schmutz

explanation blue bibcodes open ADS page with paths to full text

Author name code: schmutz
ADS astronomy entries on 2022-09-14
author:"Schmutz, Werner"

---------------------------------------------------------
Title: Minima Epoches of BF Draconis Observed by the TESS Satellite
Authors: Schmutz, Werner
2022RNAAS...6..173S Altcode:
The epochs of 80 minima from 2019 to 2022 of the eclipsing binary BF
Dra have been measured from photometric fluxes obtained by the TESS
satellite with uncertainties of 3 s and 6 s for primary and secondary
minima, respectively. There is a clear negative linear trend of the
interval length between primary and secondary minima, which confirms
previous analyses that the system's orbit has an apsidal motion. It
is found that the periastron advances 1.43 ± 0.03 deg/century, i.e.,
the apsidal period is U = 25,200 ± 500 yr. These values agree with
previous estimates within the combined uncertainties but the present
uncertainties are lower by a factor of eight. It is also confirmed that
the residuals of the TESS-minima have a significant trend relative to
a mean long-term apsidal motion signature due to a systematic influence
of unknown origin.

---------------------------------------------------------
Title: Data Fusion of Total Solar Irradiance Composite Time Series
Using 41 Years of Satellite Measurements
Authors: Montillet, Jean-Philippe; Finsterle, Wolfgang; Kermarrec,
Gael; Sikonja, Rok; Haberreiter, Margit; Schmutz, Werner; Dudok de
Wit, Thierry
2022arXiv220704926M Altcode:
Since the late 1970s, successive satellite missions have been monitoring
the sun's activity and recording the total solar irradiance (TSI). Some
of these measurements have lasted for more than a decade. In order to
obtain a seamless record whose duration exceeds that of the individual
instruments, the time series have to be merged. Climate models can be
better validated using such long TSI time series which can also help
to provide stronger constraints on past climate reconstructions (e.g.,
back to the Maunder minimum). We propose a 3-step method based on data
fusion, including a stochastic noise model to take into account short
and long-term correlations. Compared with previous products scaled at
the nominal TSI value of 1361 W/m2, the difference is below 0.2 W/m2
in terms of solar minima. Next, we model the frequency spectrum of
this 41-year TSI composite time series with a Generalized Gauss-Markov
model to help describe an observed flattening at high frequencies. It
allows us to fit a linear trend into these TSI time series by joint
inversion with the stochastic noise model via a maximum-likelihood
estimator. Our results show that the amplitude of such trend is $\sim$
-0.004 +/- 0.004 W/(m2yr) for the period 1980 - 2021. These results
are compared with the difference of irradiance values estimated from
two consecutive solar minima. We conclude that the trend in these
composite time series is mostly an artifact due to the colored noise.

---------------------------------------------------------
Title: Solar Noise in 40-year long Total Solar Irradiance Composite
Time Series
Authors: Montillet, Jean-Philippe; Finsterle, Wolfgang; Kermarrec,
Gael; Sikonja, Rok; Haberreiter, Margit; Schmutz, Werner; Dudok de
Wit, Thierry
2021AGUFMSH45B2373M Altcode:
Since the late 70s, successive satellite missions have been monitoring
the suns activity, recording total solar irradiance observations. These
measurements provide estimates of the Earths energy imbalance,
i.e. the difference of energy absorbed and emitted by our planet. With
this amount of TSI data, solar irradiance reconstruction models can
be better validated which can also improve studies looking at past
climate reconstructions (e.g., Maunder minimum). Various algorithms have
been proposed to merge the various TSI measurements recorded over the
last 4 decades. We develop a 2-step algorithm based on data fusion,
including a stochastic noise model to take into account the short
and long-term correlations. We develop a wavelet filter in order to
eliminate specific correlations introduced by the data fusion. Comparing
with previous products,the mean value difference is below 0.1 W/m2and
the discrepancy with the solar minima is mostly below 0.05 W/m2. Next,
we model the frequency spectrum of this 40-year TSI composite time
series with a Generalized Gauss-Markov model(with white noise) due to
an observe flattening at high frequencies. It allows us to fit a linear
trend in these TSI time series by joint inversion with the stochastic
noise model via a maximum-likelihood estimator. Our results show that
the amplitude of such trend is 0.004±0.005 W/(m2.yr). We conclude
that the trend in these composite time series is mostly an artifact
due to the solar noise.

---------------------------------------------------------
Title: First observations from the SPICE EUV spectrometer on Solar
Orbiter
Authors: Fludra, A.; Caldwell, M.; Giunta, A.; Grundy, T.; Guest,
S.; Leeks, S.; Sidher, S.; Auchère, F.; Carlsson, M.; Hassler, D.;
Peter, H.; Aznar Cuadrado, R.; Buchlin, É.; Caminade, S.; DeForest,
C.; Fredvik, T.; Haberreiter, M.; Harra, L.; Janvier, M.; Kucera, T.;
Müller, D.; Parenti, S.; Schmutz, W.; Schühle, U.; Solanki, S. K.;
Teriaca, L.; Thompson, W. T.; Tustain, S.; Williams, D.; Young, P. R.;
Chitta, L. P.
2021A&A...656A..38F Altcode: 2021arXiv211011252F
 Aims: We present first science observations taken during the
commissioning activities of the Spectral Imaging of the Coronal
Environment (SPICE) instrument on the ESA/NASA Solar Orbiter
mission. SPICE is a high-resolution imaging spectrometer operating at
extreme ultraviolet (EUV) wavelengths. In this paper we illustrate
the possible types of observations to give prospective users a
better understanding of the science capabilities of SPICE. 
Methods: We have reviewed the data obtained by SPICE between April
and June 2020 and selected representative results obtained with
different slits and a range of exposure times between 5 s and 180
s. Standard instrumental corrections have been applied to the raw
data. Results: The paper discusses the first observations
of the Sun on different targets and presents an example of the full
spectra from the quiet Sun, identifying over 40 spectral lines from
neutral hydrogen and ions of carbon, oxygen, nitrogen, neon, sulphur,
magnesium, and iron. These lines cover the temperature range between
20 000 K and 1 million K (10 MK in flares), providing slices of the
Sun's atmosphere in narrow temperature intervals. We provide a list
of count rates for the 23 brightest spectral lines. We show examples
of raster images of the quiet Sun in several strong transition region
lines, where we have found unusually bright, compact structures in the
quiet Sun network, with extreme intensities up to 25 times greater
than the average intensity across the image. The lifetimes of these
structures can exceed 2.5 hours. We identify them as a transition
region signature of coronal bright points and compare their areas and
intensity enhancements. We also show the first above-limb measurements
with SPICE above the polar limb in C III, O VI, and Ne VIII lines, and
far off limb measurements in the equatorial plane in Mg IX, Ne VIII,
and O VI lines. We discuss the potential to use abundance diagnostics
methods to study the variability of the elemental composition that can
be compared with in situ measurements to help confirm the magnetic
connection between the spacecraft location and the Sun's surface,
and locate the sources of the solar wind. Conclusions: The
SPICE instrument successfully performs measurements of EUV spectra
and raster images that will make vital contributions to the scientific
success of the Solar Orbiter mission.

---------------------------------------------------------
Title: A journey of exploration to the polar regions of a star:
probing the solar poles and the heliosphere from high helio-latitude
Authors: Harra, Louise; Andretta, Vincenzo; Appourchaux, Thierry;
Baudin, Frédéric; Bellot-Rubio, Luis; Birch, Aaron C.; Boumier,
Patrick; Cameron, Robert H.; Carlsson, Matts; Corbard, Thierry;
Davies, Jackie; Fazakerley, Andrew; Fineschi, Silvano; Finsterle,
Wolfgang; Gizon, Laurent; Harrison, Richard; Hassler, Donald M.;
Leibacher, John; Liewer, Paulett; Macdonald, Malcolm; Maksimovic,
Milan; Murphy, Neil; Naletto, Giampiero; Nigro, Giuseppina; Owen,
Christopher; Martínez-Pillet, Valentín; Rochus, Pierre; Romoli,
Marco; Sekii, Takashi; Spadaro, Daniele; Veronig, Astrid; Schmutz, W.
2021ExA...tmp...93H Altcode: 2021arXiv210410876H
A mission to view the solar poles from high helio-latitudes (above 60°)
will build on the experience of Solar Orbiter as well as a long heritage
of successful solar missions and instrumentation (e.g. SOHO Domingo et
al. (Solar Phys. 162(1-2), 1-37 1995), STEREO Howard et al. (Space
Sci. Rev. 136(1-4), 67-115 2008), Hinode Kosugi et al. (Solar
Phys. 243(1), 3-17 2007), Pesnell et al. Solar Phys. 275(1-2),
3-15 2012), but will focus for the first time on the solar poles,
enabling scientific investigations that cannot be done by any other
mission. One of the major mysteries of the Sun is the solar cycle. The
activity cycle of the Sun drives the structure and behaviour of the
heliosphere and of course, the driver of space weather. In addition,
solar activity and variability provides fluctuating input into the
Earth climate models, and these same physical processes are applicable
to stellar systems hosting exoplanets. One of the main obstructions
to understanding the solar cycle, and hence all solar activity,
is our current lack of understanding of the polar regions. In this
White Paper, submitted to the European Space Agency in response to the
Voyage 2050 call, we describe a mission concept that aims to address
this fundamental issue. In parallel, we recognise that viewing the Sun
from above the polar regions enables further scientific advantages,
beyond those related to the solar cycle, such as unique and powerful
studies of coronal mass ejection processes, from a global perspective,
and studies of coronal structure and activity in polar regions. Not
only will these provide important scientific advances for fundamental
stellar physics research, they will feed into our understanding of
impacts on the Earth and other planets' space environment.

---------------------------------------------------------
Title: XMM-Newton X-Ray Observations of the Unusual Wolf-Rayet Star
WR 66
Authors: Skinner, Stephen L.; Schmutz, Werner; Güdel, Manuel; Zhekov,
Svetozar A.
2021RNAAS...5..125S Altcode:
We summarize results of an XMM-Newton X-ray observation of the
WN8h-type Wolf-Rayet star WR 66 which shows unusual 3.5-4.1 hr optical
variations. One possible explanation is a compact companion (cc) which,
if present, could give rise to luminous X-ray emission. WR 66 was
marginally detected and its inferred X-ray luminosity (Lx)
is orders of magnitude below that expected from wind accretion onto
a neutron star, but is comparable to that of the WN8h stars WR 16 and
WR 124. If luminous X-ray emission from an accreting WR+cc system is
present then it is absorbed and escapes detection. Other explanations
of the faintly detected X-ray emission of WN8h stars are not ruled out.

---------------------------------------------------------
Title: Data Fusion of Total Solar Irradiance Composite Time Series
Using 40 years of Satellite Measurements: First Results
Authors: Montillet, Jean-Philippe; Finsterle, Wolfgang; Schmutz,
Werner; Haberreiter, Margit; Sikonja, Rok
2021EGUGA..23.4382M Altcode:
Since the late 70"s, successive satellite missions have been
monitoring the sun"s activity, recording total solar irradiance
observations. These measurements are important to estimate the Earth"s
energy imbalance, i.e. the difference of energy absorbed and emitted
by our planet. Climate modelers need the solar forcing time series in
their models in order to study the influence of the Sun on the Earth"s
climate. With this amount of TSI data, solar irradiance reconstruction
models can be better validated which can also improve studies looking
at past climate reconstructions (e.g., Maunder minimum). Various
algorithms have been proposed in the last decade to merge the
various TSI measurements over the 40 years of recording period. We
have developed a new statistical algorithm based on data fusion. The
stochastic noise processes of the measurements are modeled via a dual
kernel including white and coloured noise. We show our first results
and compare it with previous releases (PMOD,ACRIM, ... ).

---------------------------------------------------------
Title: Changes in the Total Solar Irradiance and climatic effects
Authors: Schmutz, Werner K.
2021JSWSC..11...40S Altcode:
The correlation between the averaged reconstructed March temperature
record for Kyoto, Japan, and the reconstructed Total Solar Irradiance
(TSI) over 660 years from 1230 to 1890 gives evidence with 98%
probability that the Little Ice Age with four cold periods is forced
by variations of TSI. If the correlation is restricted to the period
1650-1890, with two cold periods in the 17th and 19th century and
for which two independent reconstructed March temperature records are
available, the probability of solar forcing increases to 99.99%. As
solar irradiance variations have a global effect there has to be a
global climatic solar forcing impact. However, by how much global
temperature were lower during these minima and with what amplitude
TSI was varying is not accurately known. The two quantities, global
temperature and TSI, are linked by the energy equilibrium equation for
the Earth system. The derivation of this equation with respect to a
variation of the solar irradiance has two terms: A direct forcing term,
which can be derived analytically and quantified accurately from the
Stefan-Boltzmann law, and a second term, describing indirect influences
on the surface temperature. If a small TSI variation should force a
large temperature variation, then it has to be the second indirect
term that strongly amplifies the effect of the direct forcing. The
current knowledge is summarized by three statements:&lt;list
list-type="dash"&gt;&lt;list-item&gt;During the minima periods in the
13th, 15/16th, 17th, and 19th centuries the terrestrial climate was
colder by 0.5-1.5 °C; &lt;/list-item&gt;&lt;list-item&gt;Indirect
Top-down and Bottom-up mechanisms do not amplify direct forcing by a
large amount, i.e. indirect solar forcing is of the same magnitude (or
smaller) as direct solar forcing; &lt;/list-item&gt;&lt;list-item&gt;The
radiative output of the Sun cannot be lower by more than 2
Wm−2 below the measured present-day TSI value during
solar cycle minimum. &lt;/list-item&gt;&lt;/list&gt;These three
statements contradict each other and it is concluded that at least one
is not correct. Which one is a wrong statement is presently not known
conclusively. It is argued that it is the third statement and it is
speculated that over centennial time scales the Sun might vary its
radiance significantly more than observed so far during the last 40
years of space TSI measurements. To produce Maunder minimum type cold
climate excursions, a TSI decrease of the order of 10 Wm−2
is advocated.

---------------------------------------------------------
Title: Relative coronal abundance diagnostics with Solar Orbiter/SPICE
Authors: Zambrana Prado, N.; Buchlin, E.; Peter, H.; Young, P. R.;
Auchere, F.; Carlsson, M.; Fludra, A.; Hassler, D.; Aznar Cuadrado,
R.; Caminade, S.; Caldwell, M.; DeForest, C.; Fredvik, T.; Harra,
L.; Janvier, M.; Kucera, T. A.; Giunta, A. S.; Grundy, T.; Müller,
D.; Parenti, S.; Schmutz, W. K.; Schühle, U.; Sidher, S.; Teriaca,
L.; Thompson, W. T.; Williams, D.
2020AGUFMSH038..09Z Altcode:
Linking solar activity on the surface and in the corona to the inner
heliosphere is one of Solar Orbiter's main goals. Its UV spectrometer
SPICE (SPectral Imaging of the Coronal Environment) will provide
relative abundance measurements which will be key in this quest
as different structures on the Sun have different abundances as a
consequence of the FIP (First Ionization Potential) effect. Solar
Orbiter's unique combination of remote sensing and in-situ instruments
coupled with observation from other missions such as Parker Solar
Probe will allow us to compare in-situ and remote sensing composition
data. With the addition of modeling, these new results will allow us
to trace back the source of heliospheric plasma. As high telemetry
will not always be available with SPICE, we have developed a method
for measuring relative abundances that is both telemetry efficient
and reliable. Unlike methods based on Differential Emission Measure
(DEM) inversion, the Linear Combination Ratio (LCR) method does not
require a large number of spectral lines. This new method is based
on linear combinations of UV spectral lines. The coefficients of
the combinations are optimized such that the ratio of two linear
combinations of radiances would yield the relative abundance of two
elements. We present some abundance diagnostics tested on different
combinations of spectral lines observable by SPICE.

---------------------------------------------------------
Title: Dynamics and thermal structure in the quiet Sun seen by SPICE
Authors: Peter, H.; Aznar Cuadrado, R.; Schühle, U.; Teriaca, L.;
Auchere, F.; Carlsson, M.; Fludra, A.; Hassler, D.; Buchlin, E.;
Caminade, S.; Caldwell, M.; DeForest, C.; Fredvik, T.; Harra, L. K.;
Janvier, M.; Kucera, T. A.; Giunta, A. S.; Grundy, T.; Müller, D.;
Parenti, S.; Schmutz, W. K.; Sidher, S.; Thompson, W. T.; Williams,
D.; Young, P. R.
2020AGUFMSH038..03P Altcode:
We will present some of the early data of the Spectral Imaging of the
Coronal Environment (SPICE) instrument on Solar Orbiter. One of the
unique features of SPICE is its capability to record a wide range of
wavelengths in the extreme UV with the possibility to record spectral
lines giving access to a continuous plasma temperature range from 10.000
K to well above 1 MK. The data taken so far were for commissioning
purposes and they can be used for a preliminary evaluation of the
science performance of the instrument. Here we will concentrate on
sample spectra covering the whole wavelength region and on the early
raster maps acquired in bright lines in the quiet Sun close to disk
center. Looking at different quiet Sun features we investigate the
thermal structure of the atmosphere and flow structures. For this
we apply fits to the spectral profiles and check the performance in
terms of Doppler shifts and line widths to retrieve the structure of
the network in terms of dynamics. While the amount of data available
so far is limited, we will have a first look on how quiet Sun plasma
responds to heating events. For this, we will compare spectral lines
forming at different temperatures recorded at strictly the same time.

---------------------------------------------------------
Title: First Results From SPICE EUV Spectrometer on Solar Orbiter
Authors: Fludra, A.; Caldwell, M.; Giunta, A. S.; Grundy, T.; Guest,
S.; Sidher, S.; Auchere, F.; Carlsson, M.; Hassler, D.; Peter, H.;
Aznar Cuadrado, R.; Buchlin, E.; Caminade, S.; DeForest, C.; Fredvik,
T.; Harra, L. K.; Janvier, M.; Kucera, T. A.; Leeks, S.; Mueller,
D.; Parenti, S.; Schmutz, W. K.; Schühle, U.; Teriaca, L.; Thompson,
W. T.; Tustain, S.; Williams, D.; Young, P. R.
2020AGUFMSH038..02F Altcode:
SPICE (Spectral Imaging of Coronal Environment) is one of the remote
sensing instruments onboard Solar Orbiter. It is an EUV imaging
spectrometer observing the Sun in two wavelength bands: 69.6-79.4 nm
and 96.6-105.1 nm. SPICE is capable of recording full spectra in these
bands with exposures as short as 1s. SPICE is the only Solar Orbiter
instrument that can measure EUV spectra from the disk and low corona
of the Sun and record all spectral lines simultaneously. SPICE uses
one of three narrow slits, 2"x11', 4”x11', 6”x11', or a wide slit
30”x14'. The primary mirror can be scanned in a direction perpendicular
to the slit, allowing raster images of up to 16' in size. We
present an overview of the first SPICE data taken on several days
during the instrument commissioning carried out by the RAL Space team
between 2020 April 21 and 2020 June 14. We also include results from
SPICE observations at the first Solar Orbiter perihelion at 0.52AU,
taken between June 16-21st. We give examples of full spectra
from the quiet Sun near disk centre and provide a list of key spectral
lines emitted in a range of temperatures between 10,000 K and over 1
million K, from neutral hydrogen and ions of carbon, oxygen, nitrogen,
neon, sulphur and magnesium. We show examples of first raster images
in several strong lines, obtained with different slits and a range
of exposure times between 5s and 180s. We describe the temperature
coverage and density diagnostics, determination of plasma flows, and
discuss possible applications to studies of the elemental abundances
in the corona. We also show the first off-limb measurements with SPICE,
as obtained when the spacecraft pointed at the limb.

---------------------------------------------------------
Title: A New Methodology to Process the Total Solar Irradiance
observations Using Machine Learning and Data Fusion
Authors: Montillet, J. P.; Finsterle, W.; Schmutz, W. K.
2020AGUFMA237...06M Altcode:
Across the last decades, various space missions have measured the
total solar irradiance (TSI) such as the Variability of Irradiance and
Gravity Oscillations (VIRGO) experiment on the Solar and Heliospheric
Observatory (SOHO) starting in 1996. Since the beginning of its
recording time, one challenge is to correct the measurements from the
degradation of the TSI sensors in space. Various groups have proposed
different methodologies to produce a continuous TSI time series (TSI
composite) which is essential to monitor the sun activity and its
influence on the Earth's climate. However, the benchmark to test
all those solutions is source of a debate in the community. Moreover,
the input data for the TSI composite are the degradation-corrected
measurements provided by each individual instrument team. Here, we
propose a different approach using a machine learning and data fusion
algorithm to produce automatically the degradation-corrected TSI time
series based on a small number of generic assumptions. The algorithm
is applied to the VIRGO/PMO6, VIRGO/DIARAD and PREMOS/PMO6 data. The
time series agree between each other in terms of mean value with a
difference of ~ 0.14 W/m2 (PREMOS), ~ 0.23 W/m2 (VIRGO) and ~ -0.18 W/m2
(DIARAD). Finally, taking a conservative value of 0.3 W/m2 between our
different TSI products, induces a variation of the global mean surface
temperature of ~ 0.02 K based on global climate simulations, which is
within the uncertainties of simulated global mean surface temperatures,
hence not impacting significantly any climate forcing scenarios.

---------------------------------------------------------
Title: Calibrating optical distortions in the Solar Orbiter SPICE
spectrograph
Authors: Thompson, W. T.; Schühle, U.; Young, P. R.; Auchere, F.;
Carlsson, M.; Fludra, A.; Hassler, D.; Peter, H.; Aznar Cuadrado, R.;
Buchlin, E.; Caldwell, M.; DeForest, C.; Fredvik, T.; Harra, L. K.;
Janvier, M.; Kucera, T. A.; Giunta, A. S.; Grundy, T.; Müller, D.;
Parenti, S.; Caminade, S.; Schmutz, W. K.; Teriaca, L.; Williams,
D.; Sidher, S.
2020AGUFMSH0360029T Altcode:
The Spectral Imaging of the Coronal Environment (SPICE) instrument on
Solar Orbiter is a high-resolution imaging spectrometer operating
at extreme ultraviolet (EUV) wavelengths from 70.4-79.0 nm and
97.3-104.9 nm. A single-mirror off-axis paraboloid focuses the solar
image onto the entrance slit of the spectrometer section. A Toroidal
Variable Line Space (TVLS) grating images the entrance slit onto a
pair of MCP-intensified APS detectors. Ray-tracing analysis prior
to launch showed that the instrument was subject to a number of
small image distortions which need to be corrected in the final data
product. We compare the ray tracing results with measurements made in
flight. Co-alignment with other telescopes on Solar Orbiter will also
be examined.

---------------------------------------------------------
Title: First results from the EUI and SPICE observations of Alpha
Leo near Solar Orbiter first perihelion
Authors: Buchlin, E.; Teriaca, L.; Giunta, A. S.; Grundy, T.; Andretta,
V.; Auchere, F.; Peter, H.; Berghmans, D.; Carlsson, M.; Fludra, A.;
Harra, L.; Hassler, D.; Long, D.; Rochus, P. L.; Schühle, U.; Aznar
Cuadrado, R.; Caldwell, M.; Caminade, S.; DeForest, C.; Fredvik, T.;
Gissot, S.; Heerlein, K.; Janvier, M.; Kraaikamp, E.; Kucera, T. A.;
Müller, D.; Parenti, S.; Schmutz, W. K.; Sidher, S.; Smith, P.;
Stegen, K.; Thompson, W. T.; Verbeeck, C.; Williams, D.; Young, P. R.
2020AGUFMSH0360024B Altcode:
On June 16th 2020 Solar Orbiter made a dedicated observing campaign
where the spacecraft pointed to the solar limb to allow some of the
high resolution instruments to observe the ingress (at the east limb)
and later the egress (west limb) of the occultation of the star Alpha
Leonis by the solar disk. The star was chosen because its luminosity and
early spectral type ensure high and stable flux at wavelengths between
100 and 122 nanometers, a range observed by the High Resolution EUI
Lyman alpha telescope (HRI-LYA) and by the long wavelength channel
of the SPICE spectrograph. Star observations, when feasible, allow
to gather a great deal of information on the instrument performances,
such as the radiometric performance and the instrument optical point
spread function (PSF). We report here the first results from the
above campaign for the two instruments.

---------------------------------------------------------
Title: First results from combined EUI and SPICE observations of
Lyman lines of Hydrogen and He II
Authors: Teriaca, L.; Aznar Cuadrado, R.; Giunta, A. S.; Grundy, T.;
Parenti, S.; Auchere, F.; Vial, J. C.; Fludra, A.; Berghmans, D.;
Carlsson, M.; Harra, L.; Hassler, D.; Long, D.; Peter, H.; Rochus,
P. L.; Schühle, U.; Buchlin, E.; Caldwell, M.; Caminade, S.; DeForest,
C.; Fredvik, T.; Gissot, S.; Heerlein, K.; Janvier, M.; Kraaikamp,
E.; Kucera, T. A.; Mueller, D.; Schmutz, W. K.; Sidher, S.; Smith, P.;
Stegen, K.; Thompson, W. T.; Verbeeck, C.; Williams, D.; Young, P. R.
2020AGUFMSH0360003T Altcode:
The Solar Orbiter spacecraft carries a powerful set of remote
sensing instruments that allow studying the solar atmosphere with
unprecedented diagnostic capabilities. Many such diagnostics require
the simultaneous usage of more than one instrument. One example of that
is the capability, for the first time, to obtain (near) simultaneous
spatially resolved observations of the emission from the first three
lines of the Lyman series of hydrogen and of He II Lyman alpha. In fact,
the SPectral Imaging of the Coronal Environment (SPICE) spectrometer
can observe the Lyman beta and gamma lines in its long wavelength
(SPICE-LW) channel, the High Resolution Lyman Alpha (HRI-LYA) telescope
of the Extreme Ultraviolet Imager (EUI) acquires narrow band images in
the Lyman alpha line while the Full Disk Imager (FSI) of EUI can take
images dominated by the Lyman alpha line of ionized Helium at 30.4 nm
(FSI-304). Being hydrogen and helium the main components of our star,
these very bright transitions play an important role in the energy
budget of the outer atmosphere via radiative losses and the measurement
of their profiles and radiance ratios is a fundamental constraint to
any comprehensive modelization effort of the upper solar chromosphere
and transition region. Additionally, monitoring their average ratios
can serve as a check out for the relative radiometric performance of
the two instruments throughout the mission. Although the engineering
data acquired so far are far from ideal in terms of time simultaneity
(often only within about 1 h) and line coverage (often only Lyman beta
was acquired by SPICE and not always near simultaneous images from all
three telescopes are available) the analysis we present here still
offers a great opportunity to have a first look at the potential of
this diagnostic from the two instruments. In fact, we have identified
a series of datasets obtained at disk center and at various positions
at the solar limb that allow studying the Lyman alpha to beta radiance
ratio and their relation to He II 30.4 as a function of the position
on the Sun (disk center versus limb and quiet Sun versus coronal holes).

---------------------------------------------------------
Title: The Solar Orbiter SPICE instrument. An extreme UV imaging
spectrometer
Authors: SPICE Consortium; Anderson, M.; Appourchaux, T.; Auchère, F.;
Aznar Cuadrado, R.; Barbay, J.; Baudin, F.; Beardsley, S.; Bocchialini,
K.; Borgo, B.; Bruzzi, D.; Buchlin, E.; Burton, G.; Büchel, V.;
Caldwell, M.; Caminade, S.; Carlsson, M.; Curdt, W.; Davenne, J.;
Davila, J.; Deforest, C. E.; Del Zanna, G.; Drummond, D.; Dubau,
J.; Dumesnil, C.; Dunn, G.; Eccleston, P.; Fludra, A.; Fredvik, T.;
Gabriel, A.; Giunta, A.; Gottwald, A.; Griffin, D.; Grundy, T.; Guest,
S.; Gyo, M.; Haberreiter, M.; Hansteen, V.; Harrison, R.; Hassler,
D. M.; Haugan, S. V. H.; Howe, C.; Janvier, M.; Klein, R.; Koller,
S.; Kucera, T. A.; Kouliche, D.; Marsch, E.; Marshall, A.; Marshall,
G.; Matthews, S. A.; McQuirk, C.; Meining, S.; Mercier, C.; Morris,
N.; Morse, T.; Munro, G.; Parenti, S.; Pastor-Santos, C.; Peter, H.;
Pfiffner, D.; Phelan, P.; Philippon, A.; Richards, A.; Rogers, K.;
Sawyer, C.; Schlatter, P.; Schmutz, W.; Schühle, U.; Shaughnessy,
B.; Sidher, S.; Solanki, S. K.; Speight, R.; Spescha, M.; Szwec, N.;
Tamiatto, C.; Teriaca, L.; Thompson, W.; Tosh, I.; Tustain, S.; Vial,
J. -C.; Walls, B.; Waltham, N.; Wimmer-Schweingruber, R.; Woodward,
S.; Young, P.; de Groof, A.; Pacros, A.; Williams, D.; Müller, D.
2020A&A...642A..14S Altcode: 2019arXiv190901183A; 2019arXiv190901183S
 Aims: The Spectral Imaging of the Coronal Environment (SPICE)
instrument is a high-resolution imaging spectrometer operating at
extreme ultraviolet wavelengths. In this paper, we present the concept,
design, and pre-launch performance of this facility instrument on the
ESA/NASA Solar Orbiter mission. Methods: The goal of this paper
is to give prospective users a better understanding of the possible
types of observations, the data acquisition, and the sources that
contribute to the instrument's signal. Results: The paper
discusses the science objectives, with a focus on the SPICE-specific
aspects, before presenting the instrument's design, including optical,
mechanical, thermal, and electronics aspects. This is followed by a
characterisation and calibration of the instrument's performance. The
paper concludes with descriptions of the operations concept and data
processing. Conclusions: The performance measurements of the
various instrument parameters meet the requirements derived from the
mission's science objectives. The SPICE instrument is ready to perform
measurements that will provide vital contributions to the scientific
success of the Solar Orbiter mission.

---------------------------------------------------------
Title: The Solar Orbiter EUI instrument: The Extreme Ultraviolet
Imager
Authors: Rochus, P.; Auchère, F.; Berghmans, D.; Harra, L.; Schmutz,
W.; Schühle, U.; Addison, P.; Appourchaux, T.; Aznar Cuadrado,
R.; Baker, D.; Barbay, J.; Bates, D.; BenMoussa, A.; Bergmann, M.;
Beurthe, C.; Borgo, B.; Bonte, K.; Bouzit, M.; Bradley, L.; Büchel,
V.; Buchlin, E.; Büchner, J.; Cabé, F.; Cadiergues, L.; Chaigneau,
M.; Chares, B.; Choque Cortez, C.; Coker, P.; Condamin, M.; Coumar,
S.; Curdt, W.; Cutler, J.; Davies, D.; Davison, G.; Defise, J. -M.;
Del Zanna, G.; Delmotte, F.; Delouille, V.; Dolla, L.; Dumesnil, C.;
Dürig, F.; Enge, R.; François, S.; Fourmond, J. -J.; Gillis, J. -M.;
Giordanengo, B.; Gissot, S.; Green, L. M.; Guerreiro, N.; Guilbaud,
A.; Gyo, M.; Haberreiter, M.; Hafiz, A.; Hailey, M.; Halain, J. -P.;
Hansotte, J.; Hecquet, C.; Heerlein, K.; Hellin, M. -L.; Hemsley, S.;
Hermans, A.; Hervier, V.; Hochedez, J. -F.; Houbrechts, Y.; Ihsan,
K.; Jacques, L.; Jérôme, A.; Jones, J.; Kahle, M.; Kennedy, T.;
Klaproth, M.; Kolleck, M.; Koller, S.; Kotsialos, E.; Kraaikamp, E.;
Langer, P.; Lawrenson, A.; Le Clech', J. -C.; Lenaerts, C.; Liebecq,
S.; Linder, D.; Long, D. M.; Mampaey, B.; Markiewicz-Innes, D.;
Marquet, B.; Marsch, E.; Matthews, S.; Mazy, E.; Mazzoli, A.; Meining,
S.; Meltchakov, E.; Mercier, R.; Meyer, S.; Monecke, M.; Monfort,
F.; Morinaud, G.; Moron, F.; Mountney, L.; Müller, R.; Nicula, B.;
Parenti, S.; Peter, H.; Pfiffner, D.; Philippon, A.; Phillips, I.;
Plesseria, J. -Y.; Pylyser, E.; Rabecki, F.; Ravet-Krill, M. -F.;
Rebellato, J.; Renotte, E.; Rodriguez, L.; Roose, S.; Rosin, J.;
Rossi, L.; Roth, P.; Rouesnel, F.; Roulliay, M.; Rousseau, A.; Ruane,
K.; Scanlan, J.; Schlatter, P.; Seaton, D. B.; Silliman, K.; Smit,
S.; Smith, P. J.; Solanki, S. K.; Spescha, M.; Spencer, A.; Stegen,
K.; Stockman, Y.; Szwec, N.; Tamiatto, C.; Tandy, J.; Teriaca, L.;
Theobald, C.; Tychon, I.; van Driel-Gesztelyi, L.; Verbeeck, C.;
Vial, J. -C.; Werner, S.; West, M. J.; Westwood, D.; Wiegelmann, T.;
Willis, G.; Winter, B.; Zerr, A.; Zhang, X.; Zhukov, A. N.
2020A&A...642A...8R Altcode:
Context. The Extreme Ultraviolet Imager (EUI) is part of the remote
sensing instrument package of the ESA/NASA Solar Orbiter mission
that will explore the inner heliosphere and observe the Sun from
vantage points close to the Sun and out of the ecliptic. Solar Orbiter
will advance the "connection science" between solar activity and the
heliosphere. Aims: With EUI we aim to improve our understanding
of the structure and dynamics of the solar atmosphere, globally as well
as at high resolution, and from high solar latitude perspectives. 
Methods: The EUI consists of three telescopes, the Full Sun Imager and
two High Resolution Imagers, which are optimised to image in Lyman-α
and EUV (17.4 nm, 30.4 nm) to provide a coverage from chromosphere
up to corona. The EUI is designed to cope with the strong constraints
imposed by the Solar Orbiter mission characteristics. Limited telemetry
availability is compensated by state-of-the-art image compression,
onboard image processing, and event selection. The imposed power
limitations and potentially harsh radiation environment necessitate
the use of novel CMOS sensors. As the unobstructed field of view of
the telescopes needs to protrude through the spacecraft's heat shield,
the apertures have been kept as small as possible, without compromising
optical performance. This led to a systematic effort to optimise the
throughput of every optical element and the reduction of noise levels
in the sensor. Results: In this paper we review the design
of the two elements of the EUI instrument: the Optical Bench System
and the Common Electronic Box. Particular attention is also given to
the onboard software, the intended operations, the ground software,
and the foreseen data products. Conclusions: The EUI will
bring unique science opportunities thanks to its specific design,
its viewpoint, and to the planned synergies with the other Solar
Orbiter instruments. In particular, we highlight science opportunities
brought by the out-of-ecliptic vantage point of the solar poles,
the high-resolution imaging of the high chromosphere and corona,
and the connection to the outer corona as observed by coronagraphs.

---------------------------------------------------------
Title: The nature of the companion in the Wolf-Rayet system EZ
Canis Majoris
Authors: Koenigsberger, G.; Schmutz, W.
2020A&A...639A..18K Altcode: 2020arXiv200506028K
Context. EZ Canis Majoris is a classical Wolf-Rayet star whose binary
nature has been debated for decades. It was recently modeled as an
eccentric binary with a periodic brightening at periastron of the
emission originating in a shock heated zone near the companion. 
Aims: The focus of this paper is to further test the binary model and
to constrain the nature of the unseen close companion by searching
for emission arising in the shock-heated region. Methods: We
analyze over 400 high resolution International Ultraviolet Explorer
spectra obtained between 1983 and 1995 and XMM-Newton observations
obtained in 2010. The light curve and radial velocity (RV) variations
were fit with the eccentric binary model and the orbital elements
were constrained. Results: We find RV variations in the
primary emission lines with a semi-amplitude K1 ∼ 30 km
s-1 in 1992 and 1995, and a second set of emissions with an
anti-phase RV curve with K2 ∼ 150 km s-1. The
simultaneous model fit to the RVs and the light curve yields the orbital
elements for each epoch. Adopting a Wolf-Rayet mass M1 ∼ 20
M⊙ leads to M2 ∼ 3-5 M⊙, which
implies that the companion could be a late B-type star. The eccentric
(e = 0.1) binary model also explains the hard X-ray light curve obtained
by XMM-Newton and the fit to these data indicates that the duration
of maximum is shorter than the typical exposure times. Conclusions:
The anti-phase RV variations of two emission components and the
simultaneous fit to the RVs and the light curve are concrete evidence
in favor of the binary nature of EZ Canis Majoris. The assumption that
the emission from the shock-heated region closely traces the orbit
of the companion is less certain, although it is feasible because
the companion is significantly heated by the WR radiation field and
impacted by the WR wind.

---------------------------------------------------------
Title: First TSI results and status report of the CLARA/NorSat-1
solar absolute radiometer
Authors: Walter, Benjamin; Andersen, Bo; Beattie, Alexander; Finsterle,
Wolfgang; Kopp, Greg; Pfiffner, Daniel; Schmutz, Werner
2020IAUGA..30..358W Altcode:
The Compact Lightweight Absolute Radiometer (CLARA) is orbiting Earth
on-board the Norwegian NorSat-1 micro-satellite since 14th
of July 2017. The first light total solar irradiance (TSI) measurement
result of CLARA is 1360.18 W m-2 for the so far single
reliable Channel B. Channel A and C measured significantly lower
(higher) TSI values and were found being sensitive to satellite pointing
instabilities. These channels most likely suffer from electrical
interference between satellite components and CLARA, an effect that
is currently under investigation. Problems with the satellite attitude
control currently inhibit stable pointing of CLARA to the Sun.

---------------------------------------------------------
Title: Solar disk radius measured by Solar occultation by the Moon
using bolometric and photometric instruments on board the PICARD
satellite
Authors: Thuillier, G.; Zhu, P.; Shapiro, A. I.; Sofia, S.; Tagirov,
R.; van Ruymbeke, M.; Perrin, J. -M.; Sukhodolov, T.; Schmutz, W.
2020IAUGA..30..361T Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Solar Orbiter EUI instrument: The Extreme Ultraviolet
Imager
Authors: Rochus, P. L.; Auchere, F.; Berghmans, D.; Harra, L.; Schmutz,
W. K.; Schühle, U.
2019AGUFMSH21D3291R Altcode:
The Extreme Ultraviolet Imager (EUI) is part of the remote sensing
instrument package of the ESA/NASA Solar Orbiter mission that will
explore the inner heliosphere and observe the Sun from vantage points
close to the Sun and out-of-the-ecliptic. EUI aims at improving our
understanding of the structure and dynamics of the solar atmosphere. EUI
will take images of the solar atmosphere, globally as well as at high
resolution, and from high solar latitude perspectives. EUI consists
of 3 telescopes that are optimized to image in Lyman-a and EUV 17.4nm
and 30.4 nm to provide a coverage from chromosphere up to corona. EUI
is designed to cope with the strong constraints that Solar Orbiter has
as a deep space mission. Limited telemetry availability is compensated
by state-of-the-art image compression, on board image processing and
event selection. The imposed power limitations and potentially harsh
radiation environment lead to the usage of novel CMOS sensors. As
the unobstructed field of view of the telescopes needs to protrude
through the spacecraft heat shield, the apertures were kept as small as
possible. This lead to a systematic effort to optimize the throughput
of every optical element and the reduction of noise levels in the
sensor. In this paper we review the design of the two elements of
the EUI instrument: the Optical Bench System and the Common Electronic
Box. Particular attention is also given to the on board software,
the intended operations, the ground software and the foreseen data
products. EUI will bring unique science opportunities thanks to its
specific design, its viewpoint and thanks to the planned synergies with
the other Solar Orbiter instruments. We highlight in particular science
opportunities brought by the out-of-ecliptic vantage point of the solar
poles, the high resolution imaging of the high chromosphere and corona,
and the connection to the outer corona as observed by coronagraphs.

---------------------------------------------------------
Title: Long uninterrupted photometric observations of the Wolf-Rayet
star EZ CMa by the Toronto BRITE satellite reveal a very fast
apsidal motion
Authors: Schmutz, W.; Koenigsberger, G.
2019A&A...624L...3S Altcode: 2019arXiv190309501S
Context. The variability of the Wolf-Rayet star EZ CMa has been
documented for close to half a century, and a clear periodicity of
∼3.7 days is established. However, all attempts to prove that it
is a binary have failed because the photometric, spectroscopic, and
polarimetric variations are not coherent over more than a few orbital
cycles. Aims: In this Letter we show that the lack of coherence
in the variability can be explained with a very rapid apsidal motion
in a binary orbit. Methods: We measured the times of minima
in a recently published exceptionally long photometric light curve
obtained by the Toronto BRITE satellite. The apsidal motion and the
system eccentricity are determined from the length of the time intervals
between these minima, which alternate in their duration, following a
pattern that is clearly associated with apsidal motion. These minima are
superposed on brightness enhancements of the emission from a shock zone,
which occur at about the times of periastron phases. Results:
We determine the orbital periodicity, Pa = 3.63 d, and the
period of the apsidal motion, U ≃ 100 d, which together yield an
average sidereal period of Ps = 3.77 d. The eccentricity
is found to be close to 0.1. The rate of periapsis retreat changes
significantly over the period of observation and is determined to be
-16° P-1a at the beginning of the observing
period and -10° P-1a at the end. 
Conclusions: We demonstrate that by introducing a fast apsidal motion,
the basic photometric variability is very well explained. The binary
nature of EZ CMa is now established. This might imply that other
apparently single Wolf-Rayet stars that emit hard X-rays, similar to
EZ CMa, are also binaries.

---------------------------------------------------------
Title: High energy processes in Wolf-Rayet stars
Authors: Skinner, S. L.; Schmutz, W.; Güdel, M.; Zhekov, S.
2019AN....340...50S Altcode: 2018arXiv181203954S
Wolf-Rayet (WR) stars are massive (≥10 M⊙) evolved stars
undergoing advanced nuclear burning in their cores, rapidly approaching
the end of their lives as supernovae. Their powerful winds enrich the
interstellar medium with heavy elements, providing raw material for
future generations of stars. We briefly summarize high-energy processes
in WR stars, focusing mainly on their X-ray emission. We present new
results from Chandra observations of the eclipsing WR + O binary CQ
Cep covering a full orbit which stringently test X-ray emission models.

---------------------------------------------------------
Title: The EUI instrument onboard Solar Orbiter: the EUV corona
imaged differently
Authors: Berghmans, David; Rochus, Pierre; Auchère, Frédéric;
Harra, Louise; Schmutz, Werner; Schühle, Udo
2018csc..confE..73B Altcode:
The ESA Solar Orbiter mission is designed to determine how the Sun
creates and controls the heliosphere. The spacecraft will bring
a combination of in situ and remote sensing instruments out of the
ecliptic (&gt;30°) and close to the sun (0.3 solar-radii). The launch
of Solar Orbiter is expected (not earlier than) Feb 2019. The Extreme
Ultraviolet Imager is part of the remote-sensing package of Solar
Orbiter, to be operating during 3 ten-day periods of each orbit around
the Sun, which last roughly half a year. These 3 periods will correspond
to perihelion and maximal solar latitude north and south. The Extreme
Ultraviolet Imager is itself a suite of three UV and EUV telescopes
that observe the solar atmosphere both globally as well as at very
high resolution. The two high-resolution imagers (HRIs) will image the
solar atmosphere in the chromospheric Lyman alpha line and the coronal
17nm pass band with a resolution of 0.5 arcsec. From perihelion, this
will correspond to a pixel footprint on the solar disc of (110km)^2
. The Full Sun Imager (FSI), working at the 17.4 nm and 30.4 nm EUV
passbands, will provide a global view of the solar atmosphere and is
therefore an essential building block for the "connection science"
of the Solar Orbiter mission. The FSI field of view is large enough
(228arcmin) that, even at perihelion and at maximal off-points by Solar
Orbiter, the full solar disk remains in the field of view. This large
FOV and the FSI's high sensitivity will allow to image the "transition
corona" where the topology of streamers and pseudo-streamers fades in
the solar wind. Furthermore, FSI will be the first to image all this
from out of the ecliptic. In this talk we will give an overview of the
EUI instrument. We will focus on the novel aspects of EUI that will
allow it to image beyond what previous EUV imagers could show us: EUV
imaging from the highest solar latitude, with the widest field-of-view
and at highest spatial resolution.

---------------------------------------------------------
Title: From solar to stellar brightness variations. The effect
of metallicity
Authors: Witzke, V.; Shapiro, A. I.; Solanki, S. K.; Krivova, N. A.;
Schmutz, W.
2018A&A...619A.146W Altcode: 2018arXiv180904360W
Context. Comparison studies of Sun-like stars with the Sun suggest an
anomalously low photometric variability of the Sun compared to Sun-like
stars with similar magnetic activity. Comprehensive understanding
of stellar variability is needed to find a physical reason for this
observation. Aims: We investigate the effect of metallicity
and effective temperature on the photometric brightness change
of Sun-like stars seen at different inclinations. The considered
range of fundamental stellar parameters is sufficiently small so
the stars investigated here still count as Sun-like or even as solar
twins. Methods: To model the brightness change of stars with
solar magnetic activity, we extended a well-established model of
solar brightness variations based on solar spectra, Spectral And
Total Irradiance REconstruction (SATIRE), to stars with different
fundamental parameters. For this we calculated stellar spectra for
different metallicities and effective temperature using the radiative
transfer code ATLAS9. Results: We show that even a small change
(e.g. within the observational error range) of metallicity or effective
temperature significantly affects the photometric brightness change
compared to the Sun. We find that for Sun-like stars, the amplitude
of the brightness variations obtained for Strömgren (b + y)/2 reaches
a local minimum for fundamental stellar parameters close to the solar
metallicity and effective temperature. Moreover, our results show that
the effect of inclination decreases for metallicity values greater than
the solar metallicity. Overall, we find that an exact determination of
fundamental stellar parameters is crucially important for understanding
stellar brightness changes.

---------------------------------------------------------
Title: First Detection of Solar Flare Emission in Mid-ultraviolet
Balmer Continuum
Authors: Dominique, Marie; Zhukov, Andrei N.; Heinzel, Petr;
Dammasch, Ingolf E.; Wauters, Laurence; Dolla, Laurent; Shestov,
Sergei; Kretzschmar, Matthieu; Machol, Janet; Lapenta, Giovanni;
Schmutz, Werner
2018ApJ...867L..24D Altcode: 2018arXiv181009835D
We present the first detection of solar flare emission at
mid-ultraviolet wavelengths around 2000 Å by the channel 2 of the
Large-Yield RAdiometer (LYRA) on board the PRoject for OnBoard Autonomy
2 mission. The flare (SOL20170906) was also observed in the channel
1 of LYRA centered at the H I Lyα line at 1216 Å, showing a clear
non-thermal profile in both channels. The flare radiation in channel 2
is consistent with the hydrogen Balmer continuum emission produced by an
optically thin chromospheric slab heated up to 10,000 K. Simultaneous
observations in channels 1 and 2 allow the separation of the line
emission (primarily from the Lyα line) from the Balmer continuum
emission. Together with the recent detection of the Balmer continuum
emission in the near-ultraviolet by the Interface Region Imaging
Spectrometer, the LYRA observations strengthen the interpretation
of broadband flare emission as the hydrogen recombination continua
originating in the chromosphere.

---------------------------------------------------------
Title: Revised historical solar irradiance forcing
Authors: Egorova, T.; Schmutz, W.; Rozanov, E.; Shapiro, A. I.;
Usoskin, I.; Beer, J.; Tagirov, R. V.; Peter, T.
2018A&A...615A..85E Altcode: 2018arXiv180400287E
Context. There is no consensus on the amplitude of historical solar
forcing. The estimated magnitude of the total solar irradiance (TSI)
difference between the Maunder minimum and the present time ranges
from 0.1 to 6 W m-2 making the simulation of the past and
future climate uncertain. One reason for this disagreement is the
applied evolution of the quiet Sun brightness in solar irradiance
reconstruction models. This work addresses the role of the quiet Sun
model choice and updated solar magnetic activity proxies on the solar
forcing reconstruction. Aims: We aim to establish a plausible
range for the solar irradiance variability on decadal to millennial
timescales. Methods: The spectral solar irradiance (SSI) is
calculated as a weighted sum of the contributions from sunspot umbra,
sunspot penumbra, faculae, and quiet Sun, which are pre-calculated with
the NLTE Spectral SYnthesis code (NESSY). We introduce activity belts
of the contributions from sunspots and faculae and a new structure
model for the quietest state of the Sun. We assume that the brightness
of the quiet Sun varies in time proportionally to the secular (22-yr
smoothed) variation of the solar modulation potential. Results:
A new reconstruction of the TSI and SSI covering the period 6000 BCE -
2015 CE is presented. The model simulates solar irradiance variability
during the satellite era well. The TSI change between the Maunder and
recent minima ranges between 3.7 and 4.5 W m-2 depending
on the applied solar modulation potential. The implementation of
a new quietest Sun model reduces, by approximately a factor of two,
the relative solar forcing compared to the largest previous estimation,
while the application of an updated solar modulation potential increases
the forcing difference between the Maunder minimum and the present
by 25-40%.

---------------------------------------------------------
Title: The EUI flight instrument of Solar Orbiter: from optical
alignment to end-to-end calibration
Authors: Halain, J. -P.; Renotte, E.; Auchère, F.; Berghmans, D.;
Delmotte, F.; Harra, L.; Schmutz, W.; Schühle, U.; Aznar Cuadrado,
R.; Dumesnil, C.; Gyo, M.; Kennedy, T.; Verbeeck, C.; Barbay, J.;
Giordanengo, B.; Gissot, S.; Gottwald, A.; Heerlein, K.; Hellin,
M. -L.; Hermans, A.; Hervier, V.; Jacques, L.; Laubis, C.; Mazzoli,
A.; Meining, S.; Mercier, R.; Philippon, A.; Roose, S.; Rossi, L.;
Scholze, F.; Smith, P.; Teriaca, L.; Zhang, X.; Rochus, P.
2018SPIE10699E..0HH Altcode:
The Extreme Ultraviolet Imager (EUI) instrument for the Solar Orbiter
mission will image the solar corona in the extreme ultraviolet (17.1
nm and 30.4 nm) and in the vacuum ultraviolet (121.6 nm) spectral
ranges. The development of the EUI instrument has been successfully
completed with the optical alignment of its three channels' telescope,
the thermal and mechanical environmental verification, the electrical
and software validations, and an end-toend on-ground calibration of
the two-units' flight instrument at the operating wavelengths. The
instrument has been delivered and installed on the Solar Orbiter
spacecraft, which is now undergoing all preparatory activities before
launch.

---------------------------------------------------------
Title: Chandra Observations of the Eclipsing Wolf-Rayet Binary CQ
CepOver a Full Orbital Cycle
Authors: Skinner, Steve L.; Guedel, Manuel; Schmutz, Werner; Zhekov,
Svetozar
2018AAS...23232003S Altcode:
We present results of Chandra X-ray observations and simultaneous
optical light curves of the short-period (1.64 d) eclipsing WN6+O9
binary system CQ Cep obtained in 2013 and 2017 covering a full
binary orbit. Our primary objective was to compare the observed
X-ray properties with colliding wind shock theory, which predicts
that the hottest shock plasma (T &gt; 20 MK) will form on or near the
line-of-centers between the stars. Thus, X-ray variability is expected
during eclipses when the hottest plasma is occulted. The X-ray spectrum
is strikingly similar to apparently single WN6 stars such as WR 134 and
spectral lines reveal plasma over a broad range of temperatures T ~ 4 -
40 MK. Both primary and secondary optical eclipses were clearly detected
and provide an accurate orbital period determination (P = 1.6412 d). The
X-ray emission remained remarkably steady throughout the orbit and
statistical tests give a low probability of variability. The lack of
significant X-ray variabililty during eclipses indicates that the X-ray
emission is not confined along the line-of-centers but is extended on
larger spatial scales, contrary to colliding wind predictions.

---------------------------------------------------------
Title: Small-scale heating events in the solar atmosphere: lifetime,
total energy and magnetic properties
Authors: Guerreiro, Nuno; Haberreiter, Margit; Hansteen, Viggo;
Schmutz, Werner
2018EGUGA..2014516G Altcode:
Small-scale heating events (SSHEs) are believed to play a fundamental
role in the heating of the solar corona, the pervading redshifts in
the transition region, and the acceleration of spicules. We present
a method to identify and track SSHEs over their lifetime and apply
it to two simulation models. We identify the locations where the
energy dissipation is maximum inside the SSHEs volume and we trace the
SSHEs by following the spatial and temporal evolution of the maximum
energy dissipation inside the SSHEs volume. The method is effective
in following the SSHE and allows us to determine their lifetime,
total energy and properties of the plasma as well as the magnetic
field orientation in the vicinity of the SSHEs. We conclude that
the SSHEs that have the potential to heat the corona live less than
4 minutes. Moreover, the typically energy release ranges from 1020
erg to 1024 erg. In addition, the directional change of the magnetic
field lines on both sides of the current sheet constituting the SSHEs
at the time of the absolute maximum energy dissipation ranges from 5
to 15 degree. This work is very relevant for the interpretation and
the potential observational evidence of the SSHEs from upcoming data
from the Spectral Imaging of the Coronal Environment instrument (SPICE)
and the Extreme UV imager (EUI) onboard the Solar Orbiter Mission.

