Wilson, R.
Bibcode: 1971RSPTA.270...81B
Altcode:
During a rocket flight in April 1969, spectra were obtained of a region
of the solar disk and at the solar limb. The absolute disk intensities
derived from these data have been used to compute models of the
transition region, making the assumptions that the relative abundances
of different elements remain constant throughout the atmosphere,
and that the electron pressure varies according to the equation of
hydrostatic equilibrium. The models obtained are characterized by very
steep temperature gradients. The relative intensities of emission lines
in the disk and limb spectra have enabled the height of the emitting
regions to be determined independently of the above assumptions, and
independently of atomic data and absolute intensities. A comparison
is made of the structure found by the two methods, and within the
accuracy of the present data these are consistent. Emission from low
temperature (~ 104 K) material is observed from heights up
to 104 km above the transition region, and this probably
originates in spicules.
Title: Helium-Like Ion Forbidden Line Emission, and Solar Active
Regions
Authors: Freeman, F. F.; Gabriel, A. H.; Jones, B. B.; Jordan, Carole
Bibcode: 1971RSPTA.270..127F
Altcode:
A theory has been developed for interpreting the intensity of the
1s2 1S-1s2s 3S forbidden line in
helium-like ions in terms of electron density at the source. In a
recent soft X-ray rocket experiment, this transition has been observed
simultaneously from C V, N VI and O VII. New values for the forbidden
transition probabilities are derived in a semi-empirical manner using
this data. The new values lead to derived solar densities in active
regions of between 1011 and 1013 cm-3.
Title: Report of the honorary auditors for the year 1970.
Authors: Jordan, C.; Peckover, R. S.
Bibcode: 1971QJRAS..12..221J
Altcode:
No abstract at ADS
Title: Atomic data of importance for ultraviolet and X-ray
astronomy. Joint discussion during the XIVth general assembly of
the IAU, Brighton 1970.
Authors: Jordan, C.; Wilson, R.
Bibcode: 1971HiA.....2..463J
Altcode:
No abstract at ADS
Title: The Determination of Chromospheric-Coronal Structure from
Solar XUV Observations
Authors: Jordan, C.; Wilson, R.
Bibcode: 1971ASSL...27..219J
Altcode: 1971psc..conf..219J
No abstract at ADS
Title: The Relative Intensities of Lines from Bei-like Ions in the
Solar Spectrum
Authors: Jordan, C.
Bibcode: 1971HiA.....2..519J
Altcode:
No abstract at ADS
Title: The relative intensities of lines from the Be I-like ions in
the solar spectrum.
Authors: Jordan, C.
Bibcode: 1971adiu.conf..519J
Altcode:
No abstract at ADS
Title: Report of the honorary auditors for the year 1969.
Authors: Bowell, E. L. G.; Jordan, C.
Bibcode: 1970QJRAS..11..161B
Altcode:
No abstract at ADS
Title: Helium-like ion forbidden line emission from the sun
Authors: Gabriel, A. H.; Jordan, C.
Bibcode: 1970PhLA...32..166G
Altcode:
A recent theory for interpreting relative line intensities from
helium-like ions is re-examined in the light of newer data. New
semi-empirical values for the transition probability 1s2
1S - 1s2s 3S, are proposed, which lead to higher
measured electron densities.
Title: Ionization equilibria for high ions of Fe and NI
Authors: Jordan, Carole
Bibcode: 1970MNRAS.148...17J
Altcode:
Calculations of ionization equilibria, ionization and recombination
rates for high ions of Fe and Ni are presented.
Title: A Model of the Chromosphere-Corona Transition Region from
Limb to Disk Intensity Ratios
Authors: Burton, W. M.; Jordan, C.; Ridgeley, A.; Wilson, R.
