Author name code: baschek
ADS astronomy entries on 2022-09-14
author:"Baschek, Bodo"
------------------------------------------------------------------------
Title: Drifter observations of submesoscale flow kinematics in the
coastal ocean
Authors: Ohlmann, J. C.; Molemaker, M. J.; Baschek, B.; Holt, B.;
Marmorino, G.; Smith, G.
Bibcode: 2017GeoRL..44..330O
Altcode:
Fronts and eddies identified with aerial guidance are seeded with
drifters to quantify submesoscale flow kinematics. The Lagrangian
observations show mean divergence and vorticity values that can exceed
5 times the Coriolis frequency. Values are the largest observed in
the field to date and represent an extreme departure from geostrophic
dynamics. The study also quantifies errors and biases associated with
Lagrangian observations of the underlying velocity strain tensor. The
greatest error results from undersampling, even with a large number
of drifters. A significant bias comes from inhomogeneous sampling
of convergent regions that accumulate drifters within a few hours of
deployment. The study demonstrates a Lagrangian sampling paradigm for
targeted submesoscale structures over a broad range of scales and
presents flow kinematic values associated with vertical velocities
O(10) m h-1 that can have profound implications on ocean
biogeochemistry.
Title: Markov Chain Monte Carlo solutions for radiative transfer
problems
Authors: von Waldenfels, W.; Wehrse, R.; Baschek, B.
Bibcode: 2011A&A...525A..70V
Altcode:
Algorithms for the solution of the radiative transfer equation that
are simultaneously accurate, fast, and easy to implement are still
highly desirable, in particular for multidimensional media. We present
a stochastic algorithm that solves the transfer equation by assuming
that the transfer of radiation can be modelled as a Markov process. It
is a generalization of the classical Monte Carlo method and can be
applied to the solution of the Milne equation.
Title: Talk in honor of Albrecht Unsöld's 100th anniversary:
Physics of stellar atmospheres-new aspects of old problems
Authors: Baschek, Bodo
Bibcode: 2006RvMA...19...61B
Altcode:
No abstract at ADS
Title: How do updrafts and embedded convection influence riming?
Authors: Baschek, B.; Schefold, R.; Barthazy, E.
Bibcode: 2004erad.conf..261B
Altcode:
No abstract at ADS
Title: The diffusion of radiation in moving media. IV. Flux vector,
effective opacity, and expansion opacity
Authors: Wehrse, R.; Baschek, B.; von Waldenfels, W.
Bibcode: 2003A&A...401...43W
Altcode:
For a given velocity and temperature field in a differentially moving
3D medium, the vector of the radiative flux is derived in the diffusion
approximation. Due to the dependence of the velocity gradient on the
direction, the associated effective opacity in general is a tensor. In
the limit of small velocity gradients analytical expression are obtained
which allow us to discuss the cases when the direction of the flux
vector deviates from that of the temperature gradient. Furthermore the
radiative flux is calculated for infinitely sharp, Poisson distributed
spectral lines resulting in simple expressions that provide basic
insight into the effect of the motions. In particular, it is shown how
incomplete line lists affect the radiative flux as a function of the
velocity gradient. Finally, the connection between our formalism and the
concept of the expansion opacity introduced by Karp et al. (\cite{karp})
is discussed.
Title: The diffusion of radiation in moving media. III. Stochastic
representation of spectral lines
Authors: Wehrse, R.; Baschek, B.; von Waldenfels, W.
Bibcode: 2002A&A...390.1141W
Altcode:
In this paper we present analytical expressions for the radiative flux,
the effective extinction coefficient, and the radiative acceleration
deep inside a differentially moving, very optically thick medium
with many spectral lines. It is shown that the line contribution is
essentially given by the characteristic function of wavelength averages
of the extinction coefficient. It can be calculated either by means of
the generalized opacity distribution function or by means of a Poisson
point process model. Several examples are given to demonstrate the
basic consequences of line densities, widths, and strengths, as well
as velocity gradients on the diffusive flux. We demonstrate that for
Poisson distributed lines the diffusive flux decreases with increasing
absolute values of the velocity gradient (i.e. that the flux has a
maximum for static media), and that such lines have hardly a direct
influence on the radiative acceleration.