---------------------------------------------------------
Title: Order out of Randomness: Self-Organization Processes in
Astrophysics
Authors: Aschwanden, Markus J.; Scholkmann, Felix; Béthune, William;
Schmutz, Werner; Abramenko, Valentina; Cheung, Mark C. M.; Müller,
Daniel; Benz, Arnold; Chernov, Guennadi; Kritsuk, Alexei G.; Scargle,
Jeffrey D.; Melatos, Andrew; Wagoner, Robert V.; Trimble, Virginia;
Green, William H.
2018SSRv..214...55A Altcode: 2017arXiv170803394A
Self-organization is a property of dissipative nonlinear processes
that are governed by a global driving force and a local positive
feedback mechanism, which creates regular geometric and/or
temporal patterns, and decreases the entropy locally, in contrast
to random processes. Here we investigate for the first time a
comprehensive number of (17) self-organization processes that
operate in planetary physics, solar physics, stellar physics,
galactic physics, and cosmology. Self-organizing systems create
spontaneous " order out of randomness", during the evolution from an
initially disordered system to an ordered quasi-stationary system,
mostly by quasi-periodic limit-cycle dynamics, but also by harmonic
(mechanical or gyromagnetic) resonances. The global driving force
can be due to gravity, electromagnetic forces, mechanical forces
(e.g., rotation or differential rotation), thermal pressure, or
acceleration of nonthermal particles, while the positive feedback
mechanism is often an instability, such as the magneto-rotational
(Balbus-Hawley) instability, the convective (Rayleigh-Bénard)
instability, turbulence, vortex attraction, magnetic reconnection,
plasma condensation, or a loss-cone instability. Physical models
of astrophysical self-organization processes require hydrodynamic,
magneto-hydrodynamic (MHD), plasma, or N-body simulations. Analytical
formulations of self-organizing systems generally involve coupled
differential equations with limit-cycle solutions of the Lotka-Volterra
or Hopf-bifurcation type.

---------------------------------------------------------
Title: First TSI observations of the new Compact Lightweight Absolute
Radiometer (CLARA)
Authors: Walter, B.; Finsterle, W.; Koller, S.; Levesque, P. L.;
Pfiffner, D.; Schmutz, W. K.
2017AGUFMSH43B2811W Altcode:
Continuous and precise Total Solar Irradiance (TSI) measurements
are indispensable to evaluate the influence of short- and long-term
solar radiative emission variations on the Earth's energy budget. The
existence of a potentially long-term trend in the suns activity and
whether or not such a trend could be climate effective is still a matter
of debate. The Compact Lightweight Absolute Radiometer (CLARA) is one
of PMOD/WRC's future contributions to the almost seamless series of
space borne TSI measurements since 1978. CLARA is one of three payloads
of the Norwegian micro satellite NORSAT-1, along with Langmuir probes
for space plasma research and an Automatic Identification System (AIS)
receiver to monitor maritime traffic in Norwegian waters. NORSAT-1
was launched July 14th 2017 and the nominal operation of CLARA will
start after the instrument commissioning beginning August 21st2017. We
present the design, calibration and first TSI observations of CLARA,
a new generation of active cavity Electrical Substitution Radiometers
(ESR) comprising the latest radiometer developments of PMOD/WRC:
i) A three-cavity design for degradation tracking and redundancy,
ii) a digital control loop with feed forward system allowing for
measurement cadences of 30s, iii) an aperture arrangement to reduce
internal scattered light and iv) a new cavity and heatsink design to
minimize non-equivalence, size and weight of the instrument. CLARA was
end-to-end calibrated against the SI traceable cryogenic radiometer of
the TSI Radiometer Facility (TRF) in Boulder (Colorado). The absolute
measurement uncertainties for the three SI-traceable TSI detectors of
CLARA are 567, 576 and 912 ppm (k = 1).

---------------------------------------------------------
Title: ASPIICS: a giant, white light and emission line coronagraph
for the ESA proba-3 formation flight mission
Authors: Lamy, P. L.; Vivès, S.; Curdt, W.; Damé, L.; Davila, J.;
Defise, J. -M.; Fineschi, S.; Heinzel, P.; Howard, Russel; Kuzin,
S.; Schmutz, W.; Tsinganos, K.; Zhukov, A.
2017SPIE10565E..0TL Altcode:
Classical externally-occulted coronagraphs are presently limited in
their performances by the distance between the external occulter and
the front objective. The diffraction fringe from the occulter and
the vignetted pupil which degrades the spatial resolution prevent
useful observations of the white light corona inside typically 2-2.5
solar radii (Rsun). Formation flying offers and elegant solution to
these limitations and allows conceiving giant, externally-occulted
coronagraphs using a two-component space system with the external
occulter on one spacecraft and the optical instrument on the
other spacecraft at a distance of hundred meters [1, 2]. Such
an instrument ASPIICS (Association de Satellites Pour l'Imagerie
et l'Interférométrie de la Couronne Solaire) has been selected
by the European Space Agency (ESA) to fly on its PROBA-3 mission
of formation flying demonstration which is presently in phase B
(Fig. 1). The classical design of an externally-occulted coronagraph is
adapted to the formation flying configuration allowing the detection
of the very inner corona as close as 0.04 solar radii from the solar
limb. By tuning the position of the occulter spacecraft, it may even be
possible to reach the chromosphere and the upper part of the spicules
[3]. ASPIICS will perform (i) high spatial resolution imaging of the
continuum K+F corona in photometric and polarimetric modes, (ii) high
spatial resolution imaging of the E-corona in two coronal emission lines
(CEL): Fe XIV and He I D3, and (iii) two-dimensional spectrophotometry
of the Fe XIV emission line. ASPIICS will address the question of the
coronal heating and the role of waves by characterizing propagating
fluctuations (waves and turbulence) in the solar wind acceleration
region and by looking for oscillations in the intensity and Doppler
shift of spectral lines. The combined imaging and spectral diagnostics
capabilities available with ASPIICS will allow mapping the velocity
field of the corona both in the sky plane (directly on the images)
and along the line-of-sight by measuring the Doppler shifts of
emission lines in an effort to determine how the different components
of the solar wind, slow and fast are accelerated. With a possible
launch in 2014, ASPIICS will observe the corona during the maximum of
solar activity, insuring the detection of many Coronal Mass Ejections
(CMEs). By rapidly alternating high-resolution imaging and spectroscopy,
CMEs will be thoroughly characterized.

---------------------------------------------------------
Title: In-flight performance of the solar UV radiometer LYRA/PROBA-2
Authors: Stockman, Y.; BenMoussa, A.; Dammasch, I.; Defise, J. -M.;
Dominique, M.; Halain, J. -P.; Hochedez, J. -F.; Koller, S.; Schmutz,
W.; Schühle, U.
2017SPIE10565E..0AS Altcode:
LYRA is a solar radiometer, part of the PROBA-2 micro-satellite payload
(Fig. 1). The PROBA-2 [1] mission has been launched on 02 November
2009 with a Rockot launcher to a Sun-synchronous orbit at an altitude
of 725 km. Its nominal operation duration is two years with possible
extension of 2 years. PROBA-2 is a small satellite developed under
an ESA General Support Technology Program (GSTP) contract to perform
an in-flight demonstration of new space technologies and support a
scientific mission for a set of selected instruments [2]. PROBA-2 host
17 technological demonstrators and 4 scientific instruments. The mission
is tracked by the ESA Redu Mission Operation Center. One of the four
scientific instruments is LYRA that monitors the solar irradiance at a
high cadence (&gt; 20 Hz) in four soft X-Ray to VUV large passbands: the
"Lyman-Alpha" channel, the "Herzberg" continuum range, the "Aluminium"
and "Zirconium" filter channels. The radiometric calibration is
traceable to synchrotron source standards [3]. LYRA benefits from wide
bandgap detectors based on diamond. It is the first space assessment
of these revolutionary UV detectors for astrophysics. Diamond sensors
make the instruments radiation-hard and solar-blind (insensitive to
the strong solar visible light) and, therefore, visible light blocking
filters become superfluous. To correlate the data of this new detector
technology, silicon detectors with well known characteristics are also
embarked. Due to the strict allocated mass and power budget (5 kg, 5W),
and poor priority to the payload needs on such platform, an optimization
and a robustness of the instrument was necessary. The first switch-on
occured on 16 November 2009. Since then the instrument performances
have been monitored and analyzed during the commissioning period. This
paper presents the first-light and preliminary performance analysis.

---------------------------------------------------------
Title: LYRA, solar uv radiometer on the technology demonstration
platform PROBA-2
Authors: Stockman, Y.; Hochedez, J. -F.; Schmutz, W.; BenMoussa, A.;
Defise, J. -M.; Denis, F.; D'Olieslaeger, M.; Dominique, M.; Haenen,
K.; Halain, J. -P.; Koller, S.; Koizumi, S.; Mortet, V.; Rochus, P.;
Schühle, U.; Soltani, A.; Theissen, A.
2017SPIE10567E..3KS Altcode:
LYRA is a solar radiometer part of the PROBA 2 micro satellite
payload. LYRA will monitor the solar irradiance in four soft X-Ray -
VUV passbands. They have been chosen for their relevance to Solar
Physics, Aeronomy and SpaceWeather: 1/ Lyman Alpha channel, 2/
Herzberg continuum range, 3/ Aluminium filter channel (including
He II at 30.4 nm) and 4/ Zirconium filter channel. The radiometric
calibration is traceable to synchrotron source standards. The
stability will be monitored by on-board calibration sources (LEDs),
which allow us to distinguish between potential degradations of the
detectors and filters. Additionally, a redundancy strategy maximizes
the accuracy and the stability of the measurements. LYRA will benefit
from wide bandgap detectors based on diamond: it will be the first
space assessment of revolutionary UV detectors. Diamond sensors
make the instruments radiation-hard and solar-blind (insensitive to
visible light) and therefore, make dispensable visible light blocking
filters. To correlate the data of this new detector technology, well
known technology, such as Si detectors are also embarked. The SWAP
EUV imaging telescope will operate next to LYRA on PROBA-2. Together,
they will provide a high performance solar monitor for operational
space weather nowcasting and research. LYRA demonstrates technologies
important for future missions such as the ESA Solar Orbiter.

---------------------------------------------------------
Title: The nature of solar brightness variations
Authors: Shapiro, A. I.; Solanki, S. K.; Krivova, N. A.; Cameron,
R. H.; Yeo, K. L.; Schmutz, W. K.
2017NatAs...1..612S Altcode: 2017arXiv171104156S
Determining the sources of solar brightness variations1,2,
often referred to as solar noise3, is important because
solar noise limits the detection of solar oscillations3,
is one of the drivers of the Earth's climate system4,5 and
is a prototype of stellar variability6,7—an important
limiting factor for the detection of extrasolar planets. Here,
we model the magnetic contribution to solar brightness variability
using high-cadence8,9 observations from the Solar Dynamics
Observatory (SDO) and the Spectral And Total Irradiance REconstruction
(SATIRE)10,11 model. The brightness variations caused by
the constantly evolving cellular granulation pattern on the solar
surface were computed with the Max Planck Institute for Solar System
Research (MPS)/University of Chicago Radiative Magnetohydrodynamics
(MURaM)12 code. We found that the surface magnetic field
and granulation can together precisely explain solar noise (that
is, solar variability excluding oscillations) on timescales from
minutes to decades, accounting for all timescales that have so far
been resolved or covered by irradiance measurements. We demonstrate
that no other sources of variability are required to explain the
data. Recent measurements of Sun-like stars by the COnvection ROtation
and planetary Transits (CoRoT)13 and Kepler14
missions uncovered brightness variations similar to that of the Sun,
but with a much wider variety of patterns15. Our finding
that solar brightness variations can be replicated in detail with
just two well-known sources will greatly simplify future modelling of
existing CoRoT and Kepler as well as anticipated Transiting Exoplanet
Survey Satellite16 and PLAnetary Transits and Oscillations
of stars (PLATO)17 data.

---------------------------------------------------------
Title: NESSY: NLTE spectral synthesis code for solar and stellar
atmospheres
Authors: Tagirov, R. V.; Shapiro, A. I.; Schmutz, W.
2017A&A...603A..27T Altcode:
Context. Physics-based models of solar and stellar magnetically-driven
variability are based on the calculation of synthetic spectra for
various surface magnetic features as well as quiet regions, which
are a function of their position on the solar or stellar disc. Such
calculations are performed with radiative transfer codes tailored for
modeling broad spectral intervals. Aims: We aim to present the
NLTE Spectral SYnthesis code (NESSY), which can be used for modeling
of the entire (UV-visible-IR and radio) spectra of solar and stellar
magnetic features and quiet regions. Methods: NESSY is a further
development of the COde for Solar Irradiance (COSI), in which we have
implemented an accelerated Λ-iteration (ALI) scheme for co-moving
frame (CMF) line radiation transfer based on a new estimate of the
local approximate Λ-operator. Results: We show that the new
version of the code performs substantially faster than the previous one
and yields a reliable calculation of the entire solar spectrum. This
calculation is in a good agreement with the available observations.

---------------------------------------------------------
Title: Numerical simulations and infrared spectro-interferometry
reveal the wind collision region in γ2 Velorum
Authors: Lamberts, A.; Millour, F.; Liermann, A.; Dessart, L.; Driebe,
T.; Duvert, G.; Finsterle, W.; Girault, V.; Massi, F.; Petrov, R. G.;
Schmutz, W.; Weigelt, G.; Chesneau, O.
2017MNRAS.468.2655L Altcode: 2017arXiv170101124L
Colliding stellar winds in massive binary systems have been studied
through their radio, optical lines and strong X-ray emission
for decades. More recently, near-infrared spectro-interferometric
observations have become available in a few systems, but isolating the
contribution from the individual stars and the wind collision region
still remains a challenge. In this paper, we study the colliding
wind binary γ2 Velorum and aim at identifying the wind
collision zone from infrared interferometric data, which provide unique
spatial information to determine the wind properties. Our analysis is
based on multi-epoch Very Large Telescope Interferometer/Astronomical
Multi-BEam Recombiner (VLTI/AMBER) data that allows us to separate
the spectral components of both stars. First, we determine the
astrometric solution of the binary and confirm previous distance
measurements. We then analyse the spectra of the individual stars,
showing that the O star spectrum is peculiar within its class. Then,
we perform three-dimensional hydrodynamic simulations of the system
from which we extract model images, visibility curves and closure phases
that can be directly compared with the observed data. The hydrodynamic
simulations reveal the 3D spiral structure of the wind collision region,
which results in phase-dependent emission maps. Our model visibility
curves and closure phases provide a good match when the wind collision
region accounts for 3-10 per cent γ2 Vel's total flux
in the near-infrared. The dialogue between hydrodynamic simulations,
radiative transfer models and observations allows us to fully exploit
the observations. Similar efforts will be crucial to study circumstellar
environments with the new generation of VLTI instruments like GRAVITY
and MATISSE.

---------------------------------------------------------
Title: Solar disc radius determined from observations made during
eclipses with bolometric and photometric instruments on board the
PICARD satellite
Authors: Thuillier, G.; Zhu, P.; Shapiro, A. I.; Sofia, S.; Tagirov,
R.; van Ruymbeke, M.; Perrin, J. -M.; Sukhodolov, T.; Schmutz, W.
2017A&A...603A..28T Altcode:
Context. Despite the importance of having an accurate measurement of
the solar disc radius, there are large uncertainties of its value
due to the use of different measurement techniques and instrument
calibration. An item of particular importance is to establish whether
the value of the solar disc radius correlates with the solar activity
level. Aims: The main goal of this work is to measure the
solar disc radius in the near-UV, visible, and near-IR regions of
the solar spectrum. Methods: Three instruments on board the
PICARD spacecraft, namely the Bolometric Oscillations Sensor (BOS),
the PREcision MOnitoring Sensor (PREMOS), and a solar sensor (SES),
are used to derive the solar disc radius using the light curves produced
when the Sun is occulted by the Moon. Nine eclipses, from 2010 to 2013,
resulted in 17 occultations as viewed from the moving satellite. The
calculation of the solar disc radius uses a simulation of the light
curve taking into account the center-to-limb variation provided by
the Non-local thermodynamic Equilibrium Spectral SYnthesis (NESSY)
code. Results: We derive individual values for the solar disc
radius for each viewed eclipse. Tests for a systematic variation
of the radius with the progression of the solar cycle yield no
significant results during the three years of measurements within the
uncertainty of our measurements. Therefore, we derive a more precise
radius value by averaging these values. At one astronomical unit,
we obtain 959.79 arcseconds (arcsec) from the bolometric experiment;
from PREMOS measurements, we obtain 959.78 arcsec at 782 nm and
959.76 arcsec at 535 nm. We found 960.07 arcsec at 210 nm, which
is a higher value than the other determinations given the photons
at this wavelength originate from the upper photosphere and lower
chromosphere. We also give a detailed comparison of our results with
those previously published using measurements from space-based and
ground-based instruments using the Moon angular radius reference,
and different methods. Conclusions: Our results, which use the
Moon as an absolute calibration, clearly show the dependence of the
solar disc radius with wavelength in UV, visible and near-IR. Beyond
the metrological results, solar disc radius measurements will allow
the accuracy of models of the solar atmosphere to be tested. Proposed
systematic variations of the solar disc radius during the time of
observation would be smaller than the uncertainty of our measurement,
which amounts to less than 26 milliarcseconds.

---------------------------------------------------------
Title: Small-scale heating events in the solar
atmosphere. II. Lifetime, total energy, and magnetic properties
Authors: Guerreiro, N.; Haberreiter, M.; Hansteen, V.; Schmutz, W.
2017A&A...603A.103G Altcode:
Context. Small-scale heating events (SSHEs) are believed to play a
fundamental role in understanding the process responsible for heating
of the solar corona, the pervading redshifts in the transition region,
and the acceleration of spicules. Aims: We determine the
properties of the SSHEs and the atmospheric response to them in 3D
magnetohydrodynamics (3D-MHD) simulations of the solar atmosphere. Methods: We developed a method for identifying and following
SSHEs over their lifetime, and applied it to two simulation models. We
identified the locations where the energy dissipation is greatest inside
the SSHEs volume, and we traced the SSHEs by following the spatial
and temporal evolution of the maximum energy dissipation inside the
SSHEs volume. Results: The method is effective in following the
SSHEs. We can determine their lifetime, total energy, and properties of
the plasma, as well as the magnetic field orientation in the vicinity
of the SSHEs. Conclusions: We determine that the SSHEs that have
the potential to heat the corona live less than 4 min, and typically
the energy they release ranges from 1020 to 1024
erg. In addition, the directional change of the field lines on the two
sides of the current sheet constituting the SSHEs ranges from 5° to
15° at the moment of the absolute maximum energy dissipation.

---------------------------------------------------------
Title: A new observational solar irradiance composite
Authors: Haberreiter, Margit; Schöll, Micha; Dudok de Wit, Thierry;
Kretzschmar, Matthieu; Misios, Stergios; Tourpali, Kleareti; Schmutz,
Werner
2017JGRA..122.5910H Altcode:
Variations in the solar spectral irradiance (SSI) are an important
driver of the chemistry, temperature, and dynamics of the Earth's
atmosphere and ultimately the Earth's climate. To investigate the
detailed response of the Earth's atmosphere to SSI variations, a
reliable SSI data set is needed. We present an observational SSI
composite data set that is based on 20 instruments and has been
built by using probabilistic approach that takes into account the
scale-dependent uncertainty of each available SSI observation. We
compare the variability of this new composite with available SSI
reconstructions and discuss the respective modeled responses in the
Earth's atmosphere. As the composite is based on purely statistical
means, we consider it as a valuable independent data set.

---------------------------------------------------------
Title: Does the Wolf-Rayet binary CQ Cephei undergo sporadic mass
transfer events?
Authors: Koenigsberger, Gloria; Schmutz, Werner; Skinner, Stephen L.
2017A&A...601A.121K Altcode:
Context. Stellar wind mass-loss in binary systems carries away angular
momentum causing a monotonic increase in the orbital period, Ṗ&gt;
0. Despite possessing a significant stellar wind, the eclipsing
Wolf-Rayet (WR) binary system CQ Cep does not show the expected
monotonic period increase, in fact, it is sometimes reported to display
the opposite behavior. Aims: The objective of this paper is to
perform a new analysis of the rate of period change Ṗ and determine
the conditions under which Roche-lobe overflow (RLO) mass-transfer
combined with wind mass loss can explain the discrepant behavior. Methods: The historic records of times of light curve minima were
reviewed and compared with the theoretical values of Ṗ for cases in
which both wind mass-loss and RLO occur simultaneously. Results:
The observational data indicate that Ṗ alternates between positive
and negative values on a timescale of years. The negative values (Ṗ
-0.6 to -8.5 s yr-1) are significantly larger in absolute
value than the positive ones (Ṗ + 0.2 to +1.2 s yr-1). We
find that a plausible scenario for CQ Cep is one in which the O star
undergoes intense but sporadic RLO events that lead to accretion
onto the WR star, at which times Ṗ&lt; 0. At other times, Ṗ&gt;
0 when the WR wind, and possibly material swept up from the O star,
carries angular momentum away from the system. A scenario in which the
WR star is the mass donor cannot be excluded, but requires that either
the WR wind mass-loss rate undergoes large sporadic enhancements or
that an additional process that removes angular momentum from the
system be present.

---------------------------------------------------------
Title: Modeling of the middle atmosphere response to 27-day solar
irradiance variability
Authors: Sukhodolov, Timofei; Rozanov, Eugene; Ball, William T.;
Peter, Thomas; Schmutz, Werner
2017JASTP.152...50S Altcode:
The solar rotational variability (27-day) signal in the Earth's middle
atmosphere has been studied for several decades, as it was believed
to help in the understanding of the Sun's influence on climate at
longer timescales. However, all previous studies have found that this
signal is very uncertain, likely due to the influence of the internal
variability of the atmosphere. Here, we applied an ensemble modeling
approach in order to decrease internal random variations in the
modeled time series. Using a chemistry-climate model (CCM), SOCOLv3,
we performed two 30-member 3-year long (2003-2005) ensemble runs: with
and without a rotational component in input irradiance fluxes. We also
performed similar simulations with a 1-D model, in order to demonstrate
the system behavior in the absence of any dynamical feedbacks and
internal perturbations. For the first time we show a clear connection
between the solar rotation and the stratospheric tropical temperature
time-series. We show tropical temperature and ozone signal phase lag
patterns that are in agreement with those from a 1-D model. Pronounced
correlation and signal phase lag patterns allow us to properly estimate
ozone and temperature sensitivities to irradiance changes. While ozone
sensitivity is found to be in agreement with recent sensitivities
reported for the 11-year cycle, temperature sensitivity appears to
be at the lowest boundary of previously reported values. Analysis of
temperature reanalysis data, separate ensemble members, and modeling
results without a rotational component reveals that the atmosphere can
produce random internal variations with periods close to 27 days even
without solar rotational forcing. These variations are likely related
to tropospheric wave-forcing and complicate the extraction of the solar
rotational signal from observational time-series of temperature and,
to a lesser extent, of ozone. Possible ways of further improving solar
rotational signal extraction are discussed.

---------------------------------------------------------
Title: Total Solar Irradiance changes between 2010 and 2014 from
the PREcision MOnitor Sensor absolute radiometer (PREMOS/PICARD)
Authors: Cessateur, G.; Schmutz, W. K.; Ball, W.; Finsterle, W.;
Walter, B.
2016AGUFMSH42B..04C Altcode:
The PREMOS/PICARD instrument monitored total solar irradiance (TSI) from
July 2010 to April 2014. During this period other TSI instruments showed
divergent trends large enough to mask, or exacerbate, a multi-decadal
trend in the Sun's output. We present the complete PICARD mission PREMOS
TSI time series and provide an inter-comparison with other instruments
operating during the same period. Additionally, we present a unique
assessment of the backup radiometer degradation during the mission,
which provides an additional, robust estimate of the change in TSI from
2011 to 2014; this assessment leads to the conclusion that composites
of TSI observations are still too uncertain to estimate TSI between
solar cycle minima.

---------------------------------------------------------
Title: Nominal Values for Selected Solar and Planetary Quantities:
IAU 2015 Resolution B3
Authors: Prša, Andrej; Harmanec, Petr; Torres, Guillermo; Mamajek,
Eric; Asplund, Martin; Capitaine, Nicole; Christensen-Dalsgaard,
Jørgen; Depagne, Éric; Haberreiter, Margit; Hekker, Saskia; Hilton,
James; Kopp, Greg; Kostov, Veselin; Kurtz, Donald W.; Laskar, Jacques;
Mason, Brian D.; Milone, Eugene F.; Montgomery, Michele; Richards,
Mercedes; Schmutz, Werner; Schou, Jesper; Stewart, Susan G.
2016AJ....152...41P Altcode: 2016arXiv160509788P
In this brief communication we provide the rationale for and the
outcome of the International Astronomical Union (IAU) resolution
vote at the XXIXth General Assembly in Honolulu, Hawaii, in 2015,
on recommended nominal conversion constants for selected solar and
planetary properties. The problem addressed by the resolution is a lack
of established conversion constants between solar and planetary values
and SI units: a missing standard has caused a proliferation of solar
values (e.g., solar radius, solar irradiance, solar luminosity, solar
effective temperature, and solar mass parameter) in the literature,
with cited solar values typically based on best estimates at the time
of paper writing. As precision of observations increases, a set of
consistent values becomes increasingly important. To address this, an
IAU Working Group on Nominal Units for Stellar and Planetary Astronomy
formed in 2011, uniting experts from the solar, stellar, planetary,
exoplanetary, and fundamental astronomy, as well as from general
standards fields to converge on optimal values for nominal conversion
constants. The effort resulted in the IAU 2015 Resolution B3, passed at
the IAU General Assembly by a large majority. The resolution recommends
the use of nominal solar and planetary values, which are by definition
exact and are expressed in SI units. These nominal values should be
understood as conversion factors only, not as the true solar/planetary
properties or current best estimates. Authors and journal editors are
urged to join in using the standard values set forth by this resolution
in future work and publications to help minimize further confusion.

---------------------------------------------------------
Title: Assessing the beginning to end-of-mission sensitivity change
of the PREcision MOnitor Sensor total solar irradiance radiometer
(PREMOS/PICARD)
Authors: Ball, William T.; Schmutz, Werner; Fehlmann, André;
Finsterle, Wolfgang; Walter, Benjamin
2016JSWSC...6A..32B Altcode:
The switching of the total solar irradiance (TSI) backup radiometer
(PREMOS-B) to a primary role for 2 weeks at the end of the PICARD
mission provides a unique opportunity to test the fundamental
hypothesis of radiometer experiments in space, which is that the
sensitivity change of instruments due to the space environment is
identical for the same instrument type as a function of solar-exposure
time of the instruments. We verify this hypothesis for the PREMOS TSI
radiometers within the PREMOS experiment on the PICARD mission. We
confirm that the sensitivity change of the backup instrument, PREMOS-B,
is similar to that of the identically-constructed primary radiometer,
PREMOS-A. The extended exposure of the backup instrument at the end of
the mission allows for the assessment, with an uncertainty estimate,
of the sensitivity change of the primary radiometer from the beginning
of the PICARD mission compared to the end, and of the degradation
of the backup over the mission. We correct six sets of PREMOS-B
observations connecting October 2011 with February 2014, using six
ratios from simultaneous PREMOS-A and PREMOS-B exposures during the
first days of PREMOS-A operation in 2010. These ratios are then used,
without indirect estimates or assumptions, to evaluate the stability
of SORCE/TIM and SOHO/VIRGO TSI measurements, which have both operated
for more than a decade and now show different trends over the time
span of the PICARD mission, namely from 2010 to 2014. We find that by
February 2014 relative to October 2011 PREMOS-B supports the SORCE/TIM
TSI time evolution, which in May 2014 relative to October 2011 is
~0.11 W m-2, or ~84 ppm, higher than SOHO/VIRGO. Such a
divergence between SORCE/TIM and SOHO/VIRGO over this period is a
significant fraction of the estimated decline of 0.2 W m-2
between the solar minima of 1996 and 2008, and questions the reliability
of that estimated trend. Extrapolating the uncertainty indicated by
the disagreement of SORCE/TIM and PREMOS with respect to SOHO/VIRGO,
we can conclude that it is currently not possible to assess centennial
timescale changes in solar irradiance based on any of the presently
existing TSI composites. It is imperative to accurately estimate
solar irradiance changes from observations in order to extrapolate
centennial scale trends important for understanding both long-term
solar irradiance changes and the Sun's influence on the Earth's climate.

---------------------------------------------------------
Title: The qualification campaign of the EUI instrument of Solar
Orbiter
Authors: Halain, J. -P.; Rochus, P.; Renotte, E.; Hermans, A.; Jacques,
L.; Mazzoli, A.; Auchère, F.; Berghmans, D.; Harra, L.; Schühle,
U.; Schmutz, W.; Aznar Cuadrado, R.; Dumesnil, C.; Gyo, M.; Kennedy,
T.; Verbeeck, C.; Smith, P.
2016SPIE.9905E..2XH Altcode:
The Extreme Ultraviolet Imager (EUI) instrument is one of the ten
scientific instruments on board the Solar Orbiter mission to be launched
in October 2018. It will provide full-sun and high-resolution images of
the solar corona in the extreme ultraviolet (17.1 nm and 30.4 nm) and in
the vacuum ultraviolet (121.6 nm). The validation of the EUI instrument
design has been completed with the Assembly, Integration and Test
(AIT) of the instrument two-units Qualification Model (QM). Optical,
electrical, electro-magnetic compatibility, thermal and mechanical
environmental verifications were conducted and are summarized here. The
integration and test procedures for the Flight Model (FM) instrument
and sub-systems were also verified. Following the Qualification Review,
the flight instrument activities were started with the assembly of
the flight units. The mechanical and thermal acceptance tests and an
end-to-end final calibration in the (E)UV will then be conducted before
delivery for integration on the Solar Orbiter Spacecraft by end of 2016.

---------------------------------------------------------
Title: The SPICE Spectral Imager on Solar Orbiter: Linking the Sun
to the Heliosphere
Authors: Fludra, Andrzej; Haberreiter, Margit; Peter, Hardi; Vial,
Jean-Claude; Harrison, Richard; Parenti, Susanna; Innes, Davina;
Schmutz, Werner; Buchlin, Eric; Chamberlin, Phillip; Thompson,
William; Gabriel, Alan; Morris, Nigel; Caldwell, Martin; Auchere,
Frederic; Curdt, Werner; Teriaca, Luca; Hassler, Donald M.; DeForest,
Craig; Hansteen, Viggo; Carlsson, Mats; Philippon, Anne; Janvier, Miho;
Wimmer-Schweingruber, Robert; Griffin, Douglas; Davila, Joseph; Giunta,
Alessandra; Waltham, Nick; Eccleston, Paul; Gottwald, Alexander;
Klein, Roman; Hanley, John; Walls, Buddy; Howe, Chris; Schuehle, Udo
2016cosp...41E.607F Altcode:
The SPICE (Spectral Imaging of the Coronal Environment) instrument is
one of the key remote sensing instruments onboard the upcoming Solar
Orbiter Mission. SPICE has been designed to contribute to the science
goals of the mission by investigating the source regions of outflows
and ejection processes which link the solar surface and corona to the
heliosphere. In particular, SPICE will provide quantitative information
on the physical state and composition of the solar atmosphere
plasma. For example, SPICE will access relative abundances of ions to
study the origin and the spatial/temporal variations of the 'First
Ionization Potential effect', which are key signatures to trace the
solar wind and plasma ejections paths within the heliosphere. Here we
will present the instrument and its performance capability to attain the
scientific requirements. We will also discuss how different observation
modes can be chosen to obtain the best science results during the
different orbits of the mission. To maximize the scientific return of
the instrument, the SPICE team is working to optimize the instrument
operations, and to facilitate the data access and their exploitation.

---------------------------------------------------------
Title: Solar abundances with the SPICE spectral imager on Solar
Orbiter
Authors: Giunta, Alessandra; Haberreiter, Margit; Peter, Hardi;
Vial, Jean-Claude; Harrison, Richard; Parenti, Susanna; Innes, Davina;
Schmutz, Werner; Buchlin, Eric; Chamberlin, Phillip; Thompson, William;
Bocchialini, Karine; Gabriel, Alan; Morris, Nigel; Caldwell, Martin;
Auchere, Frederic; Curdt, Werner; Teriaca, Luca; Hassler, Donald M.;
DeForest, Craig; Hansteen, Viggo; Carlsson, Mats; Philippon, Anne;
Janvier, Miho; Wimmer-Schweingruber, Robert; Griffin, Douglas; Baudin,
Frederic; Davila, Joseph; Fludra, Andrzej; Waltham, Nick; Eccleston,
Paul; Gottwald, Alexander; Klein, Roman; Hanley, John; Walls, Buddy;
Howe, Chris; Schuehle, Udo; Gyo, Manfred; Pfiffner, Dany
2016cosp...41E.681G Altcode:
Elemental composition of the solar atmosphere and in particular
abundance bias of low and high First Ionization Potential (FIP)
elements are a key tracer of the source regions of the solar wind. These
abundances and their spatio-temporal variations, as well as the other
plasma parameters , will be derived by the SPICE (Spectral Imaging
of the Coronal Environment) EUV spectral imager on the upcoming
Solar Orbiter mission. SPICE is designed to provide spectroheliograms
(spectral images) using a core set of emission lines arising from ions
of both low-FIP and high-FIP elements. These lines are formed over
a wide range of temperatures, enabling the analysis of the different
layers of the solar atmosphere. SPICE will use these spectroheliograms
to produce dynamic composition maps of the solar atmosphere to be
compared to in-situ measurements of the solar wind composition of
the same elements (i.e. O, Ne, Mg, Fe). This will provide a tool to
study the connectivity between the spacecraft (the Heliosphere) and
the Sun. We will discuss the SPICE capabilities for such composition
measurements.

---------------------------------------------------------
Title: Main results of the PICARD mission
Authors: Meftah, M.; Corbard, T.; Hauchecorne, A.; Irbah, A.; Boumier,
P.; Chevalier, A.; Schmutz, W.; Ikhlef, R.; Morand, F.; Renaud, C.;
Hochedez, J. -F.; Cessateur, G.; Turck-Chièze, S.; Salabert, D.;
Rouzé, M.; van Ruymbeke, M.; Zhu, P.; Kholikov, S.; Koller, S.;
Conscience, C.; Dewitte, S.; Damé, L.; Djafer, D.
2016SPIE.9904E..0ZM Altcode:
PICARD is a mission devoted to solar variability observations through
imagery and radiometric measurements. The main goal is to provide data
for scientific investigation first in the area of solar physics, and
second in the assessment of the influence of the solar variability on
the Earth climate variability. PICARD contains a double program with
in-space and on-ground measurements. The PICARD spacecraft was launched
on June 15, 2010, commissioned in-flight in October of the same year
and was retired in April 2014. The PICARD ground-based observatory is
operational since May 2011. We shall give a short overview of the PICARD
instrumentation. New estimates of the absolute values of the total solar
irradiance, of the solar spectral irradiance at typical wavelengths,
and of the solar oblateness will be given. We will also report about
helioseismic studies. Finally, we will present our current results
about solar radius variations after six years of solar observation.

---------------------------------------------------------
Title: Detection and characterization of small-scale heating events
in the solar atmosphere from 3D-MHD simulations and their potential
role in coronal heating
Authors: Guerreiro, Nuno; Haberreiter, Margit; Schmutz, Werner;
Hansteen, Viggo
2016cosp...41E.750G Altcode:
Aiming at better understanding the mechanism(s) responsible for the
coronal heating we focus on analyzing the properties of the magnetically
generated small-scale heating events (SSHEs) in the solar atmosphere. We
present a comprehensive method to detect and follow SSHEs over time
in 3D-MHD simulations of the solar atmosphere. Applying the method
we are able to better understand the properties of the SSHEs and how
the plasma in their vicinity respond to them. We study the lifetime,
energy and spectral signatures and show that the energy flux dissipated
by them is enough to heat the corona. Ultimately, these results will
be important for the coordinated scientific exploration of SPICE and
EUI along with other instruments on board solar orbiter.

---------------------------------------------------------
Title: The origin of Total Solar Irradiance variability on timescales
less than a day
Authors: Shapiro, Alexander; Krivova, Natalie; Schmutz, Werner;
Solanki, Sami K.; Leng Yeo, Kok; Cameron, Robert; Beeck, Benjamin
2016cosp...41E1774S Altcode:
Total Solar Irradiance (TSI) varies on timescales from minutes to
decades. It is generally accepted that variability on timescales of
a day and longer is dominated by solar surface magnetic fields. For
shorter time scales, several additional sources of variability have
been proposed, including convection and oscillation. However, available
simplified and highly parameterised models could not accurately explain
the observed variability in high-cadence TSI records. We employed the
high-cadence solar imagery from the Helioseismic and Magnetic Imager
onboard the Solar Dynamics Observatory and the SATIRE (Spectral And
Total Irradiance Reconstruction) model of solar irradiance variability
to recreate the magnetic component of TSI variability. The recent 3D
simulations of solar near-surface convection with MURAM code have been
used to calculate the TSI variability caused by convection. This allowed
us to determine the threshold timescale between TSI variability caused
by the magnetic field and convection. Our model successfully replicates
the TSI measurements by the PICARD/PREMOS radiometer which span the
period of July 2010 to February 2014 at 2-minute cadence. Hence,
we demonstrate that solar magnetism and convection can account for
TSI variability at all timescale it has ever been measured (sans the
5-minute component from p-modes).

---------------------------------------------------------
Title: First light measurements of the Total Solar Irradiance
experiment CLARA on NORSAT-1
Authors: Schmutz, Werner
2016cosp...41E1753S Altcode:
NORSAT-1 is a Norwegian micro-satellite, which will be launched April
22, 2016. (In the future at the time of writing this abstract.) The
satellite carries two scientific instruments and an AIS receiver
for performing ship detection from space. One of the scientific
instruments is a Compact Light-weight Absolute RAdiometer (CLARA)
and the other is a Langmuir Probe instrument comprising four probes
mounted on booms. The latter experiment will measure electron density
and the platform's floating potential along the orbit. The University
of Oslo provides the Langmuir probes. The radiometer experiment CLARA
has been built by PMOD/WRC funded through the Swiss PRODEX program. It
will measure Total Solar Irradiance with an instrument of novel design
that is optimized for minimizing mass and size by still ensuring highest
measuring accuracy and thermal stability. The radiometers of CLARA have
been fully characterized as well as calibrated at the TRF facility. It
is expected that the first light accuracy of the absolute measurement
of Total Solar Irradiance will be better than pm0.3 W/m^{2, allowing to
probe the current TSI composite for its absolute level. The presentation
will give an overview of the CLARA instrument and its calibration. It
is expected that at the time of the COSPAR conference the first light
TSI value of CLARA/NORSAT-1 is ready for publication. Together with a
previous absolute TSI measurements available for July 27, 2010 measured
by PREMOS/PICARD the new absolute TSI measurement will be used to test
the accuracy of long term TSI trend given by the relative TSI composite.

---------------------------------------------------------
Title: Are solar brightness variations faculae- or spot-dominated?
Authors: Shapiro, A. I.; Solanki, S. K.; Krivova, N. A.; Yeo, K. L.;
Schmutz, W. K.
2016A&A...589A..46S Altcode: 2016arXiv160204447S
Context. Regular spaceborne measurements have revealed that
solar brightness varies on multiple timescales, variations on
timescales greater than a day being attributed to a surface magnetic
field. Independently, ground-based and spaceborne measurements suggest
that Sun-like stars show a similar, but significantly broader pattern
of photometric variability. Aims: To understand whether the
broader pattern of stellar variations is consistent with the solar
paradigm, we assess relative contributions of faculae and spots to
solar magnetically-driven brightness variability. We investigate
how the solar brightness variability and its facular and spot
contributions depend on the wavelength, timescale of variability,
and position of the observer relative to the ecliptic plane. 
Methods: We performed calculations with the SATIRE model, which
returns solar brightness with daily cadence from solar disc area
coverages of various magnetic features. We took coverages as seen by
an Earth-based observer from full-disc SoHO/MDI and SDO/HMI data and
projected them to mimic out-of-ecliptic viewing by an appropriate
transformation. Results: Moving the observer away from the
ecliptic plane increases the amplitude of 11-year variability as it
would be seen in Strömgren (b + y)/2 photometry, but decreases the
amplitude of the rotational brightness variations as it would appear
in Kepler and CoRoT passbands. The spot and facular contributions to
the 11-year solar variability in the Strömgren (b + y)/2 photometry
almost fully compensate each other so that the Sun appears anomalously
quiet with respect to its stellar cohort. Such a compensation does not
occur on the rotational timescale. Conclusions: The rotational
solar brightness variability as it would appear in the Kepler and
CoRoT passbands from the ecliptic plane is spot-dominated, but the
relative contribution of faculae increases for out-of-ecliptic viewing
so that the apparent brightness variations are faculae-dominated for
inclinations less than about I = 45°. Over the course of the 11-year
activity cycle, the solar brightness variability is faculae-dominated
shortwards of 1.2 μm independently of the inclination.

---------------------------------------------------------
Title: Solar spectral irradiance model validation using Solar Spectral
Irradiance and Solar Radius measurements
Authors: Thuillier, Gérard; Zhu, Ping; Shapiro, Alexander; Sofia,
Sabatino; Tagirov, Rinat; Van Ruymbeke, Michel; Schmutz, Werner
2016EGUGA..18.7407T Altcode:
The importance of the reliable solar spectral irradiance (SSI) data
for solar and climate physics is now well acknowledged. In particular,
the irradiance time series are necessary for most of the current
studies concerning climate evolution. However, space instruments
are vulnerable to the degradation due to the environment while
ground based measurements are limited in wavelength range and need
atmospheric effects corrections. This is why SSI modeling is necessary
to understand the mechanism of the solar irradiance variability and to
provide long and uninterrupted irradiance records to climate and Earth
atmosphere scientists. Here we present COSI (COde for Solar Irradiance)
model of the SSI variability. The COSI model is based on the Non
local thermodynamic Equilibrium Spectral SYnthesis Code (NESSY). We
validate NESSY by two independent datasets: - The SSI at solar minimum
occurring in 2008, - The radius variation with wavelength and absolute
values determined from PREMOS and BOS instruments onboard the PICARD
spacecraft. Comparisons between modeling and measured SSI will be
shown. However, since SSI measurements have an accuracy estimated
between 2 to 3%, the comparison with the solar radius data provides
a very important additional constrains on model. For that, 17 partial
solar occultations by the Moon are used providing solar radii clearly
showing the dependence of the solar radius with wavelength. These
results are compared with the NESSY predictions. The agreement between
NESSY and observations is within the model and measurements accuracy.

---------------------------------------------------------
Title: Solar irradiance observations with PREMOS filter radiometers
on the PICARD mission: In-flight performance and data release
Authors: Cessateur, G.; Schmutz, W.; Wehrli, C.; Gröbner, J.;
Haberreiter, M.; Kretzschmar, M.; Rozanov, E.; Schöll, M.; Shapiro,
A.; Thuillier, G.; Egorova, T.; Finsterle, W.; Fox, N.; Hochedez,
J. -F.; Koller, S.; Meftah, M.; Meindl, P.; Nyeki, S.; Pfiffner, D.;
Roth, H.; Rouzé, M.; Spescha, M.; Tagirov, R.; Werner, L.; Wyss,
J. -U.
2016A&A...588A.126C Altcode:
Context. The PREcision Monitoring Sensor (PREMOS) is a solar radiometer
on board the French PICARD mission that was launched in June 2010
and decommissioned in April 2014. Aims: The PREMOS radiometer
obtains solar irradiance measurements in specific spectral windows
in the UV, visible, and near-infrared. In this paper, the PREMOS
data and calibration methods are presented. Methods: Using
back-up channels, the degradation can theoretically be assessed to
correct operational channels. However, a strong degradation within all
PREMOS channels requires the application of additional methods, namely
using back-up channels and assessing the degradation via a proxy-based
model. Results: The corrected Level 3 PREMOS data are then used
in different contexts in order to be validated. First, the signature
of the p-mode are retrieved from the PREMOS data. The Venus transit
allows us to empirically determine the intrinsic noise level within the
PREMOS high cadence data for the visible and near-infrared channels. We
then compare the PREMOS data directly to other data sets, namely
from the SOLar-STellar Irradiance Comparison Experiment (SOLSTICE)
and the Solar Irradiance Monitor (SIM) instruments on board the SOlar
Radiation and Climate Experiment (SORCE) spacecraft. Regarding the
UV channels, we found an excellent correlation over the lifetime of
the PREMOS mission. The ratio between SORCE and PREMOS observations
is always less than 1%. Regarding the SSI measurements in the visible
and near-infrared, a comparison of short-term variations (I.e. 27-day
modulation) shows a rather good correlation by taking into consideration
the intrinsic noise within both SIM and PREMOS observations.

---------------------------------------------------------
Title: Characterization of small-scale heating events in the solar
atmosphere from 3D-MHD simulations and their potential role in
coronal heating
Authors: Guerreiro, Nuno; Haberreiter, Margit; Hansteen, Viggo;
Schmutz, Werner
2016EGUGA..1814407G Altcode:
Aiming at better understanding the mechanism(s) responsible for
the coronal heating and the ubiquitous redshifts observed in the
lower transition region we focus on analyzing the properties of
small-scale heating events (SSHEs) in the solar atmosphere. We present
a comprehensive method to follow SSHEs over time in 3D-MHD simulations
of the solar atmosphere. Applying the method we are able to better
understand the properties of the SSHEs and how the plasma in their
vicinity respond to them. We present results for the lifetime, energy
and spectral signatures of the SSHEs. Ultimately, these results will
be important for the coordinated scientific exploration of SPICE and
EUI along with other interments on board solar orbiter.

---------------------------------------------------------
Title: Solar Spectral Irradiance Observations from the PICARD/PREMOS
Radiometer
Authors: Cessateur, G.; Schöll, M.; Schmutz, W. K.; Wehrli, C.;
Groebner, J.; Haberreiter, M.; Kretzschmar, M.; Shapiro, A.; Thuillier,
G. O.; Finsterle, W.; Fox, N.; Hochedez, J. F.; Koller, S.; Meftah,
M.; Nyeki, S.; Pfiffner, D.; Roth, H.; Rouze, M.; Spescha, M.; Tagirov,
R.; Werner, L.; Wyss, J.
2015AGUFMSH32A..06C Altcode:
Space weather and space climate studies require accurate Solar Spectral
Irradiance (SSI) observations. The PREcision Monitoring Sensor (PREMOS)
instrument aboard the PICARD satellite acquired solar irradiance
measurements in specific spectral windows in the UV, visible and near
infrared from October 2010 to March 2014. This contribution aims at
presenting the Level 3 data, corrected for non solar features as well
as for degradation. These level 3 data has been tested over different
scientific cases, such as observations during the Venus transit and
the presence of the p-mode signature within high-cadence data. The
PREMOS Level 3 data have also been compared to others data sets,
namely the SOLSTICE and SIM instruments aboard SORCE, for nearly 3
and half years. An excellent correlation has been found for the UV
spectral ranges. We have also found a rather good correlation for
visible and near-infrared observations for short-term variations,
for which an error of about 200 ppm has been estimated within PREMOS
visible and near-infrared observations. The PREMOS data could also
be used to address several scientific topics, i.e. for validating
semi-empirical models of the solar irradiance. We will emphasize
about our new irradiance model, COSIR for Code of Solar Irradiance
Reconstruction, which is successful at reproducing the solar modulation
as seen in the PREMOS, SoHO/Virgo and SORCE data.

---------------------------------------------------------
Title: Characterisation of small-scale heating events in the solar
atmosphere from 3D MHD simulations and their potential role in
coronal heating
Authors: Haberreiter, M.; Guerreiro, N.; Hansteen, V. H.; Schmutz,
W. K.
2015AGUFMSH31C2442H Altcode:
The physical mechanism that heats the solar corona is one of the still
open science questions in solar physics. One of the proposed mechanism
for coronal heating are nanoflares. To investigate their role in coronal
heating we study the properties of the small-scale heating events in
the solar atmosphere using 3D MHD simulations. We present a method
to identify and track these heating events in time which allows us to
study their life time, energy, and spectral signatures. These spectal
signatures will be compared with available spectrosopic observations
obtained with IRIS and SUMER. Ultimately, these results will be
important for the coordinated scientific exploitation of SPICE and
EUI along with other instruments onboard Solar Orbiter to address the
coronal heating problem.

---------------------------------------------------------
Title: Small-scale Heating Events in the Solar
Atmosphere. I. Identification, Selection, and Implications for
Coronal Heating
Authors: Guerreiro, N.; Haberreiter, M.; Hansteen, V.; Schmutz, W.
2015ApJ...813...61G Altcode:
We present a comprehensive method to analyze small-scale heating
events in detail in a 3D magnetohydrodynamics simulation for quiet-Sun
conditions. The method determines the number, volume, and some general
geometric properties of the small-scale heating events at different
instants in a simulation with a volume of 16 × 8 × 16 Mm3,
spanning from the top of the convection zone to the corona. We found
that there are about 104 small-scale heating events at
any instant above the simulated area of 128 Mm2. They
occur mainly at heights between 1.5 and 3.0 Mm. We determine the
average value of their projected vertical extent, which ranges from
375 to 519 km over time, and we show that height, volume, and energy
distribution of the events at any instant resemble power laws. Finally,
we demonstrate that larger heating structures are a combination of much
smaller heating events and that small-scale heating events dissipate
enough energy to maintain the coronal energetic balance at any instant.

---------------------------------------------------------
Title: Erratum: Erratum to: The Infrared Solar Spectrum Measured by
the SOLSPEC Spectrometer Onboard the International Space Station
Authors: Thuillier, G.; Harder, J. W.; Shapiro, A.; Woods, T. N.;
Perrin, J. -M.; Snow, M.; Sukhodolov, T.; Schmutz, W.
2015SoPh..290.3089T Altcode: 2015SoPh..tmp..150T
No abstract at ADS

---------------------------------------------------------
Title: The role of the Fraunhofer lines in solar brightness
variability
Authors: Shapiro, A. I.; Solanki, S. K.; Krivova, N. A.; Tagirov,
R. V.; Schmutz, W. K.
2015A&A...581A.116S Altcode: 2015arXiv150705437S
Context. The solar brightness varies on timescales from minutes to
decades. A clear identification of the physical processes behind such
variations is needed for developing and improving physics-based models
of solar brightness variability and reconstructing solar brightness
in the past. This is, in turn, important for better understanding
the solar-terrestrial and solar-stellar connections. Aims:
We estimate the relative contributions of the continuum, molecular,
and atomic lines to the solar brightness variations on different
timescales. Methods: Our approach is based on the assumption that
variability of the solar brightness on timescales greater than a day
is driven by the evolution of the solar surface magnetic field. We
calculated the solar brightness variations employing the solar
disc area coverage of magnetic features deduced from the MDI/SOHO
observations. The brightness contrasts of magnetic features relative
to the quiet Sun were calculated with a non-LTE radiative transfer
code as functions of disc position and wavelength. By consecutive
elimination of molecular and atomic lines from the radiative transfer
calculations, we assessed the role of these lines in producing solar
brightness variability. Results: We show that the variations
in Fraunhofer lines define the amplitude of the solar brightness
variability on timescales greater than a day and even the phase of
the total solar irradiance variability over the 11-year cycle. We also
demonstrate that molecular lines make substantial contribution to solar
brightness variability on the 11-year activity cycle and centennial
timescales. In particular, our model indicates that roughly a quarter
of the total solar irradiance variability over the 11-year cycle
originates in molecular lines. The maximum of the absolute spectral
brightness variability on timescales greater than a day is associated
with the CN violet system between 380 and 390 nm.