Bibcode: 1969cctr.conf...35B
Altcode:
No abstract at ADS
Title: Relative Intensities of Selected SI II Multiplets in the
Spectrum of the Sun and Zeta
Authors: Jordan, Carole
Bibcode: 1969ApJ...156...49J
Altcode:
The relative intensities of five multiplets of Siii are calculated
by assuming that the excited levels are populated only by collisional
excitation from the ground term; these are compared with the values ob-
served in the spectrum of the Sun and ZETA. The observed intensity
of the multiplet at 1195 A, relative to that at 1309 A, is an order
of magnitude weaker than calculated, while the observed intensity of
the multiplet at 1817 A, relative to that at 1309 A, is an order of
magnitude stronger than calculated. It is suggested that the great
strength of the latter multiplet is due to stepwise excitations via
the metastable 3s3p2 4F levels and that the collision strength for
the transition 3s3p2 4P312 ,b/2-3s3P2 2D512 is ~1 ~ 10. A complete
solution to these problems must await more accurate cross-sections
Title: Long Wavelength Satellites to the He-like Ion Resonance Lines
in the Laboratory and in the Sun
Authors: Gabriel, A. H.; Jordan, Carole
Bibcode: 1969Natur.221..947G
Altcode:
SATELLITE lines, situated on the long wavelength side of the
He-like resonance lines in laboratory plasmas, are classified here
as transitions in highly excited Li-like ions. We also show that
intense features in the solar X-ray spectrum, of similar appearance,
are of different origin, and these are classified as the forbidden
ls2 1S0-ls2s 3S1
line of the He-like ion.
Title: The ionization equilibrium of elements between carbon and
nickel
Authors: Jordan, Carole
Bibcode: 1969MNRAS.142..501J
Altcode:
The ionization equilibrium N(ion)/N(Element), for ions of elements
abundant in the Sun, has been calculated as a function of temperature
between Te io4 0K and 108 K. Two sets of results are given. The first
includes the processes of collisional ionization, collisional excitation
followed by auto-ionization, direct radiative recombination, radiative
recombination via bound levels, and dielectronic recombination, reduced
by a density dependent term. As the variation of the electron density
with electron temperature in the solar atmosphere enters into the
calculations these results are applicable only to the solar corona
and chromosphere. The second set includes collisional ionization,
collisional excitation followed by auto-ionization, direct radiative
recombination, and the full di-electronic recombination rate. These
results are applicable to any low density plasma where the radiation
field is negligible.
Title: Interpretation of solar helium-like ion line intensities
Authors: Gabriel, A. H.; Jordan, Carole
Bibcode: 1969MNRAS.145..241G
Altcode:
Recent identification of the line from helium-like ions in the
solar soft X-ray spectrum, followed by calculation of its transition
probability, enables an analysis of the observations to be carried
out, based on intensities of the three lines 21P I1S, I1S, and 23S
11S. The relative collision rates to the excited levels and the
electron densities in the emitting regions have been determined,
subject to the limitation of available observations. Densities of 3 x
io cm- are found from lines formed over the quiet corona, but values of
between I0 and 1011 cm-3 are found from lines emitted in active regions,
and the highest electron densities occur in the hottest regions.
Title: Spectroscopic Observations of Dielectronic Recombination in
Helium-Like Ions
Authors: Gabriel, A. H.; Jordan, C.; Paget, T. M.
Bibcode: 1969peac.conf..558G
Altcode:
No abstract at ADS
Title: The Relative Abundance of Silicon and Iron in the Solar Corona
Authors: Jordan, Carole; Pottasch, S. R.
Bibcode: 1968SoPh....4..104J
Altcode:
No abstract at ADS
Title: Solar Iron Lines at 182 Å
Authors: Fawcett, B. C.; Gabriel, A. H.; Jordan, C.