---------------------------------------------------------
Title: The extreme UV imager telescope on-board the Solar Orbiter
mission: overview of phase C and D
Authors: Halain, J. -P.; Rochus, P.; Renotte, E.; Hermans, A.; Jacques,
L.; Auchère, F.; Berghmans, D.; Harra, L.; Schühle, U.; Schmutz,
W.; Zhukov, A.; Aznar Cuadrado, R.; Delmotte, F.; Dumesnil, C.; Gyo,
M.; Kennedy, T.; Smith, P.; Tandy, J.; Mercier, R.; Verbeeck, C.
2015SPIE.9604E..0GH Altcode:
The Solar Orbiter mission is composed of ten scientific instruments
dedicated to the observation of the Sun's atmosphere and its
heliosphere, taking advantage of an out-of ecliptic orbit and at
perihelion reaching a proximity close to 0.28 A.U. On board Solar
Orbiter, the Extreme Ultraviolet Imager (EUI) will provide full-Sun
image sequences of the solar corona in the extreme ultraviolet (17.1
nm and 30.4 nm), and high-resolution image sequences of the solar disk
in the extreme ultraviolet (17.1 nm) and in the vacuum ultraviolet
(121.6 nm). The EUI concept uses heritage from previous similar extreme
ultraviolet instrument. Additional constraints from the specific orbit
(thermal and radiation environment, limited telemetry download) however
required dedicated technologies to achieve the scientific objectives
of the mission. The development phase C of the instrument and its
sub-systems has been successfully completed, including thermomechanical
and electrical design validations with the Structural Thermal Model
(STM) and the Engineering Model (EM). The instrument STM and EM units
have been integrated on the respective spacecraft models and will
undergo the system level tests. In parallel, the Phase D has been
started with the sub-system qualifications and the flight parts
manufacturing. The next steps of the EUI development will be the
instrument Qualification Model (QM) integration and qualification
tests. The Flight Model (FM) instrument activities will then follow
with the acceptance tests and calibration campaigns.

---------------------------------------------------------
Title: The Infrared Solar Spectrum Measured by the SOLSPEC
Spectrometer Onboard the International Space Station
Authors: Thuillier, G.; Harder, J. W.; Shapiro, A.; Woods, T. N.;
Perrin, J. -M.; Snow, M.; Sukhodolov, T.; Schmutz, W.
2015SoPh..290.1581T Altcode: 2015SoPh..tmp...75T
A solar spectrum extending from the extreme ultraviolet to the
near-infrared is an important input for solar physics, climate
research, and atmospheric physics. Ultraviolet measurements have
been conducted since the beginning of the space age, but measurements
throughout the contiguous visible and infrared (IR) regions are much
more sparse. Ageing is a key problem throughout the entire spectral
domain, but most of the effort extended to understand degradation was
concentrated on the ultraviolet spectral region, and these mechanisms
may not be appropriate in the IR. This problem is further complicated
by the scarcity of long-term data sets. Onboard the International
Space Station, the SOLSPEC spectrometer measured an IR solar spectral
irradiance lower than the one given by ATLAS 3, e.g. by about 7 % at 1
700 nm. We here evaluate the consequences of the lower solar spectral
irradiance measurements and present a re-analysis of the on-orbit
calibration lamp and solar data trend, which lead to a revised spectrum.

---------------------------------------------------------
Title: A Chandra Observation of the Eclipsing Wolf-Rayet Binary CQ Cep
Authors: Skinner, Stephen L.; Zhekov, Svetozar A.; Güdel, Manuel;
Schmutz, Werner
2015ApJ...799..124S Altcode: 2014arXiv1411.4075S
The short-period (1.64 d) near-contact eclipsing WN6+O9 binary system CQ
Cep provides an ideal laboratory for testing the predictions of X-ray
colliding wind shock theory at close separation where the winds may
not have reached terminal speeds before colliding. We present results
of a Chandra X-ray observation of CQ Cep spanning ~1 day during which
a simultaneous Chandra optical light curve was acquired. Our primary
objective was to compare the observed X-ray properties with colliding
wind shock theory, which predicts that the hottest shock plasma (T
&gt;~ 20 MK) will form on or near the line-of-centers between the
stars. The X-ray spectrum is strikingly similar to apparently single
WN6 stars such as WR 134 and spectral lines reveal plasma over a broad
range of temperatures T ~ 4-40 MK. A deep optical eclipse was seen as
the O star passed in front of the Wolf-Rayet star and we determine an
orbital period P orb = 1.6412400 d. Somewhat surprisingly,
no significant X-ray variability was detected. This implies that the
hottest X-ray plasma is not confined to the region between the stars,
at odds with the colliding wind picture and suggesting that other X-ray
production mechanisms may be at work. Hydrodynamic simulations that
account for such effects as radiative cooling and orbital motion will
be needed to determine if the new Chandra results can be reconciled
with the colliding wind picture.

---------------------------------------------------------
Title: A Chandra Observation of the Eclipsing Wolf-Rayet Binary CQ Cep
Authors: Skinner, Steve L.; Zhekov, Svetozar; Guedel, Manuel;
Schmutz, Werner
2015AAS...22534412S Altcode:
The short-period (1.64 day) near-contact eclipsing WN6+O9 binary system
CQ Cep provides an ideal laboratory for testing the predictions of X-ray
colliding wind shock theory at close separation where the winds may
not have reached terminal speeds before colliding. We present results
of a Chandra X-ray observation of CQ Cep spanning one day during which
a simultaneous Chandra optical light curve was acquired. Our primary
objective was to compare the observed X-ray properties with colliding
wind shock theory, which predicts that the hottest shock plasma (T &gt;
20 MK) will form on or near the line-of-centers between the stars. The
X-ray spectrum is strikingly similar to apparently single WN6 stars
such as WR 134 and spectral lines reveal plasma over a broad range
of temperatures T ~ 4 - 40 MK. A deep optical eclipse was seen as
the O star passed in front of the Wolf-Rayet star but, surprisingly,
no significant X-ray variability was detected. Because of the high
inclination orbit, this implies that the hottest X-ray plasma is not
confined to the region between the stars, at odds with the colliding
wind shock picture. We will summarize the Chandra results in the
context of predictions from colliding wind theory.

---------------------------------------------------------
Title: Solar Spectral Irradiance Variability in November/December
2012: Comparison of Observations by Instruments on the International
Space Station and Models
Authors: Thuillier, G.; Schmidtke, G.; Erhardt, C.; Nikutowski, B.;
Shapiro, A. I.; Bolduc, C.; Lean, J.; Krivova, N.; Charbonneau, P.;
Cessateur, G.; Haberreiter, M.; Melo, S.; Delouille, V.; Mampaey,
B.; Yeo, K. L.; Schmutz, W.
2014SoPh..289.4433T Altcode: 2014SoPh..tmp..120T
Onboard the International Space Station (ISS), two instruments
are observing the solar spectral irradiance (SSI) at wavelengths
from 16 to 2900 nm. Although the ISS platform orientation generally
precludes pointing at the Sun more than 10 - 14 days per month, in
November/December 2012 a continuous period of measurements was obtained
by implementing an ISS `bridging' maneuver. This enabled observations to
be made of the solar spectral irradiance (SSI) during a complete solar
rotation. We present these measurements, which quantify the impact
of active regions on SSI, and compare them with data simultaneously
gathered from other platforms, and with models of spectral irradiance
variability. Our analysis demonstrates that the instruments onboard the
ISS have the capability to measure SSI variations consistent with other
instruments in space. A comparison among all available SSI measurements
during November-December 2012 in absolute units with reconstructions
using solar proxies and observed solar activity features is presented
and discussed in terms of accuracy.

---------------------------------------------------------
Title: Variability of Sun-like stars: reproducing observed photometric
trends
Authors: Shapiro, A. I.; Solanki, S. K.; Krivova, N. A.; Schmutz,
W. K.; Ball, W. T.; Knaack, R.; Rozanov, E. V.; Unruh, Y. C.
2014A&A...569A..38S Altcode: 2014arXiv1406.2383S
Context. The Sun and stars with low magnetic activity levels become
photometrically brighter when their activity increases. Magnetically
more active stars display the opposite behavior and become fainter
when their activity increases. Aims: We reproduce the observed
photometric trends in stellar variations with a model thattreats stars
as hypothetical suns with coverage by magnetic features different from
that of the Sun. Methods: The model attributes the variability
of stellar spectra to the imbalance between the contributions from
different components of the solar atmosphere, such as dark starspots
and bright faculae. A stellar spectrum is calculated from spectra
of the individual components by weighting them with corresponding
disk-area coverages. The latter are obtained by extrapolating
the solar dependences of spot and facular disk-area coverages
on chromospheric activity to stars with different levels of mean
chromospheric activity. Results: We find that the contribution
by starspots to the variability increases faster with chromospheric
activity than the facular contribution. This causes the transition from
faculae-dominated variability and direct activity-brightness correlation
to spot-dominated variability and inverse activity-brightness
correlation with increasing chromospheric activity level. We show that
the regime of the variability also depends on the angle between the
stellar rotation axis and the line-of-sight and on the latitudinal
distribution of active regions on the stellar surface. Our model
can be used as a tool for extrapolating the observed photometric
variability of the Sun to Sun-like stars at different activity levels,
which makes a direct comparison between solar and stellar irradiance
data possible. Appendices are available in electronic form at <A
href="http://www.aanda.org/10.1051/0004-6361/201323086/olm">http://www.aanda.org</A>

---------------------------------------------------------
Title: The extreme UV imager of solar orbiter: from detailed design
to flight model
Authors: Halain, J. -P.; Rochus, P.; Renotte, E.; Auchère, F.;
Berghmans, D.; Harra, L.; Schühle, U.; Schmutz, W.; Zhukov, A.;
Aznar Cuadrado, R.; Delmotte, F.; Dumesnil, C.; Gyo, M.; Kennedy,
T.; Mercier, R.; Verbeeck, F.; Thome, M.; Heerlein, K.; Hermans, A.;
Jacques, L.; Mazzoli, A.; Meining, S.; Rossi, L.; Tandy, J.; Smith,
P.; Winter, B.
2014SPIE.9144E..08H Altcode:
The Extreme Ultraviolet Imager (EUI) on-board the Solar Orbiter mission
will provide full-sun and high-resolution image sequences of the solar
atmosphere at selected spectral emission lines in the extreme and vacuum
ultraviolet. After the breadboarding and prototyping activities that
focused on key technologies, the EUI project has completed the design
phase and has started the final manufacturing of the instrument and its
validation. The EUI instrument has successfully passed its Critical
Design Review (CDR). The process validated the detailed design of
the Optical Bench unit and of its sub-units (entrance baffles, doors,
mirrors, camera, and filter wheel mechanisms), and of the Electronic
Box unit. In the same timeframe, the Structural and Thermal Model
(STM) test campaign of the two units have been achieved, and allowed
to correlate the associated mathematical models. The lessons learned
from STM and the detailed design served as input to release the
manufacturing of the Qualification Model (QM) and of the Flight Model
(FM). The QM will serve to qualify the instrument units and sub-units,
in advance of the FM acceptance tests and final on-ground calibration.

---------------------------------------------------------
Title: The Solar Irradiance Spectrum at Solar Activity Minimum
Between Solar Cycles 23 and 24
Authors: Thuillier, G.; Bolsée, D.; Schmidtke, G.; Foujols, T.;
Nikutowski, B.; Shapiro, A. I.; Brunner, R.; Weber, M.; Erhardt, C.;
Hersé, M.; Gillotay, D.; Peetermans, W.; Decuyper, W.; Pereira, N.;
Haberreiter, M.; Mandel, H.; Schmutz, W.
2014SoPh..289.1931T Altcode:
On 7 February 2008, the SOLAR payload was placed onboard the
International Space Station. It is composed of three instruments,
two spectrometers and a radiometer. The two spectrometers allow us
to cover the 16 - 2900 nm spectral range. In this article, we first
briefly present the instrumentation, its calibration and its performance
in orbit. Second, the solar spectrum measured during the transition
between Solar Cycles 23 to 24 at the time of the minimum is shown and
compared with other data sets. Its accuracy is estimated as a function
of wavelength and the solar atmosphere brightness-temperature is
calculated and compared with those derived from two theoretical models.

---------------------------------------------------------
Title: Reconstruction of the solar EUV irradiance as observed with
PROBA2/LYRA
Authors: Haberreiter, Margit; Delouille, Veronique; Del Zanna, Giulio;
Ermolli, Ilaria; Kretzschmar, Matthieu; Mampeay, Benjamin; Dominique,
Marie; Schmutz, Werner
2014EGUGA..1614449H Altcode:
The solar EUV spectrum has important effects on the upper atmosphere
of the Earth and any planet. For a detailed investigation of these
effects it is important to have a constistent data series of the EUV
spectral irradiance available. Here, we present the reconstruction of
the solar EUV irradiance based on PSPT and SOHO/EIT images and along
with synthetic spectra calculated for six different coronal features
representing the brightness variation of the solar atmosphere. The
EIT images are segmented with the SPoCA tool which allows to identify
the features based on a consistent brightness classification for each
feature. With the SOLMOD code we then calculate intensity spectra
for 10 nm to 100 nm for each of the coronal feature. Weighting the
intensity spectra with the area covered by each of the features yields
the temporal variation of the EUV spectrum. The reconstructed time
series is then validated against the spectral irradiance as observed
with PROBA2/LYRA. This is an important step towards the understanding
of the variations of the solar EUV spectrum and ultimately its detailed
effect on the Earth's upper atmosphere.

---------------------------------------------------------
Title: Analysis of Different Solar Spectral Irradiance Reconstructions
and Their Impact on Solar Heating Rates
Authors: Thuillier, G.; Melo, S. M. L.; Lean, J.; Krivova, N. A.;
Bolduc, C.; Fomichev, V. I.; Charbonneau, P.; Shapiro, A. I.; Schmutz,
W.; Bolsée, D.
2014SoPh..289.1115T Altcode:
Proper numerical simulation of the Earth's climate change requires
reliable knowledge of solar irradiance and its variability on
different time scales, as well as the wavelength dependence of this
variability. As new measurements of the solar spectral irradiance have
become available, so too have new reconstructions of historical solar
irradiance variations, based on different approaches. However, these
various solar spectral irradiance reconstructions have not yet been
compared in detail to quantify differences in their absolute values,
variability, and implications for climate and atmospheric studies. In
this paper we quantitatively compare five different reconstructions
of solar spectral irradiance changes during the past four centuries,
in order to document and analyze their differences. The impact on
atmosphere and climate studies is discussed in terms of the calculation
of short wave solar heating rates.

---------------------------------------------------------
Title: The PREMOS/PICARD Radiometer: An overview after 3 years
of observations
Authors: Cessateur, Gaël; Schmutz, Werner; Shapiro, Alexander
2014cosp...40E.469C Altcode:
Total and Spectral Solar Irradiance are key input parameters to
atmospheric/oceanic and space weather models. We present here spectral
solar irradiance data from the radiometer PREMOS onboard the PICARD
satellite for three years, which covers covers the solar spectrum from
the Ultraviolet to near-infrared. We will also introduce the algorithm
COCOSIS (for Combination of COSI Spectra) which allows us to retrieve
the solar variability of the irradiance. Our investigation shows that
COCOSIS is highly successful at reproducing solar spectral irradiance
over rotational periods for most of channels from PREMOS.

---------------------------------------------------------
Title: The TSI record from PREMOS/PICARD
Authors: Schmutz, Werner; Thuillier, Gerard; Finsterle, Wolfgang;
Walter, Benjamin; Fehlmann, Andre
2014cosp...40E2931S Altcode:
Since the launch of PICARD in 2010 the PMO6 absolute radiometers of
the PREMOS experiment had been measuring Total Solar Irradiance. We
will present the TSI data record, corrected for sensor degradation,
and review the stability of the radiometers during the entire
mission. Implications for the uncertainty of Composite Total Solar
Irradiance time Series data sets will be discussed.

---------------------------------------------------------
Title: Middle atmosphere heating rate and photolysis response to
the uncertainties in spectral solar irradiance data
Authors: Sukhodolov, Timofei; Schmutz, Werner; Shapiro, Alexander;
Tourpali, Kleareti; Peter, Thomas; Rozanov, Eugene; Bais, Alkiviadis;
Telford, Paul
2014cosp...40E3225S Altcode:
Solar radiation is the main source of energy for the Earth’s
atmosphere and in many respects defines its composition, photochemistry,
temperature profile and dynamics. Therefore, the uncertainties in the
magnitude and spectral composition of the spectral solar irradiance
(SSI) evolution during the declining phase of 23rd solar cycle have
substantial implications for the modeling of the middle atmosphere
evolution, leading to a pronounced differences in the heating rates
and also affecting photolysis rates. To estimate the role of SSI
uncertainties we have compared the most important photolysis rates
(O2, O3, and NO2) and heating rates calculated with the reference
radiation code libRadtran using SSI for June 2004 and February 2009
obtained from two models (NRL, COSI) and one observation data set
based on SORCE observations. We have also evaluated the ability of
the several photolysis and heating rates calculation methods widely
used in atmospheric models to reproduce the absolute values of the
photolysis rates and their response to the implied SSI changes.

---------------------------------------------------------
Title: Identification and characterization of small-scale heating
events in the solar atmosphere from 3D MHD simulations
Authors: Guerreiro, Nuno; Haberreiter, Margit; Schmutz, Werner;
Hansteen, Viggo
2014cosp...40E1095G Altcode:
We studied the properties of small scale heating events (in the nano
and micro-flare regime) in the solar atmosphere using existing 3D
MHD simulations. We put forward a method for event identification
and categorization. We determine the spatial extend of the events
and their frequency and energy distributions. These results aim at
improving the understanding of small scale heating events and their
role for the heating of the solar corona.

---------------------------------------------------------
Title: Assessment of the spectral solar cycle variations in the
visual and near IR from VIRGI/SOHO data
Authors: Schmutz, Werner; Haberreiter, Margit; Shapiro, Alexander;
Cessateur, Gaël; Wehrli, Christoph; Adams, Wilnelia
2014cosp...40E2929S Altcode:
According to Harder et al. (2009) SIM measurements onboard the SORCE
satellite reveal a several times higher spectral solar variability in
UV than previously estimated. In compensation, to maintain the known
amplitude of the Total Solar Irradiance variations, the visual was
observed to be in anti-phase. Haigh et al. (2010) has demonstrated
that this different-then-thought wavelength dependence has profound
implications for the response of the terrestrial climate. In Wehrli
et al. (A&amp;A 556, L3 2013) we have presented evidence that annual
averages of the VIRGO filter radiometer data in the 500 nm channel are
significantly positively correlated with TSI. In this presentation we
present an update including the most recent SPM VIRGO radiometer data
and give an estimate of the amplitudes of the spectral solar cycle
variations in the VIRGO channels. The implication is that the highly
significant positive correlation at 500 nm excludes the postulated
anti-phase solar cycle variations at this wavelength. Harder et
al. (2009) also published large UV variations and this proposal is
assessed from the point of view that Total Solar Irradiance Variations
are know. It is concluded that large UV amplitudes, as proposed, are
not excluded even if the 500 nm variations are in-phase with the solar
cycle, given the amplitudes measured in the VIRGO/SOHO channels.

---------------------------------------------------------
Title: CLARA - A compact and light-weight absolute radiometer on
the NORSAT-1 mission
Authors: Schmutz, Werner; Finsterle, Wolfgang; Walter, Benjamin;
Suter, Markus; Andersen, Bo; Osmundsen, Magne
2014cosp...40E2930S Altcode:
PMOD/WRC is building the Compact and Light-weight Absolut RAdiometer
(CLARA) to fly on the Norwegian Space Centre's (NCS) NORSAT-1
mission. CLARA is based on a new design by PMOD/WRC which minimizes
size and weight while improving the radiometric performance. The
NORSAT-1 mission is planned to be launched to a polar LEO in Q4 2015
or Q1 2016. NSC intends to extend the initial three-years mission for
as long as the platform and payload remain functional.

---------------------------------------------------------
Title: On-Orbit Degradation of Solar Instruments
Authors: BenMoussa, A.; Gissot, S.; Schühle, U.; Del Zanna, G.;
Auchère, F.; Mekaoui, S.; Jones, A. R.; Walton, D.; Eyles, C. J.;
Thuillier, G.; Seaton, D.; Dammasch, I. E.; Cessateur, G.; Meftah,
M.; Andretta, V.; Berghmans, D.; Bewsher, D.; Bolsée, D.; Bradley,
L.; Brown, D. S.; Chamberlin, P. C.; Dewitte, S.; Didkovsky, L. V.;
Dominique, M.; Eparvier, F. G.; Foujols, T.; Gillotay, D.; Giordanengo,
B.; Halain, J. P.; Hock, R. A.; Irbah, A.; Jeppesen, C.; Judge,
D. L.; Kretzschmar, M.; McMullin, D. R.; Nicula, B.; Schmutz, W.;
Ucker, G.; Wieman, S.; Woodraska, D.; Woods, T. N.
2013SoPh..288..389B Altcode: 2013arXiv1304.5488B
We present the lessons learned about the degradation observed in
several space solar missions, based on contributions at the Workshop
about On-Orbit Degradation of Solar and Space Weather Instruments
that took place at the Solar Terrestrial Centre of Excellence (Royal
Observatory of Belgium) in Brussels on 3 May 2012. The aim of this
workshop was to open discussions related to the degradation observed
in Sun-observing instruments exposed to the effects of the space
environment. This article summarizes the various lessons learned
and offers recommendations to reduce or correct expected degradation
with the goal of increasing the useful lifespan of future and ongoing
space missions.

---------------------------------------------------------
Title: Correlation of spectral solar irradiance with solar activity
as measured by VIRGO
Authors: Wehrli, C.; Schmutz, W.; Shapiro, A. I.
2013A&A...556L...3W Altcode: 2013arXiv1307.1285W
Context. The variability of solar spectral irradiance (SSI) over
the rotational period and its trend over the solar activity cycle
are important for understanding the Sun-Earth connection as well as
for observational constraints for solar models. Recently the Spectral
Irradiance Monitor (SIM) experiment on the Solar Radiation and Climate
Experiment (SORCE) has published an unexpected negative correlation
with total solar irradiance (TSI) of the visible spectral range. It
is compensated by a strong and positive variability of the near UV
range. Aims: We aim to verify whether the anti-correlated
SIM-trend in the visible can be confirmed by independent observations
of the Variability of solar IRadiance and Gravity Oscillations
(VIRGO) experiment on the SOlar and Heliospheric Observatory (SOHO)
satellite. The challenge of all space experiments measuring solar
irradiance are sensitivity changes of their sensors due to exposure to
intense UV radiation, which are difficult to assess in orbit. 
Methods: We exclude the first six years prior to 2002 where one or
more fast processes contributed to instrumental changes and analyse
a ten-year timeseries of VIRGO sun photometer data between 2002 and
2012. The variability of SSI is correlated with the variability
of the TSI, which is taken as a proxy for solar activity. 
Results: Observational evidence indicates that after six years only
one single long-term process governs the degradation of the backup sun
photometer in VIRGO which is operated once a month. This degradation
can be well approximated by a linear function over ten years. The
analysis of the residuals from the linear trend yield robust positive
correlations of spectral irradiance at 862, 500, and 402 nm with
total irradiance. In the analysis of annual averages of these data the
positive correlations change into weak negative correlations, but with
little statistical significance for the 862 nm and 402 nm data. At
500 nm the annual spectral data are still positively correlated with
TSI. The persisting positive correlation at 500 nm is in contradiction
to the SIM results. Appendix A is available in electronic form
at <A href="http://www.aanda.org">http://www.aanda.org</A>

---------------------------------------------------------
Title: The LYRA Instrument Onboard PROBA2: Description and In-Flight
Performance
Authors: Dominique, M.; Hochedez, J. -F.; Schmutz, W.; Dammasch,
I. E.; Shapiro, A. I.; Kretzschmar, M.; Zhukov, A. N.; Gillotay, D.;
Stockman, Y.; BenMoussa, A.
2013SoPh..286...21D Altcode: 2013arXiv1302.6525D
The Large Yield Radiometer (LYRA) is an XUV-EUV-MUV (soft X-ray to
mid-ultraviolet) solar radiometer onboard the European Space Agency
Project for On-Board Autonomy 2 (PROBA2) mission, which was launched
in November 2009. LYRA acquires solar-irradiance measurements at
a high cadence (nominally 20 Hz) in four broad spectral channels,
from soft X-ray to MUV, which have been chosen for their relevance
to solar physics, space weather, and aeronomy. We briefly review
the design of the instrument, give an overview of the data products
distributed through the instrument website, and describe how the data
are calibrated. We also briefly present a summary of the main fields
of research currently under investigation by the LYRA consortium.

---------------------------------------------------------
Title: Impact of a potential 21st century "grand solar minimum"
on surface temperatures and stratospheric ozone
Authors: Anet, J. G.; Rozanov, E. V.; Muthers, S.; Peter, T.;
BröNnimann, S.; Arfeuille, F.; Beer, J.; Shapiro, A. I.; Raible,
C. C.; Steinhilber, F.; Schmutz, W. K.
2013GeoRL..40.4420A Altcode:
We investigate the effects of a recently proposed 21st century Dalton
minimum like decline of solar activity on the evolution of Earth's
climate and ozone layer. Three sets of two member ensemble simulations,
radiatively forced by a midlevel emission scenario (Intergovernmental
Panel on Climate Change RCP4.5), are performed with the atmosphere-ocean
chemistry-climate model AOCCM SOCOL3-MPIOM, one with constant solar
activity, the other two with reduced solar activity and different
strength of the solar irradiance forcing. A future grand solar minimum
will reduce the global mean surface warming of 2 K between 1986-2005
and 2081-2100 by 0.2 to 0.3 K. Furthermore, the decrease in solar UV
radiation leads to a significant delay of stratospheric ozone recovery
by 10 years and longer. Therefore, the effects of a solar activity
minimum, should it occur, may interfere with international efforts
for the protection of global climate and the ozone layer.

---------------------------------------------------------
Title: Detection of Solar Rotational Variability in the Large Yield
RAdiometer (LYRA) 190 - 222 nm Spectral Band
Authors: Shapiro, A. V.; Shapiro, A. I.; Dominique, M.; Dammasch,
I. E.; Wehrli, C.; Rozanov, E.; Schmutz, W.
2013SoPh..286..289S Altcode: 2012arXiv1205.2377S; 2012SoPh..tmp..121S
We analyze the variability of the spectral solar irradiance during
the period from 7 January 2010 until 20 January 2010 as measured by
the Herzberg channel (190 - 222 nm) of the Large Yield RAdiometer
(LYRA) onboard PROBA2. In this period of time, observations by the
LYRA nominal unit experienced degradation and the signal produced by
the Herzberg channel frequently jumped from one level to another. Both
factors significantly complicate the analysis. We present the algorithm
that allowed us to extract the solar variability from the LYRA data
and compare the results with SORCE/SOLSTICE measurements and with
modeling based on the Code for the Solar Irradiance (COSI).

---------------------------------------------------------
Title: Eclipses Observed by Large Yield RAdiometer (LYRA) - A
Sensitive Tool to Test Models for the Solar Irradiance
Authors: Shapiro, A. I.; Schmutz, W.; Dominique, M.; Shapiro, A. V.
2013SoPh..286..271S Altcode: 2012SoPh..tmp..171S; 2012arXiv1201.6546S
We analyze the light curves of the recent solar eclipses measured
by the Herzberg channel (200 - 220 nm) of the Large Yield RAdiometer
(LYRA) onboard Project for OnBoard Autonomy (PROBA2). The measurements
allow us to accurately retrieve the center-to-limb variations (CLV) of
the solar brightness. The formation height of the radiation depends on
the observing angle, so the examination of the CLV provide information
about a broad range of heights in the solar atmosphere. We employ the
1D NLTE radiative transfer COde for Solar Irradiance (COSI) to model
the measured light curves and corresponding CLV dependencies. The
modeling is used to test and constrain the existing 1D models of the
solar atmosphere, e.g. the temperature structure of the photosphere
and the treatment of the pseudo-continuum opacities in the Herzberg
continuum range. We show that COSI can accurately reproduce not only the
irradiance from the entire solar disk, but also the measured CLV. Hence
it can be used as a reliable tool for modeling the variability of the
spectral solar irradiance.

---------------------------------------------------------
Title: The latitudinal dependence of the solar radiance
Authors: Finsterle, Wolfgang; Shapiro, Alexander; Schmutz, Werner;
Krivova, Natalie
2013EGUGA..1511672F Altcode:
Active regions and sunspots occur predominantly at low to mid
heliographic latitudes. Hence, it seems reasonable to assume that the
radiant output of the sun is not spherically symmetrical. Due to the
relatively small inclination (~7.25°) of the solar rotation axis this
asphericity is difficult to detect in integrated disk data taken from an
ecliptic-bound vantage point. A histogram analysis of 13 years of VIRGO
TSI data revealed a slight north-south asymmetry with maximal deviations
of ±4 parts in 10^5. Interestingly, the north-south asymmetry persists
even after subtracting the simulated TSI data by Krivova et al. (2003)
from the VIRGO TSI measurements. The Krivova time series attributes
the TSI to magnetic activity patterns as observed by MDI (sunspots,
faculae, and plage). The asymmetry thus seems to be of a different
origin, i.e. unrelated to sunspots, faculae, or plage, although smaller
magnetic structures might contribute to the asymmetry. We will also
investigate a potential asymmetry in the equator-to-pole temperature
gradient. At this point we can only speculate if the observed asymmetry
is characteristic of solar cycle 23, which is covered by the VIRGO time
series, or more fundamental. In any case it would be very interesting to
extend the TSI vs. latitude curve towards higher heliographic latitudes.

---------------------------------------------------------
Title: A Collaborative FP7 Effort towards the First European
Comprehensive SOLar Irradiance Data Exploitation (SOLID)
Authors: Haberreiter, Margit; Dasi, Maria; Delouille, Veronique; Del
Zanna, Giulio; Dudok de Wit, Thierry; Ermolli, Ilaria; Kretzschmar,
Matthieu; Krivova, Natalie; Mason, Helen; Qahwaji, Rami; Schmutz,
Werner; Solanki, Sami; Thuillier, Gerard; Tourpali, Kleareti; Unruh,
Yvonne; Verbeeck, Cis; Weber, Mark; Woods, Tom
2013EGUGA..1513079H Altcode:
Variations of solar irradiance are the most important natural factor
in the terrestrial climate and as such, the time dependent spectral
solar irradiance is a crucial input to any climate modelling. There
have been previous efforts to compile solar irradiance but it is
still uncertain by how much the spectral and total solar irradiance
changed on yearly, decadal and longer time scales. Observations of
irradiance data exist in numerous disperse data sets. Therefore, it
is important to bring together the European expertise in the field
to analyse and merge the complete set of European irradiance data,
complemented by archive data that include data from non-European
missions. We report on the initiation of a collaborative effort to unify
representatives from all European solar space experiments and European
teams specialized in multi-wavelength solar image processing. It is
intended to include the European groups involved in irradiance modelling
and reconstruction. They will work with two different state of the art
approaches to produce reconstructed spectral and total solar irradiance
data as a function of time. These results will be used to bridge
gaps in time and wavelength coverage of the observational data. This
will allow the proposing SOLID team to reduce the uncertainties in
the irradiance time series - an important requirement by the climate
community - and to provide uniform data sets of modelled and observed
solar irradiance data from the beginning of the space era to the
present including proper error and uncertainty estimates. Climate
research needs these data sets and therefore, the primary benefit
is for the climate community, but the stellar community, planetary,
lunar, and ionospheric researchers are also interested in having at
their disposition incident radiation of the Sun. The proposing team
plans to realize a wide international synergy in solar physics from
7 European countries, and collaborators from the US, complemented by
representatives from the climate community, who will accompany their
research work with wide dissemination activities.

---------------------------------------------------------
Title: Modeling the variability of Sun-like stars
Authors: Shapiro, Alexander; Knaack, Reto; Krivova, Natalie; Schmutz,
Werner; Solanki, Sami; Unruh, Yvonne
2013EGUGA..15.9981S Altcode:
We present a model which attributes the variability of the stellar
radiative energy flux to the imbalance between the contributions from
dark starspots and bright faculae. The stellar radiative energy flux
variations are modeled from the individual component's spectra, by
weighting them with corresponding filling factors. The filling factors
are deduced by extrapolating the sunspot and facular filling factors
dependencies on solar CaII S-index to stars with different levels
of the chromospheric activity. Our approach allows us to model the
stellar photometric variability vs. activity dependency and reproduce
the transition from spot-dominated to facula-dominated regimes of
variability. We show how the effect of inclination (arising due to the
random position of the Earth-bound observer relative to the directions
of stellar rotational axis) can affect these dependencies and present
the modeling of the individual stellar photometric light curves.

---------------------------------------------------------
Title: VizieR Online Data Catalog: Sun chromospheric CaII-HK emission
(Shapiro+, 2013)
Authors: Shapiro, A. I.; Schmutz, W.; Cessateur, G.; Rozanov, E.
2013yCat..35520114S Altcode: 2013yCat..35529114S
Monitoring of the photometric and chromospheric HK emission data
series of stars similar to the Sun in age and average activity
level showed that there is an empirical correlation between the
average stellar chromospheric activity level and the photometric
variability. In general, more active stars show larger photometric
variability. Interestingly, the measurements and reconstructions
of the solar irradiance show that the Sun is significantly less
variable than indicated by the empirical relationship. We aim
to identify possible reasons for the Sun to be currently outside of
this relationship. We employed different scenarios of solar HK
emission and irradiance variability and compared them with available
time series of Sun-like stars. (6 data files).

---------------------------------------------------------
Title: What can we learn about the Sun with PREMOS/PICARD?
Authors: Cessateur, Gaël; Shapiro, Alexander; Schmutz, Werner;
Krivova, Natalie; Solanki, Sami K.; Yeo, Kok Leng; Thuillier, Gérard
2013EGUGA..1511720C Altcode:
Total and Spectral Solar Irradiance are key input parameters to
atmospheric/oceanic and space weather models. We present here
spectral solar irradiance data from the radiometer PREMOS onboard
the PICARD satellite. This instrument convers the solar spectrum from
the Ultraviolet to near-infrared, and provides valuable information
and nourishes theoretical models. Based on redundancy strategies,
instrumental degradation has been mostly corrected, revealing
surprising behavior from the visible and near-infrared filters. We
compare these data with those from the VIRGO/SOHO and SOLSTIC/SORCE
experiments. Finally we use COSI to model the variability of the
irradiance, assuming that the latter is determined by the evolution
of the solar surface magnetic field as seen with SDO/HMI data. A
direct comparison shows a very good correlation for most of channels
from PREMOS.

---------------------------------------------------------
Title: Recent variability of the solar spectral irradiance and its
impact on climate modelling
Authors: Ermolli, I.; Matthes, K.; Dudok de Wit, T.; Krivova,
N. A.; Tourpali, K.; Weber, M.; Unruh, Y. C.; Gray, L.; Langematz,
U.; Pilewskie, P.; Rozanov, E.; Schmutz, W.; Shapiro, A.; Solanki,
S. K.; Woods, T. N.
2013ACP....13.3945E Altcode: 2012ACPD...1224557E; 2013arXiv1303.5577E
The lack of long and reliable time series of solar spectral irradiance
(SSI) measurements makes an accurate quantification of solar
contributions to recent climate change difficult. Whereas earlier SSI
observations and models provided a qualitatively consistent picture of
the SSI variability, recent measurements by the SORCE (SOlar Radiation
and Climate Experiment) satellite suggest a significantly stronger
variability in the ultraviolet (UV) spectral range and changes in the
visible and near-infrared (NIR) bands in anti-phase with the solar
cycle. A number of recent chemistry-climate model (CCM) simulations
have shown that this might have significant implications on the
Earth's atmosphere. Motivated by these results, we summarize here
our current knowledge of SSI variability and its impact on Earth's
climate. We present a detailed overview of existing SSI
measurements and provide thorough comparison of models available to
date. SSI changes influence the Earth's atmosphere, both directly,
through changes in shortwave (SW) heating and therefore, temperature
and ozone distributions in the stratosphere, and indirectly, through
dynamical feedbacks. We investigate these direct and indirect effects
using several state-of-the art CCM simulations forced with measured
and modelled SSI changes. A unique asset of this study is the use
of a common comprehensive approach for an issue that is usually
addressed separately by different communities. We show
that the SORCE measurements are difficult to reconcile with earlier
observations and with SSI models. Of the five SSI models discussed
here, specifically NRLSSI (Naval Research Laboratory Solar Spectral
Irradiance), SATIRE-S (Spectral And Total Irradiance REconstructions
for the Satellite era), COSI (COde for Solar Irradiance), SRPM (Solar
Radiation Physical Modelling), and OAR (Osservatorio Astronomico di
Roma), only one shows a behaviour of the UV and visible irradiance
qualitatively resembling that of the recent SORCE measurements. However,
the integral of the SSI computed with this model over the entire
spectral range does not reproduce the measured cyclical changes of the
total solar irradiance, which is an essential requisite for realistic
evaluations of solar effects on the Earth's climate in CCMs. We show that within the range provided by the recent SSI observations
and semi-empirical models discussed here, the NRLSSI model and SORCE
observations represent the lower and upper limits in the magnitude
of the SSI solar cycle variation. The results of the
CCM simulations, forced with the SSI solar cycle variations estimated
from the NRLSSI model and from SORCE measurements, show that the direct
solar response in the stratosphere is larger for the SORCE than for the
NRLSSI data. Correspondingly, larger UV forcing also leads to a larger
surface response. Finally, we discuss the reliability
of the available data and we propose additional coordinated work,
first to build composite SSI data sets out of scattered observations
and to refine current SSI models, and second, to run coordinated
CCM experiments.

---------------------------------------------------------
Title: The place of the Sun among the Sun-like stars
Authors: Shapiro, A. I.; Schmutz, W.; Cessateur, G.; Rozanov, E.
2013A&A...552A.114S Altcode: 2013arXiv1303.2245S
Context. Monitoring of the photometric and chromospheric HK emission
data series of stars similar to the Sun in age and average activity
level showed that there is an empirical correlation between the
average stellar chromospheric activity level and the photometric
variability. In general, more active stars show larger photometric
variability. Interestingly, the measurements and reconstructions
of the solar irradiance show that the Sun is significantly less
variable than indicated by the empirical relationship. Aims:
We aim to identify possible reasons for the Sun to be currently
outside of this relationship. Methods: We employed different
scenarios of solar HK emission and irradiance variability and
compared them with available time series of Sun-like stars. 
Results: We show that the position of the Sun on the diagram of
photometric variability versus chromospheric activity changes with
time. The present solar position is different from its temporal
mean position as the satellite era of continuous solar irradiance
measurements has accidentally coincided with a period of unusually
high and stable solar activity. Our analysis suggests that although
present solar variability is significantly smaller than indicated by
the stellar data, the temporal mean solar variability might be in
agreement with the stellar data. We propose that the continuation
of the photometric program and its expansion to a larger stellar
sample will ultimately allow us to constrain the historical solar
variability. Appendices A and B are available in electronic
form at <A href="http://www.aanda.org">http://www.aanda.org</A>All
time series are only available at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr">cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/552/A114">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/552/A114</A>

---------------------------------------------------------
Title: Modeling the detailed Lyman-α line profile
Authors: Schoell, Micha; Haberreiter, Margit; Schmutz, Werner;
Shapiro, Alexander
2013EGUGA..1512813S Altcode:
The variability of the solar spectral irradiance is an important
driver in global circulation models. The Lyman-α spectral line is of
particular interest as it exhibits a high variability and has strong
impact on the ozone concentration and temperature in the Earth's
atmosphere. For a complete understanding of the variation of the
Lyman-α line it is important to be able to model its detailed line
profile. We present recent work on the improvement of the modeling
efforts of this important spectral line. We employ an updated version
of the COde for Solar Irradiance (COSI) along with existing model
atmospheres with an improved implementation of the temperature and
turbulent velocity in the chromosphere and transition region. With
the latest modifications we are able to reproduce high resolution
observations taken with the SUMER instrument onboard of SOHO. This is
an important step towards the reliable reconstruction of the irradiance
in the Lyman-α spectral line.

---------------------------------------------------------
Title: The Sun among the Sun-like stars
Authors: Cessateur, Gaël; Shapiro, Alexander; Schmutz, Werner;
Rozanov, Eugene
2013EGUGA..15.8980C Altcode:
Monitoring of the photometric and chromospheric HK emission data
series of stars similar to the Sun in average activity level and
age showed that there is a correlation between the stellar average
chromospheric activity level and photometric variability. We aim to
understand whether the Sun obeys the empirical relationship prompted
by the stellar data and to identify possible reasons for the Sun to
be currently outside of this relationship.

---------------------------------------------------------
Title: Quasi-Periodic Pulsations during the onset of solar flares:
multi-instrumental comparison
Authors: West, M. J.; Dolla, L.; Marque, C.; Seaton, D. B.; Van
Doorsselaere, T.; Dominique, M.; Berghmans, D.; Cabanas, C.; De Groof,
A.; Schmutz, W.; Verdini, A.; Zender, J.; Zhukov, A. N.
2013enss.confE..82W Altcode:
Quasi-periodic pulsations have been observed in the rising phase of
solar flares for many years. Observations have been made over a wide
spectral range, extending from X-rays to radio wavelengths. The
current generation of spacebourne instruments, especially SDO,
EVE and ESP, have exceptionally high sampling rates and allow us
to make more detailed observations of this phenomena. In this work,
we compare short-period oscillations (around 10 s) observed in flare
events by multiple instruments: the radiometer channels of SDO/EVE-ESP
(soft X-ray, coronal and chromospheric passbands), the EUV channels of
the radiometer PROBA2/LYRA, the RHESSI passbands and short-wavelength
radio observations.

---------------------------------------------------------
Title: The EUI instrument on board the Solar Orbiter mission: from
breadboard and prototypes to instrument model validation
Authors: Halain, J. -P.; Rochus, P.; Renotte, E.; Appourchaux, T.;
Berghmans, D.; Harra, L.; Schühle, U.; Schmutz, W.; Auchère, F.;
Zhukov, A.; Dumesnil, C.; Delmotte, F.; Kennedy, T.; Mercier, R.;
Pfiffner, D.; Rossi, L.; Tandy, J.; BenMoussa, A.; Smith, P.
2012SPIE.8443E..07H Altcode:
The Solar Orbiter mission will explore the connection between the Sun
and its heliosphere, taking advantage of an orbit approaching the Sun at
0.28 AU. As part of this mission, the Extreme Ultraviolet Imager (EUI)
will provide full-sun and high-resolution image sequences of the solar
atmosphere at selected spectral emission lines in the extreme and vacuum
ultraviolet. To achieve the required scientific performances under the
challenging constraints of the Solar Orbiter mission it was required
to further develop existing technologies. As part of this development,
and of its maturation of technology readiness, a set of breadboard and
prototypes of critical subsystems have thus been realized to improve
the overall instrument design. The EUI instrument architecture, its
major components and sub-systems are described with their driving
constraints and the expected performances based on the breadboard and
prototype results. The instrument verification and qualification plan
will also be discussed. We present the thermal and mechanical model
validation, the instrument test campaign with the structural-thermal
model (STM), followed by the other instrument models in advance of
the flight instrument manufacturing and AIT campaign.

---------------------------------------------------------
Title: Confronting a solar irradiance reconstruction with solar and
stellar data
Authors: Judge, P. G.; Lockwood, G. W.; Radick, R. R.; Henry, G. W.;
Shapiro, A. I.; Schmutz, W.; Lindsey, C.
2012A&A...544A..88J Altcode:
Context. A recent paper by Shapiro and colleagues (2011, A&amp;A,
529, A67) reconstructs spectral and total irradiance variations of
the Sun during the holocene. Aims. In this note, we comment on why
their methodology leads to large (0.5%) variations in the solar TSI on
century-long time scales, in stark contrast to other reconstructions
which have ∼ 0.1% variations. Methods. We examine the amplitude
of the irradiance variations from the point of view of both solar
and stellar data. Results. Shapiro et al.'s large amplitudes arise
from differences between the irradiances computed from models A and C
of Fontenla and colleagues, and from their explicit assumption that
the radiances of the quiet Sun vary with the cosmic ray modulation
potential. We suggest that the upper photosphere, as given by model A,
is too cool, and discuss relative contributions of local vs. global
dynamos to the magnetism and irradiance of the quiet Sun. We compare
the slow (&gt;22 yr) components of the irradiance reconstructions with
secular changes in stellar photometric data that span 20 years or less,
and find that the Sun, if varying with such large amplitudes, would
still lie within the distribution of stellar photometric variations
measured over a 10-20 year period. However, the stellar time series
are individually too short to see if the reconstructed variations will
remain consistent with stellar variations when observed for several
decades more. Conclusions. By adopting model A, Shapiro et al. have
over-estimated quiet-Sun irradiance variations by about a factor of
two, based upon a re-analysis of sub-mm data from the James Clerk
Maxwell telescope. But both estimates are within bounds set by current
stellar data. It is therefore vital to continue accurate photometry of
solar-like stars for at least another decade, to reveal secular and
cyclic variations on multi-decadal time scales of direct interest to
the Sun.

---------------------------------------------------------
Title: Solar Spectral Irradiance as observed by LYRA/PROBA2 and
PREMOS/PICARD
Authors: Cessateur, Gaël.; Kretzschmar, Matthieu; Krivova, Natalie;
Schmutz, Werner; Solanki, Sami K.; Thuillier, Gerard; Shapiro,
Alexander; Schoell, Micha; Shapiro, Anna; Dominique, Marie; Tagirov,
Rinat; Wehrli, Christoph; Yeo, Kok Leng
2012cosp...39..287C Altcode: 2012cosp.meet..287C
No abstract at ADS

---------------------------------------------------------
Title: Comparison of Solar Irradiance reconstructions with stellar
data
Authors: Schmutz, Werner; Shapiro, Alexander
2012cosp...39.1725S Altcode: 2012cosp.meet.1725S
A recent paper by Shapiro and colleagues reconstructs spectral and
total irradiance variations of the Sun during the holocene. They
derive a total and spectral solar irradiance that was substantially
lower during the Maunder minimum than the one observed today. The
difference is remarkably larger than other estimations published in
the recent literature. In this presentation we examine the spectral
reconstructions in the light of stellar data. We compare the observed
and predicted solar variability with that of stars as observed by
Radick et al. (1998), Lockwood et al. (2007) and Hall et al. (2009)
in the b and y filters for the last 10- 20 years.

---------------------------------------------------------
Title: Modeling of the atmospheric response to a strong decrease of
the solar activity
Authors: Rozanov, Eugene V.; Egorova, Tatiana A.; Shapiro, Alexander
I.; Schmutz, Werner K.
2012IAUS..286..215R Altcode:
We estimate the consequences of a potential strong decrease of the
solar activity using the model simulations of the future driven by
pure anthropogenic forcing as well as its combination with different
solar activity related factors: total solar irradiance, spectral
solar irradiance, energetic electron precipitation, solar protons and
galactic cosmic rays. The comparison of the model simulations shows that
introduced strong decrease of solar activity can lead to some delay of
the ozone recovery and partially compensate greenhouse warming acting
in the direction opposite to anthropogenic effects. The model results
also show that all considered solar forcings are important in different
atmospheric layers and geographical regions. However, in the global
scale the solar irradiance variability can be considered as the most
important solar forcing. The obtained results constitute probably the
upper limit of the possible solar influence. Development of the better
constrained set of future solar forcings is necessary to address the
problem of future climate and ozone layer with more confidence.

---------------------------------------------------------
Title: New X-Ray Detections of WNL Stars
Authors: Skinner, Stephen L.; Zhekov, Svetozar A.; Güdel, Manuel;
Schmutz, Werner; Sokal, Kimberly R.
2012AJ....143..116S Altcode: 2012arXiv1203.5098S
Previous studies have demonstrated that putatively single nitrogen-type
Wolf-Rayet stars (WN stars) without known companions are X-ray
sources. However, almost all WN star X-ray detections so far have been
of earlier WN2-WN6 spectral subtypes. Later WN7-WN9 subtypes (also
known as WNL stars) have proved more difficult to detect, an important
exception being WR 79a (WN9ha). We present here new X-ray detections of
the WNL stars WR 16 (WN8h) and WR 78 (WN7h). These new results, when
combined with previous detections, demonstrate that X-ray emission is
present in WN stars across the full range of spectral types, including
later WNL stars. The two WN8 stars observed to date (WR 16 and WR 40)
show unusually low X-ray luminosities (Lx ) compared to
other WN stars, and it is noteworthy that they also have the lowest
terminal wind speeds (v ∞). Existing X-ray detections of
about a dozen WN stars reveal a trend of increasing Lx with
wind luminosity Lwind = (1/2)Ṁv2∞,
suggesting that wind kinetic energy may play a key role in establishing
X-ray luminosity levels in WN stars.

---------------------------------------------------------
Title: Solar Spectral Irradiance as observed by LYRA/PROBA2 and
PREMOS/PICARD
Authors: Cessateur, G.; Shapiro, A. I.; Dominique, M.; Kretzschmar,
M.; Krivova, N.; Shapiro, A. V.; Schmutz, W.; Schoell, M.; Solanki,
S.; Tagirov, R.; Thuillier, G.; Wehrli, C.; Yeo, K. L.
2012EGUGA..14.8254C Altcode:
Total and Spectral Solar Irradiance are key input parameters to
atmospheric/oceanic and space weather models. Both vary on time-scales
ranging from days to millennia, although a complete picture of the
solar irradiance variability is still missing. The recent launch of
two European missions PROBA-2 with LYRA radiometer onboard and PICARD
with PREMOS package onboard provides therefore valuable information and
nourishes theoretical models. Both instruments covers the solar spectrum
from the EUV to near-infrared. Here we present spectral solar irradiance
data from these two recent missions. After a proper correction of the
degradation and non-solar signatures, we compare these data with those
from the VIRGO/SOHO and SOLSTICE+SIM/SORCE experiments. Both LYRA and
PREMOS have also observed several solar eclipses, which allows us to
accurately retrieve the center-to-limb variations (CLVs) of the quiet
Sun's brightness at the wavelengths of the corresponding channels. CLVs
play indeed an important role in modelling of the solar irradiance
variability. We show that calculations with the published COde for
Solar Irradiance (COSI) yield CLVs that are in good agreement with
measurements. Finally we use COSI to model the variability of the
irradiance, assuming that the latter is determined by the evolution
of the solar surface magnetic field as seen with SDO/HMI data. These
theoretical results are compared to PREMOS and LYRA measurements.

---------------------------------------------------------
Title: Time Delays in Quasi-periodic Pulsations Observed during the
X2.2 Solar Flare on 2011 February 15
Authors: Dolla, L.; Marqué, C.; Seaton, D. B.; Van Doorsselaere,
T.; Dominique, M.; Berghmans, D.; Cabanas, C.; De Groof, A.; Schmutz,
W.; Verdini, A.; West, M. J.; Zender, J.; Zhukov, A. N.
2012ApJ...749L..16D Altcode: 2012arXiv1203.6223D
We report observations of quasi-periodic pulsations (QPPs) during the
X2.2 flare of 2011 February 15, observed simultaneously in several
wavebands. We focus on fluctuations on timescale 1-30 s and find
different time lags between different wavebands. During the impulsive
phase, the Reuven Ramaty High Energy Solar Spectroscopic Imager
channels in the range 25-100 keV lead all the other channels. They
are followed by the Nobeyama RadioPolarimeters at 9 and 17 GHz and the
extreme-ultraviolet (EUV) channels of the Euv SpectroPhotometer (ESP)
on board the Solar Dynamic Observatory. The zirconium and aluminum
filter channels of the Large Yield Radiometer on board the Project for
On-Board Autonomy satellite and the soft X-ray (SXR) channel of ESP
follow. The largest lags occur in observations from the Geostationary
Operational Environmental Satellite, where the channel at 1-8 Å leads
the 0.5-4 Å channel by several seconds. The time lags between the
first and last channels is up to ≈9 s. We identified at least two
distinct time intervals during the flare impulsive phase, during which
the QPPs were associated with two different sources in the Nobeyama
RadioHeliograph at 17 GHz. The radio as well as the hard X-ray channels
showed different lags during these two intervals. To our knowledge,
this is the first time that time lags are reported between EUV and
SXR fluctuations on these timescales. We discuss possible emission
mechanisms and interpretations, including flare electron trapping.

---------------------------------------------------------
Title: A New Solar Spectral Irradiance Reconstruction based on MGII
and Neutral Monitoring Indices for Use in Climate Modelling
Authors: Thuillier, G.; Bolsée, D.; DeLand, M.; Melo, S. M. L.;
Schmutz, W.; Shapiro, A.
2012EGUGA..14.8248T Altcode:
For atmosphere and climate studies, the solar spectral irradiance
may be necessary at a time where no data exist. Use of proxies is
then mandatory. In order to represent the solar forcing as variable
in chemistry-climate numerical models, we need consistent series of
temporal solar total and spectral variability covering over the periods
of interest. While measurements are available, there is currently
no harmonized series with some understanding of its accuracy and
precision that can be readily implemented in model simulations. In
this paper we present a new method to reconstruct the solar spectrum
irradiance in the Ly α-400 nm region, and its variability, based
on the Mg II index and neutron monitor data. This approach has the
advantage of being independent of the absolute calibration and aging
of the instruments. First, the Mg II index is derived using solar
spectra from Ly α (121 nm) to 410 nm measured from 1978 to 2010 by
several space missions. The variability of the spectra with respect
to a chosen reference spectrum as a function of time and wavelength
is scaled to the derived Mg II index. Then, the set of coefficients
expressing the spectral variability can be applied to a chosen reference
spectrum to reconstruct the solar spectra within a given time frame
or a Mg II index values. The accuracy of this method is estimated by
calculating the standard deviation between the measured spectra and
their reconstruction. For the second step, the relationship between
the Mg II index and the neutron monitor data is searched for the
30-year of Mg II index availability. Finally, the reconstruction at
a given date consists in using the neutron monitor data at that date,
derive the corresponding Mg II index and use the coefficients of SSI
variability to obtain the SSI at that date using a chosen reference
spectrum. One major advantage is that using technology of today, we
can reconstruct the solar spectral irradiance consistently from today
to times when cosmogenic isotope data are available. This calibration
can be re-accessed at any time, if necessary. Reconstruction for the
Maunder minimum will be shown as well as variation of stratospheric
components concentration inferred by solar variability.

---------------------------------------------------------
Title: Signature of the 27-day solar rotation cycle in mesospheric
OH and H2O observed by the Aura Microwave Limb Sounder
Authors: Shapiro, A. V.; Rozanov, E.; Shapiro, A. I.; Wang, S.;
Egorova, T.; Schmutz, W.; Peter, Th.
2012ACP....12.3181S Altcode: 2011ACPD...1128477S
The mesospheric hydroxyl radical (OH) is mainly produced by the
water vapor (H2O) photolysis and could be considered as
a proxy for the influence of the solar irradiance variability on the
mesosphere. We analyze the tropical mean response of the mesospheric OH
and H2O data as observed by the Aura Microwave Limb Sounder
(MLS) to 27-day solar variability. The analysis is performed for two
time periods corresponding to the different phases of the 11-yr cycle:
from December 2004 to December 2005 (the period of "high activity"
with a pronounced 27-day solar cycle) and from August 2008 to August
2009 ("solar minimum" period with a vague 27-day solar cycle). We
demonstrate, for the first time, that in the mesosphere the daily time
series of OH concentrations correlate well with the solar irradiance
(correlation coefficients up to 0.79) at zero time-lag. At the same
time H2O anticorrelates (correlation coefficients up to
-0.74) with the solar irradiance at non-zero time-lag. We found that
the response of OH and H2O to the 27-day variability of the
solar irradiance is strong for the period of the high solar activity
and negligible for the solar minimum conditions. It allows us to
suggest that the 27-day cycle in the solar irradiance and in OH and
H2O are physically connected.

---------------------------------------------------------
Title: The Solar Spectral Irradiance as a Function of the Mg II
Index for Atmosphere and Climate Modelling
Authors: Thuillier, G.; DeLand, M.; Shapiro, A.; Schmutz, W.; Bolsée,
D.; Melo, S. M. L.
2012SoPh..277..245T Altcode:
We present a new method to reconstruct the solar spectrum irradiance in
the Ly α - 400 nm region, and its variability, based on the Mg II index
and neutron-monitor measurements. Measurements of the solar spectral
irradiance available in the literature have been made with different
instruments at different times and different spectral ranges. However,
climate studies require harmonised data sets. This new approach has the
advantage of being independent of the absolute calibration and aging of
the instruments. First, the Mg II index is derived using solar spectra
from Ly α (121 nm) to 410 nm measured from 1978 to 2010 by several
space missions. The variability of the spectra with respect to a chosen
reference spectrum as a function of time and wavelength is scaled
to the derived Mg II index. The set of coefficients expressing the
spectral variability can be applied to the chosen reference spectrum to
reconstruct the solar spectra within a given time frame or Mg II index
values. The accuracy of this method is estimated using two approaches:
direct comparison with particular cases where solar spectra are
available from independent measurements, and calculating the standard
deviation between the measured spectra and their reconstruction. From
direct comparisons with measurements we obtain an accuracy of about
1 to 2%, which degrades towards Ly α. In a further step, we extend
our solar spectral-irradiance reconstruction back to the Maunder
Minimum introducing the relationship between the Mg II index and the
neutron-monitor data. Consistent measurements of the Mg II index are
not available prior to 1978. However, we remark that over the last
three solar cycles, the Mg II index shows strong correlation with the
modulation potential determined from the neutron-monitor data. Assuming
that this correlation can be applied to the past, we reconstruct the
Mg II index from the modulation potential back to the Maunder Minimum,
and obtain the corresponding solar spectral-irradiance reconstruction
back to that period. As there is no direct measurement of the spectral
irradiance for this period we discuss this methodology in light of
the other proposed approaches available in the literature. The use of
the cosmogenic-isotope data provides a major advantage: it provides
information about solar activity over several thousands years. Using
technology of today, we can calibrate the solar irradiance against
activity and thus reconstruct it for the times when cosmogenic-isotope
data are available. This calibration can be re-assessed at any time,
if necessary.

---------------------------------------------------------
Title: Influence of the Precipitating Energetic Particles on
Atmospheric Chemistry and Climate
Authors: Rozanov, E.; Calisto, M.; Egorova, T.; Peter, T.; Schmutz, W.
2012omee.book..151R Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Modeling of the Solar Spectral Irradiance as observed by
LYRA/PROBA2 and PREMOS/PICARD
Authors: Shapiro, A.; Cessateur, G.; Dominique, M.; Krivova, N. A.;
Lachat, D.; Rozanov, E.; Schmutz, W. K.; Shapiro, A. V.; Tagirov,
R. V.; Thuillier, G. O.; Wehrli, C.
2011AGUFMGC22A..07S Altcode:
Measurements and modeling of the solar irradiance have gained
an increased attention during the last few decades. Nevertheless a
complete picture of the solar variability is still missing. Therefore
a launch of every new space mission devoted to the measurements of the
spectral solar irradiance provides a crucial piece of complementary
information and nourishes the theoretical models. We present here
spectral solar irradiance data from the recent European missions PROBA-2
(launched on November 2, 2009) and PICARD (launched on June 15, 2010)
and their theoretical interpretation. The PREMOS package onboard PICARD
comprises two experiments, one observing solar irradiance in five (two
UV, one visible and two near infrared) spectral channels with filter
radiometers the other measuring TSI with absolute radiometers. LYRA
is a solar VUV radiometer onboard PROBA-2, which is a technologically
oriented ESA micro-mission, and is observing the solar irradiance
in two UV and two EUV spectral channels. The passbands of the UV
channels in the both experiments were selected on the ground of
relevance for the terrestrial ozone concentration. The PREMOS and
LYRA measurements were carefully corrected for the degradation and
cleaned for non-solar signatures. We provide a comparison with the
VIRGO/SOHO and SOLSTICE+SIM/SORCE data. Both LYRA and PREMOS have
observed several solar eclipses. The analysis of these observations
allows us to accurately retrieve the center-to-limb variations (CLV)
of the solar brightness, which play an important role in the modeling
of the solar irradiance variability on the time scale of the solar
rotation. We show that the calculations with the recently developed
and published COde for Solar Irradiance (COSI) yield the CLV which
are in a good agreement with the measurements. The irradiance in
all channels shows a clear variability on time-scale of the solar
rotation. The amplitude and the profile of the variability strongly
depend on the wavelength. We use COSI as a tool for modeling the
variability of the irradiance, assuming that the latter is determined
by the evolution of the solar surface magnetic field. The theoretical
results are compared with the PREMOS and LYRA measurements. Finally
we show that COSI and other semi-empirical and empirical models allow
to reconstruct the entire solar spectrum from the observations in a
few passbands. Hence the PREMOS and LYRA measurements can be used as
a proxies for the nowcasting of the solar irradiance (UV-visible-IR)
with the high cadence rate and spectral resolution.

---------------------------------------------------------
Title: The Solar Spectral Irradiance Measured on Board the
International Space Station and the Picard Spacecraft
Authors: Thuillier, G. O.; Bolsee, D.; Schmidtke, G.; Schmutz, W. K.
2011AGUFMGC22A..05T Altcode:
On board the International Space Station, the spectrometers SOL-ACES
and SOLSPEC measure the solar spectrum irradiance from 17 to 150
nm and 170 to 2900 nm, respectively. On board PICARD launched on
15 June 2010, the PREMOS instrument consists in a radiometer and
several sunphotometers operated at several fixed wavelengths. We
shall present spectra at different solar activity levels as well
as their quoted accuracy. Comparison with similar data from other
missions presently running in space will be shown incorporating the
PREMOS measurements. Some special solar events will be also presented
and interpreted.

---------------------------------------------------------
Title: PREMOS Absolute Radiometer Calibration and Implications to
on-orbit Measurements of the Total Solar Irradiance
Authors: Fehlmann, A.; Kopp, G.; Schmutz, W. K.; Winkler, R.;
Finsterle, W.; Fox, N.
2011AGUFMGC21C..05F Altcode:
On orbit measurements starting in the late 1970's, have revealed the 11
year cycle of the Total Solar Irradiance (TSI). However, the absolute
results from individual experiments differ although all instrument
teams claim to measure an absolute value. Especially the data from the
TIM/SORCE experiment confused the community as it measures 0.3 % lower
than the other instruments, e.g. VIRGO/SOHO by PMOD/WRC, which clearly
exceeds the uncertainty stated for the absolute characterization of the
experiments. The PREMOS package on the PICARD platform launched in June
2010 is the latest space experiment by PMOD/WRC measuring the TSI. We
have put great effort in the calibration and characterization of this
instrument in order to resolve the inter-instrument differences. We
performed calibrations at the National Physical Laboratory (NPL) in
London and the Laboratory for Atmospheric and Space Physics (LASP)
in Boulder against national SI standards for radiant power using a
laser beam with a diameter being smaller than the aperture of the
instrument. These measurements together with the World Radiometric
Reference (WRR) calibration in Davos allowed to compare the WRR and
the SI radiant power scale. We found that the WRR lies 0.18 % above
the SI radiant power scale which explains a part of the VIRGO-TIM
difference. The Total solar irradiance Radiometer Facility (TRF) at
the LASP allows to generate a beam that over fills the apertures of
our instruments, giving the presently best available representation
of solar irradiance in a laboratory. These irradiance calibrations
revealed a stray light contribution between 0.09 and 0.3 % to the
measurements which had been underestimated in the characterization
of our instruments. Using the irradiance calibrations, we found that
the WRR lies 0.32 % above the TRF scale which in turn explains the
full VIRGO-TIM difference. The first light PREMOS measurements in
space confirmed our findings. If we use the WRR calibration, PREMOS
yields a TSI value of 1365.5 ± 1.2 W/m2 (k=1) which is
in excellent agreement with VIRGO (1365.4 W/m2). Else,
applying the TRF calibration to PREMOS, we obtain a TSI value of 1360.9
± 0.4 W/m2 (k=1) which is in excellent agreement with TIM
(1361.3 W/m2).

---------------------------------------------------------
Title: LYRA and SWAP, the two Solar Instruments on-board PROBA2
Authors: Dominique, M.; Berghmans, D.; Schmutz, W. K.; Dammasch, I.;
De Groof, A.; Halain, J.; Hochedez, J.; Kretzschmar, M.; Seaton, D. B.
2011AGUFMSH13B1949D Altcode:
PROBA2 (http://proba2.sidc.be) is an ESA micro-satellite that was
launched in November 2009. Two instruments on-board, SWAP and LYRA, are
devoted to solar observations. SWAP (PI: D. Berghmans) is an EUV imager
observing the corona with a bandpass centered on 174 Å at a cadence of
1-2 min. Its high contrast images, large FOV and flexible off-pointing
capabilities make SWAP particularly well suited for the study of coronal
eruptions. LYRA (PI: M. Dominique) is a UV-EUV radiometer observing
in four spectral channels, chosen for their relevance in solar physics
and aeronomy. Its very fast acquisition cadence (up to 100 Hz) allows
scientists to perform detailed analysis of solar flares. We discuss
the characteristics of both instruments, review their performance and
evolution, and highlight their complementarity to other missions. We
also present the data products that can be downloaded from the mission
website and give an overview of the various investigations for which
SWAP and LYRA data are currently used (CMEs, flares, solar variability,
and many others).

---------------------------------------------------------
Title: Solar total irradiance in cycle 23
Authors: Krivova, N. A.; Solanki, S. K.; Schmutz, W.
2011A&A...529A..81K Altcode: 2011arXiv1102.3077K
Context. The most recent minimum of solar activity was deeper and
longer than the previous two minima as indicated by different proxies
of solar activity. This is also true for the total solar irradiance
(TSI) according to the PMOD composite. Aims: The apparently
unusual behaviour of the TSI has been interpreted as evidence against
solar surface magnetism as the main driver of the secular change
in the TSI. We test claims that the evolution of the solar surface
magnetic field does not reproduce the observed TSI in cycle 23. Methods: We use sensitive, 60-min averaged MDI magnetograms and
quasi-simultaneous continuum images as an input to our SATIRE-S model
and calculate the TSI variation over cycle 23, sampled roughly every
two weeks. The computed TSI is then compared with the PMOD composite of
TSI measurements and with the data from two individual instruments,
SORCE/TIM and UARS/ACRIM II, that monitored the TSI during the
declining phase of cycle 23 and over the previous minimum in 1996,
respectively. Results: Excellent agreement is found between the
trends shown by the model and almost all sets of measurements. The
only exception is the early, i.e. 1996 to 1998, PMOD data. Whereas
the agreement between the model and the PMOD composite over the
period 1999-2009 is almost perfect, the modelled TSI shows a steeper
increase between 1996 and 1999 than implied by the PMOD composite. On
the other hand, the steeper trend in the model agrees remarkably well
with the ACRIM II data. A closer look at the VIRGO data, which are the
basis of the PMOD composite after 1996, reveals that only one of the
two VIRGO instruments, the PMO6V, shows the shallower trend present
in the composite, whereas the DIARAD measurements indicate a steeper
trend. Conclusions: Based on these results, we conclude that (1)
the sensitivity changes of the PMO6V radiometers within VIRGO during
the first two years have very likely not been correctly evaluated;
and that (2) the TSI variations over cycle 23 and the change in the
TSI levels between the minima in 1996 and 2008 are consistent with
the solar surface magnetism mechanism.

---------------------------------------------------------
Title: A new approach to the long-term reconstruction of the solar
irradiance leads to large historical solar forcing
Authors: Shapiro, A. I.; Schmutz, W.; Rozanov, E.; Schoell, M.;
Haberreiter, M.; Shapiro, A. V.; Nyeki, S.
2011A&A...529A..67S Altcode: 2011arXiv1102.4763S
Context. The variable Sun is the most likely candidate for the
natural forcing of past climate changes on time scales of 50 to
1000 years. Evidence for this understanding is that the terrestrial
climate correlates positively with the solar activity. During
the past 10 000 years, the Sun has experienced the substantial
variations in activity and there have been numerous attempts to
reconstruct solar irradiance. While there is general agreement on
how solar forcing varied during the last several hundred years -
all reconstructions are proportional to the solar activity - there
is scientific controversy on the magnitude of solar forcing. 
Aims: We present a reconstruction of the total and spectral solar
irradiance covering 130 nm-10 μm from 1610 to the present with an
annual resolution and for the Holocene with a 22-year resolution. Methods: We assume that the minimum state of the quiet Sun in time
corresponds to the observed quietest area on the present Sun. Then
we use available long-term proxies of the solar activity, which are
10Be isotope concentrations in ice cores and 22-year smoothed
neutron monitor data, to interpolate between the present quiet Sun and
the minimum state of the quiet Sun. This determines the long-term trend
in the solar variability, which is then superposed with the 11-year
activity cycle calculated from the sunspot number. The time-dependent
solar spectral irradiance from about 7000 BC to the present is then
derived using a state-of-the-art radiation code. Results: We
derive a total and spectral solar irradiance that was substantially
lower during the Maunder minimum than the one observed today. The
difference is remarkably larger than other estimations published in
the recent literature. The magnitude of the solar UV variability,
which indirectly affects the climate, is also found to exceed previous
estimates.We discuss in detail the assumptions that lead us to this
conclusion. Appendix is only available in electronic form at <A
href="http://www.aanda.org">http://www.aanda.org</A>

---------------------------------------------------------
Title: The atmospheric effects of October 2003 solar proton event
simulated with the chemistry-climate model SOCOL using complete and
parameterized ion chemistry
Authors: Egorova, T.; Rozanov, E.; Ozolin, Y.; Shapiro, A.; Calisto,
M.; Peter, Th.; Schmutz, W.
2011JASTP..73..356E Altcode:
October 2003 solar proton events (SPE) is rather well covered by the
observations; therefore its studies represent a good way for model
validation and intercomparison. Here we apply chemistry-climate model
(CCM) SOCOL with complete (SOCOLi) and parameterized ion
chemistry to evaluate the accuracy of a commonly used ion chemistry
parameterization scheme. We performed ensemble experiments with and
without SPE to characterize the effect of the October 2003 SPE on the
NOx, HOx, ClOx and O3 in
the middle atmosphere. Preliminary comparison of the simulated effects
against MIPAS observations revealed rather good general agreement
for most of the species. Comparison of the results obtained with
complete and parameterized ion chemistry representation showed that
the model with parameterized ion chemistry underestimates the effect
of SPE on chemical composition of the middle atmosphere by up to 40%
for NOx and N2O, up to 70% for HOx and
ClOx and up to 600% for HNO3. The parameterization
is more accurate for ozone, however the model with parameterized ion
chemistry underestimates ozone depletion by up to 15% during the SPE
in the mesosphere and by 10% 2 weeks later in the stratosphere, which
can be important for the long-term effects of SPE on the ozone layer.

---------------------------------------------------------
Title: Sensitivity of the Earth’s middle atmosphere to short-term
solar variability and its dependence on the choice of solar irradiance
data set
Authors: Shapiro, A. V.; Rozanov, E.; Egorova, T.; Shapiro, A. I.;
Peter, Th.; Schmutz, W.
2011JASTP..73..348S Altcode:
We simulate the time evolution of the neutral and charged species in
the terrestrial middle atmosphere using a 1-D radiative-convective
model with interactive neutral and ion chemistry driven by four
different sets of daily spectral solar irradiance (SSI) available in
the literature for the year 2000. Obtained daily time series of ozone,
hydroxyl and electron densities are used to calculate their sensitivity
to the short-term SSI variability at 205 nm. All applied SSI data
sets possess 27-day solar rotation cycle; however, its amplitude and
phase as well as the correlation between considered SSI time series
differ among data sets leading to the different behavior of the
atmospheric response. Contrary, the ozone and hydroxyl sensitivities
to the SSI changes during solar rotation cycle are almost identical
for all applied SSI data sets in the stratosphere. In the mesosphere,
the difference in correlation between SSI in Herzberg continuum and
Lyman-α line in considered SSI data sets leads to substantial scatter
of the sensitivity estimates based on 205 nm. Our results show that for
the sensitivity analysis in the stratosphere based on the SSI at 205
nm any considered SSI data sets can be applied. For the mesosphere,
where the sensitivity strongly varies among applied SSI data sets
more robust results can be obtained using the sensitivity calculations
based on the SSI in Lyman-α line.

---------------------------------------------------------
Title: The Sun-Climate Connection Through Measurements and Modeling:
The Picard Investigation
Authors: Thuillier, Gérard; Dewitte, Steven; Schmutz, Werner;
Picard Team
2011sswh.book..365T Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Shape of the Solar Limb: Models and Observations
Authors: Thuillier, G.; Claudel, J.; Djafer, D.; Haberreiter, M.; Mein,
N.; Melo, S. M. L.; Schmutz, W.; Shapiro, A.; Short, C. I.; Sofia, S.
2011SoPh..268..125T Altcode: 2010SoPh..tmp..202T; 2010SoPh..tmp..226T
In this paper we compare observed, empirical, and modelled solar limb
profiles and discuss their potential use to derive physical properties
of the solar atmosphere. The PHOENIX, SolMod3D, and COSI radiative
transfer codes as well as VAL-C models are used to calculate the
solar limb shape under different assumptions. The main properties
of each model are shown. The predicted limb shape as a function of
wavelength for different features on the solar disk, such as quiet Sun,
sunspots, and faculae, is investigated. These models provide overall
consistent limb shapes with some discrepancies that are discussed
here in terms of differences in solar atmosphere models, opacities,
and the algorithms used to derive the solar limb profile. Our analysis
confirms that the most common property of all models is limb shapes that
are much steeper than what is observed, or predicted by the available
empirical models. Furthermore, we have investigated the role of the
Fraunhofer lines within the spectral domain used for the solar limb
measurements. Our results show that the presence of the Fraunhofer
lines significantly displaces the limb inflection point from its
position estimated assuming only the photospheric continuum. The PICARD
satellite, launched on 15 June 2010, will provide measurements of the
limb shape at several wavelengths. This work shows that the precision of
these measurements allows for discrimination among the available models.

---------------------------------------------------------
Title: New X-ray Detections Of Late Nitrogen-type (WNL) Wolf-Rayet
Stars
Authors: Skinner, Steve L.; Guedel, M.; Schmutz, W.; Zhekov, S.
2011AAS...21733819S Altcode: 2011BAAS...4333819S
We present results of recent X-ray observations of nitrogen-type
Wolf-Rayet (WR) stars, focusing on late WN7 - WN9 subtypes. These
observations were obtained as part of a broader X-ray survey of single
WN stars using XMM-Newton and Chandra aimed at determining their X-ray
properties and identifying plausible emission mechanisms. None of
the WN survey targets is known to be a member of a binary system. We
report unambiguous detections of WR 78 (WN7h) and WR 79a (WN9ha), and a
possible (faint) detection of WR 16 (WN8h). These new WNL detections,
along with previous detections of WN2 - WN6 stars, demonstrate
that WN stars are X-ray sources across their full range of spectral
subtypes. The X-ray luminosities of WN stars span a broad range (even
among stars of similar spectral subtype) with typical values log Lx =
31.5 - 33.5 (ergs/s). There is some evidence that Lx is proportional
to wind kinetic energy. WN star X-ray spectra show higher absorption
than expected from optical extinction, likely due to their powerful
metal-rich winds. Their spectra reveal strong emission lines from
ionized metals and spectral fits typically require two components
consisting of cool (kT &lt; 1 keV) and hot (kT &gt; 2 keV) plasma. Only
cool plasma is anticipated if the X-rays arise in radiative wind shocks,
so the presence of hot plasma implies other as yet unidentified X-ray
production mechanisms are at work. Magnetic fields may play a role,
but in contrast to magnetically-active solar-like stars, WN stars do not
show large-amplitude X-ray flares in observations typically spanning a
half day. But, more extensive monitoring at higher time-resolution is
needed. Alternatively, unseen companions at close separation could play
a role in WN star X-ray emission in some cases (esp. higher Lx objects),
either via their intrinsic emission or as colliding wind secondaries.

---------------------------------------------------------
Title: New SSI and TSI reconstruction suggests large value of the
radiative solar forcing
Authors: Shapiro, A.; Schmutz, W. K.; Thuillier, G.; Rozanov, E.;
Haberreiter, M.; Schoell, M.; Shapiro, A.; Nyeki, S.
2010AGUFMGC21B0875S Altcode:
We have developed and published the COde for Solar Irradiance (COSI)
which allows us to calculate the entire solar spectrum. COSI reproduces
the spectral irradiance measured by SOLSTICE (up to 320 nm) and SIM
(from 320 nm onward) onboard the SORCE satellite during the 2008 solar
minimum as well as SOLSPEC during the ATLAS 3 mission in 1994 with high
accuracy. COSI is also used as a tool for modeling the variability of
the solar irradiance. In our new reconstruction we represent the quiet
Sun as a combination of two components. The first corresponds to the
least active areas of the Sun as presently observed, while the second
component is responsible for the magnetic activity of the quiet Sun. The
time-dependent filling factors of these components are calculated based
on the solar activity as derived from cosmogenic isotope concentrations
in natural archieves. This allows us to obtain a time-dependent
reconstructed solar spectrum from 7000 BC to the present with a temporal
resolution of 22 years. From 1610 onward we have additional information
from sunspot numbers, which allows the reconstruction of the spectral
solar irradiance with a yearly resolution. These basic assumptions
lead to a total and spectral solar irradiance that was substantially
lower during the Maunder minimum than observed today. The difference
is remarkably larger than other estimations published in the recent
literature. Using our reconstruction as an input to a chemistry-climate
model we show that the enhanced UV variability results in significant
variations of stratospheric ozone and temperature.

---------------------------------------------------------
Title: The effect of flares on total solar irradiance
Authors: Kretzschmar, Matthieu; de Wit, Thierry Dudok; Schmutz,
Werner; Mekaoui, Sabri; Hochedez, Jean-François; Dewitte, Steven
2010NatPh...6..690K Altcode: 2010arXiv1003.5258K
Flares are powerful bursts of energy released by relatively
poorly understood processes that take place in the atmospheres of
stars. However, although solar flares, from our own Sun, are the most
energetic events in the solar system, in comparison to the total output
of the Sun they are barely noticeable. Consequently, the total amount
of radiant energy they generate is not precisely known, and their
potential contribution to variations in the total solar irradiance
incident on the Earth has so far been overlooked. In this work, we
identify a measurable signal from relatively moderate solar flares in
total solar irradiance data. We find that the total energy radiated
by flares exceeds by two orders of magnitude the flare energy radiated
in the soft-X-ray domain only, indicating a major contribution in the
visible domain. These results have implications for our understanding
of solar-flare activity and the variability of our star.

---------------------------------------------------------
Title: NLTE solar irradiance modeling with the COSI code
Authors: Shapiro, A. I.; Schmutz, W.; Schoell, M.; Haberreiter, M.;
Rozanov, E.
2010A&A...517A..48S Altcode: 2010arXiv1004.3048S
Context. The solar irradiance is known to change on time scales
of minutes to decades, and it is suspected that its substantial
fluctuations are partially responsible for climate variations. Aims: We are developing a solar atmosphere code that allows the
physical modeling of the entire solar spectrum composed of quiet Sun
and active regions. This code is a tool for modeling the variability
of the solar irradiance and understanding its influence on Earth. Methods: We exploit further development of the radiative transfer
code COSI that now incorporates the calculation of molecular lines. We
validated COSI under the conditions of local thermodynamic equilibrium
(LTE) against the synthetic spectra calculated with the ATLAS code. The
synthetic solar spectra were also calculated in non-local thermodynamic
equilibrium (NLTE) and compared to the available measured spectra. In
doing so we have defined the main problems of the modeling, e.g., the
lack of opacity in the UV part of the spectrum and the inconsistency
in the calculations of the visible continuum level, and we describe
a solution to these problems. Results: The improved version
of COSI allows us to reach good agreement between the calculated
and observed solar spectra as measured by SOLSTICE and SIM onboard
the SORCE satellite and ATLAS 3 mission operated from the Space
Shuttle. We find that NLTE effects are very important for the modeling
of the solar spectrum even in the visual part of the spectrum and for
its variability over the entire solar spectrum. In addition to the
strong effect on the UV part of the spectrum, NLTE effects influence
the concentration of the negative ion of hydrogen, which results in a
significant change of the visible continuum level and the irradiance
variability. Figures 13 and 14 are only available in electronic
form at <A href="http://www.aanda.org">http://www.aanda.org</A>

---------------------------------------------------------
Title: Towards a New Formation Flying Solar Coronagraph
Authors: Lamy, P.; Vives, S.; Curdt, W.; Dame, L.; Davila, J.; Defise,
J. M.; Fineschi, S.; Heinzel, P.; Kuzin, S.; Schmutz, W.; Tsinganos,
K.; Turck-Chieze, S.; Zhukov, A.
2010ASPC..424...15L Altcode:
We briefly describe an investigation aiming at the development of a
giant solar coronagraph instrument onboard of two satellites, separated
by about 150 m in formation flight for the detailed observation of the
solar coronal plasma. The European Space Agency (ESA) has selected this
instrument as the only payload onboard the Proba 3 satellites which
will be launched in 2013. The Greek team is developing the command
control board of the coronagraph.

---------------------------------------------------------
Title: Chandra Detects the Rare Oxygen-type Wolf-Rayet Star WR 142
and OB Stars in Berkeley 87
Authors: Sokal, Kimberly R.; Skinner, Stephen L.; Zhekov, Svetozar A.;
Güdel, Manuel; Schmutz, Werner
2010ApJ...715.1327S Altcode: 2010arXiv1004.0462S
We present first results of a Chandra X-ray observation of the rare
oxygen-type Wolf-Rayet (WR) star WR 142 (= Sand 5 = St 3) harbored
in the young, heavily obscured cluster Berkeley 87. Oxygen-type WO
stars are thought to be the most evolved of the WRs and progenitors
of supernovae or gamma-ray bursts. As part of an X-ray survey of
supposedly single WR stars, we observed WR 142 and the surrounding
Berkeley 87 region with Chandra ACIS-I. We detect WR 142 as a faint
yet extremely hard X-ray source. Due to weak emission, its nature as a
thermal or non-thermal emitter is unclear and thus we discuss several
emission mechanisms. Additionally, we report seven detections and
eight non-detections by Chandra of massive OB stars in Berkeley 87,
two of which are bright yet soft X-ray sources whose spectra provide
a dramatic contrast to the hard emission from WR 142.

---------------------------------------------------------
Title: X-ray Emission from Nitrogen-Type Wolf-Rayet Stars
Authors: Skinner, Stephen L.; Zhekov, Svetozar A.; Güdel, Manuel;
Schmutz, Werner; Sokal, Kimberly R.
2010AJ....139..825S Altcode: 2009arXiv0912.1326S
We summarize new X-ray detections of four nitrogen-type Wolf-Rayet
(WR) stars obtained in a limited survey aimed at establishing the
X-ray properties of WN stars across their full range of spectral
subtypes. None of the detected stars is so far known to be a close
binary. We report Chandra detections of WR 2 (WN2), WR 18 (WN4),
and WR 134 (WN6), and an XMM-Newton detection of WR79a (WN9ha). These
observations clearly demonstrate that both WNE and WNL stars are X-ray
sources. We also discuss Chandra archive detections of the WN6h stars
WR 20b, WR 24, and WR 136 and ROSAT non-detections of WR 16 (WN8h)
and WR 78 (WN7h). The X-ray spectra of all WN detections show prominent
emission lines and an admixture of cool (kT &lt; 1 keV) and hot (kT &gt;
2 keV) plasma. The hotter plasma is not predicted by radiative wind
shock models and other as yet unidentified mechanisms are at work. Most
stars show X-ray absorption in excess of that expected from visual
extinction (A V), likely due to their strong winds or cold
circumstellar gas. Existing data suggest a falloff in X-ray luminosity
toward later WN7-9 subtypes, which have higher L bol but
slower, denser winds than WN2-6 stars. This provides a clue that wind
properties may be a more crucial factor in determining emergent X-ray
emission levels than bolometric luminosity.

---------------------------------------------------------
Title: Effects of the solar spectral irradiance changes during the
first half of 20th century on chemistry and climate
Authors: Rozanov, Eugene; Dorf, Davos; Arfeuille, F.; Brünnimann, S.;
Calisto, M.; Egorova, T.; Fischer, A.; Heckendorn, P.; Luo, B. -P.;
Peter, T.; Rozanov, E.; Shapiro, A. V.; Schmutz, W.; Schraner, M.;
Stenke, A.; Zubov, V.
2010cosp...38...21R Altcode: 2010cosp.meet...21R
The attribution of climate and chemistry changes in the past requires
understanding of the role of different natural forcing such as volcanic
eruptions and solar irradiance. The first half of the 20th century
is characterized by an increase in solar activity (and presumably
solar irradi-ance) reaching the maximum in the year 1957. Therefore,
to elucidate the contribution of the solar irradiance to the climate
change we have carried out two 60-year long transient ensemble
simulations with the chemistry-climate model SOCOL spanning the first
half of 20th century, driven by the prescribed time evolution of the
sea surface temperature, sea ice distribution, volcanic aerosols,
greenhouse gases, ozone depleting substances, sources of CO and NOx,
land use, and quasi-biennial oscillation. For the first run we have
applied constant solar spectral irradiance, while the second run has
been driven by time dependent solar spectral irradiance. The simulated
time series of different atmospheric quantities have been analyzed to
estimate the climate and chemistry response to the changes of solar
spectral irradiance. The analyses showed statistically significant
solar signal from the mesosphere down to the surface. The max-imum ozone
response ( 4%) is found in the tropical middle stratosphere, while the
temperature response maximizes in the tropical stratopause reaching
1.2K. The contribution of the solar spectral irradiance variability to
the global mean surface temperature changes is rather small; however,
the downward propagation of the solar signal leads to noticeable land
surface temper-ature response over some geographical locations. Its
magnitude can reach 0.6 K over Siberia, Scandinavia, Central USA and
Canada. The cooling due to solar irradiance is observed over Northern
Canada, China and Northern Africa.

---------------------------------------------------------
Title: Modeling the impact of the solar UV irradiance on the middle
atmosphere
Authors: Rozanov, Eugene; Egorova, Tatiana; Shapiro, Anna; Shapiro,
Alexander; Schmutz, Werner
2010cosp...38.1103R Altcode: 2010cosp.meet.1103R
Modeling of the middle atmosphere response to the short-term variability
of the solar spec-tral irradiance (SSI) is important to understand the
mechanisms responsible for the Sun-Earth connections. The analysis
of the recent publications shows that there is still substantial
dis-agreement between the simulated and observed responses of the middle
atmosphere to the daily SSI variability. Among other problems this
disagreement can be caused by not perfect quality of the available SSI
data sets which are necessary to drive models and extract the response
of the middle atmosphere from the observed time series. To elucidate
the role of the SSI data we exploited column and full versions of the
climate-chemistry-ionosphere model SOCOL, which is based on a general
circulation model and includes complete representation of the chemistry
of neutral and ionized species in the atmosphere from the ground up
to the mesopause. We have performed a series of experiments driven by
different available observed and reconstructed daily SSI data sets to
estimate the middle atmosphere response to the SSI variability during
the solar rotation cycle as well as to the short-time increase of the
solar UV irradiance occurred in January 2004. Our results showed that
the sensitivity analysis in the stratosphere gives similar results
for all SSI data sets when it is based on the SSI at 205 nm, while for
the mesosphere the sensitivity based on the SSI in Lyman-line is more
robust. The analysis of the correlation between ozone, hydroxyl and
electron densities daily time series simulated with different SSI data
sets showed substantial disagreement which emphasizes the necessity of
more accurate representation of SSI for the nowcasting of the middle
atmosphere state. The comparison of the short-term changes in the
middle atmosphere in January 2004 with the appropriate obser-vations
allows the evaluation of the model performance, which will be discussed
together with the perspectives of the model application for the space
weather nowcasting using the solar UV irradiance data acquired by LYRA
instrument onboard ESA PROBA-2 satellite and available in near-real
time.

---------------------------------------------------------
Title: First results from the LYRA solar UV radiometer
Authors: Hochedez, Jean-François; Dammasch, I.; Schmutz, Werner
2010cosp...38.1090H Altcode: 2010cosp.meet.1090H
On November 2, 2009, the PROBA2 space mission of ESA was launched
into a sun-synchronous polar orbit allowing quasi-permanent solar
observation. Onboard PROBA2, LYRA is the first radiometer in space
that benefits from diamond ultraviolet detectors. LYRA consists of four
large pass band channels. Each channel observes the irradiance of the
Sun behind a thin metallic foil or behind an interference filter. The
detectors are either UV silicon diodes or diamond detectors, the latter
having been specifically designed for LYRA. The combination of the
spectral transmission of the filters and of the responsivity of the
detectors makes the twelve LYRA channels sensitive to different soft
X-ray and UV pass bands. Their exact choice was made in relation
to scientific questions in solar physics, aeronomy, and Space
Weather. `First Light' of the experiment occurred on January 6, 2010,
and LYRA was subsequently commissioned successfully. After few days,
it measured the first solar flares of the new solar cycle, with an
unprecedented high time resolution of 0.5 s. In the spring of 2010,
LYRA data will start feeding research investigations and space weather
forecasts. The proposed talk presents early results obtained with the
measurements of the first months in space.

---------------------------------------------------------
Title: Modeling of the current TSI and SSI and its reconstruction
to the past
Authors: Shapiro, Alexander; Schmutz, Werner; Thuillier, Gerard;
Schoell, Micha; Haberreiter, Margit; Rozanov, Eugene
2010cosp...38..134S Altcode: 2010cosp.meet..134S
We have developed and published the COde for Solar Irradiance (COSI)
which provides physical modeling of the entire solar spectrum as a
contribution from the quiet Sun and active regions. This code allows
us to reach a good agreement between the calculated and observed solar
spectrum as measured by SOLSTICE and SIM onboard the SORCE satellite
and ATLAS 3 mission operated from the Space Shuttle. We find that NLTE
effects are very important for the modeling of the solar spectrum even
in the visible part of the spectrum and for its variability over the
entire solar spectrum. We employ the assumption that the quiet Sun
consists of two components. The first corresponds to the average quiet
network and it is responsible for all magnetic activity of the quiet
Sun. The second represents the Sun that is basically free from any
magnetic activity. We use the reconstructed open magnetic flux data as
well as the TSI and SSI observed by SORCE during this peculiar solar
minimum to find the filling factors of these components. We use the
sunspot numbers to reconstruct the filling factors of the solar active
components. This approach allows us to obtain an annually averaged
TSI and SSI back to the Maunder Minimum. These basic assumptions lead
to aTSI and SSI that was substantially different during the Maunder
minimum than as it is observed today. The difference is remarkably
larger than other estimations published in the recent literature.

---------------------------------------------------------
Title: Total Solar Irradiance: Present status of TSI observations
Authors: Schmutz, Werner; Fehlmann, Andr; Finsterle, Wolfgang;
Rozanov, Eugene
2010cosp...38.1689S Altcode: 2010cosp.meet.1689S
Total Solar Irradiance is measured by pyrheliometers. These instruments
are either fully charac-terized and measure in absolute units or they
are traceable to the World Radiometric Reference (WRR) at the World
Radiation Center in Davos. The WRR in turn is so far only traceable
to SI in power but not in irradiance. The added difficulty when
discussing metrology of pyrheliome-ters in space is that the WRR is
operated in air. Thus, so far, measurements of TSI in space rely on
the full characterization of the instruments and a fully traceable TSI
measurements has not yet been flown. This talk will give an overview
over existing space observations of TSI and discusses the dif-ferences
in the absolute and relative values between the various experiments. The
challenge for future experiments is to get full traceability of the
measurements in space. There are two upcoming experiments, PREMOS on
PICARD and GLORY/TIM, which will yield TSI measurements which will be
SI traceable.

---------------------------------------------------------
Title: ASPIICS / PROBA-3: a formation flying externally-occulted
giant coronagraph mission
Authors: Lamy, Philippe; Damé, Luc; Curdt, W.; Davila, J.; Defise,
J. M.; Fineschi, S.; Heinzel, P.; Howard, R.; Kuzin, S.; Schmutz,
W.; Tsinganos, K.; Turck-Chièze, S.; Zhukov, A.
2010cosp...38.2858L Altcode: 2010cosp.meet.2858L
Classical externally-occulted coronagraphs are presently limited in
their performances by the distance between the external occulter and
the front objective. The diffraction fringe from the occulter and
the vignetted pupil which degrades the spatial resolution prevent
useful observa-tions of the white light corona inside typically 2-2.5
Rsun. Formation flying offers an elegant solution to these limitations
and allows conceiving giant, externally-occulted coronagraphs
us-ing a two-component space system with the external occulter on
one spacecraft and the optical instrument on the other spacecraft
at distances of hundred meters. Such an instrument has just been
selected by ESA to fly (by the end of 2013) on its PROBA-3 mission,
presently in phase B, to demonstrate formation flying. It will perform
both high spatial resolution imaging of the solar corona as well as
2-dimensional spectroscopy of several emission lines (in partic-ular
the forbidden line of FeXIV at 530.285 nm) from the coronal base out
to 3 Rsun using a Fabry-Perot interferometer. The classical design of
an externally-occulted coronagraph is adapted to the formation flying
configuration allowing the detection of the very inner corona as close
as 0.05 Rsun from the solar limb. By tuning the position of the occulter
spacecraft, it may even be possible to try reaching the chromosphere
and the upper part of the spicules. ASPIICS/PROBA-3 mission, payload
and scientific objectives are detailed.

---------------------------------------------------------
Title: The Absolute Solar Irradiance Spectrum at Solar Minimum
Activity Measured by the SOLSPEC and SOL-ACES Spectrometers from 17
to 3000 nm Placed on Board the International Space Station
Authors: Thuillier, Gerard; Bolsee, David; Schmidtke, Gerhard; Schmutz,
Werner; Shapiro, Alexander; Nikutowski, Bernd
2010cosp...38...17T Altcode: 2010cosp.meet...17T
Two instruments placed on the COLOMBUS laboratory on the International
Space Station constitute a payload named SOLAR measuring the
spectral solar irradiance from 17 to 3000 nm for solar, atmospheric
and climatology physics for which the sun-climate connection also
re-quires the precise and absolute knowledge of the solar spectral
irradiance. Given the significant improvements in atmosphere, climate
and solar modelling, accurate data are needed. SOL-SPEC primary
objectives are the measurement of the Sun absolute spectral irradiance
and its variability from 165 to 3080 nm. SOLSPEC has been developed
by LATMOS (France), Institut d'Aéronomie Spatiale (Belgique), and
Landessternwarte (Germany). It has been calibrated in the absolute scale
by using the blackbody of the Physikalisch-Technische Bundesanstalt
(PTB), Braunschweig. SOL-ACES primary objectives are the measurements
of the Sun absolute spec-tral irradiance from 17 to 140 nm. This
instrument as developed by the Fraunhofer Institute (Freiburg, Germany)
uses three-current ionisation chambers repeatedly filled with different
gases to re-calibrate the three spectrometers, which are changing their
efficiencies e.g. by the interaction with solar radiation. We present a
composite solar spectrum for the July 2008 period, at a very low solar
as occurred at the end of solar cycle 23. It has been built using
SOLSPEC, SOL-ACES and TIMED SEE data. Comparison with data obtained
during the ATLAS 3 period (November 1994), SORCE measurements and
theoretical modelling using the COSI code will be presented. Differences
will be commented (difference of the two activity levels, accuracy).

---------------------------------------------------------
Title: Chandra X-ray Observations of the Young Stellar Cluster
Berkeley 87 and its Oxygen-type Wolf-Rayet Star WR 142
Authors: Skinner, Steve L.; Sokal, K. R.; Zhekov, S. A.; Guedel, M.;
Schmutz, W.
2010AAS...21547811S Altcode: 2010BAAS...42Q.567S
Berkeley 87 is a heavily-reddened young open cluster lying in an
obscured region of Cygnus. Age estimates for cluster members are
typically in the range 1 - 3 Myr. Berkeley 87 is noteworthy as an
example of a galactic open cluster harboring a rare oxygen-type
Wolf-Rayet star, WR 142 (= Sand 5 = St 3; spectral type WO2). WO
stars are the most highly-evolved WR stars and are likely supernova
or gamma-ray burst (GRB) progenitors. The wind of WR 142 has a
exceptionally high terminal speed in excess of 5000 km/s and may be
producing shock waves in the surrounding cluster. We present results of
a Chandra ACIS-I observation of Berkeley 87 centered on WR 142. The
Chandra spectrum of WR 142 is exceptionally hard for a WR star,
and shows excess low-energy absorption above that expected from its
visual extinction. Some of this excess absorption likely arises in
its powerful metal-rich wind. We compare its spectrum with the much
softer X-ray spectra of cluster OB stars. We discuss the Chandra image
of Berkeley 87, which reveals a large and diverse population of X-ray
emitting young stars.

---------------------------------------------------------
Title: Multi-spacecraft observation of a magnetic cloud
Authors: de Lucas, Aline; Dal Lago, Alisson; Schwenn, Rainer; Clúa de
Gonzalez, Alicia L.; Marsch, Eckart; Lamy, Philippe; Damé, Luc; Curdt,
W.; Davila, J.; Defise, J. M.; Fineschi, S.; Heinzel, P.; Howard, R.;
Kuzin, S.; Schmutz, W.; Tsinganos, K.; Turck-Chièze, S.; Zhukov, A.
2010cosp...38.1921D Altcode: 2010cosp.meet.1921D
Classical externally-occulted coronagraphs are presently limited in
their performances by the distance between the external occulter and
the front objective. The diffraction fringe from the occulter and
the vignetted pupil which degrades the spatial resolution prevent
useful observa-tions of the white light corona inside typically 2-2.5
Rsun. Formation flying offers an elegant solution to these limitations
and allows conceiving giant, externally-occulted coronagraphs
us-ing a two-component space system with the external occulter on
one spacecraft and the optical instrument on the other spacecraft
at distances of hundred meters. Such an instrument has just been
selected by ESA to fly (by the end of 2013) on its PROBA-3 mission,
presently in phase B, to demonstrate formation flying. It will perform
both high spatial resolution imaging of the solar corona as well as
2-dimensional spectroscopy of several emission lines (in partic-ular
the forbidden line of FeXIV at 530.285 nm) from the coronal base out
to 3 Rsun using a Fabry-Perot interferometer. The classical design of
an externally-occulted coronagraph is adapted to the formation flying
configuration allowing the detection of the very inner corona as close
as 0.05 Rsun from the solar limb. By tuning the position of the occulter
spacecraft, it may even be possible to try reaching the chromosphere
and the upper part of the spicules. ASPIICS/PROBA-3 mission, payload
and scientific objectives are presented.

---------------------------------------------------------
Title: The PICARD Mission: an investigation based on measurements
dedicated to solar and climate modeling
Authors: Thuillier, Gerard; Schmutz, Werner; Dewitte, Steven
2010cosp...38.1094T Altcode: 2010cosp.meet.1094T
PICARD mission is dedicated to the study of the solar activity
origin using several key solar measurements. The project also includes
development of the solar convective zone and climate models to evaluate
the consequences for the Earth'climate of the solar activity. The
measure-ments are the total and spectral solar irradiance, solar
diameter, limb shape, solar asphericity, and helioseismic waves,
which are key inputs for solar physics modeling. The measurements
will be carried out by two absolute radiometers, sunphotometers, and a
metrological imag-ing telescope onboard a microsatellite built by the
French Space Agency CNES, with launch scheduled for March 2010. The
radiometers are similar to the ones flown on board SOHO. The imaging
telescope contains an angular reference allowing a permanent control
of the instrument geometric scale, which is referred to angular stars
distances. Optical distortion and flatfield of the imaging telescope
are foreseen to be regularly measured. The measurements in space will
have correlative measurements from ground using an identical imaging
telescope, associated to the measurement of the local turbulence
and aerosols localization and concentration. The op-portunity of
diameter measurements by solar eclipse method will be used and
finally the Solar Disk Sextant instrument will be regularly flown
as an external measurement validation. An after launch activities
is scheduled for three months, which consists in several instrument
checks and recording of some scientific data. Given the launch date,
these preliminary measurements will be shown. Images in UV, CaII line
and solar photospheric continuum will be presented with some analysis
of their contains. Furthermore, preliminary information concerning
the radiometric and spectrometric measurements will be given.

---------------------------------------------------------
Title: Response of the middle atmosphere to short-term solar
irradiance variability during different Quasi-Biennial Oscillation
phases
Authors: Shapiro, Anna; Rozanov, Eugene; Shapiro, Alexander; Egorova,
Tatiana; Schmutz, Werner; Peter, Thomas
2010cosp...38..138S Altcode: 2010cosp.meet..138S
Variability of the spectral solar irradiance (SSI) is known to cause
changes in the chemistry and dynamics of the middle atmosphere. Because
the analysis of the observed temperature responses to the decadal scale
is difficult owing to rather short time series we aim on the study
of the middle atmosphere response to the short-term SSI variability
associated with the Sun rotation cycle. One of the main problems
here is that the response of the atmosphere usually derived using
the cross-correlation analysis depends on the atmospheric state and
internal variability. In particular, the distribution and variability
of the temperature and gas species in the tropical middle atmosphere
depends on the phase of quasi-biennial oscillation (QBO). We have
applied the chemistry-climate model SOCOL and simulated the dependence
of the middle atmosphere response to the short-term solar variability
during different QBO phases with a series of ensemble runs. We have
found that the hydroxyl sensitivities to the SSI changes during solar
rotation cycle are almost identical for the different QBO phases if we
forced the model by identical photolysis while the ozone sensitivities
to the SSI changes are different for some layers of the stratosphere.

---------------------------------------------------------
Title: Model studies of the solar limb shape variation with wavelenght
within the PICARD project.
Authors: Melo, Stella M. L.; Thuillier, Gerard; Claudel, Jennyfer;
Haberreiter, Margit; Mein, Nicole; Schmutz, Werner; Shapiro, Alexander;
Sofia, Sabatino; Short, Christopher I.
2010cosp...38.1756M Altcode: 2010cosp.meet.1756M
Solar images in the visible wavelength range show that the disk centre
is brighter than the limb region. This phenomenon, which is both known
as "centre to limb variation (CLV)", or "limb darkening function", is
know to depend on wavelength. Since the CLV is determined by the density
and temperature stratification, as well as the chemical composition
of the so-lar photosphere, its measurement is important to validate
theoretical assumption made when building numerical models of the
solar atmosphere. The definition of the solar diameter is nor-mally
adopted as the separation between two inflection points at opposite
ends of a line passing through the center of the solar disk. Therefore,
in order to understand long term variability on the solar diameter, it
is important to understand what drives the dependence of the position
of the inflection point on wavelength. In this paper we use different
available solar atmosphere models to study this dependence. The results
presented here refer to quiet Sun conditions and encompass the visible
and near infra-red spectral regions, which are the regions of interest
for the PICARD Satellite Mission. In a first step we utilize the solar
atmosphere parameters with a radiative transfer code. This allows for
the study of the impact of different factors such as opacities, electron
density and temperature from different models on the results. Then, we
compare results obtained using each solar atmosphere model. Our results
are compared with existent ground based measurements performed by the
Pic du Midi telescope, the balloon board measurements with the Solar
Disk Sextant experiment, and with the measurements by the Michelson
Doppler Imager on board SoHO satellite. The model simulations show that
the position of the inflection point is sensitive to the different
parameters and model assumptions. Furthermore, our study shows, for
the first time, that the position of the inflection point changes
dramatically with and outside of Fraunhofer lines.

---------------------------------------------------------
Title: Pre-flight calibration of LYRA, the solar VUV radiometer on
board PROBA2
Authors: Benmoussa, A.; Dammasch, I. E.; Hochedez, J. -F.; Schühle,
U.; Koller, S.; Stockman, Y.; Scholze, F.; Richter, M.; Kroth, U.;
Laubis, C.; Dominique, M.; Kretzschmar, M.; Mekaoui, S.; Gissot, S.;
Theissen, A.; Giordanengo, B.; Bolsee, D.; Hermans, C.; Gillotay,
D.; Defise, J. -M.; Schmutz, W.
2009A&A...508.1085B Altcode:
Aims. LYRA, the Large Yield Radiometer, is a vacuum ultraviolet
(VUV) solar radiometer, planned to be launched in November 2009 on
the European Space Agency PROBA2, the Project for On-Board Autonomy
spacecraft. Methods: The instrument was radiometrically
calibrated in the radiometry laboratory of the Physikalisch-Technische
Bundesanstalt (PTB) at the Berlin Electron Storage ring for SYnchroton
radiation (BESSY II). The calibration was done using monochromatized
synchrotron radiation at PTB's VUV and soft X-ray radiometry beamlines
using reference detectors calibrated with the help of an electrical
substitution radiometer as the primary detector standard. Results:
A total relative uncertainty of the radiometric calibration of the LYRA
instrument between 1% and 11% was achieved. LYRA will provide irradiance
data of the Sun in four UV passbands and with high temporal resolution
down to 10 ms. The present state of the LYRA pre-flight calibration
is presented as well as the expected instrument performance.

---------------------------------------------------------
Title: Solar Surface Magnetism and Irradiance on Time Scales from
Days to the 11-Year Cycle
Authors: Domingo, V.; Ermolli, I.; Fox, P.; Fröhlich, C.; Haberreiter,
M.; Krivova, N.; Kopp, G.; Schmutz, W.; Solanki, S. K.; Spruit, H. C.;
Unruh, Y.; Vögler, A.
2009SSRv..145..337D Altcode:
The uninterrupted measurement of the total solar irradiance during the
last three solar cycles and an increasing amount of solar spectral
irradiance measurements as well as solar imaging observations
(magnetograms and photometric data) have stimulated the development
of models attributing irradiance variations to solar surface
magnetism. Here we review the current status of solar irradiance
measurements and modelling efforts based on solar photospheric
magnetic fields. Thereby we restrict ourselves to the study of solar
variations from days to the solar cycle. Phenomenological models
of the solar atmosphere in combination with imaging observations of
solar electromagnetic radiation and measurements of the photospheric
magnetic field have reached high enough quality to show that a large
fraction (at least, about 80%) of the solar irradiance variability
can be explained by the radiative effects of the magnetic activity
present in the photosphere. Also, significant progress has been made
with magnetohydrodynamic simulations of convection that allow us to
relate the radiance of the photospheric magnetic structures to the
observations.