Bibcode: 1968ApJ...152L.119F
Altcode:
No abstract at ADS
Title: The Relative Intensities of CI Lines in the Solar EUV Spectrum
Authors: Jordan, Carole
Bibcode: 1967SoPh....2..441J
Altcode:
The relative intensity of two CI lines at 1993.6 Å and 1657.4
Å, observed in the limb spectrum of the sun, is a factor 2.6 ×
103 larger than that expected if both lines were optically
thin. It is shown that the observed intensity ratio may be explained in
terms of the transfer of photons from λ 1657.4 Å to λ 1993.6 Å due
to a large optical depth in the line at 1657.4 Å. The observed upper
limit on the relative intensity of two further lines at 1992.0 Å and
1657.0 Å has been used to show that the line at 1993.6 Å is optically
thin. Hence it is shown that τ(1657.4 Å) = 1300, and τ(1993.6 Å)
= 0.44. These values provide an independent evaluation of optical
depths against which chromospheric models may be checked. Assuming a
mean temperature of Te = 8000 °K, and a mean scale height
of 350 km, the optical depths lead to a mean hydrogen-particle density
of N (H) = 1.4 × 1012 cm−3.
Title: Temperature distribution in the solar corona
Authors: Jordan, C.
Bibcode: 1966AJ.....71..860J
Altcode:
No abstract at ADS
Title: The abundance of iron in the solar corona
Authors: Jordan, Carole
Bibcode: 1966MNRAS.132..515J
Altcode:
A comparison of the observed intensities of lines within Fe X, XI,
XIV and XV multiplets, in the far ultra-violet solar spectrum, enables
the population of the excited level of the ground term (N to be found,
relative to that of the ground level (Ng). This factor NuIN0 is needed
in the determination of the abundance from the equivalent widths
of forbidden emission lines in the near-visible spectrum. Hence,
it has been possible to calculate the abundance of iron in the solar
corona. The value obtained is log N(Fe)/N(H) = - . This is in accordance
with other corona] estimates, but is an order of magnitude greater than
the value from photospheric determinations. The values of NuiNg have
also been used in combination with theoretical excitation crosssections,
to calculate the electron density, Ne.
Title: The relative abundance of silicon iron and nickel in the
solar corona
Authors: Jordan, Carole
Bibcode: 1966MNRAS.132..463J
Altcode:
The method of analysis, developed by Pottasch, for the relative
abundance of elements represented in the far ultra-violet part of the
solar spectrum has been extended to include recently identified lines of
iron and nickel. The calculations of the ionization equilibrium included
the process of dielectronic recombination. The results indicate that the
abundance of iron relative to nickel is the same in the corona as in the
photosphere, but that the abundance of irdn relative to silicon is an
order of magnitude larger in the corona than in the photosphere. The
distribution of fR N02dh with temperature now indicates a general
coronal temperature of 1 4 X io6 0K and a decrease in the quantity of
coronal material for temperatures in excess of this value.
Title: Analysis of the solar ultraviolet spectrum
Authors: Jordan, Carole
Bibcode: 1965PhDT........42J
Altcode:
No abstract at ADS
Title: Selenological implications drawn from the distortions of
craters in the Hipparchus region of the Moon
Authors: Fielder, Gilbert; Jordan, Carole
Bibcode: 1962P&SS....9....3F
Altcode:
Measurements of craters in the Hipparchus region of the Moon are used
to show that the craters are distorted preferentially, their longer
axes most frequently lying parallel to the most prominent family of
the grid system. It is shown that the mean percentage distortions
generally increase with the age of a crater, and that the larger
craters are generally older than the smaller ones. Taken qualitatively,
the present results may be used to confirm the conclusions which were
reached earlier for the Vaporum region of the Moon; namely, that the
compressive stresses which produced the observed distortions acted for
a longer time on an old crater than on a young crater. The quantitative
differences between the two sets of results may be explained readily
in terms of the relative strengths of the two principal stress-systems
which produced the grid system in these parts of the Moon. These two
systems must have formed in the same era, rather than during separate
eras. Finally, the results are used to isolate the most recently
formed craters. The probability that these craters are distributed at
random is found to be 0.7, so that it is not unlikely that they are
of impact origin.