---------------------------------------------------------
Title: Solution to the discrepancy between the seismic and
photospheric solar radius
Authors: Haberreiter, M.; Kosovichev, A. G.; Schmutz, W.
2009EGUGA..11.3961H Altcode:
Two methods are usually used to observationally determine the solar
radius: One is the observation of the intensity profile at the limb,
the other one uses f-mode frequencies to derive a 'seismic' solar
radius which is then corrected to optical depth unity. The two methods
are inconsistent and lead to a difference in the solar radius of
approx. 0.3 Mm. Based on radiative transfer calculations we show that
this discrepancy can be explained by the difference between the height
at disk center where tau500=1 and the inflection point of the intensity
profile on the limb. We calculate the intensity profile of the limb
for the MDI continuum and the continuum at 5000 A for two atmosphere
structures and compare the position of the inflection points with the
radius at optical depth unity. The calculated difference between the
'seismic' radius and the inflection point is 0.347 Mm with respect to
optical depth unity and 0.333 Mm with respect to the Rossland mean
opacity. We conclude that the standard solar radius in evolutionary
models has to be lowered by 0.333 Mm and is 695.66 Mm. This correction
reconciles inflection point measurements and the seismic radius within
the uncertainty. This finding is very important for the analysis of
the solar diameter measurements with the SODISM instrument on PICARD.

---------------------------------------------------------
Title: POLAR investigation of the Sun—POLARIS
Authors: Appourchaux, T.; Liewer, P.; Watt, M.; Alexander, D.;
Andretta, V.; Auchère, F.; D'Arrigo, P.; Ayon, J.; Corbard, T.;
Fineschi, S.; Finsterle, W.; Floyd, L.; Garbe, G.; Gizon, L.; Hassler,
D.; Harra, L.; Kosovichev, A.; Leibacher, J.; Leipold, M.; Murphy,
N.; Maksimovic, M.; Martinez-Pillet, V.; Matthews, B. S. A.; Mewaldt,
R.; Moses, D.; Newmark, J.; Régnier, S.; Schmutz, W.; Socker, D.;
Spadaro, D.; Stuttard, M.; Trosseille, C.; Ulrich, R.; Velli, M.;
Vourlidas, A.; Wimmer-Schweingruber, C. R.; Zurbuchen, T.
2009ExA....23.1079A Altcode: 2008ExA...tmp...40A; 2008arXiv0805.4389A
The POLAR Investigation of the Sun (POLARIS) mission uses a combination
of a gravity assist and solar sail propulsion to place a spacecraft
in a 0.48 AU circular orbit around the Sun with an inclination of 75°
with respect to solar equator. This challenging orbit is made possible
by the challenging development of solar sail propulsion. This first
extended view of the high-latitude regions of the Sun will enable
crucial observations not possible from the ecliptic viewpoint or from
Solar Orbiter. While Solar Orbiter would give the first glimpse of
the high latitude magnetic field and flows to probe the solar dynamo,
it does not have sufficient viewing of the polar regions to achieve
POLARIS’s primary objective: determining the relation between the
magnetism and dynamics of the Sun’s polar regions and the solar cycle.

---------------------------------------------------------
Title: The DynaMICCS perspective. A mission for a complete and
continuous view of the Sun dedicated to magnetism, space weather
and space climate
Authors: Turck-Chièze, S.; Lamy, P.; Carr, C.; Carton, P. H.;
Chevalier, A.; Dandouras, I.; Defise, J. M.; Dewitte, S.; Dudok de Wit,
T.; Halain, J. P.; Hasan, S.; Hochedez, J. F.; Horbury, T.; Levacher,
P.; Meissonier, M.; Murphy, N.; Rochus, P.; Ruzmaikin, A.; Schmutz,
W.; Thuillier, G.; Vivès, S.
2009ExA....23.1017T Altcode: 2008ExA...tmp...42T
The DynaMICCS mission is designed to probe and understand the dynamics
of crucial regions of the Sun that determine solar variability,
including the previously unexplored inner core, the radiative/convective
zone interface layers, the photosphere/chromosphere layers and the
low corona. The mission delivers data and knowledge that no other
known mission provides for understanding space weather and space
climate and for advancing stellar physics (internal dynamics)
and fundamental physics (neutrino properties, atomic physics,
gravitational moments...). The science objectives are achieved
using Doppler and magnetic measurements of the solar surface,
helioseismic and coronographic measurements, solar irradiance at
different wavelengths and in-situ measurements of plasma/energetic
particles/magnetic fields. The DynaMICCS payload uses an original
concept studied by Thalès Alenia Space in the framework of the
CNES call for formation flying missions: an external occultation of
the solar light is obtained by putting an occulter spacecraft 150 m
(or more) in front of a second spacecraft. The occulter spacecraft,
a LEO platform of the mini sat class, e.g. PROTEUS, type carries
the helioseismic and irradiance instruments and the formation flying
technologies. The latter spacecraft of the same type carries a visible
and infrared coronagraph for a unique observation of the solar corona
and instrumentation for the study of the solar wind and imagers. This
mission must guarantee long (one 11-year solar cycle) and continuous
observations (duty cycle &gt; 94%) of signals that can be very weak
(the gravity mode detection supposes the measurement of velocity
smaller than 1 mm/s). This assumes no interruption in observation
and very stable thermal conditions. The preferred orbit therefore is
the L1 orbit, which fits these requirements very well and is also an
attractive environment for the spacecraft due to its low radiation and
low perturbation (solar pressure) environment. This mission is secured
by instrumental R and D activities during the present and coming
years. Some prototypes of different instruments are already built
(GOLFNG, SDM) and the performances will be checked before launch on
the ground or in space through planned missions of CNES and PROBA ESA
missions (PICARD, LYRA, maybe ASPIICS).

---------------------------------------------------------
Title: Wolf-Rayet Stars at the Highest Angular Resolution
Authors: Millour, Florentin; Chesneau, Olivier; Driebe, Thomas; Matter,
Alexis; Schmutz, Werner; Lopez, Bruno; Petrov, Romain G.; Groh, José
H.; Bonneau, Daniel; Dessart, Luc; Hofmann, Karl-Heinz; Weigelt, Gerd
2009Msngr.135...26M Altcode:
Interferometric observations of high-mass evolved stars provide new and
very valuable information of their nature. With the unique capabilities
of the VLTI, direct images of their closest environment where mass
loss and dust formation occur, can be obtained. The breakthrough of
the VLTI in terms of angular resolution as well as spectral resolution
allows competing theoretical models, based on indirect constraints,
to be tested. The high angular resolution made available by the VLTI
shows that there is still a lot to discover about these massive stars.

---------------------------------------------------------
Title: A Survey of X-ray Emission from Wolf-Rayet Stars
Authors: Skinner, Steve L.; Zhekov, S.; Guedel, M.; Schmutz, W.;
Sokal, K.
2009AAS...21349120S Altcode: 2009BAAS...41..470S
Previous X-ray studies of Wolf-Rayet (WR) stars have focused mainly
on WR binary systems whose luminous high-temperature X-ray emission
is thought to originate (at least partially) in colliding wind shocks
between the two stars. Much less is known about the X-ray emission
of putatively single WR stars, for which evidence of binarity is
lacking. We present new results from an ongoing X-ray survey of single
WR stars conducted with Chandra and XMM-Newton. Our objectives are
to quantify the X-ray properties of single WRs and identify plausible
emission mechanisms. Specifically, we would like to know if single
WR stars emit predominantly soft X-rays (kT &lt; 1 keV), as occurs in
some O-type stars and is predicted for radiative wind shocks formed by
the line-driven instability (LDI) mechanism. Observations to date have
failed to detect any X-ray emission from single carbon-rich WC stars. In
contrast, some nitrogen-rich WN stars have been detected. Recent
Chandra observations of both WR 2 (WN2) and WR 134 (WN6) reveal luminous
X-ray emission (log Lx 32. erg/s) comparable to that
of some WR + OB binaries, including a hot plasma component (kT &gt;&gt;
1 keV). The presence of high-temperature plasma is not in agreement with
the cool plasma expected for radiative wind shocks. Either these X-ray
luminous WN stars harbor unseen companions or an alternative to the
conventional LDI radiative wind shock model will be needed. This
research was supported by NASA grants GO8-9008X (SAO) and NNG05GA10G
(GSFC).

---------------------------------------------------------
Title: NLTE model calculations for the solar atmosphere with an
iterative treatment of opacity distribution functions
Authors: Haberreiter, M.; Schmutz, W.; Hubeny, I.
2008A&A...492..833H Altcode: 2008arXiv0810.3471H
Context: Modeling the variability of the solar spectral irradiance is
a key factor in understanding the Sun's influence on the climate of
the Earth. Aims: As a first step toward calculating the solar
spectral irradiance variations, we reproduce the solar spectrum
for the quiet Sun over a broad wavelength range with an emphasis
on the UV. Methods: We introduce the radiative transfer code
COSI, which calculates solar synthetic spectra under conditions
of non-local thermodynamic equilibrium (NLTE). A self-consistent
simultaneous solution of the radiative transfer and the statistical
equation for the level populations guarantees that the correct physics
is considered for wavelength regions where the assumption of local
thermodynamic equilibrium (LTE) breaks down. The new concept of
iterated opacity distribution functions (NLTE-ODFs) is presented,
through which all line opacities are included in the NLTE radiative
transfer calculation. Results: We show that it is essential to
include the line opacities in the radiative transfer to reproduce the
solar spectrum in the UV. Conclusions: Through the implemented
scheme of NLTE-ODFs, the COSI code is successful in reproducing the
spectral energy distribution of the quiet Sun. Table 2 is only
available in electronic form at http://www.aanda.org

---------------------------------------------------------
Title: P-mode leakage and Lyman-α intensity
Authors: Finsterle, W.; Haberreiter, M.; Kosovichev, S.; Schmutz, W.
2008IAUS..247...74F Altcode: 2007IAUS..247...74F
We present an observational test of the hypothesis that leaking p
modes heat the solar chromosphere. The amplitude of the leaking p
modes in magneto-acoustic portals is determined using MOTH and MDI
data. We simulate the propagation of these modes into the chromosphere
to determine the height where the wave energy is dissipated by shock
waves. A statistical approach is then used to check if this heating
process could account for the observed variability of the intensity
in the Lyman-α emission.

---------------------------------------------------------
Title: Solving the Discrepancy between the Seismic and Photospheric
Solar Radius
Authors: Haberreiter, M.; Schmutz, W.; Kosovichev, A. G.
2008ApJ...675L..53H Altcode:
Two methods are used to observationally determine the solar radius:
One is the observation of the intensity profile at the limb; the other
one uses f-mode frequencies to derive a "seismic" solar radius which is
then corrected to optical depth unity. The two methods are inconsistent
and lead to a difference in the solar radius of ~0.3 Mm. Because of the
geometrical extension of the solar photosphere and the increased path
lengths of tangential rays the Sun appears to be larger to an observer
who measures the extent of the solar disk. Based on radiative transfer
calculations we show that this discrepancy can be explained by the
difference between the height at disk center where τ5000 =
1 (τRoss = 2/3) and the inflection point of the intensity
profile on the limb. We calculate the intensity profile of the limb
for the MDI continuum and the continuum at 5000 Å for two atmosphere
structures and compare the position of the inflection points with
the radius at τ5000 = 1 (τRoss = 2/3). The
calculated difference between the seismic radius and the inflection
point is 0.347 +/- 0.006 Mm with respect to τ5000 = 1,
and 0.333 +/- 0.008 Mm with respect to τRoss = 2/3. We
conclude that the standard solar radius in evolutionary models has to
be lowered by 0.333 +/- 0.008 Mm and is 695.66 Mm. Furthermore, this
correction reconciles inflection point measurements and the seismic
radii within the uncertainties.

---------------------------------------------------------
Title: XMM-Newton X-ray observations of the Wolf-Rayet binary system
WR 147
Authors: Skinner, S. L.; Zhekov, S. A.; Güdel, M.; Schmutz, W.
2007MNRAS.378.1491S Altcode: 2007MNRAS.tmp..491S; 2007arXiv0704.3235S
We present results of an ~20-ks X-ray observation of the Wolf-Rayet
(WR) binary system WR 147 obtained with XMM-Newton. Previous studies
have shown that this system consists of a nitrogen-type WN8 star plus
an OB companion whose winds are interacting to produce a colliding
wind shock. X-ray spectra from the pn and MOS detectors confirm
the high extinction reported from infrared studies and reveal hot
plasma including the first detection of the Fe Kα line complex at
6.67 keV. Spectral fits with a constant-temperature plane-parallel
shock model give a shock temperature kTshock = 2.7 keV
(Tshock ~ 31 MK), close to but slightly hotter than the
maximum temperature predicted for a colliding wind shock. Optically
thin plasma models suggest even higher temperatures, which are not
yet ruled out. The X-ray spectra are harder than can be accounted
for using 2D numerical colliding wind shock models based on nominal
mass-loss parameters. Possible explanations include: (i) underestimates
of the terminal wind speeds or wind abundances, (ii) overly simplistic
colliding wind models or (iii) the presence of other X-ray emission
mechanisms besides colliding wind shocks. Further improvement of
the numerical models to include potentially important physics such
as non-equilibrium ionization will be needed to rigorously test the
colliding wind interpretation.

---------------------------------------------------------
Title: XMM-Newton Studies of the Wolf-Rayet Colliding-Wind Binaries
WR 25 (WN6h+O4f) and WR 11 (WC8+O7.5III)
Authors: van der Hucht, K. A.; Raassen, A. J. J.; Mewe, R.; Antokhin,
I. I.; Rauw, G.; Vreux, J. -M.; Schild, H.; Schmutz, W.
2007ASPC..367..159V Altcode:
We report the analysis of high- and medium-resolution X-ray spectra
of the Wolf-Rayet (WR) objects WR25 (HD93162, WN6h+O4f) and WR11
(γ2 Velorum, WC8+O7.5III, P =78.53 d), obtained
with the reflection grating spectrometers (rgs) and the european
photon imaging cameras (epicmos and &lt;small&gt;PN&lt;/small&gt;)
&lt;small&gt;CCD&lt;/small&gt; spectrometers on board the XMM-Newton
satellite.

---------------------------------------------------------
Title: Long-term reconstruction of the total solar irradiance based
on neutron monitor and sunspot data
Authors: Schöll, M.; Steinhilber, F.; Beer, J.; Haberreiter, M.;
Schmutz, W.
2007AdSpR..40..996S Altcode:
A new approach for the reconstruction of the past total solar irradiance
(TSI) based on neutron monitor (NM) data and sunspot number (SSN) is
presented. Our assumption is that the long-term trend of the TSI can be
reconstructed by using radionuclide data while the reconstruction of
the short-term trend can be achieved by using SSN. The reconstructed
TSI correlates well, r2 = 0.84, with space-based TSI
measurements. This work will serve as the basis for the reconstruction
of the TSI back to the Maunder minimum and beyond by replacing NM with
radionuclide data, for which longer time series exist.

---------------------------------------------------------
Title: LYRA - a solar UV radiometer using diamond detectors
Authors: Theissen, A.; Benmoussa, A.; Schühle, U.; Hochedez, J. -F.;
Schmutz, W.
2007msfa.conf...27T Altcode:
LYRA, the Lyman-α radiometer, is a highcadence (100 Hz) solar
VUV radiometer which will measure diskintegrated irradiances in 4
wavelength channels. Special emphasis is given on novel detectors based
on diamond which will be tested for the first time in space. Two kinds
of detectors are employed: MSM and PiNtype detectors. Their particular
advantage compared to silicon detectors lies in their solar blindness
with a UV/visible reduction ratio of at least four orders of magnitude,
which simplifies the design of UV instruments.

---------------------------------------------------------
Title: Simulation of the stratospheric ozone and temperature response
to the solar irradiance variability during sun rotation cycle
Authors: Rozanov, E.; Egorova, T.; Schmutz, W.; Peter, Th.
2006JASTP..68.2203R Altcode: 2006JATP...68.2203R
Despite substantial progress in atmospheric modeling, the agreement of
the simulated atmospheric response to decadal scale solar variability
with the solar signal in different atmospheric quantities obtained from
the statistical analysis of the observations cannot be qualified as
successful. An alternative way to validate the simulated solar signal
is to compare the sensitivity of the model to the solar irradiance
variability on shorter time scales. To study atmospheric response to
the 28-day solar rotation cycle, we used the chemistry climate model
SOCOL that represents the main physical chemical processes in the
atmosphere from the ground up to the mesopause. An ensemble simulation
has been carried out, which is comprised of nine 1-year long runs,
driven by the spectral solar irradiance prescribed on a daily basis
using UARS SUSIM measurements for the year 1992. The correlation of
zonal mean hydroxyl, ozone and temperature averaged over the tropics
with solar irradiance time series have been analyzed. The hydroxyl has
robust correlations with solar irradiance in the upper stratosphere
and mesosphere, because the hydroxyl concentration is defined mostly by
the photolysis. The simulated sensitivity of the hydroxyl to the solar
irradiance changes is in good agreement with previous estimations. The
ozone and temperature correlations are more complicated because
their behavior depends on non-linear dynamics and transport in the
atmosphere. The model simulates marginally significant ozone response
to the solar irradiance variability during the Sun rotation cycle, but
the simulated temperature response is not robust. The physical nature of
this is not clear yet. It seems likely that the temperature (and partly
the ozone) daily fields possess their own internal variability, which
is not stable and can differ from year to year reflecting different
dynamical states of the system.

---------------------------------------------------------
Title: The DynaMICS perspective
Authors: Turck-Chièze, S.; Schmutz, W.; Thuillier, G.; Jefferies,
S.; Pallé; Dewitt, S.; Ballot, J.; Berthomieu, G.; Bonanno, A.;
Brun, A. S.; Christensen-Dalsgaard, J.; Corbard, T.; Couvidat, S.;
Darwich, A. M.; Dintrans, B.; Domingo, V.; Finsterle, W.; Fossat,
E.; Garcia, R. A.; Gelly, B.; Gough, D.; Guzik, J.; Jiménez, A. J.;
Jiménez-Reyes, S.; Kosovichev, A.; Lambert, P.; Lefebvre, S.; Lopes,
I.; Martic, M.; Mathis, S.; Mathur, S.; Nghiem, P. A. P.; Piau, L.;
Provost, J.; Rieutord, M.; Robillot, J. M.; Rogers, T.; Roudier, T.;
Roxburgh, I.; Rozelot, J. P.; Straka, C.; Talon, S.; Théado, S.;
Thompson, M.; Vauclair, S.; Zahn, J. P.
2006ESASP.624E..24T Altcode: 2006soho...18E..24T
No abstract at ADS

---------------------------------------------------------
Title: X-ray Observations of Binary and Single Wolf-Rayet Stars with
XMM-Newton and Chandra
Authors: Skinner, Stephen; Güdel, Manuel; Schmutz, Werner; Zhekov,
Svetozar
2006Ap&SS.304...97S Altcode: 2005astro.ph.11137S; 2006Ap&SS.tmp...73S
We present an overview of recent X-ray observations of Wolf-Rayet (WR)
stars with XMM-Newton and Chandra. These observations are aimed at
determining the differences in X-ray properties between massive WR +
OB binary systems and putatively single WR stars. A new XMM spectrum of
the nearby WN8 + OB binary WR 147 shows hard absorbed X-ray emission
(including the Fe Kα line complex), characteristic of colliding
wind shock sources. In contrast, sensitive observations of four
of the closest known single WC (carbon-rich) WR stars have yielded
only non-detections. These results tentatively suggest that single
WC stars are X-ray quiet. The presence of a companion may thus be an
essential factor in elevating the X-ray emission of WC + OB stars to
detectable levels.

---------------------------------------------------------
Title: Scientific Objectives of the Novel Formation Flying Mission
Aspiics
Authors: Turck-Chièze, S.; Schmutz, W.; Thuillier, G.; Jefferies,
S.; Pallé; Dewitt, S.; Ballot, J.; Berthomieu, G.; Bonanno, A.;
Brun, A. S.; Christensen-Dalsgaard, J.; Corbard, T.; Couvidat, S.;
Darwich, A. M.; Dintrans, B.; Domingo, V.; Finsterle, W.; Fossat,
E.; Garcia, R. A.; Gelly, B.; Gough, D.; Guzik, J.; Jiménez, A. J.;
Jiménez-Reyes, S.; Kosovichev, A.; Lambert, P.; Lefebvre, S.; Lopes,
I.; Martic, M.; Mathis, S.; Mathur, S.; Nghiem, P. A. P.; Piau, L.;
Provost, J.; Rieutord, M.; Robillot, J. M.; Rogers, T.; Roudier, T.;
Roxburgh, I.; Rozelot, J. P.; Straka, C.; Talon, S.; Théado, S.;
Thompson, M.; Vauclair, S.; Zahn, J. P.
2006ESASP.617E.164L Altcode: 2006soho...17E.164L
No abstract at ADS

---------------------------------------------------------
Title: Development of an SI Traceable Absolute Radiometer for Space
and Ground-Based Use
Authors: Schlifkowitz, U.; Finsterle, W.; Schmutz, W.
2006ESASP.617E.159S Altcode: 2006soho...17E.159S
No abstract at ADS

---------------------------------------------------------
Title: The EUV Variability Experiment (EVE) on the Solar Dynamics
Observatory (SDO): Science Plan and Instrument Overview
Authors: Turck-Chièze, S.; Schmutz, W.; Thuillier, G.; Jefferies,
S.; Pallé; Dewitt, S.; Ballot, J.; Berthomieu, G.; Bonanno, A.;
Brun, A. S.; Christensen-Dalsgaard, J.; Corbard, T.; Couvidat, S.;
Darwich, A. M.; Dintrans, B.; Domingo, V.; Finsterle, W.; Fossat,
E.; Garcia, R. A.; Gelly, B.; Gough, D.; Guzik, J.; Jiménez, A. J.;
Jiménez-Reyes, S.; Kosovichev, A.; Lambert, P.; Lefebvre, S.; Lopes,
I.; Martic, M.; Mathis, S.; Mathur, S.; Nghiem, P. A. P.; Piau, L.;
Provost, J.; Rieutord, M.; Robillot, J. M.; Rogers, T.; Roudier, T.;
Roxburgh, I.; Rozelot, J. P.; Straka, C.; Talon, S.; Théado, S.;
Thompson, M.; Vauclair, S.; Zahn, J. P.
2006ESASP.617E.165W Altcode: 2006soho...17E.165W
No abstract at ADS

---------------------------------------------------------
Title: The Dynamics Project
Authors: Turck-Chièze, S.; Schmutz, W.; Thuillier, G.; Jefferies,
S.; Pallé; Dewitt, S.; Ballot, J.; Berthomieu, G.; Bonanno, A.;
Brun, A. S.; Christensen-Dalsgaard, J.; Corbard, T.; Couvidat, S.;
Darwich, A. M.; Dintrans, B.; Domingo, V.; Finsterle, W.; Fossat,
E.; Garcia, R. A.; Gelly, B.; Gough, D.; Guzik, J.; Jiménez, A. J.;
Jiménez-Reyes, S.; Kosovichev, A.; Lambert, P.; Lefebvre, S.; Lopes,
I.; Martic, M.; Mathis, S.; Mathur, S.; Nghiem, P. A. P.; Piau, L.;
Provost, J.; Rieutord, M.; Robillot, J. M.; Rogers, T.; Roudier, T.;
Roxburgh, I.; Rozelot, J. P.; Straka, C.; Talon, S.; Théado, S.;
Thompson, M.; Vauclair, S.; Zahn, J. P.
2006ESASP.617E.162T Altcode: 2006soho...17E.162T
No abstract at ADS

---------------------------------------------------------
Title: VizieR Online Data Catalog: Wolf-Rayet population in M83
(Hadfield+, 2005)
Authors: Hadfield, L. J.; Crowther, P. A.; Schild, H.; Schmutz, W.
2006yCat..34390265H Altcode:
We have observed M83 with the ESO Very Large Telescope UT4 (Yepun)
and Focal Reduced/Low Dispersion Spectrograph #2 (FORS2). The detector
consists of a mosaic of two 2048x1024 MIT/LL CCDs which in conjunction
with the standard collimator provides a field-of-view 6.8'x6.8'
and an image scale of 0.126"/pixel. Photometric observations of M83
were made between May-June 2002 with follow-up spectroscopic data
being acquired during April-June 2003. FORS2 was used on 2 June
2002 to obtain narrow-band images with central wavelengths 4684{AA},
4781{AA} and band widths of 66{AA} and 68{AA} respectively. These were
obtained consecutively for each Field in seeing conditions between
0.6-0.8" with individual exposures of 1800s. The {lambda}4684 filter
is coincident with the strong WR emission features which incorporates
the N III ({lambda}4640{AA}), C III ({lambda}4650{AA}) and He II
({lambda}4686{AA}) emission lines, whereas the latter samples a
wavelength region relatively free from emission, providing a measure
of the continuum level. (3 data files).

---------------------------------------------------------
Title: LYRA, a solar UV radiometer on Proba2
Authors: Hochedez, J. -F.; Schmutz, W.; Stockman, Y.; Schühle, U.;
Benmoussa, A.; Koller, S.; Haenen, K.; Berghmans, D.; Defise, J. -M.;
Halain, J. -P.; Theissen, A.; Delouille, V.; Slemzin, V.; Gillotay, D.;
Fussen, D.; Dominique, M.; Vanhellemont, F.; McMullin, D.; Kretzschmar,
M.; Mitrofanov, A.; Nicula, B.; Wauters, L.; Roth, H.; Rozanov, E.;
Rüedi, I.; Wehrli, C.; Soltani, A.; Amano, H.; van der Linden, R.;
Zhukov, A.; Clette, F.; Koizumi, S.; Mortet, V.; Remes, Z.; Petersen,
R.; Nesládek, M.; D'Olieslaeger, M.; Roggen, J.; Rochus, P.
2006AdSpR..37..303H Altcode:
LYRA is the solar UV radiometer that will embark in 2006 onboard
Proba2, a technologically oriented ESA micro-mission. LYRA is
designed and manufactured by a Belgian Swiss German consortium (ROB,
PMOD/WRC, IMOMEC, CSL, MPS and BISA) with additional international
collaborations. It will monitor the solar irradiance in four UV
passbands. They have been chosen for their relevance to Solar Physics,
Aeronomy and Space Weather: (1) the 115 125 nm Lyman-α channel,
(2) the 200 220 nm Herzberg continuum range, (3) the Aluminium
filter channel (17 70 nm) including He II at 30.4 nm and (4) the
Zirconium filter channel (1 20 nm). The radiometric calibration will
be traceable to synchrotron source standards (PTB and NIST). The
stability will be monitored by onboard calibration sources (LEDs),
which allow to distinguish between potential degradations of the
detectors and filters. Additionally, a redundancy strategy maximizes
the accuracy and the stability of the measurements. LYRA will benefit
from wide bandgap detectors based on diamond: it will be the first space
assessment of a pioneering UV detectors program. Diamond sensors make
the instruments radiation-hard and solar-blind: their high bandgap
energy makes them insensitive to visible light and, therefore, make
dispensable visible light blocking filters, which seriously attenuate
the desired ultraviolet signal. Their elimination augments the effective
area and hence the signal-to-noise, therefore increasing the precision
and the cadence. The SWAP EUV imaging telescope will operate next to
LYRA on Proba2. Together, they will establish a high performance solar
monitor for operational space weather nowcasting and research. LYRA
demonstrates technologies important for future missions such as the
ESA Solar Orbiter.

---------------------------------------------------------
Title: Simultaneous measurement of the total solar irradiance and
solar diameter by the PICARD mission
Authors: Thuillier, Gérard; Dewitte, Steven; Schmutz, Werner;
Picard Team
2006AdSpR..38.1792T Altcode:
A mission dedicated to simultaneous measurements of the solar diameter,
spectral, and total solar irradiance is presently in development
for launch end of the year 2008 on board of a microsatellite under
the responsibility of Centre National d'Etudes Spatiales. The payload
will consist of an imaging telescope, three filter radiometers with in
total twelve channels, and two independent absolute radiometers. The
scientific aims are presented as well as the concepts and properties of
the instrumentation. This mission is named PICARD after the pioneering
work of Jean Picard (1620-1682) who precisely determined the solar
diameter during the Maunder minimum.

---------------------------------------------------------
Title: The PICARD mission: scientific objectives and status of
development
Authors: Thuillier, G.; Dewitte, S.; Schmutz, W.
2006cosp...36..170T Altcode: 2006cosp.meet..170T
Jean Picard a French astronomer measured the solar diameter during
the Maunder minimum and his observations opened an important question
about the diameter variation with solar activity The solar diameter
solar activity relationship remains unclear till this time however
it is an important relation for solar physics The PICARD mission
will carry out several key measurements such as total and spectral
solar irradiance solar diameter limb shape solar asphericity and
helioseismologic observations These measurements represent key inputs
to validate solar models and to understand the origin of the solar
activity These measurements will be carried out by three metrological
instruments under the responsibility of Belgium France and Switzerland
which will provide absolute radiometers sunphotometers and an imaging
telescope The platform is a microsatellite built by the French Space
Agency CNES The launch is foreseen by October 2008 This date will
allow to have PICARD and Solar Dynamics Observatory NASA in space at
the same period for complementary simultaneous measurements Given the
specific observations by each mission a strong synergy exists between
these two programs Past and present solar diameter measurements reveal
discrepancies among results with solar activity consisting either
correlation anticorrelation or no variation To understand the role of
the atmosphere ground based instruments will be also run during the
mission allowing PICARD to extent its domain of interest toward the
atmosphere physics by comparing ground and space simultaneous

---------------------------------------------------------
Title: Space Weather with ESA's PROBA2 Mission
Authors: Lawrence, G.; Berghmans, D.; Hochedez, J. -F.; Ben-Moussa,
A.; Defise, J. -M.; Delouille, V.; Dominique, M.; Katsitannis, A.;
Lecat, J. -H.; Nicula, B.; Schmutz, W.; Slemzin, V.; Theissen, A.
2005ESASP.592..685L Altcode: 2005ESASP.592E.137L; 2005soho...16E.137L
No abstract at ADS

---------------------------------------------------------
Title: Development of a phase-sensitive absolute radiometer for
space and ground-based use
Authors: Schlifkowitz, Uwe; Finsterle, Wolfgang; Schmutz, Werner
2005ESASP.590..467S Altcode: 2005erbp.conf..467S
Absolute radiometers with a phase-sensitive signal analysis are already
being used in space successfully (Lawrence et al. (2000)). These
instruments are operated with relatively long shutter periods of
several minutes. Unfortunately, they have a large thermal capacity
and are rather large and heavy and are therefore unsuitable for use on
space missions where there is only a limited amount of load capacity
available. The aim of our project is to develop a radiometer with
a relatively small cavity and thermal capacity, which is based on
phase-sensitive signal analysis as well, and which will have a much
better accuracy than traditional instruments. With the help of the
phase-sensitive analysis, many thermal sources of irritation, such as
the so-called non-equivalence of the electric and radiative heating,
can be eliminated. We hope to be able to run a radiometer experiment
on both Solar Orbiter and Solar Dynamic Observatory (SDO) spacecraft,
where the main advantage of reduced weight comes in. As a side effect,
radiometers with small shutter periods are suitable for ground-based use
as well, as they can handle fast changes in irradiance, i.e. altitude
of the sun.

---------------------------------------------------------
Title: SWAP: an EUV imager for solar monitoring on board of PROBA2
Authors: Katsiyannis, Athanassios C.; Berghmans, David; Hochedez,
Jean-Francois; Nicula, Bogdan; Lawrence, Gareth; Defise, Jean-Marc;
Ben-Moussa, Ali; Delouille, Veronique; Dominique, Marie; Lecat,
Jean-Herve; Schmutz, W.; Theissen, Armin; Slemzin, Vladimir
2005SPIE.5901..236K Altcode:
PROBA2 is an ESA technology demonstration mission to be launched in
early 2007. The two primary scientific instruments on board of PROBA2
are SWAP (Sun Watcher using Active Pixel System detector and Image
Processing) and the LYRA VUV radiometer. SWAP provides a full disk
solar imaging capability with a bandpass filter centred at 17.5 nm
(FeIX-XI) and a fast cadence of ≈1 min. The telescope is based on
an off-axis Ritchey Chretien design while an extreme ultraviolet (EUV)
enhanced APS CMOS will be used as a detector. As the prime goal of the
SWAP is solar monitoring and advance warning of Coronal Mass Ejections
(CME), on-board intellige nce will be implemented. Image recognition
software using experimental algorithms will be used to detect CMEs
during the first phase of eruption so the event can be tracked by
the spacecraft without huma n intervention. LYRA will monitor solar
irradiance in four different VUV passbands with a cadence of up to
100 Hz. The four channels were chosen for their relevance to solar
physics, aeronomy and space weather: 115-125 nm (Lyman-α), 200-220
nm Herzberg continuum, the 17-70 nm Aluminium filter channel (that
includes the HeII line at 30.4 nm) and the 1-20 nm Zirconium filter
channel. On-board calibration sources will monitor the stability of
the detectors and the filters throughout the duration of the mission.

---------------------------------------------------------
Title: A spectroscopic search for the non-nuclear Wolf-Rayet
population of the metal-rich spiral galaxy M 83
Authors: Hadfield, L. J.; Crowther, P. A.; Schild, H.; Schmutz, W.
2005A&A...439..265H Altcode: 2005astro.ph..6343H
We present a catalogue of non-nuclear regions containing Wolf-Rayet
stars in the metal-rich spiral galaxy M 83 (NGC 5236). From a total
of 283 candidate regions identified using He ii λ4686 imaging with
VLT-FORS2, Multi Object Spectroscopy of 198 regions was carried out,
confirming 132 WR sources. From this sub-sample, an exceptional content
of ~1035 ± 300 WR stars is inferred, with N(WC)/N(WN) ~ 1.2, continuing
the trend to larger values at higher metallicity amongst Local Group
galaxies, and greatly exceeding current evolutionary predictions at
high metallicity. Late-type stars dominate the WC population of M
83, with N(WC8-9)/N(WC4-7) = 9 and WO subtypes absent, consistent
with metallicity dependent WC winds. Equal numbers of late to early
WN stars are observed, again in contrast to current evolutionary
predictions. Several sources contain large numbers of WR stars. In
particular, #74 (alias region 35 from de Vaucouleurs et al.) contains
~230 WR stars, and is identified as a Super Star Cluster from inspection
of archival HST/ACS images. Omitting this starburst cluster would
result in revised statistics of N(WC)/N(WN) ~ 1 and N(WC8-9)/N(WC4-7) ~
6 for the "quiescent" disk population. Including recent results for the
nucleus and accounting for incompleteness in our spectroscopic sample,
we suspect the total WR population of M 83 may exceed 3000 stars.

---------------------------------------------------------
Title: The Disk Wolf-Rayet Population of the Nuclear Starburst
Galaxy M83
Authors: Crowther, Paul A.; Hadfield, Lucy J.; Schild, Hans; Schmutz,
Werner
2005ASSL..329...21C Altcode: 2005sdlb.proc...21C
No abstract at ADS

---------------------------------------------------------
Title: Reconstruction of the solar UV irradiance back to 1974
Authors: Haberreiter, M.; Krivova, N. A.; Schmutz, W.; Wenzler, T.
2005AdSpR..35..365H Altcode:
The variability of the solar UV irradiance has strong effects on
the terrestrial atmosphere. In order to study the solar influence
for times when no UV observations are available, it is necessary to
reconstruct the variation of the UV irradiance with time on the basis
of proxies. We present reconstructions of the solar UV irradiance based
on the analysis of space-based and ground-based magnetograms of the
solar disk going back to 1974. With COde for Solar Irradiance (COSI)
we calculate solar intensity spectra for the quiet Sun and different
active regions and combine them according to their fractional area on
the solar disk, whereby their time-dependent contributions over the
solar cycle lead to a variability in radiation. COSI calculates the
continuum and line formation under conditions which are out of local
thermodynamic equilibrium (non-LTE). The applied temperature and
density structures include the chromosphere and transition region,
which is particularly important for the UV. The reconstructions are
compared with observations.

---------------------------------------------------------
Title: Modeling of the Joule heating influence on the circulation
and ozone concentration in the middle atmosphere
Authors: Zubov, V.; Rozanov, E.; Shirochkov, A.; Makarova, L.; Egorova,
T.; Kiselev, A.; Ozolin, Yu.; Karol, I.; Schmutz, W.
2005JASTP..67..155Z Altcode: 2005JATP...67..155Z
A chemistry climate model is used to evaluate of the possible influence
of Joule heating induced by the solar wind and interplanetary magnetic
field (IMF) elements on the ozone concentration and dynamics of
the Earth atmosphere. The Joule heating rates in the stratosphere
are parameterized on the base of the time series of the solar wind
and IMF parameters taken from the NASA database (Interplanetary
Medium Data Book, NASA, USA, 1999) for 1996. The results of the
10-year-long model run with the additional Joule source of heat are
compared with the output of the unperturbed (control) 20-year-long
model run. Both simulations are performed in equilibrium mode with
prescribed boundary conditions and for the minimum of the 11-year solar
cycle. The comparison of the model outputs shows that the simulated
atmosphere is rather sensitive to the introduced Joule heating. The most
significant changes were found in the lower stratosphere of the northern
hemisphere (NH). The NH lower-stratospheric temperature increases by 1
3 K almost throughout the whole year with the significance level at 95%
or higher. In boreal summer, the changes of the ozone concentration are
anti-correlated with the temperature as expected from the gas phase
photochemical theory. In boreal autumn and spring, the variations of
the ozone mixing ratio can be affected not only by the local temperature
changes but also by the redistribution of the meridional circulation in
the stratosphere. In the southern hemisphere (SH), the additional Joule
heating leads to a significant increase of the stratospheric temperature
for the austral winter (∼2K). The most substantial SH ozone changes
(∼10%) are found in the lower stratosphere during the austral spring.

---------------------------------------------------------
Title: Influence of solar 11-year variability on chemical composition
of the stratosphere and mesosphere simulated with a chemistry-climate
model
Authors: Egorova, T.; Rozanov, E.; Zubov, V.; Schmutz, W.; Peter, Th.
2005AdSpR..35..451E Altcode:
An understanding of observed global chemistry and climate changes
caused by solar activity changes is a high priority in modern
geosciences. Here, we discuss the influence of the ultraviolet
spectral irradiance variability during solar cycle on chemical
composition of the stratosphere and mesosphere with chemistry-climate
model that fully describes the interactions between chemical and
thermo-dynamical processes. We have performed several 20-year
long steady-state runs and found a significant influence of solar
irradiation on the chemical composition in the stratosphere and
mesosphere. An enhanced photolysis during solar maximum results in
destruction of methane, nitrous oxide and CFCs providing an increase
in the chemical activity of the atmosphere with more pronounced
effects in the mesosphere. In the mesosphere, an increase of HO
x caused by more intensive water vapor photolysis results
in significant ozone depletion there. More intensive methane oxidation
gives statistically significant rise to the stratospheric humidity. The
influence of dynamical perturbations has been identified over high
latitude areas. The response of OH is found to be in a good agreement
with observation data. The response of the other species is hard to
validate, because of the lack of theoretical and observational studies.

---------------------------------------------------------
Title: Preface (The Sun, solar analogs and the climate)
Authors: Rüedi, Isabelle; Güdel, Manuel; Schmutz, Werner
2005ssac.confD...5R Altcode: 2005SAAS...34D...5R
No abstract at ADS

---------------------------------------------------------
Title: Solar signal in atmospheric ozone, temperature and dynamics
simulated with CCM SOCOL in transient mode
Authors: Rozanov, E.; Schraner, M.; Egorova, T.; Ohmura, A.; Wild,
M.; Schmutz, W.; Peter, T.
2005MmSAI..76..876R Altcode:
We have carried out a set of transient runs of the Chemistry-Climate
Model SOCOL covering 1975-2000 driven by time evolving sea surface
temperature and sea ice distributions, sulfate aerosol loading, spectral
solar irradiance, greenhouse gases and ozone destroying substances. We
present the solar signal in the atmosphere extracted from these
transient runs. For the estimation of the atmospheric response to
the solar irradiance variability we use multiple regression analysis
to define the contribution of the imposed solar radiance changes to
the time evolution of the simulated quantities and to estimate their
sensitivity to the solar irradiance changes from the solar maximum
to minimum cases. The solar signal extracted from the transient runs
has been compared to the solar signal obtained from the steady-state
simulations with the same model. In general, the ozone response obtained
from the transient simulation is closer to the observation data analysis
than the results obtained from the steady-state experiment. The ozone
response in the lower mesosphere and upper stratosphere to the solar
irradiance changes is mostly positive (≈ 1-2%). Above 30 km the
ozone response is well pronounced (&lt; 5%) and occurs at 40 km over
the middle latitudes. The ozone response is smaller (&lt; 2%) in the
tropical middle stratosphere, while two additional maximums appear in
the UTLS over the northern high and southern middle latitudes. The solar
signal in the temperature extracted from the transient runs resembles
the results of the steady-state run by the location and magnitude of
the warming spots. The differences appear to be substantial only in the
UTLS region over the middle latitudes. They comprise in the additional
warming with magnitude exceeding 0.6 K. These elevated temperatures
presumably reflect an intensification of the polar vortices. The solar
signal obtained for several other simulated quantities is also analyzed.

---------------------------------------------------------
Title: The Sun, Solar Analogs and the Climate
Authors: Haigh, Joanna D.; Lockwood, Michael; Giampapa, Mark S.;
Rüedi, Isabelle; Güdel, Manuel; Schmutz, Werner
2005ssac.conf.....H Altcode: 2005SAAS...34.....H
This book presents the lecture notes of the 34th Saas-Fee Advanced
Course "The Sun, Solar Analogs and the Climate" given by leading
scientists in the field. Emphasis is on the observed variability of
the Sun and the present understanding of the variability's origin
as well as its impact on the Earth's climate. The solar variability
is then studied in the broader context of solar-type stars, allowing
for better understanding of the solar-activity cycle and the magnetic
activity in general. This book provides an accessible and up-to-date
introduction to the field for graduate students and serves as a modern
source of reference for active researchers in this field.

---------------------------------------------------------
Title: Assessment of the ozone and temperature variability during
1979 1993 with the chemistry-climate model SOCOL
Authors: Rozanov, E.; Schraner, M.; Schnadt, C.; Egorova, T.; Wild,
M.; Ohmura, A.; Zubov, V.; Schmutz, W.; Peter, Th.
2005AdSpR..35.1375R Altcode:
The chemistry-climate model SOCOL has been applied for the study of
ozone and temperature anomalies during 1979-1993. Temperature and
ozone anomalies have been obtained for a set of model runs forced
by all major stratospheric forcing mechanisms. Forcings have been
prescribed separately and together to assess their individual influence
on stratospheric ozone and temperature. The results of these simulations
have been compared to available satellite data. The model captures well
ozone depletion and cooling in the upper stratosphere due to increases
in the abundance of greenhouse gases and ozone depleting substances in
the atmosphere. In the lower stratosphere, the model reproduces the
warming over tropical and middle latitudes caused by the El-Chichon
and Pinatubo eruptions. However, the simulated ozone response is
overestimated in comparison with SAGE data. The best agreement
with observations has been obtained for the run with all forcings
included. This emphasizes the importance of the volcanic and solar
forcings for the correct reproduction of observed trends. Comparison of
near-global total ozone anomalies confirms an overestimation of ozone
depletion just after volcanic eruptions, while the overall agreement
with the model is fairly good.

---------------------------------------------------------
Title: The Wolf-Rayet Population in Region B of NGC 5253
Authors: Sidoli, F.; Smith, L. J.; Crowther, P. A.; Vacca, W. D.;
Schmutz, W.
2004ASPC..322..217S Altcode:
We present Keck+HIRES data of Region B in NGC 5253 and compare for
the first time the observed WR line profiles of this cluster to new
evolutionary synthesis models which can synthesize WR features. Using
this technique we determine the massive star population for the cluster.

---------------------------------------------------------
Title: Parameterization of the heating in the middle stratosphere
due to solar wind-induced electric currents
Authors: Makarova, L. N.; Shirochkov, A. V.; Nagurny, A. P.; Rozanov,
E.; Schmutz, W.
2004JASTP..66.1173M Altcode: 2004JATP...66.1173M
A new mechanism of thermal heating in the middle stratosphere by
the solar wind-induced electric currents is proposed. This process
occurs mostly at 20-30km altitude where a permanent layer of heavy
ion-clusters is produced by the galactic cosmic rays and by some other
sporadically occurring sources. The currents in this layer control
the electric fields in the stratosphere. Numerical estimation of
the possible atmospheric heating rate due to this process shows that
such heating could reach 1-2K/day that is comparable to the heating
due to the absorption of the solar UV radiation. Thus, the electric
fields and currents induced by the solar wind energy are candidates
for producing relevant additional heating in the middle stratosphere
(altitudes 20-30km). This process may alter the thermal structure of
the polar stratosphere and the structure of the polar stratospheric
vortex, and as a result, the global climate/weather system. In this
paper, we describe the parameterization of this heating suitable for
the application in climate and general circulation models.

---------------------------------------------------------
Title: Wind clumping and the wind-wind collision zone in the
Wolf-Rayet binary γ2 Velorum observations at high and
low state. XMM-Newton observations at high and low state
Authors: Schild, H.; Güdel, M.; Mewe, R.; Schmutz, W.; Raassen,
A. J. J.; Audard, M.; Dumm, T.; van der Hucht, K. A.; Leutenegger,
M. A.; Skinner, S. L.
2004A&A...422..177S Altcode: 2004astro.ph..4610S
We present XMM-Newton observations of γ2 Velorum (WR 11,
WC8+O7.5III, P = 78.53 d), a nearby Wolf-Rayet binary system, at
its X-ray high and low states. At high state, emission from a hot
collisional plasma dominates from about 1 to 8 keV. At low state,
photons between 1 and 4 keV are absorbed. The hot plasma is identified
with the shock zone between the winds of the primary Wolf-Rayet star
and the secondary O giant. The absorption at low state is interpreted
as photoelectric absorption in the Wolf-Rayet wind. This absorption
allows us to measure the absorbing column density and to derive a mass
loss rate .M = 8 × 10-6 M⊙ yr-1
for the WC8 star. This mass loss rate, in conjunction with a previous
Wolf-Rayet wind model, provides evidence for a clumped WR wind. A
clumping factor of 16 is required. The X-ray spectra below 1 keV (12 Å)
show no absorption and are essentially similar in both states. There
is a rather clear separation in that emission from a plasma hotter
than 5 MK is heavily absorbed in low state while the cooler plasma is
not. This cool plasma must come from a much more extended region than
the hot material. The Neon abundance in the X-ray emitting material is
2.5 times the solar value. The unexpected detection of C V (25.3 Å)
and C VI (31.6 Å) radiative recombination continua at both phases
indicates the presence of a cool (∼40 000 K) recombination region
located far out in the binary system. Based on observations
obtained with XMM-Newton, an ESA science mission with instruments and
contributions directly funded by ESA Member States and the USA (NASA).

---------------------------------------------------------
Title: XMM-Newton X-ray observations of γ2 Velorum
(WC8 + O7.5III)
Authors: Raassen, A. J. J.; Mewe, R.; van der Hucht, K. A.; Schmutz,
W.; Schild, H.; Dumm, T.; Güdel, M.; Audard, M.; Leutenegger, M. A.;
Skinner, S. L.
2004NuPhS.132..697R Altcode:
The spectrum of the binary system γ2 Velorum (WC8 + O7.5III)
has been observed with RGS and EPIC-MOS aboard XMM-Newton. The system
shows a 'high state' when the O-star is between the Wolf-Rayet star
and the observer (near periastron) and a 'low state' when most of the
spectrum is absorbed by the dense stellar wind of the Wolf-Rayet star
(near apastron). The spectrum has been model-led by a 4-T plasma,
using SPEX. The absorption affects the hot temperature component (kT =
1.5 keV) that is formed by the collision of the Wolf-Rayet wind and
the O-star wind, and the second hot component (kT = 0.65 keV) for which
the origin is still unclear. Part of the spectrum is not sensitive to
the absorption by the stellar wind. This concerns a low-temperature
component (kT = 0.23 keV) and features that are produced by plasma that
has been photoionized by X-ray radiation from the hot component. In
the RGS spectrum features of Radiative Recombination Continua (RRC)
of C VI and C V of this photoionized plasma are detected.

---------------------------------------------------------
Title: An exceptional population of late-type WC stars in the
metal-rich spiral galaxy M 83
Authors: Crowther, P. A.; Hadfield, L. J.; Schild, H.; Schmutz, W.
2004A&A...419L..17C Altcode: 2004astro.ph..3636C
We have surveyed the metal-rich spiral galaxy M 83 (NGC 5236) for
its Wolf-Rayet population using VLT-FORS2 narrow-band imaging and
follow-up spectroscopy. From a total of 280 candidates identified using
He II λ4686 imaging, Multi Object Spectroscopy of 198 sources was
carried out, revealing 132 objects containing bona-fide Wolf-Rayet
features. From this sample, an exceptional W-R content of ∼1030
is inferred, with N(WC)/N(WN) ∼ 1.3, continuing the trend to larger
values at higher metallicity amongst Local Group galaxies. More dramatic
is the dominance of late-type WC stars in M 83 with N(WC8-9)/N(WC4-7)
= 9 which we attribute to the sensitivity of the classification line C
III λ5696 to mass-loss, providing the strength of WC winds scale with
metallicity. One young massive compact cluster, #74 in our catalogue,
hosts 20% of the entire galactic population, namely ∼180 late WC
stars and ∼50 late WN stars. Based on observations made with
ESO Telescopes at the Paranal Observatory under programme ID 69.B-0125.

---------------------------------------------------------
Title: Chemical and dynamical response to the 11-year variability
of the solar irradiance simulated with a chemistry-climate model
Authors: Egorova, T.; Rozanov, E.; Manzini, E.; Haberreiter, M.;
Schmutz, W.; Zubov, V.; Peter, T.
2004GeoRL..31.6119E Altcode: 2004GeoRL..3106119E
Atmospheric effects of the solar irradiance variations during 11-year
solar cycle are investigated using a chemistry-climate model. The model
is enhanced by a more detailed parameterization of the oxygen and ozone
UV heating rates. The simulated ozone response to the imposed solar
forcing shows a positive correlation in the tropical stratosphere
and a negative correlation in the tropical mesosphere, in agreement
with theoretical expectation. The model suggests an acceleration of
the polar night jets in both hemispheres and a dipole structure in
the temperature changes at high latitudes. The model results also
show an alteration of the tropospheric circulation air resulting in
a statistically significant warming of 1 K in the annual mean surface
air temperature over North America and Siberia. This supports the idea
of a solar-climate connection.

---------------------------------------------------------
Title: Evaluation of UV and Visible radiation influence on dynamics
and chemistry of the atmosphere with CCM SOCOL.
Authors: Egorova, T.; Rozanov, E.; Zubov, V.; Manzini, E.; Haberreiter,
M.; Schmutz, W.; Peter, T.
2004cosp...35..718E Altcode: 2004cosp.meet..718E
To separate the influence of UV and visible radiation on the global
atmosphere and to investigate the effects of solar variability during
11-year solar cycle we have carried out four 20-year long steady state
simulations with observed spectral solar fluxes: (1) Solar minimum; (2)
Solar maximum; (3) Solar maximum for UV radiation only; and (4) Solar
maximum for Visible radiation only. As a modeling tool we have used
the chemistry-climate model SOCOL. The obtained results for experiment
runs have been compared with the solar minimum case. The simulated ozone
response is positively correlated with solar irradiance in the tropical
stratosphere and negatively correlated in the mesosphere, which is in
an agreement with theoretical expectation. For the experiment 2 the
model suggests a weak acceleration of the polar night jets resulting in
a dipole structure in the temperature response over the high latitudes
of both hemispheres. These dynamical changes lead to an alternation of
the tropospheric circulation, which in turn, influences the surface
air temperature resulting in a statistically significant warming of
1 K in the annual mean surface air temperature over North America
and Siberia. The pattern in surface temperature changes resembles
the signal of positive AO phases, which implies downward propagation
of the solar signal via intensification of the polar night jets. For
the simulation where only the visible radiation was enhanced we have
also obtained a stratospheric response. This response appears only
over the high latitudes and is caused by upward propagating dynamical
perturbations. Our analysis of the surface air temperature response
shows that the visible and UV radiation dominates in different
geographical regions providing a substantial combined effect.

---------------------------------------------------------
Title: Reconstruction of solar UV irradiance back to 1974
Authors: Haberreiter, M.; Krivova, N. A.; Schmutz, W.; Wenzler, T.
2004cosp...35.2707H Altcode: 2004cosp.meet.2707H
The variability of the solar UV irradiance has strong effects on
the terrestrial atmosphere. In order to study the solar influence
for times when no UV observations are available, it is necessary to
reconstruct the variation of the UV irradiance with time on the basis
of proxies. We present reconstructions of the solar UV irradiance based
on the analysis of space-based and ground-based magnetograms of the
solar disk going back to 1974. With COSI (COde for Solar Irradiance)
we calculate solar intensity spectra for the quiet Sun and different
active regions and combine them according to their fractional area on
the solar disk, whereby their time-dependent contributions over the
solar cycle lead to a variability in radiation. COSI calculates the
continuum and line formation in non-local thermodynamic equilibrium
(non-LTE). The applied temperature and density structures include the
chromosphere and transition region, which is particularly important
for the UV. The reconstructions are compared with observations.

---------------------------------------------------------
Title: Assessment of the Ozone and Temperature Trends for 1975-2000
with a transient Chemistry-Climate Model
Authors: Rozanov, E.; Schraner, M.; Wild, M.; Egorova, T.; Zubov,
V.; Manzini, E.; Austin, J.; Ohmura, A.; Schmutz, W.; Peter, T.
2004cosp...35.2640R Altcode: 2004cosp.meet.2640R
We have simulated the changes of the atmospheric state during the last
25 years of the 20th century with the Chemistry-Climate
Model SOCOL extending form the ground up to 80 km. We have carried out
four 25-year long transient runs forced by the observed sea surface
temperature/sea ice (SST/SI) distributions. For the first simulation
only the time evolving SST/SI are prescribed. For the second and third
simulations we have added the time evolution of the Greenhouse Gases
(GHG) and Ozone Destructing Substances (ODS). In the forth simulation we
consider the forcing due to the both GHG and ODS. The obtained trends
in the ozone and temperature are compared with available observation
data. The obtained time evolution of the temperature and ozone fields
for the forth run are closer to the observation data than the results
of all other runs. The model captures the formation of the ozone
“hole” over the southern high-latitudes, cooling and ozone depletion
in the upper stratosphere and warming in the troposphere. However,
a substantial total ozone depletion observed in 1992-1993 is not
captured by the model, because of the lack of volcanic aerosols
after the Pinatubo eruption in our experiments. We expect that this
feature will be correctly reproduced in the ongoing experiment where
the volcanic aerosol is taken into account. The model simulates an
increase of the stratospheric water vapor mixing ratio by of about
7%/decade which is most likely connected to the tropospheric warming
and subsequent increase of the water vapor in the upper troposphere.

---------------------------------------------------------
Title: Solar-Blind Diamond Detectors for Lyra, the Solar VUV
Radiometer on Board Proba II
Authors: Benmoussa, A.; Hochedez, J. -F.; Schmutz, W. K.; Schühle,
U.; Nesládek, M.; Stockman, Y.; Kroth, U.; Richter, M.; Theissen,
A.; Remes, Z.; Haenen, K.; Mortet, V.; Koller, S.; Halain, J. P.;
Petersen, R.; Dominique, M.; D'Olieslaeger, M.
2003ExA....16..141B Altcode:
Fabrication, packaging and experimental results on the calibration
of metal-semiconductor-metal (MSM) photodetectors made on diamond
are reported. LYRA (Lyman-α RAdiometer onboard PROBA-2) will use
diamond detectors for the first time in space for a solar physics
instrument. A set of measurement campaigns was designed to obtain the
XUV-to-VIS responsivity of the devices and other characterizations. The
measurements of responsivity in EUV and VUV spectral ranges (40 240
nm) have been carried out by the Physkalisch-Technische Bundesanstalt
(PTB) in Germany at the electron storage ring BESSY II. The longer
wavelength range from 210 to 1127 nm was measured with monochromatic
light by using a Xe-lamp at IMO-IMOMEC. The diamond detectors exhibit a
photoresponse which lie in the 35 65 mA/W range at 200 nm (corresponding
to an external quantum efficiency of 20 40%) and indicate a visible
rejection ratio (200 500 nm) higher than four orders of magnitude.

---------------------------------------------------------
Title: Traceable radiometry underpinning terrestrial- and
helio-studies (TRUTHS)
Authors: Fox, N.; Aiken, J.; Barnett, J. J.; Briottet, X.; Carvell,
R.; Frohlich, C.; Groom, S. B.; Hagolle, O.; Haigh, J. D.; Kieffer,
H. H.; Lean, J.; Pollock, D. B.; Quinn, T.; Sandford, M. C. W.;
Schaepman, M.; Shine, K. P.; Schmutz, W. K.; Teillet, P. M.; Thome,
K. J.; Verstraete, M. M.; Zalewski, E.
2003AdSpR..32.2253F Altcode:
The Traceable Radiometry Underpinning Terrestrial- and Helio-
Studies (TRUTHS) mission offers a novel approach to the provision
of key scientific data with unprecedented radiometric accuracy
for Earth Observation (EO) and solar studies, which will also
establish well-calibrated reference targets/standards to support
other EO missions. This paper presents the TRUTHS mission and its
objectives. TRUTHS will be the first satellite mission to calibrate
its EO instrumentation directly to Sl in orbit, overcoming the usual
uncertainties associated with drifts of sensor gain and spectral shape
by using an electrical rather than an optical standard as the basis
of its calibration. The range of instruments flown as part of the
payload will also provide accurate input data to improve atmospheric
radiative transfer codes by anchoring boundary conditions, through
simultaneous measurements of aerosols, particulates and radiances
at various heights. Therefore, TRUTHS will significantly improve the
performance and accuracy of EO missions with broad global or operational
aims, as well as more dedicated missions. The provision of reference
standards will also improve synergy between missions by reducing
errors due to different calibration biases and offer cost reductions
for future missions by reducing the demands for on-board calibration
systems. Such improvements are important for the future success of
strategies such as Global Monitoring for Environment and Security (GMES)
and the implementation and monitoring of international treaties such
as the Kyoto Protocol. TRUTHS will achieve these aims by measuring
the geophysical variables of solar and lunar irradiance, together
with both polarised and unpolarised spectral radiance of the Moon,
Earth and its atmosphere. Published by Elsevier Ltd on behalf of COSPAR.

---------------------------------------------------------
Title: The PICARD mission
Authors: Thuillier, Gérard; Joukoff, Alexandre; Schmutz, Werner
2003ESASP.535..251T Altcode: 2003iscs.symp..251T
PICARD is an investigation dedicated to the Sun-climate connection. The
mission objectives are the study of the solar forcing on the Earth's
climate, and the physics of the Sun. It consists of simultaneous
measurements of the absolute total and spectral solar irradiance,
the diameter and solar shape, and to carry out helioseismologic
observations to probe the Sun's interior. These measurements obtained
all along the mission will allow to study their variations as a function
of the solar activity. The observations will be carried out by three
instruments placed on board a microsatellite built by Centre National
d'Etudes Spatiales (France). Ground-based observations will complement
the space observations.

---------------------------------------------------------
Title: Modelling the solar UV radiation
Authors: Haberreiter, M.; Schmutz, W.
2003ESASP.535..289H Altcode: 2003iscs.symp..289H
We model the solar spectrum with emphasis on the UV range with
the spherical non-LTE atmosphere code COSI (COde for Solar
Irradiance). Presently, we explicitly treat 31 levels in non-LTE
and apply to 17 levels of neutral metals the latest theoretical
photoionization cross sections. The atmosphere models are based
on the observed temperature and density structures by Fontenla et
al. (1999), which include the chromosphere and transition region. We
compare synthetic spectra from 2000 to 7500 Å in local thermodynamic
equilibrium (LTE) with calculations from a Kurucz model, as well as
theoretical Balmer line profiles computed in non-LTE with observations.

---------------------------------------------------------
Title: XMM-Newton high-resolution x-ray spectroscopy of the Wolf-Rayet
object WR25 (WN6HA+04F)
Authors: Raassen, A. J. J.; van der Hucht, K. A.; Mewe, R.; Antokhin,
I.; Rauw, G.; Vreux, J. -M.; Schmutz, W.; Güdel, M.
2003AdSpR..32.1161R Altcode:
We report the analysis of the X-ray spectrum of the Wolf-Rayet star WR
25, observed by RGS and EPIC-MOS on board XMM-Newton. Temperatures up
to 40 MK have been determined. Strong absorption, exceeding the value
due to the Inter Stellar Medium (ISM) has been detected and assigned
to the dense stellar wind.

---------------------------------------------------------
Title: XMM-Newton high-resolution X-ray spectroscopy of the
Wolf-Rayet object WR 25 in the Carina OB1 association
Authors: Raassen, A. J. J.; van der Hucht, K. A.; Mewe, R.; Antokhin,
I. I.; Rauw, G.; Vreux, J. -M.; Schmutz, W.; Güdel, M.
2003A&A...402..653R Altcode:
We report the analysis of the first high-resolution X-ray spectra of
the Wolf-Rayet (WR) object WR 25 (HD 93162, WN6ha+O4f) obtained with
the Reflection Grating Spectrometers (RGS) and the European Photon
Imaging Cameras (EPIC-MOS and PN) CCD spectrometers on board the
XMM-Newton satellite. The spectrum exhibits bright emission lines
of the H- and He-like ions of Ne, Mg, Si and S, as well as Fe XVII
i to Fe XX and Fe XXV lines. Line fluxes have been measured. The
RGS and EPIC spectra have been simultaneously fitted to obtain
self-consistent temperatures, emission measures, and elemental
abundances. Strong absorption by the dense WR stellar wind and the
interstellar medium (ISM) is observed equivalent to NH =
7 x 1021 cm-2. Multi-temperature (DEM) fitting
yields two dominant components around temperatures of 7.0 and 32 MK,
respectively. The XMM intrinsic (i.e. unabsorbed, corrected for the
stellar wind absorption and the absorption of ISM) X-ray luminosity
of WR 25 is Lx(0.5-10 keV) = 1.3 x 1034 erg
s-1, and Lx(0.5-10 keV) = 0.85 x 1034
erg s-1, (when correcting for the ISM only) assuming d=3.24
kpc. The obtained chemical abundances are subsolar, except for S. This
may be real, but could equally well be due to a weak coupling to
the continuum, which is strongly influenced by the absorption column
density and the subtracted background. The expected high N-abundance,
as observed in the optical wavelength region, could not be confirmed due
to the strong wind absorption, blocking out its spectral signature. The
presence of the Fe XXV emission-line complex at ~ 6.7 keV is argued as
being indicative for colliding winds inside a WR+O binary system. Based on observations obtained with XMM-Newton, an ESA science
mission with instruments and contributions directly funded by ESA
Member States and the USA (NASA).

---------------------------------------------------------
Title: A large Wolf-Rayet population in NGC 300 uncovered by VLT-FORS2
Authors: Schild, H.; Crowther, P. A.; Abbott, J. B.; Schmutz, W.
2003A&A...397..859S Altcode: 2002astro.ph..9259S
We have detected 58 Wolf-Rayet candidates in the central region
of the nearby spiral galaxy NGC 300, based on deep VLT-FORS2
narrow-band imaging. Our survey is close to complete except for
heavily reddened WR stars. Of the objects in our list, 16 stars
were already spectroscopically confirmed as WR stars by Schild &amp;
Testor and Breysacher et al., to which 4 stars are added using low
resolution FORS2 datasets. The WR population of NGC 300 now totals
60, a threefold increase over previous surveys, with WC/WN&gt;=1/3,
in reasonable agreement with Local Group galaxies for a moderately
sub-solar metallicity. We also discuss the WR surface density in the
central region of NGC 300. Finally, analyses are presented for two
apparently single WC stars - #29 (alias WR3, WC5) and #48 (alias WR13,
WC4) located close to the nucleus, and at a deprojected radius of
2.5 kpc, respectively. These are among the first models of WR stars
in galaxies beyond the Local Group, and are compared with early WC
stars in our Galaxy and LMC. Based on observations made with ESO
Telescopes at the Paranal Observatory under programme ID 65.H-0705(A).

---------------------------------------------------------
Title: Wolf-Rayet stars at 1 - 2 Mpc
Authors: Crowther, Paul A.; Abbott, Jay B.; Drissen, Laurent; Schild,
Hansrüdi; Schmutz, Werner; Royer, Pierre; Smartt, Stephen J.
2003IAUS..212..547C Altcode:
We present new narrow-band imaging and optical spectroscopy of
Wolf-Rayet stars in the Local Group dwarf galaxy IC 10 (Gemini-N-
GMOS) and Sculptor group spiral galaxy NGC 300 (VLT FORS 2}).

---------------------------------------------------------
Title: Representation of Opacity Data in Solar Model Atmosphere
Calculations
Authors: Haberreiter, M.; Rozanov, E.; Rüedi, I.; Schmutz, W.
2003ASPC..288..165H Altcode: 2003sam..conf..165H
Rozanov et al. (2002) have determined that the influence of the
solar irradiance variability on the chemical composition in the
stratosphere is dominated by two narrow bands in the UV centered around
215 nm and 265 nm. We have evaluated the dominant opacity sources
at these wavelengths and find it necessary to include the complex
continuum absorption cross sections from the lower levels of neutral
metals. We present our straightforward solution how to describe these
opacities. There is the obvious need to treat the line blanketing
which mainly depends on the completeness of the line list. We base
our calculations on a combination of the spherically symmetric non-LTE
`Kiel-code' and the spectral synthesis by the SYNSPEC code. In order
to evaluate the quality of our computations we compare our predictions
with the UV spectrum observed by SUSIM.

---------------------------------------------------------
Title: XMM-Newton and Very Large Array Observations of the Variable
Wolf-Rayet Star EZ Canis Majoris: Evidence for a Close Companion?
Authors: Skinner, Stephen L.; Zhekov, Svetozar A.; Güdel, Manuel;
Schmutz, Werner
2002ApJ...579..764S Altcode: 2002astro.ph..7171S
We present new X-ray and radio observations of the Wolf-Rayet star
EZ CMa (HD 50896) obtained with XMM-Newton and the Very Large Array
(VLA). This WN4 star exhibits optical and UV variability at a period
of 3.765 days whose cause is unknown. Binarity may be responsible, but
the existence of a companion has not been proven. The radio spectral
energy distribution of EZ CMa determined from VLA observations at five
frequencies is in excellent agreement with predictions for free-free
wind emission, and the ionized mass-loss rate allowing for distance
uncertainties is M=3.8(+/-2.6)×10-5 Msolar
yr-1. The CCD X-ray spectra show prominent Si XIII and
S XV emission lines and can be acceptably modeled as an absorbed
multitemperature optically thin plasma, confirming earlier
ASCA results. Nonsolar abundances are inferred with Fe notably
deficient. The X-ray emission is dominated by cooler plasma at a
temperature kTcool~0.6 keV, but a harder component is also
detected, and the derived temperature is kThot~3.0-4.2
keV if the emission is thermal. This is too high to be explained by
radiative wind shock models, and the X-ray luminosity of the hard
component is 3 orders of magnitude lower than expected for accretion
onto a neutron star companion. We show that the hard emission could be
produced by the Wolf-Rayet wind shocking onto a normal (nondegenerate)
stellar companion at close separation. Finally, using comparable data
sets we demonstrate that the X-ray and radio properties of EZ CMa are
strikingly similar to those of the WN5-6 star WR 110. This similarity
points to common X-ray and radio emission processes in WN stars and
discredits the idea that EZ CMa is anomalous within its class.

---------------------------------------------------------
Title: Towards a spherical code for the evaluation of solar UV-bands
that influence the chemical composition in the stratosphere
Authors: Haberreiter, M.; Hubeny, I.; Rozanov, E.; Rüedi, I.; Schmutz,
W.; Wenzler, T.
2002ESASP.508..209H Altcode: 2002soho...11..209H
We present our analysis of data taken by SUSIM onboard UARS. We
reconstruct the variability of the UV irradiance and compare it to
available data. Up to now we model the solar irradiance according to
the 3-component model by Unruh et al. (1999) based on LTE synthetic
spectra modeled with Kurucz' ATLAS9 code. Our new approach will be that
with COSI (COde for Solar Irradiance) we model solar continuum and
line formation in spherical symmetry and in non-local thermodynamic
equilibrium (non-LTE). We present our first synthetic solar spectra
(calculated in LTE) and validate them against spectra computed with
Kurucz' ATLAS9 code.

---------------------------------------------------------
Title: XMM-Newton Detection of Hard X-Ray Emission in the
Nitrogen-Type Wolf-Rayet Star WR 110
Authors: Skinner, Stephen L.; Zhekov, Svetozar A.; Güdel, Manuel;
Schmutz, Werner
2002ApJ...572..477S Altcode: 2002astro.ph..3270S
We have used the excellent sensitivity of XMM-Newton to obtain
the first high-quality X-ray spectrum of a Wolf-Rayet (W-R) star
that is not known to be a member of a binary system. Our target,
the nitrogen-type star WR 110 (HD 165688), was also observed and
detected with the Very Large Array at four different frequencies. The
radio flux density increases with frequency according to a power law
Sν~ν+0.64+/-0.10, in very good agreement with
the behavior expected for free-free wind emission. The radio data give
an ionized mass-loss rate M=4.9×10-5 Msolar
yr-1 for an assumed spherical constant-velocity wind. The
undispersed CCD X-ray spectra reveal strong emission lines from
He-like ions of Mg, Si, and S. The emission measure distribution
shows a dominant contribution from cool plasma with a characteristic
temperature kTcool~0.5 keV (~6 MK). Little or no excess
absorption of this cool component above the value expected from the
visual extinction is present. We conclude that the bulk of the cool
plasma detected by XMM-Newton lies at hundreds of stellar radii or
more if the wind is approximately spherical and homogeneous, but
it could lie closer to the star if the wind is clumped. If the cool
plasma is due to instability-driven wind shocks, then typical shock
velocities are vs~340-550 km s-1 and the average
filling factor of X-ray-emitting gas in the wind is no larger than
f~10-6. A surprising result is the unambiguous detection of
a hard X-ray component that is clearly seen in the hard-band images
and the spectra. This hard component accounts for about half of the
observed flux and can be acceptably fitted by a hot, optically thin
thermal plasma or a power-law model. If the emission is thermal,
then a temperature kThot&gt;=3 keV is derived. Such high
temperatures are not predicted by current instability-driven wind
shock models, and a different mechanism is thus required to explain the
hard X-rays. We examine several possible mechanisms and show that the
hard emission could be accounted for by the W-R wind shocking onto a
close stellar companion that has so far escaped detection. However,
until persuasive evidence for binarity is found, we are left with
the intriguing possibility that the hard X-ray emission is produced
entirely by the Wolf-Rayet star.

---------------------------------------------------------
Title: Estimation of the ozone and temperature sensitivity to the
variation of spectral solar flux
Authors: Rozanov, E.; Egorova, T.; Fröhlich, C.; Haberreiter, M.;
Peter, T.; Schmutz, W.
2002ESASP.508..181R Altcode: 2002soho...11..181R
We have applied a 1-D steady-state radiative-convective model
with interactive photochemistry to estimate the sensitivity of
temperature and ozone mixing ratio to the observed variability of
the extraterrestrial spectral solar irradiance. We have carried out
several runs using the spectral solar flux for minimum and maximum solar
activity conditions. The results show that the ozone and temperature
in the stratosphere are mostly sensitive to the solar flux variations
in the spectral area between 200 and 220 nm, where they positively
correlate with solar flux intensity. In the upper stratosphere and
mesosphere the effects of the solar flux variability in the Lyman-α
line and Schumann-Runge band are found to be very important. The
obtained results have an implication for the optimal choice of
wavelength to be measured from a satellite and for the understanding
of what kind of radiation code should be used in a GCM aimed to study
solar-climate connections.

---------------------------------------------------------
Title: Solar Irradiance Variations over Solar Cycles 21 to 23
Authors: Pap, J. M.; Kuhn, J.; Jones, H.; Turmon, M.; Arge, N.;
Schmutz, W.; Floyd, L.
2002AAS...200.2803P Altcode: 2002BAAS...34..679P
In this paper we describe the science requirements and a new measurement
strategy to better understand solar variability and its potential effect
on climate. We study the relation between the variations in solar total
and UV irradiances and solar magnetic fields as observed within the last
three decades. The results of our analysis raise important questions:
(1) is there a significant non-magnetic component in the observed
irradiance variations?; (2) may polar magnetic fields play a role
in irradiance changes?; (3) is there a strict linear relationship
between solar variability and irradiance variations as the current
irradiance models used in climate studies assume? The results presented
in this paper underscore the need to further develop new measurement
and analysis techniques to study and predict the climate impact of
solar variability.

---------------------------------------------------------
Title: XMM-newton high-resolution x-ray - spectroscopy of wr 25
Authors: Raassen, A.; van der Hucht, K.; Mewe, R.; Antokhin, I.;
Guedel, M.; Schmutz, W.
2002cosp...34E1592R Altcode: 2002cosp.meetE1592R
We report the analysis of the first high-resolution X-ray spectra of
the WN6ha star WR 25 (HD 93162) obtained with the reflection grating
spectrometers (rgs) and the european photon imaging cameras (epic-
mos and -pn) ccd spectrometers on board XMM-Newton. The spec- trum
exhibits bright emission lines of the H- and He-like ions of Ne, Mg,
Si and S, as well as lines of Fe xvii to Fe xx and Fe xxv. Line fluxes
have been determined. The rgs and epic spectra have been simultane-
ously fitted to obtain self-consistent temperatures, emission measures,
and elemental abundances. Multi-temperature fitting yields two dom-
inant components around temperatures of 7 and 30 MK, respectively. An
interstellar absorption value, related to the optically thick wind of
the WR star is obtaines as NH in the range 3-6 1021 cm-2 . The pres-
ence of the Fe xxv emission-line complex at6.7 keV is argued as being
indicative for colliding winds inside the WR+O binary system.

---------------------------------------------------------
Title: Long-term solar irradiance variations: results and perspectives
Authors: Pap, J.; Fleck, B.; Frohlich, C.; Jones, H.; Kuhn, J.;
Schmutz, W.
2002cosp...34E.553P Altcode: 2002cosp.meetE.553P
In this paper we show the recent result on irradiance variations and
their relation to solar magnetic activity over solar cycles 21 to
23. Comparison of the multi-decade long irradiance and magnetic field
measurements indicates that the shape and magnitude of irradiance
variations are different from that of magnetic indices. Specifically,
while magnetic indices show that solar cycle 23 is weaker than the two
previous cycles, the long-term variation of total solar irradiance
over solar cycles 21 to 23 is rather symmetrical, showing that its
maximum and minimum levels were about the same within their measuring
uncertainties. These results raise questions like: (1) is there a
strict linear relationship between solar variability and irradiance
variations as the current irradiance models used in climate studies
assume?; (2) what is the role of polar magnetic fields in irradiance
changes?; (3) is there a significant non-magnetic component in the
observed irradiance variations? The results presented in this paper
underscore the need to further develop new measurement and analysis
techniques to study and predict the climate impact of solar variability.

---------------------------------------------------------
Title: Model Assessment Of The Short And Long-Terms Solar UV
Variability Effects On The Climate And Global Ozone.
Authors: Rozanov, E.; Egorova, T.; Haberreiter, M.; Schmutz, W.
2002cosp...34E.802R Altcode: 2002cosp.meetE.802R
A search for the mechanisms responsible for the detected solar-climate
connections is under way. One potential candidate is he variability of
the Solar UV radiationt because it can influence the temperature and
dynamics in the entire atmosphere throughout the perturbation of the
ozone and radiative heating in the middle atmosphere. We have applied a
3-D GCM with interactive chemistry to evaluate the sensitivity of the
ozone, temperature and dynamics in the stratosphere and mesosphere to
the changes of the Solar irradiance along 11-year Solar activity and
28-day Sun rotation cycles. The simulated changes of the global ozone,
temp erature and zonal wind are extensively compared to the available
observation data obtained from different satellite instruments. We also
compare the simulated responses to those obtained from the experiment
with the non-interactive chemical-transport model to emphasize the
role of climate-chemistry interaction.

---------------------------------------------------------
Title: JOSO national report 2000-2001 - Switzerland
Authors: Schmutz, W.
2002joso.book..116S Altcode:
This report reviews the advances in solar physics in Switzerland
in 2000-2001. The solar physics is carried out at: 1) Institute of
Astronomy, ETH Zurich, 2) Physikalisch-Meteorologisches Observatorium
Davos, World Radiation Centre (PMOD/WRC) Davos.

---------------------------------------------------------
Title: COSI - a new spherical NLTE COde for the calculation of
Solar Irradiance
Authors: Haberreiter, M.; Rozanov, E.; Schmutz, W.
2002cosp...34E.789H Altcode: 2002cosp.meetE.789H
The influence of the solar irradiance variability on the chemical
composition in the stratosphere and mesosphere is dominated by Lyand
two wavelength bands from 200 to 220 nm and 260 to 280 nm (Rozanov
et al., 2002). We model the variablity in these wavelengths using the
approach from Unruh et al. (1999). However, as nonLTE continuum and line
formation is important for wavelengths below 200 nm, we reconstruct the
solar UV spectra with COSI - a combination of the spherical 'Kielcode'
(Hamann &amp;Schmutz, 1987) and the spectrum synthesis program SYNSPEC
(Hubeny, 1988). With COSI we also account for the center to limb
variations of the solar irradiance. We present our results and compare
them to our analysis of SUSIM data.

---------------------------------------------------------
Title: Stellar and circumstellar variability of the Be star mu Cen IV
Authors: Rivinius, Th.; Stefl, S.; Stahl, O.; Wolf, B.; Kaufer,
A.; Baade, D.; Dumm, Th.; Gäng, Th.; Gracia, J.; Gummersbach, C.;
Jankovics, Kaper L.; Kovacs, J.; Lehmann, H.; Mandel, H.; Peitz,
J.; Schafer, D.; Schweickhardt, J.; Schmutz, W.; Szeifert, Th.;
Tubbesing, S.
2001JAD.....7....5R Altcode:
For the bright southern Be star mu Cen, we publish all spectra that
have been used in the previous papers of this series. An overview of
the data is given and the published results obtained with these data
are summarized. All data have been obtained from La Silla. In detail,
these are 28 spectra taken with Flash at the ESO 50-cm (400 nm to 670
nm), 426 blue and 443 red spectra taken with Heros using the ESO 50-cm
and the ESO 1.52-m (350 nm to 860 nm), 47 spectra taken with Feros at
the ESO 1.5-m (370 nm to 920 nm), 2 x 348 spectra taken with the Boller
and Chivens at the ESO 1.52-m (345 nm to 510 nm), and 310 spectra of
He I 6678 and 27 spectra of Si III 4553 taken with the CAT/CES. mu
Cen was found to be a multiperiodic non-radially pulsating star, with
indications for a coupling between the multiperiodic beating and the
star-to-disk mass transfer.

---------------------------------------------------------
Title: 2 Micron Narrowband Adaptive Optics Imaging in the Arches
Cluster
Authors: Blum, R. D.; Schaerer, D.; Pasquali, A.; Heydari-Malayeri,
M.; Conti, P. S.; Schmutz, W.
2001AJ....122.1875B Altcode: 2001astro.ph..6496B
Canada-France-Hawaii-Telescope adaptive optics bonnette images
through narrowband filters in the K band are presented for the Arches
cluster. Continuum fluxes, line fluxes, and equivalent widths are
derived from high angular resolution images, some nearly diffraction
limited, for the well-known massive stars in the Arches cluster. Images
were obtained in the lines He I 2.06 μm, H I Brγ (2.17 μm), and
He II 2.19 μm, as well as continuum positions at 2.03, 2.14, and
2.26 μm. In addition, fluxes are presented for H I Pα (1.87 μm)
and a nearby continuum position (1.90 μm) from Hubble Space Telescope
archival data.2 The 2 μm and Pα data reveal two new emission-line
stars and three fainter candidate emission-line objects. Indications
for a spectral change of one object between earlier observations in
1992-1993 and our data from 1999 are found. The ratio of He II 2.19
μm to Brγ emission exhibits a narrow distribution among the stars,
suggesting a narrow evolutionary spread centered predominantly on
spectral types O4 If or Wolf-Rayet stars of the WN7 subtype. From the
approximate spectral types of the identified emission-line stars and
comparisons with evolutionary models we infer a cluster age between
~2 and 4.5 Myr.

---------------------------------------------------------
Title: SIM3D: Solar Irradiance Monitor-3D-view
Authors: Schmutz, W.; Fröhlich, C.; Rüedi, I.; Roth, H.; Wehrli,
Ch.; Wyss, J.
2001ESASP.493..447S Altcode: 2001sefs.work..447S
No abstract at ADS

---------------------------------------------------------
Title: Chandra Detection of a Close X-Ray Companion and Rich
Emission-Line Spectrum in the Wolf-Rayet Binary γ Velorum
Authors: Skinner, Stephen L.; Güdel, Manuel; Schmutz, Werner; Stevens,
Ian R.
2001ApJ...558L.113S Altcode:
We present first results of a high-resolution X-ray observation of the
nearby Wolf-Rayet binary system γ2 Velorum (WC8 + O7.5)
using the Chandra High-Energy Transmission Grating (HETG). Emission
lines from Mg, Si, S, Ne, and Fe dominate the spectrum and imply a range
of plasma temperatures from ~4 MK up to at least ~25 MK. The strongest
lines are broadened, but no Doppler shifts are detected. He-like
triplets show strong forbidden lines with no significant weakening
from collisional effects or photoexcitation, contrasting sharply
with the diluted forbidden lines of single O-type supergiants such
as ζ Puppis. These results imply that some lines such as the Ne IX
triplet are formed in cooler plasma at tens of stellar radii or more
from the O star, well outside of the central wind interaction region
located near the O star surface. Lastly, we report the discovery of a
new X-ray source lying only 4.8" north of γ2 Vel that is
very likely a low-mass pre-main-sequence star.

---------------------------------------------------------
Title: Long-term spectroscopic monitoring of the Luminous Blue
Variable AG Carinae
Authors: Stahl, O.; Jankovics, I.; Kovács, J.; Wolf, B.; Schmutz,
W.; Kaufer, A.; Rivinius, Th.; Szeifert, Th.
2001A&A...375...54S Altcode:
We have extensively monitored the Luminous Blue Variable AG Car (HD
94910) spectroscopically. Our data cover the years 1989 to 1999. In
this period, the star underwent almost a full S Dor cycle from visual
minimum to maximum and back. Over several seasons, up to four months of
almost daily spectra are available. Our data cover most of the visual
spectral range with a high spectral resolution (lambda /Delta lambda
~ 20 000). This allows us to investigate the variability in many
lines on time scales from days to years. The strongest variability
occurs on a time scale of years. Qualitatively, the variations can
be understood as changes of the effective temperature and radius,
which are in phase with the optical light curve. Quantitatively, there
are several interesting deviations from this behaviour, however. The
Balmer lines show P Cygni profiles and have their maximum strength
(both in equivalent width and line flux) after the peak of the optical
light curve, at the descending branch of the light curve. The line-width
during maximum phase is smaller than during minimum, but it has a local
maximum close to the peak of the visual light curve. We derive mass-loss
rates over the cycle from the Hα line and find the highest mass loss
rates (log dot {M}/({M}_sun yr-1) ~ -3.8, about a factor of
five higher than in the minimum, where we find log dot {M}/({M}_sun
yr-1) ~ -4.5) after the visual maximum. Line-splitting is
very commonly observed, especially on the rise to maximum and on the
descending branch from maximum. The components are very long-lived
(years) and are probably unrelated to similar-looking line-splitting
events in normal supergiants. Small apparent accelerations of the
components are observed. The change in radial velocity could be
due to successive narrowing of the components, with the absorption
disappearing at small expansion velocities first. In general, the
line-splitting is more likely the result of missing absorption at
intermediate velocities than of excess absorption at the velocities
of the components. The HeI lines and other lines which form deep in
the atmosphere show the most peculiar variations. The HeI lines show
a central absorption with variable blue- and red-shifted emission
components. Due to the variations of the emission components, the HeI
lines can change their line profile from a normal P Cyg profile to an
inverse P Cyg-profile or double-peak emission. In addition, very broad
(+/-1500 km s-1) emission wings are seen at the strongest
HeI lines of AG Car. At some phases, a blue-shifted absorption is also
present. The central absorption of the HeI lines is blue-shifted before
and red-shifted after maximum. Possibly, we directly see the expansion
and contraction of the photosphere. If this explanation is correct, the
velocity of the continuum-forming layer is not dominated by expansion
but is only slightly oscillating around the systemic velocity. Based
on observations collected at the European Southern Observatory at La
Silla, Chile.

---------------------------------------------------------
Title: High resolution spectroscopy of symbiotic stars. VI. Orbital
and stellar parameters for AR Pavonis
Authors: Schild, H.; Dumm, T.; Mürset, U.; Nussbaumer, H.; Schmid,
H. M.; Schmutz, W.
2001A&A...366..972S Altcode: 2000astro.ph.11562S
We present new dynamical parameters of the AR Pav binary system. Our
observations consist of a series of high resolution optical/NIR spectra
from which we derive the radial velocity curve of the red giant as
well as its rotation velocity. Assuming co-rotation, we determine the
stellar radius (130 Rsun) of the red giant. Based on this
we derive the red giant's luminosity and mass (2.0 Msun)
as well as the distance of the system (4.9 kpc). The binary mass
function finally yields the companion's mass (0.75 Msun)
and the binary separation (1.95 AU). We find that the red giant does
not fill its Roche lobe. We review the radial velocity data of Thackeray
&amp; Hutchings (\cite{Thacker74}), and compare it with our red giant's
orbit. We find that their RV curves of the blue absorption system and
the permitted emission lines are in anti-phase with the red giant,
and that the forbidden emission lines are shifted by a quarter of
a period. The blue absorptions and the permitted emission lines are
associated with the hot companion but not in a straightforward way. The
blue absorption system only tracks the hot component's orbital motion
whilst it is in front of he red giant, whereas at other phases line
blanketing by interbinary material leads to perturbations. We finally
present UV light curves based on IUE archive spectra. We clearly detect
eclipses in the continuum at all wavelengths. The eclipse light curves
are unusual in that they show a slow and gradual decline prior to
eclipse which is followed by a sharp increase after eclipse. Based on
observations obtained at the European Southern Observatory, La Silla,
Chile; the observations were granted for the ESO programs 47.7-081,
48.7-083, 49.7-041, 50.7-129, 51.7-093, 52.7-068, 53.7-083, 54.E-061,
55.E-446, 56.E-526.

---------------------------------------------------------
Title: The γ Velorum binary system. II. WR stellar parameters and
the photon loss mechanism
Authors: De Marco, O.; Schmutz, W.; Crowther, P. A.; Hillier, D. J.;
Dessart, L.; de Koter, A.; Schweickhardt, J.
2000A&A...358..187D Altcode: 2000astro.ph..4081D
In this paper we derive stellar parameters for the Wolf-Rayet star
in the gamma Velorum binary system (WR11), from a detailed non-LTE
model of its optical and infrared spectra. Compared to the study
of Schaerer et al., the parameters of the WC8 star are revised to a
hotter effective temperature (T_eff ~ 57 kK), a higher luminosity (log
(L/Lsun) = 5.00), and a lower mass-loss rate (log(dot {M} /
Msun/yr) = -5.0, using a 10% clumping filling factor). These
changes lead to a significant decrease in wind efficiency number, from
144 to 7, so that the driving mechanism of the wind of this WR star
may be simply radiation pressure on lines. The derived spectroscopic
luminosity is found to be 40% lower than that derived by De Marco
&amp; Schmutz through the mass-luminosity relationship for WR stars
(log (L/Lsun) = 5.2). The paper furthermore presents a
comparison of the independently-developed modelling programs, cmfgen
and isa-wind. Overall, there seems to be very reasonable agreement
between the derived parameters for WR11, except for the carbon content,
which is 2 times higher for cmfgen (C/He=0.15 vs. 0.06, by number). The
comparison also confirms a disparity in the predicted flux at $lambda
mbda$&lt;400 Ä, found by Crowther et al., which will have effects
on several nebular line strengths. The paper also presents the first
independent check of the photon loss mechanism proposed by Schmutz. We
conclude that, not only is it important to include very many lines
to realistically model line blanketing, but in particular those ones
that critically interact with strong resonance lines (e.g. He ii\
lambda 303.78). The inclusion of these latter lines may significantly
alter the wind ionization structure. Based on observations collected
at the European Southern Observatory at La Silla, Chile. ESO proposals
Nrs. 56.D-327, 57.D-517 and 56.D-0700}

---------------------------------------------------------
Title: A wind accretion wake in RW Hydrae?
Authors: Dumm, T.; Folini, D.; Nussbaumer, H.; Schild, H.; Schmutz,
W.; Walder, R.
2000A&A...354.1014D Altcode:
RW Hydrae is an eclipsing detached binary star system, consisting of a
mass losing M-giant and a hot white dwarf on circular orbits. We analyze
UV observations of RW Hydrae. Approximately at phi = 0.78, clearly
unrelated to the primary eclipse, we detect in the UV light curve an
event with significantly reduced UV flux. The spectral characteristics
of this event indicate Rayleigh scattering due to a high column density
of neutral hydrogen in the line of sight to the hot white dwarf. We
model this observation in the framework of an accretion wake trailing
the white dwarf. This interpretation is analogous to comparable models
for zeta Aur systems and X-ray binaries. We find qualitative agreement
between our 3D hydrodynamical accretion simulation and the observed UV
light curve of RW Hya. Based on observations with the International
Ultraviolet Explorer and observations with the NASA/ESA Hubble Space
Telescope, obtained at the Space Telescope Science Institute, which is
operated by the Association of Universities for Research in Astronomy,
Inc. under NASA contract No. NAS5-26555.

---------------------------------------------------------
Title: WR Stars in Star Forming Regions
Authors: Schmutz, Werner; Vacca, Wiliam D.
2000fepc.conf..307S Altcode:
WR galaxies are characterized by broad emission features at 4686 A
and occasionally at 4640 A and 5805 A. The features are attributed to
stellar emission from a large population of WR stars. The presence of
WR stars allows a determination of the age of the starburst. In a few
WR galaxies the 4640 emission line has been measured to be as large
or larger than the He II 4686 line. We demonstrate that a 4640/4686
ratio larger than unity cannot be produced by any known population of
WR stars and discuss the implications for the interpretation of the
star formation histories in WR galaxies.

---------------------------------------------------------
Title: High resolution spectroscopy of symbiotic stars. V. Orbital
and stellar parameters for FG Ser (AS 296)
Authors: Mürset, U.; Dumm, T.; Isenegger, S.; Nussbaumer, H.; Schild,
H.; Schmid, H. M.; Schmutz, W.
2000A&A...353..952M Altcode:
For the eclipsing symbiotic binary FG Ser (AS 296) we have obtained a
series of high resolution optical spectra. Combining the measured radial
velocity variations for the red giant with published eclipse photometry
gives a binary period of 650 days. We derive the radial velocity curve
of the red giant, yielding the orbital parameters of the system and a
mass function of mtief f=0.039 Msun. We further determine the
rotation velocity of the red giant, and assuming corotation derive its
photospheric radius. Together with the spectral type surface temperature
this yields the position of the red giant in the HR-diagram and a
mass estimate of Mtief c=1.7 Msun. Combining this value
with mtief f results in a mass of Mtief h=0.60 Msun for the
hot star. With a binary separation of 1.95 AU and a radius of the red
giant of 105 Rsun we find that FG Ser is a detached binary
with the red giant well inside the Roche lobe. Based on observations
obtained at the European Southern Observatory, La Silla, Chile; the
observations were granted for the ESO programs 47.7-081, 48.7-083,
49.7-041, 50.7-129, 51.7-093, 52.7-068, 53.7-083, 54.E-061, 55.E-446,
56.E-526 }

---------------------------------------------------------
Title: PICARD: Solar Diameter, Irradiance and Climate
Authors: Damé, L.; Cugnet, David; Herse, Michel; Crommelynck,
Dominique; Dewitte, Stevens; Joukoff, Alexandre; Ruedi, Isabelle;
Schmutz, Werner; Wehrli, Christoph; Delmas, Christian; Laclare,
Francis; Rozelot, Jean-Pierre
2000ESASP.463..223D Altcode: 2000sctc.proc..223D
No abstract at ADS

---------------------------------------------------------
Title: Wolf-Rayet nebulae as tracers of stellar ionizing
fluxes. I. M1-67
Authors: Crowther, Paul A.; Pasquali, A.; De Marco, Orsola; Schmutz,
W.; Hillier, D. J.; de Koter, A.
1999A&A...350.1007C Altcode: 1999astro.ph..8200C
We use WR124 (WN8h) and its associated nebula M1-67, to test theoretical
non-LTE models for Wolf-Rayet (WR) stars. Lyman continuum ionizing
flux distributions derived from a stellar analysis of WR124, are
compared with nebular properties via photo-ionization modelling. Our
study demonstrates the significant role that line blanketing plays
in affecting the Lyman ionizing energy distribution of WR stars,
of particular relevance to the study of H ii regions containing
young stellar populations. We confirm previous results that non-line
blanketed WR energy distributions fail to explain the observed nebular
properties of M1-67, such that the predicted ionizing spectrum is
too hard. A line blanketed analysis of WR124 is carried out using
the method of Hillier &amp; Miller (1998), with stellar properties in
accord with previous results, except that the inclusion of clumping in
the stellar wind reduces its wind performance factor to only ~ 2. The
ionizing spectrum of the line blanketed model is much softer than for a
comparable temperature unblanketed case, such that negligible flux is
emitted with energy above the He i lambda 504 edge. Photo-ionization
modelling, incorporating the observed radial density distribution for
M1-67 reveals excellent agreement with the observed nebular electron
temperature, ionization balance and line strengths. An alternative
stellar model of WR124 is calculated, following the technique of de
Koter et al. (1997), augmented to include line blanketing following
Schmutz et al. (1991). Good consistency is reached regarding the
stellar properties of WR124, but agreement with the nebular properties
of M1-67 is somewhat poorer than for the Hillier &amp; Miller code.

---------------------------------------------------------
Title: Circumstellar matter around M-giants in symbiotic binaries:
SY MUSCAE and RW Hydrae
Authors: Dumm, T.; Schmutz, W.; Schild, H.; Nussbaumer, H.
1999A&A...349..169D Altcode:
For the eclipsing symbiotic binary system SY Mus we present evidence
for an asymmetric density distribution around the M-giant. We obtain
this result from an improved orbital solution. We determine a revised
orbital period of P=625.0+/- 0.5 d from UV eclipse observations and
a re-analysis of the visual light curve. Based on new radial velocity
observations, we measure the epoch of mid-eclipse accurately to within
+/- 6 days, or 1/100 of the period. At ingress the eclipse curve
is steeper and closer to mid-eclipse than at egress. From measured
column densities of neutral hydrogen during egress we conclude that
the mass loss rate of the M-giant is of the order of dot {M} ~5*10(-7)
Msun/yr. The eclipse of the UV light in SY Mus and RW Hya
can be partially explained by Rayleigh scattering but there is also an
additional source of opacity. HST high resolution UV observations of RW
Hya during egress reveal that this additional flux attenuation is due
to blanketing by numerous absorption lines, predominantly Fe ii. Line
blanketing is an important effect that has to be taken into account to
explain the eclipse of SY Mus and of other symbiotic binaries. Based
on observations made with IUE, HST and at the European Southern
Observatory at La Silla (Chile). ESO observations were granted for the
proposals 47.7-081, 48.7-083, 49.7-041, 50.7-129, 51.7-093, 52.7-068,
53.7-083, 54.E-061, 55.E-446, 56.E-526 57.D-684, 58.D-248, 59.D-700,
60.D-714. The visual brightness estimates were done by the RASNZ.

---------------------------------------------------------
Title: ORFEUS spectroscopy of the O BT VI lines in symbiotic stars
and the Raman scattering process
Authors: Schmid, H. M.; Krautter, J.; Appenzeller, I.; Barnstedt,
J.; Dumm, T.; Fromm, A.; Gölz, M.; Grewing, M.; Gringel, W.; Haas,
C.; Hopfensitz, W.; Kappelmann, N.; Krämer, G.; Lindenberger, A.;
Mandel, H.; Mürset, U.; Schild, H.; Schmutz, W.; Widmann, H.
1999A&A...348..950S Altcode:
We present orfeus spectra of the O vi lambda lambda 1032,1038 emission
lines in the symbiotic stars AG Dra, V1016 Cyg, RR Tel, CD-43(deg)
14304, AG Peg and Z And. The O vi emission lines can convert into broad
and highly polarized emission lines at lambda 6825 and lambda 7082
in a Raman scattering process by neutral hydrogen. From a comparison
of direct and Raman scattered radiation we extract new information
on the scattering geometry in symbiotic systems. The nebular O vi
emission lines are in all objects redshifted by about +40 km s(-1)
. This can be explained as a radiative line transfer effect in a
slowly expanding emission region. A comparable redshift is measured
in the Raman scattered O vi lines. In AG Peg the O vi emissions show
beside a narrow nebular line a broad component from a fast stellar wind
outflow. Many interstellar absorption lines of molecular hydrogen are
detected, particularly near the O vi lambda 1038 component. With model
calculations we investigate their impact on the O vi lines. From the
dereddened line fluxes of the direct and Raman scattered O vi lines we
derive the scattering efficiency, which is defined as photon flux ratio
N_Raman/N_O VI. The efficiencies derived for RR Tel, V1016 Cyg and Z
And indicate that about 30% of the released O vi lambda 1032 photons
interact with the neutral scattering region. The efficiencies for AG
Dra and CD-43(deg14304) are much higher, which may suggest that the O
vi nebulosity is embedded in a H(0) -region. The D-type system RR Tel
shows strong line profile differences between the direct O vi emission,
which is single-peaked, and the Raman scattered emission, which is
double-peaked. This indicates that the neutral scattering region in
RR Tel “sees” different O vi line profiles, implying that the O vi
nebulosity is far from spherically symmetric. In a tentative model we
suggest for RR Tel an O vi flow pattern where material streams from
the cool giant towards the hot component, which further accelerates
the gas radially. For the S-type systems AG Dra, CD-43(deg14304)
and Z And the line profile differences between the direct and the
Raman scattered O vi emissions are less pronounced. This may suggest
that the O vi profiles depend less on the emission direction than
in the D-type system RR Tel. For AG Peg we detect for the first time
the Raman scattered emission at lambda 6825. The Raman line shows a
narrow, nebular component as the O vi line, but no equivalent emission
to the broad O vi wind component. The higher conversion efficiency
for the narrow component indicates that the nebular O vi emission
is significantly closer to the cool giant than the hot, mass losing
component, and strongly supports previous colliding wind models for
this object. Based on observations taken during the orfeus-spas i and
orfeus-spas ii space shuttle missions, and ground based data collected
at the ESO 2.2m and 3.6m telescopes at La Silla, Chile, and the 4.2m
William Herschel Telescope at La Palma, Canary Islands. ESO observations
were granted for the programs 52.7-040 and 58.D-0866.

---------------------------------------------------------
Title: Revised mass determination of the super massive Wolf-Rayet
star WR 22
Authors: Schweickhardt, J.; Schmutz, W.; Stahl, O.; Szeifert, Th.;
Wolf, B.
1999A&A...347..127S Altcode:
We analyze the orbital motion of the WN 7+abs + O binary WR 22 based
on 88 high resolution optical spectra obtained in 1996. We determine a
period of P=80.336 +/- 0.0013 d and a radial velocity semi-amplitude
K_WR = 70.6 +/- 0.8 km s^{-1} for the Wolf-Rayet star. By averaging
six He i lines it is possible to detect the weak absorptions of the
O companion. The spectral class of the O star is O 9 III (O 8-O 9.5)
but the luminosity class is uncertain and brightness arguments indicate
a luminosity class V. For the orbit of the O companion we derive K_O =
190 +/- 10 km s^{-1}. This leads to a mass ratio q = M_WR/M_O = 2.69
+/- 0.14. We obtain masses of 55.3 +/- 7.3: M_{\odot} and 20.6 +/-
1.7: M_{\odot} for the WR and for the O star, respectively. Our mass
determination revises down considerably the last published value for
the mass of the Wolf-Rayet component but even with the new mass WR
22 remains “the most massive Wolf-Rayet star ever weighed”. Based
on observations collected at the European Southern Observatory at La
Silla, Chile. ESO proposals Nr. 56.D-327 and 57.D-517.

---------------------------------------------------------
Title: On the 4640 Angstrom feature in Wolf-Rayet galaxies
Authors: Schmutz, W.; Vacca, W. D.
1999NewA....4..197S Altcode:
Several Wolf-Rayet galaxies exhibit broad emission features around 4640
Å in their optical spectra. These features are usually identified
as N III and C III/C IV emission lines from WR stars. In a few WR
galaxies the flux in this feature has been measured to be as large or
larger than that in the corresponding He IIλ4686 stellar emission
line. We demonstrate that a 4640/4686 flux ratio larger than unity
cannot be produced by any known population of WR stars. In particular,
we show that the enhanced ratio cannot be explained by the presence of
carbon lines from WC stars. We examine the possible origins of the broad
λ4640 feature and offer several possible explanations for the enhanced
strength in this emission feature. The most plausible explanations
involve the presence of large numbers of Of stars in the starburst
regions and/or the contamination of the stellar lines by nebular
emission features. We discuss the implications that both possibilities
have for the interpretation of the star formation histories in WR
galaxies, as derived from their massive star content. We find that
the instantaneous burst scenario cannot be correct for any metal-rich
region whose optical spectrum exhibits both an enhanced 4640/4686 flux
ratio and C IV 5808 emission from WC stars. These regions must have
experienced a "multiple-burst" star-formation event, composed of several
instantaneous bursts separated by short time intervals (a few Myr).

---------------------------------------------------------
Title: The γ Velorum binary system. I. O star parameters and
light ratio
Authors: De Marco, Orsola; Schmutz, W.
1999A&A...345..163D Altcode:
In this paper we demonstrate how previous determinations of the light
ratio between the O and Wolf-Rayet stellar components of the gamma
Vel system are affected by large uncertainties. This is due, amongst
other things, to the difficulty of measuring the equivalent widths
of emission and absorption lines. We then present a new technique to
de-blend and measure spectral lines, in which we compensate for the
observed absorption features with synthetic profiles. From the new
values of the diagnostic line strengths we determine a hotter spectral
type for the O star companion (O7.5) than previously published. The
light ratio is then determined, together with the stellar parameters,
via a spectroscopic analysis. We obtain Delta M_V=1.47+/-0.13 mag. From
the light ratio and the system's luminosity we find M_V(O) = -5.14
mag and M_V(WR) = -3.67 mag. Simultaneously we determine ifmmode
T_eff else T_efffi(O) = 35 000 K, L(O) = 2.1x10(5) Lsun
and cal M(O) = 30 Msun. An age of 3.59x10(6) yr is derived
from these parameters and evolutionary tracks. We find that the
H/He abundance ratio is solar. From a hydro-dynamical calculation
of the radiation-driven wind we obtain dot{M}(O) = 1.8x10(-7) Msun
yr(-1) and vinfty(O) = 2500 km s(-1) . From the O star
mass derived here and the mass ratio from the literature we derive
the mass of the Wolf-Rayet star, cal M(WR) = 9 Msun. The
mass-luminosity relation for Wolf-Rayet stars then leads to L(WR) =
1.5x10(5) Lsun. We finally present the gamma Vel Wolf-Rayet
spectrum de-convolved from the O star in the range 3800-6700 Angstroms.

---------------------------------------------------------
Title: ISO observations of CH Cyg
Authors: Schild, H.; Dumm, T.; Folini, D.; Nussbaumer, H.; Schmutz, W.
1999ESASP.427..397S Altcode: 1999usis.conf..397S
The symbiotic red giant CH Cyg is a bright IR source and we discuss the
salient spectral features of its SWS and LWS spectrum. We find strong
OH and weak H2O emission between 60 and 130 μm. This is
qualitatively different from W Hya, a single semiregular M8-M9 giant,
where OH emission is absent and the dominant cooling species in the
molecular envelope is water. Apart from the well known photospheric
absorptions of CO, OH and SiO we also suspect traces of HCl. We find
relatively weak PAH features which indicate that apart from the oxygen
rich material from the red giant, there may be carbon rich material
ejected from the companion star. Much of the ISO wavelength range
is dominated by the emission of silicate dust. A good model fit can
be obtained with standard dust properties. We present a procedure by
which radii of symbiotic red giants can be determined if the J and K
magnitudes and the distance is known. The radius of the red giant in
CH Cyg is R=280+/-65 Rodot.

---------------------------------------------------------
Title: Long term spectroscopy of Wolf-Rayet binaries
Authors: Schweickhardt, J.; Schmutz, W.; Kaufer, A.; Stahl, O.;
Wolf, B.
1999IAUS..193...98S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Spectroscopic analyses of the Wolf-Rayet stars in NGC 3603.
Authors: Schmutz, W.; Drissen, L.
1999RMxAC...8...41S Altcode:
The authors report the measurements of the He I λ 10830 Å line
strengths with HST/NICMOS for the three WR stars HD 97950-A1, B,
C in NGC 3603. They combine these new observations with H I/He II
line strengths from published HST/FOS spectra to derive the stellar
parameters of the WR stars. Compared to previous results our analyses
yield similar parameters for HD 97950-A1 and C but a considerably hotter
temperature and higher luminosity for HD 97950-B. The authors confirm
that all three WR stars contain a large amount of hydrogen, possibly
close to a solar H/He ratio, which implies that these WR stars are still
in an early phase of their evolution. It appears that the three WR stars
in NGC 3603 are the most massive stars that were formed in the cluster.

---------------------------------------------------------
Title: Why should we compare Wolf-Rayet codes?
Authors: De Marco, O.; Schmutz, W.; Koesterke, L.; Hamann, W. -R.;
de Koter, A.
1999IAUS..193..231D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Revised stellar parameters of Wolf-Rayet stars
Authors: Schmutz, W.; De Marco, O.
1999IAUS..193..147S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: On WR Stars as Age Indicators in Star Forming Regions
Authors: Schmutz, W.; Vacca, W. D.
1999ASPC..192...73S Altcode: 1999sdsg.conf...73S
No abstract at ADS

---------------------------------------------------------
Title: Analyses of Wolf-Rayet Stars in Local Group Galaxies
Authors: Schmutz, W.; De Marco, O.; Schild, H.; Crowther, P.;
Howarth, I.
1999IAUS..192..277S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: On the perspectives of using XMM to study fundamental
parameters of early-type stars
Authors: Rauw, G.; van der Hucht, K. A.; Mewe, R.; Güdel, M.; Vreux,
J. -M.; Gosset, E.; Schmutz, W.; Stevens, I. R.
1999IAUS..193...90R Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The stellar parameters of the SMC Wolf-Rayet binary HD 5980
Authors: Schweickhardt, J.; Schmutz, W.
1999IAUS..193..101S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Ejected nebulae as probe of Wolf-Rayet Lyman continua
Authors: Pasquali, A.; Crowther, P. A.; Schmutz, W.; Hillier, D. J.
1999IAUS..193..380P Altcode:
No abstract at ADS

---------------------------------------------------------
Title: γ2 Velorum, photon loss and the velocity field
Authors: De Marco, O.; Schmutz, W.; de Koter, A.
1999IAUS..193..229D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: γ2 Velorum revisited
Authors: De Marco, O.; Schmutz, W.; Koesterke, L.; Hamann, W. -R.
1999IAUS..193..227D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: High resolution spectroscopy of symbiotic stars. IV. BX
Monocerotis: orbital and stellar parameters
Authors: Dumm, T.; Muerset, U.; Nussbaumer, H.; Schild, H.; Schmid,
H. M.; Schmutz, W.; Shore, S. N.
1998A&A...336..637D Altcode:
We investigate the orbit and the components of the symbiotic BX Mon
system with new high resolution spectroscopy, IUE spectra, published
photographic magnitudes, and brightness estimates from the RASNZ. We
review the available photometry and deduce a new binary period of
1401 days. We also find evidence in the IUE data that BX Mon is an
eclipsing system. With our high resolution spectroscopy we determine
the radial velocity curve of the M giant from photospheric absorption
features. BX Mon is unusual for a symbiotic star in that its hot
component is also observable in the optical wavelength region. From
corresponding absorption features we are able to measure the hot
component's radial velocity. We determine semi-amplitudes for
the cool and the hot components of 4.3 km s(-1) and 29 km s(-1) ,
respectively. The mass ratio is thus ~ 7 which is among the highest yet
found for symbiotic systems. The orbit of BX Mon is eccentric with an
ellipticity of e=0.49. The binary mass function is 0.0076 M_sun. We
determine the mass of the red giant as M_r=3.7 Msun and
the mass of the hot component as M_h=0.55 M_sun. This low M_h suggests
that even relatively high mass symbiotics are unlikely to be supernova
Type I progenitors. The distance to BX Mon of 3 kpc is determined
with the Na I lambda lambda5890 ,5896 interstellar absorption lines
and the interstellar extinction feature at 2200 Angstroms. For the
luminosity of the cool component we find L_r=3400 Lsun
and a stellar radius R_r=160 Rsun. The red giant's radius
remains within the inner Lagrangian point, even at periastron. The hot
component is unlikely to be a main sequence star. Based on observations
obtained at the European Southern Observatory, La Silla (Chile), visual
brightness data from the RASNZ, and UV spectra from the IUE archive. ESO
observations were granted for the programs 47.7-081, 48.7-083, 49.7-041,
50.7-129, 51.7-093, 52.7-068, 53.7-083, 54.E-061, 55.E-446, 56.E-526

---------------------------------------------------------
Title: HST NICMOS Observations of Circumstellar Matter Around CYG X-3
Authors: Schmutz, W.; Vacca, W. D.; Close, L.; Rayner, J.; Geballe,
T. R.; Schild, H.; Walder, R.
1998ESOC...55..123S Altcode: 1998nvlt.proc..123S
Models of the evolution of massive binaries predict that only a few such
objects should survive the common envelope phase and result in systems
containing a compact object plus a Wolf-Rayet star (c+WR). According
to these models, a vast amount of stellar material is lost during the
common envelope phase prior to the c+WR phase. We are attempting to
test these models by searching for the presence of such circumbinary
material around the only known c+WR object: Cyg X-3. Since the large
reddening towards Cyg X-3 prevents any investigation in the optical,
deep infrared exposures of Cyg X-3 with the NICMOS NIC-2 camera aboard
HST and the Pa$\alpha$ narrow band filter have been used to image the
system at high spatial resolution. The HST images have only recently
been acquired and their analysis is currently underway. Here we report
the possible detection of emission at a distance of about 0".3. This
result is preliminary and needs confirmation by NIC-1 observations
with its better sampling of the stellar profile.

---------------------------------------------------------
Title: Mass-Loss Rate and He/H Abundance of the Erupting Component
in the Small Magellanic Cloud System HD 5980
Authors: Koenigsberger, G.; Peña, M.; Schmutz, W.; Ayala, S.
1998ApJ...499..889K Altcode:
The binary Wolf-Rayet system HD 5980 in the Small Magellanic Cloud
underwent a major luminous blue variable-type eruptive event in
1994. It is the first such recorded event in which the apparent
precursor transits from WNE to WNL spectral types prior to the
eruption. In this paper we analyze the spectrum of the system obtained
when the outburst was declining (1994 December), but the dominant
spectrum was that of the eruptor. From non-LTE analysis we obtain
Ṁ=10-3 M⊙ yr-1, N[He]/N[H]
= 0.43 (by number; Y = 0.63 by mass), v∞ = 600 km
s-1, T* = 35,500 K, and Leruptor = 3
× 106L⊙. A comparison of the He/H abundance
derived here and an estimate obtained from published data of 20
yr ago leads us to conclude that the member of the binary system
that underwent the eruption is the star formerly classified as an
O7 supergiant. The considerable amount of He in this star indicates
that it is in transition to becoming an H-poor W-R. By comparing the
stellar parameters with single-star evolutionary tracks, we derive
that the progenitor was more massive than 120 M⊙, and
that its current mass is close to 80 M⊙.

---------------------------------------------------------
Title: Wind accretion in the symbiotic binary system RW Hya
Authors: Dumm, T.; Folini, D.; Muerset, U.; Nussbaumer, H.; Schild,
H.; Schmutz, W.; Walder, R.
1998AGAb...14...34D Altcode: 1998AGM....14..C18D
RW Hya is a detached eclipsing symbiotic binary system with known
stellar and orbital parameters, consisting of a mass-loosing M2 giant
and a white dwarf. HST spectra indicate the absence of a fast wind
from the white dwarf, consequently we expect the companion to accrete
material from the wind of the M giant. We have done a three-dimensional
wind accretion simulation which we compare with observations. IUE and
HST UV observations show that out of eclipse, for a short period of
\Delta \phi=0.04 there is a reduction of the white dwarf continuum by
Rayleigh and dust scattering. We interpret this effect as the signature
of the accretion shock cone. Accretion models predict a shock cone with
enhanced density. In this cone, we expect the formation of neutral
hydrogen and dust. When the white dwarf is then viewed through this
structure its radiation gets obscured. We numerically solve the 3D
Euler equations with a polytropical index \gamma=1, yielding the
circumstellar velocity and density structure in RW Hya. The momentum
of the M giant wind which is a free parameter in the simulation, is
set by the observed orbital orientation of the shock cone. Based on the
theoretical circumstellar structure, we can calculate nebular emission
line profiles for different viewing angles. We present a time series
of observed optically thin emission lines. In these observations,
we aim at separating the observed line profile into two components,
one originating in the accretion shock cone, the other formed in the
ionized red giant wind. In RW Hya we then get the chance to compare
observations of the wind accretion region with numerical simulations.

---------------------------------------------------------
Title: ORFEUS Spectroscopy of the OVI Lines in Symbiotic Stars and
the Raman Scattering Process
Authors: Schmid, H. M.; Appenzeller, I.; Krautter, J.; Mandel, H.;
Dumm, T.; Mürset, U.; Schild, H.; Schmutz, W.; Barnstedt, J.; Gölz,
M.; Grewing, M.; Gringel, W.; Haas, C.; Hopfensitz, W.; Kappelmann,
N.; Krämer, G.
1998ESASP.413..357S Altcode: 1998uabi.conf..357S
No abstract at ADS

---------------------------------------------------------
Title: Non-LTE Model Atmospheres with Line Blanketing and Photon Loss
Authors: Schmutz, W.
1998ASPC..131..119S Altcode: 1998phls.conf..119S
No abstract at ADS

---------------------------------------------------------
Title: High resolution spectroscopy of symbiotic stars. III. Radial
velocity curve for CD--43(deg) 14304
Authors: Schmid, H. M.; Dumm, T.; Murset, U.; Nussbaumer, H.; Schild,
H.; Schmutz, W.
1998A&A...329..986S Altcode:
We have obtained a series of high resolution optical spectra of the
symbiotic system CD-43(deg14304) . We derive the radial velocity curve
of the cool component and determine an orbital period of about 1448 days
and a mass function of m_f=0.013M_sun for this binary. We present line
profiles of Hα and the Raman scattered line at lambda 6825 for various
orbital phases. The Hα line shows very strong variations in flux and
spectroscopic structure which are locked to the orbital phase. Much less
variability is seen in the Raman scattered line. Based on observations
obtained at the European Southern Observatory, La Silla, Chile

---------------------------------------------------------
Title: X-Ray Spectroscopy with XMM: A New Powerful Tool to Determine
Fundamental Parameters of Early-type Stars
Authors: Mewe, R.; Rauw, G.; van der Hucht, K. A.; Vreux, J. -M.;
Gosset, E.; Guedel, M.; Schmutz, W.; Stevens, I. R.; Kahn, S.
1998sxmm.confE..69M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The orbital motion of gamma^2 Velorum
Authors: Schmutz, W.; Schweickhardt, J.; Stahl, O.; Wolf, B.; Dumm,
T.; Gang, Th.; Jankovics, I.; Kaufer, A.; Lehmann, H.; Mandel, H.;
Peitz, J.; Rivinius, Th.
1997A&A...328..219S Altcode:
We analyze the orbital motion of gamma (2) Velorum based on high
resolution optical spectra obtained in 1995 and 1996. By combining our
data with values from the literature we find a period P=78.53+/- 0.01
d. We determine radial velocity semi-amplitudes K_WR= 122+/- 2 \ifmmode
kms^{-1} \else kms(-1) \fi and K_O= 38.4+/- 2 \ifmmode kms^{-1} \else
kms(-1) \fi for the Wolf-Rayet star and the O star, respectively. The
given errors are the standard deviations of the results from individual
lines. The inclination of the system is i=65(deg) . This result is
obtained by combining M_Osin(3) i from the orbital analysis with the
mass M_O= 29 \ifmmode M_{\odot} \else Msun\fi , obtained from
its luminosity and stellar evolution tracks. The mass of the Wolf-Rayet
component is M_WR=9 \ifmmode M_{\odot} \else Msun\fi . Our O
star velocity curve disagrees by 15 sigma from a previously published
result. We have identified the reason for the disagreement in the
failure to correct for the WR emission that affects the measurements
of the absorption line centers. The correction could have introduced
systematic errors that may be larger than the given precision of the
amplitudes. However, we can set an upper limit of K_O&lt;50 \ifmmode
kms^{-1} \else kms(-1) \fi from uncorrected measurements. This yields
an upper limit for the Wolf-Rayet mass of M_WR&lt;12 \ifmmode M_{\odot}
\else Msun\fi . We find systematic phase-shifts between
the velocity curves of some emission lines. We also observe that some
(but not all) emission lines deviate significantly in the 1995 data set
from the line's orbital solution defined by the 1996 observations. These
phenomena may indicate that the radial velocities of the emission lines
could be subject to systematic distortions and that the errors of the
orbital motion are larger than the internal precision given here.

---------------------------------------------------------
Title: A spectral analysis of HDE 269445 from optical and infrared
observations.
Authors: Pasquali, A.; Schmutz, W.; Nota, A.; Origlia, L.
1997A&A...327..265P Altcode:
We present new, near-IR spectroscopic observations of HDE 269445,
which we combine with published HST and IUE ultraviolet data and optical
high resolution spectra. We discuss the spectral morphology of the star
from UV to near-IR wavelengths, concentrating on profile variations in
the UV and optical H and He lines. From a spectroscopic analysis with
non-LTE model atmospheres, we derive for HDE 269445: T_*_=34000K,
R_*_=43Rsun_, log˙(M)(Msun_/yr)=-4.5 and
He/H=0.4/0.6 by number. These parameters are in good agreement with
those previously derived by Pasquali et al. (1997ApJ...478..340P)
who used only ultraviolet and optical lines. Therefore, our analysis
confirms that a combination of optical and infrared lines can
be fruitfully used to determine stellar and wind properties when
ultraviolet data are not available. Our model calculations only fit
the broad component underneath a strong core emission. We interpret
the discrepancy between the observed and the model line profiles
as the effect of a non-spherical wind which has a hot, fast polar
component and a cold, slow equatorial component. The time-variability
detected in some H and He lines indicates that the wind geometry
may be variable and the star has undergone changes in T_eff_ and
˙(M). These properties are similar to those observed for the galactic
LBV AG Carinae by Leitherer et al. (1994ApJ...428..292L) and we may
suspect that HDE 269445 is also a Luminous Blue Variable. This could
explain why HDE 269445 has defied easy spectral classification, and,
although originally classified as a Ofpe/WN9, it has always represented
a peculiarity for this spectral type.

---------------------------------------------------------
Title: Fundamental Stellar Parameters of γ2 Velorum from
HIPPARCOS Data
Authors: Schaerer, Daniel; Schmutz, Werner; Grenon, Michel
1997ApJ...484L.153S Altcode: 1997astro.ph..3061S
We report parallax measurements by the HIPPARCOS satellite of
γ2 Velorum and a few related objects. The distance
of γ2 Vel is d = 258+41-31 pc,
significantly smaller than the commonly adopted value to Vela OB2. For
ζ Puppis d = 429+120-77 pc is in agreement
with the canonical distance. The total mass of γ2 Vel
derived from its parallax, the angular size of the semimajor axis as
measured with intensity interferometry, and the period are M(W-R + O) =
29.5 +/- 15.9 Msolar. This result favors the orbital solution
of Pike et al. over that of Moffat et al. The stellar parameters for
the O star companion derived from line-blanketed non-LTE atmosphere
models are Teff = 34,000 +/- 1500 K, log L/Lsolar
= 5.3 +/- 0.15, from which an evolutionary mass of M = 29 +/- 4
Msolar and an age of 4.0+0.8-0.5
Myr is obtained from single-star evolutionary models. With non-LTE
model calculations including He and C, we derive a luminosity log
L/Lsolar ~ 4.7 +/- 0.2 for the W-R star. The mass-luminosity
relation of hydrogen-free W-R stars implies a mass of MW-R
~ 5 +/- 1.5 Msolar. From our data we favor an age of
about 10 Myr for the bulk of the Vela OB2 stars. Evolutionary scenarios
for ζ Pup and γ2 Vel are discussed in the light of our
results. Based on data from the ESA HIPPARCOS astrometry satellite.

---------------------------------------------------------
Title: Search for ionized material around Cyg X-3
Authors: Schmutz, Werner
1997hst..prop.7838S Altcode: 1997hst..prop.4164S
Models of the evolution of massive binaries predict that a few such
objects should survive the common envelope phase and result in systems
containing a compact object plus a Wolf-Rayet star {c+WR}. According
to these models, a vast amount of stellar material is lost during
the common envelope phase prior to the c+WR phase. We propose to
test these models by searching for the presence of this circumbinary
material around the only known c+WR object: Cyg X-3. Since the large
reddening towards Cyg X-3 prevents any investigation in the optical,
deep exposures with NIC-2 and the PaAlpha narrow band filter centered on
Cyg X-3 will be used to image the system at high spatial resolution. By
exposing NIC-1 and NIC-3 in parallel, we will simultaneously cover
spatial scales up to 100" . {Although NIC-3 will be out of focus
its PaAlpha images will still be superior to ground-based images.}
We have already attempted to image Cyg X-3 from the ground using
adaptive optics techniques on a 4m telescope. Our exposure yielded
a marginal detection of extended nebular emission. While further
ground based observations will not significantly inprove upon these
images, observations with NICMOS will yield much deeper images. Our
goal is to obtain a clear detection of the nebular PaAlpha emission,
the strength of which can be used to estimate the initial mass of the
WR star; its morphology can be used to constrain models of the mass
loss during the common envelope phase.

---------------------------------------------------------
Title: Photon loss from the helium Lyα line - the key to the
acceleration of Wolf-Rayet winds.
Authors: Schmutz, W.
1997A&A...321..268S Altcode:
It is demonstrated that the ionization equilibrium of helium in non-LTE
atmospheres for Wolf-Rayet stars is very sensitive to photon loss from
the Heii Lyα line. A removal of 0.001% of the photons is sufficient to
initiate an abruptly recombining ionization equilibrium. The assumption
of photon loss allows to address the wind momentum problem of Wolf-Rayet
stars. It is possible for the first time to construct a line blanketed
non-LTE model of a Wolf-Rayet star that reproduces the observed
spectrum and simultaneously, provides the radiation force to drive its
outer velocity structure. A method is developed to determine the free
model parameters L, R_phot_, ˙(M), vinfinity_, v_phot_,
C (clumping factor), and f (photon loss factor), by an analysis of an
observed Wolf-Rayet spectrum. The method is applied to the spectrum of
the WN5 star HD 50896 resulting in good fits in shape and strength to
the observed helium emission lines. In particular the profile of the
Hei λ10830 line, which is a tracer of the outer velocity structure, is
reproduced remarkably well. The hydrodynamically calculated velocity law
differs significantly from the commonly adopted β-law with β=1. The
outer part can be approximated by a β-law with β=3 if the core radius
of the atmosphere model is used, or by β=8, if the velocity law is
calculated referring to the hydrostatic radius of a stellar evolution
model in the Wolf-Rayet phase. Close to the photosphere the velocity
structure is flat with an expansion velocity of v_phot_ =~1100 km/s. The
resulting luminosity L= 5.5x10^5^ Lsun_ and terminal wind
velocity vinfinity_=2060 km/s are found to be considerably
larger than the values from previous determinations. On the other hand,
the mass loss rate is lower ˙(M)=3.2x10^-5^ Msun_yr^-1^
due to an inhomogeneous wind with a clumping factor C=~4. There is
evidence for a decrease of the clumping factor with distance from
the star. The photon loss factor is determined empirically to have a
value of f=~10^-4^. It is proposed that a Bowen resonance-fluorescence
mechanism removes a small fraction of photons from the radiation field
of the helium Lyα resonance line. Photon loss calculated theoretically
from the interaction of metal lines close in wavelength to the Heii Lyα
line yields a depth dependent factor in the range 10^-4^...10^-3^. In
the recombination zone, where the photon loss influences the ionization
structure, its value is f^*^=~10^-4^ in excellent agreement with
the empirically determined value. The lines CaV λ303.74, FeVI
λλ303.70,303.80, 303.83, and OIII λ303.80 are roughly of equal
importance. The wind momentum calculated by the present model exceeds
the single scattering limit by a factor of 6 in contrast to previous
estimates that yielded factors 50-100. With a momentum ratio of 6 the
Wolf-Rayet winds are no longer distinct from other radiation driven
winds but they fit as more extreme versions to the winds of O stars.

---------------------------------------------------------
Title: Irradiated red giant atmospheres in S-type symbiotic stars.
Authors: Schwank, M.; Schmutz, W.; Nussbaumer, H.
1997A&A...319..166S Altcode:
We present non-LTE calculations for an expanding red giant's atmosphere
ionized from the outside by the radiation of a nearby hot radiation
source. We show that the hydrogen emission lines emerge from a narrow
transition zone where hydrogen changes from ionized to neutral. In
this region the Balmer lines are optically thick, and their profiles
crucially depend on the magnitude of optical thickness which in turn,
depends on the velocity gradient within that region. Balmer decrements
of the model calculations depend on the densities in the recombination
zone of the radiatively ionized wind. We find a large variety of complex
line profiles, that in some cases could be mistaken for accretion disk
profiles. The profiles depend on the velocity law in the formation zone
at sub-sonic velocities, but contrary to expectation, the profiles
do not reflect the terminal velocity of the wind. The central part
of our model profiles compare well with the observed profile of the
eclipsing binary SY Mus at maximum light.

---------------------------------------------------------
Title: O Stars in Transition. II. Fundamental Properties and
Evolutionary Status of Ofpe/WN9 Stars from HST Ultraviolet
Observations
Authors: Pasquali, Anna; Langer, Norbert; Schmutz, Werner; Leitherer,
Claus; Nota, Antonella; Hubeny, Ivan; Moffat, Anthony F. J.
1997ApJ...478..340P Altcode:
We present new HST/FOS ultraviolet spectroscopic observations of
seven LMC Ofpe/WN9 stars. We find that Ofpe/WN9 stars have slow winds
with terminal velocities of about 400 km s-1 and high
mass-loss rates of the order of 2-5 × 10-5 M⊙
yr-1. Ofpe/WN9 stellar temperatures and radii are in the
range 30,000-39,000 K, and 19-39 R⊙, respectively. Stellar
luminosities are between log (L/L⊙) = 5.6 and 6.3. We study the Ofpe/WN9 stars winds and examine their evolutionary
status. We find that Ofpe/WN9 stars are intermediate between O and W-R
stars in terms of the wind momentum flux. We also find that the stellar
properties and wind momentum of the Ofpe/WN9 sample place them in the
evolutionary sequence: O --&gt; Of --&gt; H-rich WNL --&gt; Ofpe/WN9,
for initial stellar masses less than ~100 M⊙. In
view of persisting discrepancies of standard massive star models with
observations, we compute massive main-sequence models according to three
different evolutionary scenarios. We find that both higher mass-loss
rate and enhanced mixing between core and envelope are required in order
to yield models compatible with the derived stellar and wind properties
of Ofpe/WN9 stars. The emerging picture may be consistent with earlier
evidence of Ofpe/WN9 stars being quiescent luminous blue variables
(LBVs). This idea is further strengthened by the highly reduced surface
H mass fractions of the Ofpe/WN9 stars. We derive Xs = 0.5
to 0.3, which still excludes Ofpe/WN9 stars from being core He-burning
objects, but is almost identical to the Xs values recently
measured in LBVs. Based on observations with the NASA/ESA Hubble
Space Telescope, obtained at the Space Telescope Science Institute,
which is operated by AURA for NASA under contract NAS5-26555.

---------------------------------------------------------
Title: Summary of the General Discussion
Authors: Schmutz, W.
1997ASPC..120..115S Altcode: 1997lbv..conf..115S
No abstract at ADS

---------------------------------------------------------
Title: Radiation Pressure in LBV Winds
Authors: Schmutz, W.
1997ASPC..120..143S Altcode: 1997lbv..conf..143S
No abstract at ADS

---------------------------------------------------------
Title: HST Observations of RW Hydrae
Authors: Schmutz, W.; Dumm, T.; Folini, D.; Mürset, U.; Nussbaumer,
H.; Schild, H.; Schmid, H. M.; Walder, R.; Shore, S.
1997ppsb.conf..195S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Orbital and Stellar Parameters of BX Mon
Authors: Dumm, T.; Folini, D.; Mürset, U.; Nussbaumer, H.; Schild,
H.; Schmid, H. M.; Schmutz, W.; Walder, R.
1997ppsb.conf..199D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Irradiated Red Giant Atmospheres in S-type Symbiotic Stars
Authors: Schmutz, W.; Nussbaumer, H.
1997ppsb.conf..167S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A Database for Galaxy Evolution Modeling
Authors: Leitherer, Claus; Alloin, Danielle; Fritze-v. Alvensleben,
Uta; Gallagher, John S.; Huchra, John P.; Matteucci, Francesca;
O'Connell, Robert W.; Beckman, John E.; Bertelli, Gianpaolo; Bica,
Eduardo; Boisson, Catherine; Bonatto, Charles; Bothun, Gregory D.;
Bressan, Alessandro; Brodie, Jean P.; Bruzual, Gustavo; Burstein,
David; Buser, Roland; Caldwell, Nelson; Casuso, Emilio; Cerviño,
Miguel; Charlot, Stephane; Chavez, Miguel; Chiosi, Cesare; Christian,
Carol A.; Cuisinier, Francois; Dallier, Richard; de Koter, Alex;
Delisle, Sonya; Diaz, Angeles I.; Dopita, Michael A.; Dorman, Ben;
Fagotto, Franco; Fanelli, Michael N.; Fioc, Michel; Garcia-Vargas,
Maria Luisa; Girardi, Leo; Goldader, Jeffrey D.; Hardy, Eduardo;
Heckman, Timothy M.; Iglesias, Jorge; Jablonka, Pascale; Joly, Monique;
Jones, Lewis; Kurth, Oliver; Lancon, Ariane; Lejeune, Thibault;
Loxen, Johannes; Maeder, Andre; Malagnini, Maria Lucia; Marigo,
Paola; Mas-Hesse, J. Miguel; Meynet, Georges; Moller, Claudia S.;
Molla, Mercedes L.; Morossi, Carlo; Nasi, Emma; Nichols, Joy S.;
Odegaard, Knut J. R.; Parker, Joel Wm.; Pastoriza, Miriani G.;
Peletier, Reynier; Robert, Carmelle; Rocca-Volmerange, Brigitte;
Schaerer, Daniel; Schmidt, Alex; Schmitt, Henrique R.; Schommer,
Robert A.; Schmutz, Werner; Roos, Margarida Serote; Silva, Laura;
Stasińska, Grazyna; Sutherland, Ralph S.; Tantalo, Rosaria; Traat,
Peeter; Vallenari, Antonella; Vazdekis, Alexandre; Walborn, Nolan R.;
Worthey, Guy; Wu, Chi-Chao
1996PASP..108..996L Altcode:
This paper represents a collective effort to provide an extensive
electronic database useful for the interpretation of the spectra and
evolution of galaxies. A broad variety of empirical and theoretical
data are discussed here, and the data are made fully available in
the AAS CD-ROM Series, Vo. 7. Several empirical stellar libraries
are part of this database. They cover the ultraviolet spectral
range observed with IUE, optical data from different ground-based
telescopes, and ground-based infrared data. Spectral type coverage
depends on the wavelength, but it is mostly complete for types O
and M and luminosity classes V to I. A large metallicity range is
covered as well. Theoretical libraries of selected spectral indices of
cool stars and of stellar continuum fluxes in the temperature range
2000 K to 50,000 K, as well as Wolf-Rayet energy distributions are
presented. Several libraries of star clusters and early-type galaxies
have been selected for this database. We discuss an extensive set
of empirical spectra templates covering the wavelength region from
1200 - 9800 A, as well as narrow-band line indices in a large number
of passbands. Bench-mark spectra of nearby galaxies for model tests
are included as well. We compiled numerous evolutionary models and
isochrones for stars of all mass ranges of interest, wide metallicity
range, and for all evolutionary phases, including the pre-main-sequence
phase. The majority of the models have been computed by the Geneva
and Padova groups. Evolutionary synthesis models computed by several
independent groups are made available. They can be applied to old and
young systems, and are optimized with respect to different aspects
of input physics. The model predictions include stellar (colors,
magnitudes, absorption features) and nebular (emission-line fluxes)
properties. Finally, we present models of ionized gas to be used for
the interpretation of active galactic nuclei and young star-forming
galaxies. The community is encouraged to make use of this electronic
database and to perform a critical comparison between the individual
datasets. (SECTION: Galaxies)

---------------------------------------------------------
Title: Extragalactic symbiotic systems. IV. The supersoft X-ray
source SMC 3.
Authors: Jordan, S.; Schmutz, W.; Wolff, B.; Werner, K.; Muerset, U.
1996A&A...312..897J Altcode: 1996astro.ph..4076J
We present a consistent model for the UV and supersoft X-ray emission
from the symbiotic nova SMC3 (=RX J0048.4-7332). Following the
present picture of symbiotic stars, the model consists of radiation
from a hot star and an emission nebula excited by that star. The
observations were compared to theoretical models in which the
hot star's emission is calculated with the help of hydrostatic and
Wolf-Rayet-type non-LTE model atmospheres. Our analysis clearly shows
evidence for mass loss rates of several 10^-6^Msun_/yr. The
minimum effective temperature compatible with both the observed UV
and X-ray flux is about 260000K, which is higher than in any other
star analyzed with sophisticated NLTE model atmospheres. Since the
hydrostatic surface is hidden by the stellar wind no upper limit for
the temperature can be determined. However, we were able to determine
the total luminosity of a symbiotic nova with reasonable accuracy
(L_SMC3_=10^4.05+/-0.05^Lsun_). This value is well below
the Eddington limit (=~50000Lsun_). In order to reproduce
the observed energy distribution a carbon-to-helium ratio &gt;2.10^-4^
-- leading to an absorption edge at 0.39keV -- is necessary.

---------------------------------------------------------
Title: Combined stellar structure and atmosphere models for massive
stars. II. Spectral evolution on the main sequence.
Authors: Schaerer, D.; de Koter, A.; Schmutz, W.; Maeder, A.
1996A&A...312..475S Altcode: 1995astro.ph..8137S
In Schaerer et al. (1995, Paper I) we have presented the first
“combined stellar structure and atmosphere models” (CoStar) for
massive stars, which consistently treat the entire mass loosing star
from the center out to the outer region of the stellar wind. The
models use up-to-date input physics and state-of-the-art techniques
to model both the stellar interior and the spherically expanding
non-LTE atmosphere. The atmosphere models include line blanketing for
all elements from hydrogen to zinc. The present publication covers
the spectral evolution corresponding to the main sequence interior
evolution discussed in Paper I. The CoStar results presented in this
paper comprise: (a) flux distributions, from the EUV to the far IR, and
the ionizing fluxes in the hydrogen and helium continua, (b) absolute
optical and infrared UBVRIJHKLMN photometric magnitudes and UV colors,
(c) detailed line blanketed UV spectra, and (d) non-LTE hydrogen and
helium line spectra in the optical and IR, including theoretical K
band spectra. These results may, e.g., be used for population synthesis
models intended to study the massive star content in young starforming
regions. We compare our results with other predictions from LTE and
non-LTE plane parallel models and point out the improvements and
the importance of using adequate atmosphere models including stellar
winds for massive stars. Particular emphasis is given to comparisons
of the UV spectral evolution with observations, including continuum
indices and several metal line signatures of P-Cygni lines and broad
absorption features. Good agreement is found for most UV features. In
particular, we are able to reproduce the strong observed Fe III 1920A
feature in late O and early B giants and supergiants. This feature is
found to depend sensitively on temperature and may be used to derive
effective temperatures for these stars. We also derive a simple
formula to determine mass loss rates from the equivalent width of
hydrogen recombination lines (Hα, Pα and Bα) for OB stars showing
net emission in one or more of these lines.

---------------------------------------------------------
Title: Understanding the Simplest Symbiotic System(s) II. The 1996
Eclipse of RW Hydrae
Authors: Schmutz, Werner
1996hst..prop.6550S Altcode: 1996hst..prop.2961S
We propose to observe the symbiotic system RW Hya duringeclipse. The
observations will be compared to approved cycle 5HST observations
at quadrature. The comparison will yield astringent test of our
model for S-type symbiotic systems. Theproposed target, RW Hya, is a
typical S-type system andcarefully selected for its characteristics:
eclipsing, lineprofile variations that repeat with orbital phase,
absence ofoutbursts, and UV bright. We postulate three differentemission
regions: wind lines from the hot star, nebularemission from the wind
of the red giant facing the hot star,and most interesting, features
emerging from the wind-windinteraction zone. We predict a different
eclipse behavior foreach of these regions. The GHRS observations are
focused onweak low density intercombination lines that are suspected
tobe formed in a shock zone between the two stars and on broadline
wings and P Cygni features emergent from the stellar windof the hot
object. These features are too weak to beaccessible by IUE. If our
model is confirmed qualitatively bythe proposed test we will apply
in a later HST cycle to covera full orbit. Doppler tomography of
optically thinintercombination lines will allow to map the interaction
zonein the binary system. The results will be used for aquantitative
comparison with sophisticated hydrodynamiccalculations. Observational
constraints are desperately neededto validate our understanding of
the hydrodynamics.

---------------------------------------------------------
Title: Combined stellar structure and atmosphere models for massive
stars. I. Interior evolution and wind properties on the main sequence.
Authors: Schaerer, D.; de Koter, A.; Schmutz, W.; Maeder, A.
1996A&A...310..837S Altcode: 1995astro.ph..8134S
We present the first "combined stellar structure and atmosphere models"
(CoStar) for massive stars, which consistently treat the entire mass
loosing star from the center out to the asymptotic wind velocity. The
models use up-to-date input physics and state-of-the-art techniques to
model both the stellar interior and the spherically expanding non-LTE
atmosphere including line blanketing. Our models thus yield consistent
predictions regarding not only the basic stellar parameters, including
abundances, but also theoretical spectra along evolutionary tracks. On
the same ground they allow us to study the influence of stellar winds
on evolutionary models. In this first paper, we present our method
and investigate the wind properties and the interior evolution on
the main sequence (MS) at solar metallicity. The wind momentum
and energy deposition associated with the MS evolution is given
and the adopted wind properties are discussed. From our atmosphere
calculations, which include the effect of multiple scattering and line
overlap, we also derive theoretical estimates of mass loss driven by
radiation pressure. These values are compared with the predictions
from recent wind models of the Munich group (Pauldrach et al. 1990,
1994, Puls et al. 1995). While we find an overall agreement with
most of their results, our estimates for the mass loss rates are
larger for supergiants. Our rates are in better agreement with the
observed values than those of Puls et al. (1995). A comparison between
boundary conditions given by the conventional plane parallel and the new
spherically expanding atmosphere approach is made. For the MS evolution
the evolutionary tracks and the interior evolution are found to be
basically unchanged by the new treatment of the outer layers. However,
for stars close to the Eddington limit, a small uncertainty in the
behaviour of the deep atmosphere is found which might marginally affect
the evolution. Given the small spherical extension of the continuum
forming layers in the considered evolutionary phases, the predicted
stellar parameters differ negligibly from those obtained using plane
parallel atmospheres.

---------------------------------------------------------
Title: High resolution spectroscopy of symbiotic stars. II. RW Hydrae:
orbit, eclipses, and stellar parameters.
Authors: Schild, H.; Muerset, U.; Schmutz, W.
1996A&A...306..477S Altcode:
With IUE spectra and published optical photometry, we show that the
symbiotic star RW Hya is an eclipsing binary. We use a series of
high resolution optical spectra to determine the orbital elements and
basic parameters of the stellar components in the system. We measure
the orbital velocity amplitude of the red star and determine the
binary mass function of RW Hya. Absorption line fitting yields the
rotation velocity of the cool star, and, assuming co-rotation, its
radius and luminosity which are found to be R_r=60_Rsun_
and L_r=600_Lsun_, respectively. The masses of the red
giant and the hot companion turn out to be M_r=1.6_Msun_
and M_h=0.5_Msun_, respectively. The red giant only fills a
small fraction of its Roche lobe and the presence of an accretion disk
around the hot companion is highly unlikely. We present a series of
Hα line profiles obtained at various orbital phases. Their variation
and the eclipse light curve in the Stroemgren u and v filters indicate,
that the symbiotic nebulosity is a small compact region located close
to the red giant's surface. A broad pedestal Hα emission disappears at
times when the hot companion passes behind the red giant. This may be
an indication that a fast stellar wind streams off the hot star. The
Hα profiles also indicate that at least in RW Hya, the for symbiotic
stars typical double-peak structure is due to self-absorption. The fact
that the symbiotic nebula has only dimensions of the order of ~0.5AU
has important consequences in relation to Zanstra techniques designed
to measure the luminosity and temperature of the hot companion star.

---------------------------------------------------------
Title: Variability of luminous blue variables. II. Parameter study
of the typical LBV variations.
Authors: de Koter, A.; Lamers, H. J. G. L. M.; Schmutz, W.
1996A&A...306..501D Altcode:
We present predicted photometric and spectroscopic variations for
Luminous Blue Variables (LBVs) based on a computed grid of Non-LTE
extended and expanding atmosphere models. The effects of (i) mass
loss, (ii) terminal flow velocity, (iii) rate of acceleration of
the flow, (iv) minimum wind temperature, (v) effective gravity, and
(vi) underlying stellar radius are investigated. We show that the
characteristic variations in visual magnitude for LBVs of {DELTA}V
=~ 1 to 2 mag, which occur at constant luminosity and are therefore
associated with a change in photospheric radius and temperature,
cannot be due to the formation of a `pseudo' photosphere in the wind
induced by a dramatic increase in mass loss rate. This implies that
the origin of the mechanism responsible for the variations is located
below the atmosphere. The change in photospheric radius that can be
achieved by changing the wind parameters (i) to (iv), using observed
mass loss rates, is ~40 %. However, a change of a factor of 4 to 12,
depending on luminosity, is needed to reach the observed minimum
effective temperature of LBVs of T_eff_=~8000 K. We conclude that the
observed increase in photospheric radius is due to the combined effect
of an increase in the underlying stellar radius (vi) and a reduced
effective gravity (v). Our calculations further show that mass loss and
velocity structure variations may in principle cause visual magnitude
changes of {DELTA}V&lt;~0.2mag , however only if the optical depth
of the wind is at the outset of the order of unity. To estimate the
optical depth of the wind, we provide a simple formula. We also show
the sensitivity of the profiles of several H and He i lines to changes
in the photospheric and wind parameters and explain the behaviour of
Hα in simple physical terms.

---------------------------------------------------------
Title: On Stars in Transition. I. Optical Spectroscopy of Ofpe/WN9
and Related Stars
Authors: Nota, Antonella; Pasquali, Anna; Drissen, Laurent; Leitherer,
Claus; Robert, Carmelle; Moffat, Anthony F. J.; Schmutz, Werner
1996ApJS..102..383N Altcode:
Ofpe/WN9 stars have become one of the keys for understanding the physics
of very strong stellar winds and their consequences for the evolution
of massive stars. This paper is the first part of a comprehensive
effort to understand the role of Ofpe/WN9 stars in the uppermost part
of the Hertzsprung-Russell diagram. First, we report the results of
a complete literature search on aspects most relevant to the goal
of our study. This provides a database which will be used for the
interpretation of our observational and theoretical results. Second,
we present a complete dataset of new ground-based data. We present
here high S/N, high spectral resolution echelle observations of seven
Ofpe/WN9 stars and six closely related stars, with the objective to
establish similarities and differences between individual objects
and stellar groups, in an attempt to shed light on the true nature
of Of e/ WN9 stars. Our findings show that the Ofpe/WN9 stars
form a homogeneous group, in terms of spectral distribution and
wind properties, with characteristics somewhere in between the Of
stars on one hand (with the weakest winds) and the B[e] stars on the
other. We also find that, at least for the Of-Ofpe I WN9 stars, this
progression corresponds to an evolutionary sequence. In fact, in two
of the observed Of stars in our sample (HDE 313846 and HD 152408) the
appearance of P Cygni profiles and strengthened emission components in
both H and He I lines seems to suggest they are in a transition phase
between Of and Ofpe/WN9. We also find that five of the Ofpe I WN9
star spectra show the presence of nebular emission lines, indicating
a surrounding nebulosity. We examine all the cases individually and
conclude that only for S119 and BE 381 is there a clear case for an
expanding shell associated with the star. This would strengthen the
connection between Ofpe/WN9 stars and luminous blue variables, which
also are often surrounded by circumstellar nebulae generated during
one or more "violent outbursts" in their recent evolution history.

---------------------------------------------------------
Title: What we really know, what we don't know
Authors: Schmutz, W.
1996LIACo..33..553S Altcode: 1996wrsf.book..553S
No abstract at ADS

---------------------------------------------------------
Title: Spectroscopic Analysis of the Wind Lines of the Symbiotic
Nova AG Peg
Authors: Schmutz, W.
1996swhs.conf..366S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Wind Structure of Red Giants in Symbiotic Systems
Authors: Schmutz, W.
1996iue..prop.5133S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Fundamental Properties of Ofpe/WN9 Stars from Ultraviolet
HST Spectra1
Authors: Pasquali, A.; Schmutz, W.; Leitherer, C.; Nota, A.; Hubeny,
I.; Langer, N.; Drissen, L.; Robert, C.
1996swhs.conf..386P Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Observational Constraints on the Ionization Structure and
Velocity Low in Vel
Authors: Schmutz, W.
1996iue..prop.5137S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Cyg X-3: evidence for a black hole.
Authors: Schmutz, W.; Geballe, T. R.; Schild, H.
1996A&A...311L..25S Altcode:
The authors have observed time-variations in the profiles of several
infrared emission lines from the X-ray binary, Cyg X-3, which is
believed to consist of a Wolf-Rayet star and a compact object. It
is concluded that the variations are due to the orbital motion
of the Wolf-Rayet star and derive a mass function for Cyg X-3 of
2.3 Msun. Assuming reasonable values for the mass of the
Wolf-Rayet star and the inclination of the system, the authors obtain
a range of masses 7-40 Msun for the compact object, with a
most likely value of 17 Msun. This strongly suggests that
the compact component of Cyg X-3 is a black hole.

---------------------------------------------------------
Title: Theoretical Continuum Energy Distribution of Wolf-Rayet Stars
Authors: Schmutz, W.
1996ASPC...98...92S Altcode: 1996fstg.conf...92S
No abstract at ADS

---------------------------------------------------------
Title: Understanding the Simplest Symbiotic System(s)
Authors: Schmutz, Werner
1995hst..prop.6081S Altcode: 1995hst..prop.2554S
We intend to optain pilot observations of the symbiotic system RW
Hya. If the expected features are found we will propose to cover
a full orbital cycle of RW Hya. RW Hya is an eclipsing system that
is characterized by line profile variations that repeat with orbital
phase, in the absence of outbursts, and its brightness in the UV. The
GHRS observations of a few selected lines will focus on weak low
density intercombination lines that are suspected to be formed in a
shock zone between the two stars, on broad line wings, and on P Cygni
features thought to be due to a stellar wind from the hot object. These
features are too weak to be accessible by IUE. Doppler tomography of the
optically thin intercombination lines and eclipse observations of the
wind features will allow to locate the formation region in the binary
system. The results will be used for a quantitative comparison with
sophisticated hydrodynamic calculations. Preliminary results of such
calculations suggest that there are 3 emitting regions: the red giant's
wind ionized by the hot object, a stellar wind from the hot object,
and a wind-wind shock zone located between the stars. Observational
constraints are desperately needed to validate our understanding of
the hydrodynamics.

---------------------------------------------------------
Title: Circumstellar Nebulae around OfPe/WN9 Stars
Authors: Nota, A.; Pasquali, A.; Drissen, L.; Leitherer, C.; Robert,
C.; Schmutz, W.
1995Ap&SS.224..261N Altcode:
New high resolution echelle observations of Ofpe/WN9 stars in the Large
Magellanic Cloud have been obtained in the wavelength region 4000 - 8000
Å. We find that five Ofpe/WN9 stars display in their spectra nebular
emission lines [NII], [SII] and also [OIII], previously unreported
for BE381 and S119. At least in these two cases we can conclude that
the stars are surrounded by an associated nebula, thus strengthening
the relationship between Ofpe/WN9 stars and LBVs.

---------------------------------------------------------
Title: The distance to the Wolf-Rayet star HD 50896.
Authors: Howarth, Ian D.; Schmutz, Werner
1995A&A...294..529H Altcode:
We present high-resolution observations (R=~10^5^) of the interstellar
Na I D lines in the spectra of 23 stars which are close to HD 50896
on the plane of the sky, plus HD 50896 itself. The results are
parameterized by using simple cloud models. We confirm that HD 50896
lies beyond the cluster Cr 121 (which is in the same line of sight),
and estimate D=~1.8kpc.

---------------------------------------------------------
Title: Complete Stellar Models Interior and Spectral Evolution of
Massive Stars
Authors: Schaerer, D.; Schmutz, W.; de Koter, A.
1995IAUS..164..363S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Complete stellar models for massive stars
Authors: Schaerer, D.; de Koter, A.; Schmutz, W.
1995IAUS..163..300S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Combined Stellar Structure and Atmosphere Models: Exploratory
Results for Wolf-Rayet Stars
Authors: Schaerer, D.; de Koter, A.; Schmutz, W.
1995ASPC...78..467S Altcode: 1995aapn.conf..467S; 1994astro.ph.10046S
In this paper we present Complete Stellar models (CoStar) for massive
stars, which treat the stellar interior and atmosphere, including its
wind. Particular emphasis is given to Wolf-Rayet stars. We address
the question of the effective temperatures of WNE and WC stars. Our
first results show a satisfactory agreement between the CoStar models
and the simple temperature correction method applied by Schaller et
al. (1992). An analyses of the subphotospheric structure of the WR star
models shows the importance of metal opacity. This may be essential
for understanding the driving mechanism of Wolf-Rayet winds.

---------------------------------------------------------
Title: Proof of a fast wind in the symbiotic nova AG Pegasi.
Authors: Nussbaumer, H.; Schmutz, W.; Vogel, M.
1995A&A...293L..13N Altcode:
Hubble Space Telescope observations of the symbiotic nova AG Peg reveal
a P Cygni profile in N V λl240. This proves that the hot compact
object in the binary system loses material through a fast wind. High
resolution spectra allow to discern three different emission regions:
the wind from the hot compact star, a nebular emission region of
relatively high density located in the extended atmosphere of the red
giant, and a region of lower density most probably associated with the
location where the fast wind from the hot star collides with the wind
from the red giant.

---------------------------------------------------------
Title: Fundamental parameters of Wolf-Rayet stars. III. The
evolutionary status of WNL stars.
Authors: Crowther, P. A.; Smith, L. J.; Hillier, D. J.; Schmutz, W.
1995A&A...293..427C Altcode:
New high S/N optical observations of 9 Galactic WNL (WN7-8) stars
are presented. The spectra have been analysed using tailored
non-LTE model atmospheres by Crowther et al. (1994c). Here we
use the derived stellar parameters and abundances for a thorough
investigation of the evolutionary status and mass-loss properties
of WNL stars. We have identified two distinct groups of WNL stars
from their observed properties. The WNL+abs and WN7 stars have high
luminosities (log L/Lsun_~5.9) and form a continuity
in morphology and physical parameters from the Of stars. They
appear to be intimately related to these stars, confirming the
suspicion of Walborn (1973) and are descended from extremely
massive progenitors (M_initial_&gt;60Msun_) through the
sequence O-&gt;Of-&gt;WNL+abs-&gt;WN7(-&gt;WNE)-&gt;WC-&gt;SN. In
contrast, the evolutionary sequence for WN8 stars is identified as
O-&gt;LBV or RSG-&gt;WN8-&gt;WNE-&gt;WC-&gt;SN. These stars, with
lower luminosities (log L/Lsun_~5.5), are descended
from less massive stars, and have either red supergiant (RSG,
25Msun_&lt;M_initial_&lt;40Msun_) or Luminous Blue
Variable (LBV, 40Msun_&lt;M_initial_&lt;60Msun_)
progenitors. Indeed, we identify many properties that WN8 stars have in
common with LBVs, e.g. spatial distribution, association with ejecta
nebulae, low binary frequency, large photometric variability. We also
find that those stars with the highest terminal velocities (WN7+abs
stars) have the lowest variability while the WN8 stars and LBVs (low
wind velocities) are the most variable. The smooth progression of
mass loss properties from O supergiants to WNL stars found by Lamers
&amp; Leitherer (1993) is confirmed with the WNL+abs stars lying
intermediately between the WN8 stars and O stars. The spectroscopic
differences between Ofpe and WNL+abs stars appear to be attributable
principally to a difference in wind density. This naturally explains
the often ambiguous Of-WN spectral classification of some Of and WNL
stars (Conti &amp; Bohannan 1989). Finally, interstellar reddenings are
determined using two independent methods based on the model atmosphere
continuum distributions and the observed ubv colours. We find that
the UV reddening towards WR25 (WN7+abs) is highly anomalous (R=4.6),
confiming the findings of Tapia et al. (1988) for stars in Tr 16 in
the Carina nebula.

---------------------------------------------------------
Title: Hydrodynamnic line-blanketed atmospheres of Wolf-Rayet stars
(Invited)
Authors: Schmutz, W.
1995IAUS..163..127S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: High resolution spectroscopy of symbiotic stars I. SY Muscae:
orbital elements, M giant radius, distance
Authors: Schmutz, W.; Schild, H.; Muerset, U.; Schmid, H. M.
1994A&A...288..819S Altcode:
We have obtained a series of high resolution optical spectra of the
eclipsing symbiotic system SY Mus. We measured the radial velocity curve
of the M star component, and determined its rotation velocity. Assuming
co-rotation we obtain for its radius 86Rsun_. We determine
M4.5 for the spectral type, i.e. its temperature is 3500K. The resulting
luminosity is 1000Lsun_. The cool component is thus a giant
star with a luminosity slightly larger than average. Comparison with
evolutionary tracks yield an actual mass of 1.30Msun_. From
the binary mass function we obtain 0.43Msun_ for the hot
companion. The separation of the stellar components is 1.72AU and the
distance from the center of the red giant to the inner Lagrange point
L_1_ is 1.05AU. The red giant extends to less than 40% of the distance
to L_1_ and therefore, the SY Mus binary system is well detached. We
present line profiles of Hα and the Raman scattered line at λ6825
at various orbital phases. The Hα profile is often double-peaked
and shows rapid intensity variations near quadrature. This indicates
that the bulk of the Hα emission is produced in a small high density
region close to the red star's surface facing the hot companion. The
non-variability of the Raman scattered line at λ6825 indicates that the
Raman scattering zone is large compared to the size of the red giant. We
do not observe any change in the absorption spectrum of the red giant
as a function of phase, i.e. there is no observable irradiation effect.

---------------------------------------------------------
Title: Hydrodynamic atmosphere models for hot luminous stars.
Authors: Schaerer, D.; Schmutz, W.
1994A&A...288..231S Altcode:
We present the first line blanketed hydrodynamic models of spherically
expanding atmospheres of hot stars. The models are characterised
by a simultaneous solution of the equation of motion, the non-LTE
populations of hydrogen and helium, and radiation transfer in a line
blanketed atmosphere. The entire domain from the optically thick
photosphere out to the terminal velocity of the wind is treated. The
radiative forces are evaluated consistently with the depth-dependent
radiation field, taking into account multiple scattering by metal
lines and line overlap. This allows us to determine mass loss rates
and the velocity field resp. density structure, as well as to predict
the line blanketed energy distribution, the photospheric absorption
lines, and the emission features emerging from the wind. The major
improvements over unified non-LTE model atmospheres advocated by
the Munich group (Gabler et al. 1989) are twofold: 1) The effects
of line blanketing for the radiation transfer and statistical
equilibrium of hydrogen and helium are included in the atmosphere
calculations. 2) The radiative force (resp. line force parameters k,
α) is evaluated using the depth-dependent radiation field of the
model atmosphere We present a detailed discussion of the influence of
the photosphere-wind transition zone on line profiles and the effects
of line blanketing on a hydrodynamic non-LTE model atmosphere. Two
important results are obtained from our study: (1) We quantify the
influence of line blanketing on the atmospheric structure and on
the predicted spectrum. In particular, we qualitatively confirm the
results obtained with core-halo models and find that the corrections
of Abbott &amp; Hummer (1985) and Bohannan et al. (1986, 1990)
are also quantitatively correct. (2) We show that even "purely"
photospheric lines, on which spectroscopic determinations of basic
stellar parameters rely, are strongly affected by the velocity field
in the transition zone between the photosphere and the wind, and
not only by the mass loss rate. Thus, for the more luminous OB stars
spectroscopic analyses not only depend on three parameters (g, T_eff_,
H/He abundance), but also on the atmospheric structure of the wind
(i.e. ˙(M), v(r)). Therefore, we add new evidence to the previously
stated finding that for precise determinations of stellar parameters
and abundances of hot luminous stars, the use of plane parallel models
may lead to systematic errors. This implies that the recent finding of
discrepancies of spectroscopic masses and helium abundances compared
to predictions of standard evolutionary models could be due to the
inappropriateness of photospheric models for the analysis of luminous
stars. The stellar parameters of our models are those thought to be
representative for the O4 I(n)f star ζ Puppis. A comparison of the
synthetic spectra with the observations shows that our model fits are
not satisfactory. We find good agreement only for the key lines of a
spectroscopic analysis, i.e. Hγ, HeI λ4471, and HeII λ 4542. However,
for all lines that show wind features our predictions are clearly not
correct. Since a spectroscopic analysis is a multi-dimensional problem
it is impossible to single out one stellar parameter that is responsible
for the failure of the model. We tentatively interpret our result as
an indication that the calculated wind structure is not correct. The
reason is not obvious, but it could be simply that the commonly adopted
distance to the star is wrong. In any case, the spectrum of ζ Puppis
should be carefully reanalysed with hydrodynamic model atmospheres.

---------------------------------------------------------
Title: Geometry and Physical Conditions in the Stellar Wind of
AG Carinae
Authors: Leitherer, Claus; Allen, Richard; Altner, Bruce; Damineli,
Augusto; Drissen, Laurent; Idiart, Thais; Lupie, Olivia; Nota,
Antonella; Robert, Carmelle; Schmutz, Werner; Shore, Steven N.
1994ApJ...428..292L Altcode:
AG Carinae is one of the prototypes of the class of Luminous Blue
Variables (LBVs). Since 1990 the star has continuously brightened
in its visual continuum. We report on a multi-instrument and
-wavelength observing campaign to monitor the current activity phase
of AG Car. Ground-based photometry, polarimetry, spectroscopy,
and space-ultraviolet spectroscopy and spectropolarimetry
have been obtained. From the variability of the polarization at
ultraviolet and optical wavelengths we detect significant intrinsic
polarization. Pint greater than or equal to 0.5% is
a large value for a hot, luminous star, suggesting departure from
spherical symmetry in the wind of AG Car. The intrinsic polarization is
variable on a timescale of 2 months or less. The measured ultraviolet
polarization (intrinsic + interstellar) dropped to 0.5% in 1992 May and
returned to 1% in 1992 July. The results are interpreted in terms of a
variable outflow with a density enhancement in the equatorial plane. A
similar model was suggested for the related object R127 in the Large
Magellanic Cloud (LMC). This geometry is reminiscent of the large-scale
morphology of the gas nebula and dust 'jet' surrounding AG Car. It
is therefore likely that physical conditions close to the stellar
surface are responsible for the geometry of the spatially resolved
circumstellar material around AG Car. Despite the drastic change of
the photospheric conditions, the mass-loss rate did not increase. We
find no evidence for a positive correlation between wind density and
stellar radius. This makes models that explain the radius increase by
opacity effects in the outflow unlikely. The mechanism responsible
for the temperature and radius variations is still unknown but most
likely has its origin in subphotospheric regions.

---------------------------------------------------------
Title: High Resolution Echelle Observations of Nebulae around
Ofpe/WN9 stars
Authors: Nota, A.; Leitherer, C.; Pasquali, A.; Drissen, L.; Robert,
C.; Schmutz, W.
1994AAS...184.3113N Altcode: 1994BAAS...26..910N
New high resolution echelle observations are reported of R84, R99,
HDE269927c and BE381 in LMC, which were first classified as Ofpe/WN9
stars by Bohannan and Walborn (1989). Spectra in the wavelength region
4000-8000 Angstroms have been obtained with EMMI on the ESO/NTT, and
display nebular [NII], [OIII] emission lines for the four LMC stars,
previously unreported for HDE269927c and BE381. In the case of R99,
HDE269927c and BE381 the nebular lines Hα, Hβ and [OIII] are spatially
extended, suggesting the presence of a circumstellar nebula few arcsecs
in size. These findings further support the evidence that a link exists
between Ofpe/WN9 stars and the Luminous Blue Variables, as we had
advocated in the case of the Ofpe/WN9 star S119 in the LMC. The nebulae
appear to be asymmetric in the echelle spectra. Further investigation
will be necessary to establish if their morphology is similar to more
well known LBVS such as AG Carinae and R127.

---------------------------------------------------------
Title: GHRS observations and theoretical modeling of early type
stars in R136a
Authors: de Koter, A.; Heap, S.; Hubeny, I.; Lanz, T.; Hutchings,
J.; Lamers, H. J. G. L. M.; Maran, S.; Schmutz, W.
1994AAS...184.3106D Altcode: 1994BAAS...26..909D
We present the first spectroscopic observations of individual stars in
R136a, the most dense part of the starburst cluster 30 Doradus in the
LMC. Spectra of two stars are scheduled to be obtained with the GHRS
on board the HST: R136a5, the brightest of the complex and R136a2,
a Wolf-Rayet star of type WN. The 30 Doradus cluster is the only
starburst region in which individual stars can be studied. Therefore,
quantitative knowledge of the basic stellar parameters will yield
valuable insight into the formation of massive stars in starbursts and
into their subsequent evolution. Detailed modeling of the structure
of the atmosphere and wind of these stars will also lead to a better
understanding of the mechanism(s) that govern their dynamics. We
present the first results of our detailed quantitative spectral
analysis using state-of-the-art non-LTE model atmospheres for stars
with extended and expanding atmospheres. The models are computed using
the Improved-Sobolev Approximation wind code (ISA-WIND) of de Koter,
Schmutz &amp; Lamers (1993, A&amp;A 277, 561), which has been extended
to include C, N and Si. Our model computations are not based on the
core-halo approximation, but use a unified treatment of the photosphere
and wind. This approach is essential for Wolf-Rayet stars. Our synthetic
spectra, dominated by the P Cygni profiles of the UV resonance lines,
also account for the numerous weak metal lines of photospheric origin.

---------------------------------------------------------
Title: Hydrodynamic atmosphere models for hot luminous
stars. II. Method and improvements over unified models.
Authors: Schaerer, D.; Schmutz, W.
1994ems..conf..173S Altcode:
In a paper submitted to A&amp;A the authors present the first line
blanketed hydrodynamic models of spherically expanding atmospheres of
hot stars. This paper is complementary to the submitted paper. Here,
the authors emphasize the advantages and the weak points of their
approach and they present additional technical aspects. The models are
characterised by a simultaneous solution of the equation of motion,
the non-LTE populations of H and He, and radiation transfer in a
line blanketed atmosphere. The entire domain from the optically thick
photosphere out to the terminal velocity of the wind is treated. The
radiative forces are evaluated consistently with the depth-dependent
radiation field, taking into account multiple scattering by metal
lines and line overlap.

---------------------------------------------------------
Title: First combined stellar structure and atmosphere models:
interior and spectral evolution of massive stars
Authors: Schaerer, D.; de Koter, A.; Schmutz, W.; Maeder, A.
1994IAUGA..22..257S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: First complete stellar models: interior and spectral evolution
of massive stars
Authors: Schaerer, D.; Schmutz, W.; de Koter, A.; Maeder, A.
1994IAUGA..22...40S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A fast non-LTE code for expanding atmospheres : a test of
the validity of the Sobolev approximation.
Authors: de Koter, A.; Schmutz, W.; Lamers, J. G. L. M.
1993A&A...277..561D Altcode:
We present a new non-LTE atmosphere code to calculate the continuum
energy distribution and line profiles from stellar atmospheres with
extended outfiowing envelopes. The code is fast, which makes it suited
for empirical modelling. The statistical equilibrium equations and
the radiative transfer in the continuum are solved with an efficient
approximate lambda iteration method. The line transfer is treated
using the Sobolev approximation, including the effects of the diffuse
radiation field, and the continuous opacity inside the line resonance
zone. We investigate the validity of the Sobolev approximation
by comparing our code with one that solves the line transfer using
the co-moving frame method. We find good agreement in the calculated
emission lines for Wolf-Rayet stars, O-type stars and for Luminous
Blue Variables (LBVs). The modelling of photospheric hydrogen lines of
O-stars with our method is less reliable. For the LBVs, we conclude
that the continuum spectrum and the relatively strong wind tines,
computed using the Sobolev method, agree with those computed using the
comoving frame method. The mass-loss rate of the latter stars, derived
by fitting individual emission lines, yields a maximum difference of
30% between the two codes.

---------------------------------------------------------
Title: The LBV AG CAR in its Current Active Phase
Authors: Lupie, O. L.; Leitherer, C.; Neto, A. Damineli; Drissen, L.;
Idiart, T.; Robert, C.; Nota, A.; Altner, B.; Schmutz, W.; Shore, S.
1993AAS...182.6306L Altcode: 1993BAAS...25..908L
With an emphasis on our polarization monitoring program, we present
our observations to date of AG CARINAE, the prototype Luminous Blue
Variable (LBV). The star is experiencing an active phase, increasing in
brightness since 1990. The variability, which is semi-periodic on time
scales 10-15 years, may culminate in an eruptive episode. Although AG
Car is a well-studied LBV, the geometry and physics of its environment
are extremely complex. To obtain a better description of AG Car,
the team has been collecting many observations during the last year:
UBVRI photo-polarimetry and visual spectroscopy (Brazilian National
Observatory), UV spectropolarimetry with the Hubble Space Telescope
Faint Object Spectrograph, UBV photometry (Port Alegre Observatory),
IUE and H-alpha spectroscopy (LaSilla). UV polarization observations
were selected as part of the campaign in order to probe for asymmetric
structures ejected from the star in the innermost unresolved region
(within 100 stellar radii). The ground based photo-polarization
monitoring program enables us to track the polarimetric variability of
the entire complex and to assist in the difficult task of separating
the interstellar and intrinsic polarization components. We have found
that the UV and optical polarization and position angle are strongly
variable in time and structure is evident across the UV resonance
scattering lines. The UV and optical spectroscopy show that the Teff
is decreasing, the bolometric luminosity is remaining constant, and
the structure and ionization state of the wind is evolving. We will
discuss how these data support models which incorporate circumstellar
disks, jets, and/or plumes to explain the mass loss characteristics.

---------------------------------------------------------
Title: The Asymmetric Wind of R127
Authors: Schulte-Ladbeck, R. E.; Leitherer, C.; Clayton, G. C.;
Robert, C.; Meade, M. R.; Drissen, L.; Nota, A.; Schmutz, W.
1993ApJ...407..723S Altcode:
We present optical, linear polarimetry in broad-band UBVRI filters plus
narrow-band filters centered on the emission lines of Hα and the red [N
II] and spectropolarimetry in the wavelength range from 4120 A to 6770 A
of the luminous blue variable R127 in the Large Magellanic Cloud. Both
observations display a decrease of the percentage polarization across
the Hα emission line with respect to the continuum. We assume that Hα
is recombination-line dominated and thus intrinsically unpolarized,
and we use the continuum-subtracted line polarization to estimate
the interstellar foreground polarization. The resulting amount of
intrinsic continuum polarization of R127 is very large, of order
1%-1.5%, implying both the presence of copious free electrons and a
considerable asphericity in their distribution. The two data sets,
taken 2 months apart, display significant variations in the continuum
polarization, which confirms that the stellar-wind properties of
R127 are time-dependent in the maximum state. We discuss several
possible wind geometries and present arguments favoring a clumpy,
axisymmetric outflow.

---------------------------------------------------------
Title: Hydrodynamic atmosphere models for hot luminous stars
II. Method and improvements over unified models
Authors: Schaerer, D.; Schmutz, W.
1993SSRv...66..173S Altcode:
In a paper submitted to A&amp;A we present the first line blanketed
hydrodynamic models of spherically expanding atmospheres of hot
stars. This paper is complementary to the submitted paper. Here, we
emphasize the advantages and the weak points of our approach and we
present additional technical aspects. The models are characterised
by a simultaneous solution of the equation of motion, the non-LTE
populations of H and He, and radiation transfer in a line blanketed
atmosphere. The entire domain from the optically thick photosphere out
to the terminal velocity of the wind is treated. The radiative forces
are evaluated consistently with the depth-dependent radiation field,
taking into account multiple scattering by metal lines and line overlap.

---------------------------------------------------------
Title: Line-blanketed non-LTE atmosphere models for Wolr-Rayet stars
Authors: Schmutz, Werner
1993SSRv...66..253S Altcode:
A standard non-LTE Wolf-Rayet star atmosphere model is compared with an
identical model but including line-blanketing. The structures of the
two models are presented in detail and the implications of blanketed
models for spectroscopic analyses are discussed.

---------------------------------------------------------
Title: Unified NLTE photosphere-wind models with line blanketing
for hot stars: first results for ζ puppis
Authors: Schaerer, D.; Schmutz, W.
1993fces.conf...59S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Direction of Circumstellar Line Blanketing in the Spectra of
the Symbiotic Nova PU Vulpeculae
Authors: Schmutz, Werner; Pereira, Claudio; Mueller, David
1993AnIPS..10..311S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Analysis of the IR Spectrum of Cygnus X-3
Authors: Schmutz, W.
1993AnIPS..10..259S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Theoretical Continuum Energy Distributions for Wolf-Rayet Stars
Authors: Schmutz, Werner; Leitherer, Claus; Gruenwald, Ruth
1992PASP..104.1164S Altcode:
We discuss the problem of assigning an effective temperature to
models of stellar evolution in the Wolf-Rayet stage. We conclude
that it is best to use models with different velocity laws depending
on the stellar temperature. We follow the most simple approach and
propose to use a standard law with Beta = 1 for the cooler and Beta =
2 for the hotter Wolf-Rayet stars. We present energy distributions
from non-LTE model calculations with a Beta = 2 velocity law. The new
calculations together with published results based on Beta = 1 allow
one to synthesize realistic spectra of starburst regions. The flux
tables are available in digital form from the authors. (SECTION: Stars)

---------------------------------------------------------
Title: Near-infrared spectroscopy of galactic Wolf-Rayet stars.
Authors: Howarth, Ian D.; Schmutz, Werner
1992A&A...261..503H Altcode:
We present high-quality near-IR spectra of 24 Galactic WR stars, of
a broad range of subtypes, selected as having known distances. The
data cover the region 0.97-1.12 micron and include the 10830-A He
I triplet. Measurements of He I and He II lines, together with the
absolute magnitudes, yield temperatures, luminosities, mass-loss
rates, and terminal velocities for our sample. We extend that sample
by including results for a further 12 stars of known distance,
taken from the literature. The spectroscopic mass-loss rates are in
excellent agreement with those estimated from radio data, and exceed the
'single-scattering limit' by large factors. Mass-loss rates depend only
weakly on mass, but there is a statistically significant correlation
between surface mass flux and temperature. Terminal velocities
correlate loosely with subtype for both WR sequences. Comparison
with core-helium-burning mass luminosity tracks suggests that the
spectroscopic luminosities may be systematically too faint by about
0.5 dex. We suggest that the WNC stars in our sample may represent an
intermediate phase between WNL and WCE subtypes.

---------------------------------------------------------
Title: The SN 1986G in Centaurus A.
Authors: Cristiani, S.; Cappellaro, E.; Turatto, M.; Bergeron,
J.; Bues, I.; Buson, L.; Danziger, J.; di Serego-Alighieri, S.;
Duerbeck, H. W.; Heydari-Malayeri, M.; Krautter, J.; Schmutz, W.;
Schulte-Ladbeck, R. E.
1992A&A...259...63C Altcode:
We present photometric and spectroscopic observations of SN 1986 G,
spanning up to one year after the explosion. The overall photometric
behavior of this SN Ia results rather normal. The maximum at B =
1245+/-0.05 was reached on May 11,1986, then the decline to the
inflection point was relatively fast (β_B_ = 12.0 mag/100 d), but
similar to other SNe. We show that the fast, early decline rate is
not due, as suspected before, to the combined effect of the strong
differential absorption and peculiar spectral evolution of this
SN. Also, the late time decline rate resembles that of other SN Ia
(γ_V_ = 1.58 mag/100 d). The particular position of the SN in the
two-color diagram may be due to some undetected spectral peculiarity in
the UV-visible gap of the available observations. Although the overall
spectral evolution of SN 1986 G is typical of SN Ia, some peculiarities
are pointed out. The expansion velocities of the envelope at different
phases, deduced from the Si II 6355 A doublet, are among the slowest
ever detected. The strong broad emission at about 4100 A, usually
present in the SN Ia near-maximum spectra, is missing, affecting also
the kinematic evolution of the envelope as derived from the Mg II 4481
A line. High S/N ratio late time spectra are presented, showing several
features identified, by comparison with published synthetic spectra, as
[Fe II], (Fe III] and [Co III] lines. The broad symmetric emission line
at 6560 A, may be alternatively identified with Hα, indicating then the
presence of an outer shell of ionized hydrogen. Different procedures
have been used for determining the reddening suffered by the SN. All
agree on a total color excess E(B - v) = 1.1 mag, somewhat higher than
the previous determinations. Hence, the absorption- corrected absolute
magnitude results are comparable to the average values for SN Ia.

---------------------------------------------------------
Title: Radiation-driven wind theory: Not (yet?) working
Authors: Schmutz, Werner; Schaerer, Daniel
1992LNP...401..409S Altcode: 1992aets.conf..409S
Line-blanketed non-LTE models for spherically expanding atmospheres have
been constructed, including multiple scattering and line overlap and
without an imposed core-halo structure. They have been used to evaluate
the radiation force in the winds of two Of stars, ζ Pup and R84. We
find for both stars that radiation forces are not sufficient to drive
the observed mass-loss rates. For S Pup the disagreement is less than a
factor of two, and could in principle be explained by uncertainties in
the interpretation of the observations. However, for R84 the difference
is unequivocally due to a failure of the radiation-driven wind theory
in its present form. Having found a case where the theory does not
work we are inclined to interpret the problems for C Pup as real,
and therefore we suggest that the present theory of radiation-driven
winds is not sufficient for a complete understanding of the observed
winds of hot stars.

---------------------------------------------------------
Title: Radiation-driven wind theory: The influence of turbulence
Authors: Schaerer, Daniel; Schmutz, Werner
1992LNP...401..414S Altcode: 1992aets.conf..414S
Line-blanketed non-LTE models for spherically expanding atmospheres
without core-halo approximation, including multiple scattering and line
overlap, are used to evaluate the radiation pressure in stellar winds
of Of and Ofpe/WN9 stars. The enhancement of the radiative forces due
to microturbulence (line-broadening is discussed.

---------------------------------------------------------
Title: Calculations of non-LTE radiative transfer in extended
outflowing atmospheres using the Sobolev approximation for line
transfer
Authors: de Koter, A.; Schmutz, W.; Lamers, H. J. G. L. M.
1992LNP...401..440D Altcode: 1992aets.conf..440D
The code that we are developing for the empirical modelling of LBVs
using the Sobolev approximation ] for the line transfer, yields
accurate results that compare well with those obtained using the
co-moving frame method. By including absorption by the continuum in
the resonance region in addition to escape from the resonance region
we get a much more accurate result for the hydrogen ground level
population. The following properties make the code extremely fast:
• the Sobolev approximation for the line transfer

---------------------------------------------------------
Title: AG Carinae and the LBV Phenomenon (Invited Paper)
Authors: Leitherer, C.; Damineli Neto, A.; Schmutz, W.
1992ASPC...22..366L Altcode: 1992nvos.work..366L
No abstract at ADS

---------------------------------------------------------
Title: Near-Infrared Spectroscopy of Galactic Wolf-Rayet Stars
Authors: Howarth, Ian D.; Schmutz, Werner
1992LNP...401..104H Altcode: 1992aets.conf..104H
We present high-quality near-IR spectra of 24 Galactic WR stars, of
a broad range of subtypes, selected as having known distances. The
data cover the region 0.97μm-1.12μm and include the λ10830-Å
He I triplet. Measurements of He I and He II lines, together with
the absolute magnitudes, yield temperatures, luminosities, mass-loss
rates, and terminal velocities for our sample. We extend that sample
by including results for a further 12 stars of known distance,
taken from the literature. The spectroscopic mass-loss rates are in
excellent agreement with those estimated from radio data, and exceed
the `single-scattering limit' by large factors. Mass-loss rates depend
only weakly on mass, but there is a tight correlation between surface
mass flux and temperature. Terminal velocities correlate loosely with
subtype for both WR sequences. Principally because of revisions to
the adopted absolute magnitudes, our luminosities average slightly
fainter than found previously; that exacerbates discrepancies with
the predictions of evolutionary models, but reconciles results for
Galactic and LMC stars. However, comparison with core-helium-burning
mass-luminosity tracks suggests that the spectroscopic luminosities
may be systematically too faint by ∼0.5 dex. We suggest that the
WNC stars in our sample may represent an intermediate phase between
WNL and WCE subtypes. A full version of this paper is being submitted
to Astronomy &amp; Astrophysics.

---------------------------------------------------------
Title: Models for starburst regions: how warm are warmers?
Authors: Leitherer, C.; Gruenwald, R.; Schmutz, W.
1992pngn.conf..257L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Spectral analyses of Wolf-Rayet stars : hydrogen abundances
in WN subtypes.
Authors: Hamann, W. -R.; Duennebeil, G.; Koesterke, L.; Wessolowski,
U.; Schmutz, W.
1991A&A...249..443H Altcode:
The spectra of four WN stars are analyzed quantitatively, focusing on
the hydrogen abundances. The analyses are based on multilevel non-LTE
models for expanding atmospheres composed of helium and hydrogen. The
resulting hydrogen fraction is found to range from 10 to 40 percent by
mass, which confirms that WN atmospheres exhibit material which has
undergone nuclear burning. When the hydrogen detection is correlated
with the stellar temperature a clear separation between two groups can
be obtained, i.e., the cool stars with stellar temperature approximately
equals 35 kK exhibit hydrogen, whereas the hot stars with stellar
greater than 50 kK do not.

---------------------------------------------------------
Title: Spectral analyses of 19 Wolf-Rayet (WN) stars in the LMC.
Authors: Koesterke, L.; Hamann, W. R.; Schmutz, W.; Wessolowski, U.
1991A&A...248..166K Altcode:
The helium spectra of 19 Wolf-Rayet stars in the Large Magellanic
Cloud are analyzed, and their luminosities, radii, temperatures and
mass-loss rates are determined. The sample covers different subtypes
of the nitrogen (WN) sequence. The analyses are based on multi-level
non-LTE model calculations for the spectrum formation in spherically
expanding stellar atmospheres, composed of pure helium. The results
are compared with a Galactic sample analyzed previously with the
same methods. The stellar temperatures obtained for the LMC stars
are similar to those of Galactic stars. The "late" subtypes (WNL)
form a homogeneous group with T about 30 kK, while the temperatures of
WNE-s stars ("early" subtypes with strong lines) range from 50 kK to 90
kK. The LMC stars tend to lower luminosities (10^4.8^ to 10^5.6^ L_sun_)
than our Galactic sample, which might be a real trend irrespective
of selection effects. Terminal wind velocities and mass-loss rates
do not show systematic differences between LMC and Galaxy when stars
of same subtypes are compared. Such differences, however, would be
expected as an effect of the different metallicities if the winds were
driven by radiation pressure. The mechanical momentum in the winds
exceeds the single- scattering limit by a large factor (up to 50). The
evolutionary status of the WR stars is discussed by comparing their
positions in the HR diagram with the theoretically predicted tracks
for post-red-supergiant evolution. Although recent calculations now
show some general agreement, the predicted luminosities are still
higher than observed, especially for the LMC stars.

---------------------------------------------------------
Title: Determinations of the interstellar reddening toward Wolf-Rayet
stars of the nitrogen sequence from observed UBV color indices.
Authors: Schmutz, W.; Vacca, W. D.
1991A&AS...89..259S Altcode:
We demonstrate that continuum discontinuities, or "jumps", are present
in the spectra of some Wolf-Rayet stars and that current models of
Wolf-Rayet stars predict such jumps and provide good fits to the
observed continua. Using a relation between the size of the He II
(n = 4) jump at 3645 A and the intrinsic (b - v)_0_ color found from
the model atmospheres of Wolf-Rayet stars of the nitrogen sequence,
we derive a formula for calculating the color excesses, E_b-v_, of
WN stars. The method assumes that helium is the major opacity source
in the Wolf-Rayet atmosphere; therefore it cannot be applied to WC
stars. The method requires measurements of only the u - b and b - v
color indices; it is independent of any assumed values of the intrinsic
colors. We investigate the differences in the various photometric and
calibration systems used in the past to determine magnitudes and colors
of Wolf-Rayet stars and give correction factors which we use to put all
previous values onto one consistent system. Using the corrected values
of the u - b and b - v colors, we then calculate color excesses for WN
stars in the Galaxy and the Large and Small Magellanic Clouds from our
formula. We compare our results with previous determinations of color
excesses for WN stars and find generally good agreement for Galactic
stars. However, there are many LMC stars for which the photometric
data are not accurate enough to yield reliable reddening values.

---------------------------------------------------------
Title: Non--LTE Analysis of the Ofpe/WN9 Star HDE 269227 (R84)
Authors: Schmutz, Werner; Leitherer, Claus; Hubeny, Ivan; Vogel,
Manfred; Hamann, Wolf-Rainer; Wessolowski, Ulf
1991ApJ...372..664S Altcode:
The paper presents the results of a spectral analysis of the Ofpe/WN9
star HD 269227 (R84), which assumes a spherically expanding atmosphere
to find solutions for equations of radiative transfer. The spectra of
hydrogen and helium were predicted with a non-LTE model. Six stellar
parameters were determined for R84. The shape of the velocity law is
empirically found, since it can be probed from the terminal velocity
of the wind. The six stellar parameters are further employed in a
hydrodynamic model where stellar wind is assumed to be directed by
radiation pressure, duplicating the mass-loss rate and the terminal
wind velocity. The velocity laws found by computation and analysis
are found to agree, supporting the theory of radiation-driven stellar
wind. R84 is surmised to be a post-red supergiant which lost half of
its initial mass, possibly during the red-supergiant phase. This mass
loss is also suggested by its spectroscopic similarity to S Doradus.

---------------------------------------------------------
Title: Wolf-Rayet Stars as Starting Points or as Endpoints of the
Evolution of Massive Stars?
Authors: Lamers, H. J. G. L. M.; Maeder, A.; Schmutz, W.; Cassinelli,
J. P.
1991ApJ...368..538L Altcode:
The paper investigates the evidence for the two interpretations
of Wolf-Rayet stars suggested in the literature: (1) massive
premain-sequence stars with disks and (2) massive stars which have
lost most of their H-rich layers in a stellar wind is investigated. The
abundance determinations which are done in two different ways and which
lead to different conclusions are discussed. The composition is solar,
which would suggest interpretation (1), or the CNO abundances are
strongly anomalous, which would suggest interpretation (2). Results
from evolutionary calculations, stellar statistics, the existence of
Ofpe/WN9 transition stars and W-R stars with evolved companions show
overwhelming evidence that W-R stars are not premain-sequence stars
but that they are in a late stage of evolution. Moreover, the fact
that W-R stars are usually in clear regions of space, whereas massive
premain-sequence stars are embedded in ultracompact H II regions also
shows that W-R stars are not young premain-sequence stars.

---------------------------------------------------------
Title: The Hydrogen Abundances in WN Stars
Authors: Hamann, W. -R.; Duennebeil, G.; Wessolowski, U.; Schmutz, W.
1991IAUS..143..100H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Distance to HD 50896 (ez Cma)
Authors: Schmutz, W.; Howarth, I. D.
1991IAUS..143..639S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Nitrogen Spectra of WN Stars: the WN6 'standard' Star
HD192163 (WR136)
Authors: Wessolowski, U.; Hamann, W. -R.; Schmutz, W.
1991IAUS..143..106W Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Observations Versus Atmospheric Models of WR Stars (review)
Authors: Schmutz, W.
1991IAUS..143...39S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Non-Lte Analysis of Hot Stars Including Line Blanketing
Authors: Schmutz, W.
1991ASIC..341..191S Altcode: 1991sabc.conf..191S
No abstract at ADS

---------------------------------------------------------
Title: Determination of the Interstellar Extinction Toward WN Stars
from Observed UBV Color Indices
Authors: Vacca, W. D.; Schmutz, W.
1991IAUS..143..640V Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Short-term activity in the gamma2 Velorum system : the O-type
supergiant is a nonradially pulsating star.
Authors: Baade, D.; Schmutz, W.; van Kerkwijk, M.
1990A&A...240..105B Altcode:
The discovery of photospheric line-profile variability and associated
circumstellar effects of the O star in the Gamma(2) Velorum system
is reported. The subcomponents drift across the line profiles at
different rates. Two pattern speeds hve been tentatively measured to
be 125 and 750 km/s/day. The temporal periods are 1.94 and 0.35 day,
respectively, while the two spatial periods seem to be identical to
one another and are about one-sixth of the stellar circumference. A
rotation period in the range of 3-6 days is inferred. Two variable
emission-line components straddle the He I 667.8-nm absorption and
probably show that the O star has an extended envelope.

---------------------------------------------------------
Title: Non--LTE Model Calculations for SN 1987A and the Extragalactic
Distance Scale
Authors: Schmutz, W.; Abbott, D. C.; Russell, R. S.; Hamann, W. -R.;
Wessolowski, U.
1990ApJ...355..255S Altcode:
We present model atmospheres for the first week of SN 1987A, based
on the luminosity and density/velocity structure from hydrodynamic
models of Woosley. The models account for line blanketing, expansion,
sphericity, and departures from LTE in hydrogen and helium and
differ from previously published efforts because our models
represent ab initio calculations, i.e., they contain essentially
no free parameters. The formation of the UV spectrum is dominated
by the effects of line blanketing. In the absorption troughs, the
Balmer line profiles were fit well by our models, but the observed
emissions are significantly stronger than predicted, perhaps due to
clumping. The generally good agreement between our synthetic spectra
and observations provides independent support for the overall accuracy
of the hydrodynamic models of Woosley. We address the question of the
accuracy of the Baade-Wesselink method in a detailed discussion of its
approximations. While the application of the standard method produces
a distance within an uncertainty of 20% in the case of SN 1987A,
systematic errors up to a factor of 2 are possible, particularly if
the precursor was a red supergiant. The key parameter that determines
the systematic error of the method is the density/velocity structure,
which can vary for each individual supernova. The supernova- based
extragalactic distance scale is not yet precise enough to be of
practical interest, owing to the large possible systematic error in
the Hubble constant, H_0_ ~ 60^times 2^_divided by 2_ km s^-1^ Mpc^-1^.

---------------------------------------------------------
Title: Bolometric corrections for Wolf-Rayet stars: the influence
of wind-line-blanketing.
Authors: Schmutz, Werner
1990ASPC....7..117S Altcode: 1990phls.work..117S
Bolometric corrections are given resulting from pure helium model
atmospheres for Wolf-Rayet stars. The accuracy of these values is
discussed with regard to the major deficiencies of the models: the
neglect of metal bound-free continua and line-blanketing. If metals
are included, the model has to have a larger effective temperature
than its pure helium counterpart. A new approach to solve the
wind-line-blanketing problem is presented. The first results from this
method indicate that line-blanketing makes the star appear hotter with
respect to a given value of effective temperature. Thus the predicted
systematic errors of the bolometric corrections from the influence of
metal bound-free continua and from line-blanketing are of opposite
sense. The net systematic errors of pure helium models are not yet
known. Estimates of the maximum effects indicate that the current
values of the bolometric corrections are unlikely to be in error by
more than 1 mag.

---------------------------------------------------------
Title: The nitrogen spectra of WN stars.
Authors: Wessolowski, U.; Hamann, W. -R.; Schmutz, W.
1990AGAb....5...10W Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Analyses of 19 Wolf-Rayet stars (WN) in the Large Magellanic
Cloud.
Authors: Koesterke, L.; Hamann, W. -R.; Wessolowski, U.; Schmutz, W.
1990AGAb....5...11K Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Analyses of Wolf-Rayet Stars.
Authors: Hamann, W. -R.; Wessolowski, U.; Schmutz, W.; Schwarz, E.;
Duennebeil, G.; Koesterke, L.; Baum, E.; Leuenhagen, U.
1990RvMA....3..174H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: HD193077 - a Fast Rotating Wolf-Rayet Star
Authors: Schmutz, W.
1990ASIC..316..227S Altcode: 1990amml.conf..227S
No abstract at ADS

---------------------------------------------------------
Title: High-density winds: Wolf-Rayet stars - a progress report
about quantitative spectral analyses.
Authors: Hamann, Wolf-Rainer; Wessolowski, Ulf; Schwarz, Eberhart;
Duennebeil, Gerhard; Schmutz, Werner
1990ASPC....7..259H Altcode: 1990phls.work..259H
Based on recent progress in non-LTE model calculations for expanding
atmospheres, the authors quantitatively analyze the spectra of
Wolf-Rayet stars. The obtained stellar temperatures and luminosities are
surprisingly low. The authors show that the light curve of the eclipsing
binary V444 Cygni can be reproduced by a model with a "cool" WR star
(T* = 40 kK). This solution is not unique, but demonstrates
that there is no basic contradiction between the results from the
present spectral analysis and the light curve. Hydrogen abundances in
WN stars are determined from a careful line fit of the H/He blends. The
authors find a clear dichotomy between the "cool" (≍35 kK) stars with
detectable hydrogen, and the "hot" WN stars which are hydrogen-poor.

---------------------------------------------------------
Title: The Evidence that Wolf-Rayet Stars are in a Late Stage of
Evolution
Authors: Lamers, H. J. G. L. M.; Maeder, A.; Schmutz, W.; Cassinelli,
J. P.
1990ASIC..316..349L Altcode: 1990amml.conf..349L
No abstract at ADS

---------------------------------------------------------
Title: Atmospheric Models for Luminous Blue Variables
Authors: Leitherer, Claus; Schmutz, Werner; Abbott, David C.; Hamann,
Wolf-Rainer; Wessolowski, Ulf
1989ApJ...346..919L Altcode:
The photospheres and stellar winds of luminous blue variables are
studied theoretically. Non-LTE calculations of radiation transfer
in spherically extended, expanding atmospheres are combined with a
hydrodynamics code for radiation-driven winds. Models are calculated
which are typical for luminous blue variables in minimum and maximum
states. The recombination of iron group elements from double to singly
ionized stages, which occurs when the effective temperature falls below
10,000 K, can explain why the mass-loss rates increase when luminous
blue variables approach their maximum states; the singly charged ions
provide a much larger number of strong lines which can intercept the
radiation pressure. However, the mass-loss increase by itself cannot
account for the drop of the effective temperature in a self-consistent
way. The corresponding increase of the wind opacity causes only a
comparativley small change in the radius of continuum formation. It
is concluded that the observed variability of the photospheric radius
must be induced from deeper, subphotospheric regions.

---------------------------------------------------------
Title: Spectral analysis of 30 Wolf-Rayet stars.
Authors: Schmutz, W.; Hamann, W. -R.; Wessolowski, U.
1989A&A...210..236S Altcode:
The helium spectra of 30 Galactic WR stars are analyzed, and
the luminosities, radii, temperatures, and mass-loss rates are
determined. The analyses are based on model calculations which account
for non-LTE radiation transfer in spherically expanding atmospheres. A
three-dimensional grid of models is established for a wide range
of stellar radii, temperatures, and mass-loss rates. The variety of
resulting spectra is actually two-dimensional, as different combinations
of stellar radius and mass-loss rates may yield very similar helium
spectra at a given stellar temperature. Thus, the WR spectra can
be described by a two-dimensional classification scheme. Individual
mass-loss rates between 10 exp -3.9 and 10 exp -5.3 are found. The
luminosities of WNE subtypes scatter between 10 exp 5 and 10 exp 5.5
solar luminosities while those for the late subtypes are higher. The
WC stars are less luminous.

---------------------------------------------------------
Title: Spectral analysis of WN stars in the LMC.
Authors: Schmutz, W.; Conti, P. S.
1989ASSL..157..306S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: NLTE Analysis of R 84
Authors: Schmutz, W.; Leitherer, C.; Torres-Dodgen, A. V.; Vogel,
M.; Conti, P. S.; Hamann, W. -R.; Wessolowski, U.
1989ASSL..157..289S Altcode: 1989IAUCo.113..289S; 1989plbv.coll..289S
No abstract at ADS

---------------------------------------------------------
Title: Changes in the Atmospheric Structure of Lbv's during Eruptions
Authors: Leitherer, Claus; Abbott, David C.; Schmutz, Werner
1989ASSL..157..109L Altcode: 1989IAUCo.113..109L; 1989plbv.coll..109L
Self-consistent radiation-hydrodynamic calculations are presented which
model observations of Hubble-Sandage variables or S Doradus stars going
from their minimum to maximum states. Atmospheric models are employed
which use a spherically extended, dynamical NLTE atmosphere with 27
levels of H and He. The ionization state of the atmosphere and the
variation of the photospheric radius are studied.

---------------------------------------------------------
Title: Atmospheric Models for Lbv's at Minimum and Maximum States
Authors: Leitherer, C.; Schmutz, W.; Abbott, D. C.; Torres-Dodgen,
A. V.; Hamann, W. -R.; Wessolwski, U.
1989ASSL..157..285L Altcode: 1989IAUCo.113..285L; 1989plbv.coll..285L
No abstract at ADS

---------------------------------------------------------
Title: NLTE calculations of hydrogen line profiles for SN1987A
Authors: Schmutz, W.
1989HiA.....8..215S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: NLTE Analysis of the Luminous Blue Variable R71
Authors: Leitherer, C.; Schmutz, W.; Hubeny, I.
1988BAAS...20.1012L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Synthetic helium spectra for Wolf-Rayet stars - A grid
of models
Authors: Wessolowski, U.; Schmutz, W.; Hamann, W. -R.
1988A&A...194..160W Altcode:
Theoretical profiles of the He I lines for Wolf-Rayet stars are
presented, covering a large domain of stellar temperatures and
radii. The present results are thus augmenting the authors' grid of
synthetic He II spectra published previously. Line profiles, equivalent
widths and peak intensities are given for the most prominent He I
lines at 10830 Å and 5876 Å. As expected, the lines of neutral helium
depend sensitively on the stellar temperature. Hence they will provide
the key information for the quantitative interpretation of WR spectra.

---------------------------------------------------------
Title: Spectral analysis of the Wolf-Rayet star HD 50896.
Authors: Hamann, W. -R.; Schmutz, W.; Wessolowski, U.
1988A&A...194..190H Altcode:
The helium spectrum of the Wolf-Rayet star HD 50896 is analyzed by means
of detailed non-LTE radiation transfer calculations for spherically
expanding atmospheres. Satisfactory agreement between theory and
observation is achieved. A systematic fit procedure yields the
stellar parameters as a function of the mass-loss rate adopted. Fits
are performed for the three different values log(M/(M_sun;/yr)) =
-0.4, -4.4 or -4.7. The resulting luminosities are log(L/L_sun;) =
5.3, 4.9 or 4.4, respectively, while the radius of the "stellar core"
becomes 4.7, 2.6 or 1.5 R_sun;. Considerations concerning the distance
of HD 50896 give some preference to the first of the three quoted sets
of parameters.

---------------------------------------------------------
Title: Quantitative Spectroscopy of Wolf-Rayet Stars
Authors: Schmutz, W.
1988LNP...305..133S Altcode: 1988adse.conf..133S; 1988IAUCo.108..133S
No abstract at ADS

---------------------------------------------------------
Title: NLTE Analysis of the Wolf-Rayet Star HD193077 = WN5+ABS
Authors: Schmutz, W.; Hamann, W. -R.; Wessolowski, U.
1988LNP...305..143S Altcode: 1988adse.conf..143S; 1988IAUCo.108..143S
A model atmosphere code that accounts for the special physical
conditions in Wolf-Rayet atmospheres is used to analyse the spectrum
of the Wolf-Rayet star HD 193077 (WN5+abs). The stellar parameters are
determined such that the profiles of the helium lines He I λλ4471,
5876, He II λ5412, and the absolute visual magnitude are reproduced.

---------------------------------------------------------
Title: Spectral Analysis of the Wolf-Rayet Star HD50896
Authors: Hamann, W. -R.; Schmutz, W.; Wessolowski, U.
1988LNP...305..145H Altcode: 1988adse.conf..145H; 1988IAUCo.108..145H
The helium spectrum of the WN5 star HD 50896 (EZ Canis Majoris, WR6)
is studied. The aim is to establish a technique which allows the
determination of the parameters of a Wolf-Rayet star from a systematic
analysis of its spectral lines.

---------------------------------------------------------
Title: Analysis of 30 Wolf-Rayet Stars
Authors: Schmutz, W.; Hamann, W. -R.; Wessolowski, U.
1988LNP...305..141S Altcode: 1988IAUCo.108..141S; 1988adse.conf..141S
Temperatures, mass-loss rates and luminosities of 30 galactic Wolf-Rayet
stars (24 WN, 6 WC) are derived by fitting the observed equivalent
widths of He I λ5876 and He II λ5412 and the absolute visual
magnitude. A three-dimensional grid (T*-R*-M)
of model calculations provides the theoretical values.

---------------------------------------------------------
Title: Computed He II spectra for Wolf-Rayet stars - A grid of models
Authors: Hamann, W. -R.; Schmutz, W.
1987A&A...174..173H Altcode:
A grid of synthetic He II spectra for Wolf-Rayet stars is presented,
covering a large range in radius and temperature. The non-LTE radiation
transfer in spherically expanding atmospheres is treated in the comoving
frame, and the solution is obtained by "iteration with approximate
lambda operators". Results are given for the continuum flux distribution
and for the profiles of the most prominent lines (He II 1640 Å and
4686 Å). The lines show the strongest emission at stellar temperatures
of about 35kK, but also depend sensitively on the stellar radius.

---------------------------------------------------------
Title: NLTE Analysis of the Wolf-Rayet Star HD 193077 (WN5 + abs)
Authors: Schmutz, W.; Hamann, W. -R.; Wessolowski, U.
1987MitAG..70..336S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Analysis of 30 Wolf-Rayet Stars
Authors: Schmutz, W.; Hamann, W. -R.; Wessolowski, U.
1987MitAG..70..338S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Upper Limits for the Effective Temperature of Wolf-Rayet
Stars from the Presence of Hei
Authors: Schmutz, W.; Hamann, W. R.; Wessolowski, U.
1987IAUS..122..461S Altcode:
A recently developed non-LTE code for realistic semi-empirical models of
Wolf-Rayet atmospheres is used to calculate synthetic helium lines. From
the resulting line strengths it can be concluded that if He I lines
are present, the effective temperatures of these stars have to be
less than an upper limit. This limit depends on the stellar radius
and is approximately 40kK for R* = 20 R_sun; to 60kK for
R* = 5 R_sun;.

---------------------------------------------------------
Title: NLTE Analysis of the Wolf-Rayet Star HD 192 163 (WN 6)
Authors: Wessolowski, U.; Hamann, W. -R.; Schmutz, W.
1987MitAG..70..337W Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The ultraviolet variability of the symbiotic star HBV
475. III. The periodicity of HBV 475.
Authors: Nussbaumer, H.; Schmutz, W.; Vogel, M.
1986A&A...169..154N Altcode:
The symbiotic star HBV 475 (= V1329 Cyg) shows periodic variations
in its spectrum, both in flux and in the wavelength positions of the
emission lines. New IUE observations, extending to the October 1985
flux maximum, allow an improved period and phase determination. The
periodic variation of the line profiles are interpreted as being due
to illumination effects from a hot star on a stellar wind around a
cool star, the hot star moving on an elliptical orbit. This model is
consistent with the line flux variations observed in this object.

---------------------------------------------------------
Title: Higher mass loss rates for Wolf-Rayet stars?
Authors: Schmutz, W.; Hamann, W. -R.
1986A&A...166L..11S Altcode:
Calculations with a recently developed non-LTE code for realistic
semiempirical models of Wolf-Rayet atmospheres revealed that, for
effective temperatures below approximately 60 kK, the dominant ion
in the radio-emitting region is not He(2+), as usually assumed, but
He(+). Hence, for those Wolf-Rayet stars having effective temperatures
below the quoted threshold, previous interpretations of the radio
observations are not adequate. The inferred mass loss rates must be
enhanced by up to a factor of 2.7, to take into account the lower
free-free emissivity of He(+). Assuming all Wolf-Rayet stars to be
cooler than the critical temperature, the corrected mean mass loss
rate of the essentially distance-limited sample of Wolf-Rayet stars
published by Abbott et al. (1986) becomes 0.00004 solar masses/yr.

---------------------------------------------------------
Title: The nitrogen abundance in Wolf-Rayet WC stars.
Authors: Nussbaumer, H.; Schmutz, W.
1986A&A...154..100N Altcode:
In order to confirm the presence of nitrogen in WC stars, the IUE
spectra of the WC 8 star HD 192103 have been studied in the region
1230-1250 A. The fluxes in the spectra of HD 192103 were extracted
using two different procedures: the method described by Ramella et
al. (1983); and the background correction method of Schmutz (1985). It
is demonstrated that there is no convincing evidence of NV 2s 2S1/2-2p
2P(0)3/2 absorption at 1238.8 A in the spectrum of WC 192103.

---------------------------------------------------------
Title: The ultraviolet variability of the symbiotic star HBV
475. II. Study of line flux variations.
Authors: Mueller, B. E. A.; Nussbaumer, H.; Schmutz, W.
1986A&A...154..313M Altcode:
The symbiotic star HBV 475 (= V1329 Cyg) is one of the few symbiotics
where periodic variations in the ultraviolet line fluxes have been
observed. The authors collect the IUE observations between June 1979
and December 1984. Extending the work of Nussbaumer and Schmutz (1983),
who presented a detailed study of this object, the authors establish
the periodicity in the ultraviolet line and continuum fluxes and in
velocity shifts. There can thus be no doubt about the binary nature
of this object. The line flux variations result in a period of 975 days.

---------------------------------------------------------
Title: Synthetische Helium-Spektren für Wolf-Rayet-Sterne
Authors: Wessolowski, U.; Hamann, W. -R.; Schmutz, W.
1986MitAG..67..325W Altcode:
Eine ausführliche Version dieser Arbeit (Modellgitter unter
Berücksichtigung des erweiterten He-Atoms) wird demnächst bei
Astronomy and Astrophysics zur Veröffentlichung eingereicht.

---------------------------------------------------------
Title: Effective Temperatures of Wolf-Rayet Stars - A Progress Report
Authors: Schmutz, W.; Hamann, W. -R.; Wessolowski, U.
1986MitAG..67..326S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Observations of Galactic Single Wn Stars
Authors: Schmutz, W.
1986iue..prop.2602S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Estimation of the true background level of SWP HI-RES images.
Authors: Schmutz, W.
1985IUEEN..23...94S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The hydrogenic 2s-1s two-photon emission
Authors: Nussbaumer, H.; Schmutz, W.
1984A&A...138..495N Altcode:
The authors give an analytical expression for the probability of the
hydrogenic two-photon decay. The expression allows a very accurate
description of the two-photon continuum. For the total hydrogen 2s→1s
two-photon transition probability a value of A2q = 8.2249
s-1 is found.

---------------------------------------------------------
Title: The nitrogen abundance in WC stars.
Authors: Schmutz, W.; Morossi, C.; Ramella, M.
1984ESASP.218..325S Altcode: 1984iue..conf..325S
Willis (1982) identifies tentatively an absorption at 1235 Å in
the IUE spectrum of the WC star HD 192103 as blue shifted P Cygni
absorption of N V λ1240. The presence of nitrogen in a WC star is of
interest because this observation would disagree with the predictions of
theoretical stellar evolution calculations. The authors reanalysed the
IUE image of this Wolf-Rayet star. On the grounds of the reprocessed
spectrum and of comparisons with the same wavelength region in other
Wolf-Rayet spectra, the authors conclude that most probably nitrogen
is not observed in the WC star HD 192103.

---------------------------------------------------------
Title: The Neighbourhood of the Wolf-Rayet Star Ez Cma
Authors: Schmutz, W.
1984iue..prop.1932S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A model atmosphere for Wolf-Rayet stars
Authors: Schmutz, W.
1984PhDT.........2S Altcode:
The observed characteristics of the Wolf-Rayet (WR) stars are surveyed;
the astrophysical interpretations proposed to explain the broad lines
and the two spectral groups in WR stars are reviewed; a semiempirical
spherically symmetric He model atmosphere is constructed; and the
results of preliminary model computations are presented in tables and
graphs and discussed. The model treats the velocity and temperature
laws as free parameters, applies the Sobolev approximation to simplify
radiation transfer in the lines, and calculates the continuum radiation
field and the level populations alternately until convergence of the
level populations is achieved. The model is found to reproduce the
line strengths and continua observed in WR stars, to give luminosities
as much as twice those of previous models, and to predict a strong
dependance of line strengths on atmospheric structure (a possible
explanation for the wide scatter of observed line strengths among
stars of one subgroup).

---------------------------------------------------------
Title: On the Hydrogen Abundance in Wolf-Rayet Stars
Authors: Schmutz, W.
1984IAUS..105..269S Altcode:
With a semiempirical NLTE-model in spherical geometry the author
investigates the hydrogen abundance in Wolf-Rayet stars. He finds that
the flux contribution of the H-Balmer to the He-Pickering lines lies
between the usually applied approximate formulae for the optically
thin and optically thick case. This result can be understood with the
finding that there are no optically thin helium and hydrogen lines. The
influence of the temperature structure on the relative intensity of
the hydrogen-helium blends to the helium lines is vanishingly small,
even for peculiar temperature laws. The conclusion is that Wolf-Rayet
stars are hydrogen deficient objects.

---------------------------------------------------------
Title: Ein Modell für Atmosphären von Wolf-Rayet Sternen Title:
Ein Modell für Atmosphären von Wolf-Rayet Sternen
Authors: Schmutz, Werner K.
1984PhDT.......242S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Ein Modell fuer Atmosphaeren von Wolf-Rayet Sternen
Authors: Schmutz, Werner
1984emav.book.....S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The ultraviolet variability of the symbiotic star HBV 475.
Authors: Nussbaumer, H.; Schmutz, W.
1983A&A...126...59N Altcode:
Evidence is presented for the binary nature of the symbiotic star HBV
475 ( = V 1329 Cyg), based on ultraviolet observations taken with
the International Ultraviolet Explorer. The fluxes in the emission
lines and in the continuum observed during 1978-1982 are related. It
is found that the changes in the line and continuum fluxes observed
in the far ultraviolet (1200-3200 A) are consistent with the 950 d
period found from the visual luminosity variations. Periodicity and
amplitudes found in the wavelength shifts are shown to indicate a
size of the binary system of approximately 2 x 10 to the 14th cm. The
emission lines are found to originate in a radiatively ionized gas with
electron density in the range of 10 to the 6th to 10 to the 7th/cu cm,
and electron temperature less than 15,000 K. In addition, an indication
for a hot outer envelope around the whole system is observed.

---------------------------------------------------------
Title: IUE ultra-violet spectrophotometry of 15 galactic Wolf-rayet
stars.
Authors: Nussbaumer, H.; Schmutz, W.; Smith, L. J.; Willis, A. J.
1982A&AS...47..257N Altcode:
Low-resolution IUE ultraviolet spectrophotometry is presented
of 15 galactic WR stars, covering most subtypes in the WN and WC
sequences. The data are presented both as spectral plots and as
tabulations of the observed absolute flux distributions covering the
wavelength range of 1150-3090 A. The characteristics of these UV WR
spectra are discussed, the equivalent widths of the most prominent
emission lines having been measured. It is shown that the WR stars
adhere to the normal galactic interstellar extinction law. For each
star, color excesses, E(B-V), are derived by nulling the observed
2200 A features and by comparing relative intensities of optically
thin HeII recombination emission lines.

---------------------------------------------------------
Title: The effective temperatures of early Wolf-Rayet stars
Authors: Schmutz, W.
1982IAUS...99...23S Altcode:
Nussbaumer et al. (1981) adopted a temperature derived from a Zanstra
analysis of the He II recombination lines to account for the WR
stars that exhibit deviation from the blackbody shape. According
to the Nussbaumer analysis, there should be a continuum jump at
2050 A. New IUE observations of the WN 5 star HD 50896, however,
did not reveal any trace of such an absorption edge. This is seen as
implying that the effective temperature of this WN 5 star and probably
of all WR stars with a non-black-body energy distribution is not yet
known accurately. A detailed analysis is therefore undertaken with a
spherically symmetric atmosphere model. Though the model is not yet in
its final shape, a first result is described wherein the location of
HD 50896 in the HR-diagram is to the left of the ZAMS and the Zanstra
analysis is indeed not valid for this star.

---------------------------------------------------------
Title: Ultraviolet energy distribution of Wolf-rayet stars.
Authors: Schmutz, W.; Smith, L. J.
1980ESASP.157..249S Altcode: 1980iue..conf..249S; 1980IUE2n......249S
Low resolution spectra of 15 Wolf-Rayet stars (10 WN and 5 WC stars)
were analyzed to investigate their UV continuum distribution. The
reddening observed for Wolf-Rayet stars is found to follow the general
galactic interstellar extinction law. Color excesses for each star are
deduced from the observed strength of the 2200A feature. The combined
de-reddened UV-visible continua are compared with black body energy
distributions to deduce color temperatures. Four stars are analyzed
on the basis of Cassinelli and Hartmann's theory for extended emitting
regions.

---------------------------------------------------------
Title: IUE observations of galactic Wolf-Rayet stars
Authors: Nussbaumer, H.; Schmutz, W.; Smith, L. J.; Willis, A. J.;
Wilson, R.
1979IUE1.symp..259N Altcode:
The paper surveys the results obtained through study of a large set
of ultraviolet spectra of single WR stars obtained with IUE. Spectral
features are identified and the strengths of the observed emission
lines compared as a function of each subclass. In addition, a
correlation is found between terminal velocity and subclass in both
WN and WC sequences, and for the WC, a correlation with terminal
velocity and I.P. within an individual spectrum is found, indicating
considerable stratification in the WC atmospheres. A preliminary
analysis of the strengths of the carbon and nitrogen emission lines
observed in the spectra of HD 156385 (WC7) and HD 192163 (WN6) is
given. Significant differences are found between the C/N ratios of
the two stars, demonstrating the chemical separation between the WN
and WC sequences. Finally, it is concluded that the WN star is at an
earlier stage of evolution than the WC star.