Title: Book Review: The new cosmos. - 5th ed. / Springer, 2001
Authors: Unsold, A.; Baschek, B.
Bibcode: 2002Obs...122..125U
Altcode:
No abstract at ADS
Title: Radiative Quantities for Hydrodynamics
Authors: Wehrse, R.; Baschek, B.
Bibcode: 2002EAS.....5....1W
Altcode:
Convenient and accurate expressions for the radiative flux deep inside
an arbitrarily shaped, differentially moving, optically thick medium are
derived. Spectral lines are included either in a deterministic way or
stochastically by assuming a Poisson point process. It is shown that
the lines lead to decreasing fluxes when in the medium the absolute
value of the velocity gradient is increased. The flux vector needs
no longer to be parallel to the temperature gradient in contrast to
the radiative acceleration, which to a very good approximation is not
influenced by lines. Formulae for the corresponding mean values of
the opacity are presented and discussed.
Title: Der neue Kosmos. Einführung in die Astronomie und Astrophysik
Authors: Unsöld, Albrecht; Baschek, Bodo
Bibcode: 2002neko.book.....U
Altcode:
Der neue Kosmos bietet in überschaubarem Umfang eine zusammenhängende
Einführung in das Gesamtgebiet der Astronomie und Astrophysik. Aus den
Bereichen: Klassische Astronomie und Planetensystem, Instrumente und
Beobachtungsverfahren, Sonne und Sterne, Milchstraße und Galaxien,
Kosmologie, Entstehung des Planetensystems, Entwicklung der Erde
und des Lebens werden die Beobachtungsmethoden und die Ergebnisse
astronomischer Forschung sowie deren theoretische Grundlagen und
wechselseitigen Zusammenhänge vermittelt. Die aktualisierte 7. Auflage
berücksichtigt den raschen Fortschritt astronomischer Forschung der
letzten drei Jahre von unserem Planetensystem und den Entdeckungen
zahlreicher Planeten bei anderen Sternen, über die fernsten Galaxien
und Quasare bis zur Entwicklung der modernen Kosmologie.
Title: Fall velocity and axial ratio of snowflakes
Authors: Schefold, R.; Baschek, B.; Wüest, M.; Barthazy, E.
Bibcode: 2002erad.conf...84S
Altcode:
No abstract at ADS
Title: Opacity distribution in static and moving media
Authors: Baschek, B.; Waldenfels, W. V.; Wehrse, R.
Bibcode: 2001A&A...371.1084B
Altcode:
The use of the conventional opacity distribution function (ODF) to
deal with very many spectral lines is restricted to static media. In
this paper, its generalization to differentially moving media is
derived from the analytical solution of the comoving-frame radiative
transfer equation. This generalized ODF depends on only two parameters,
on the wavelength position (as in the static case) and in addition on a
wavelength interval Delta over which the line extinction is averaged. We
present two methods for the calculation of the generalized ODF: (i)
in analogy to the static case, it is derived from the mean values
of the extinction coefficients over wavelength intervals Delta ,
(ii) it is calculated under the assumption that the lines follow
a Poisson point process. Both approaches comprise the conventional
static case as the limit of vanishing velocities, i.e. of Delta ->
0. The averages of the extinction for all values of Delta contain
the necessary information about the Doppler shifts and about the
correlations between the extinction at different wavelengths. The
flexible statistical approximation of the lines by a Poisson point
process as an alternative to calculating the averages over all Delta
from a deterministic ``real'' spectral line list, has the advantage that
the number of parameters is reduced, that analytical expressions allow a
better insight into the effects of the lines on the radiative transfer,
and that the ODFs and their corresponding characteristic functions
can be calculated efficiently by (fast) Fourier transforms. Numerical
examples demonstrate the effects of the relevant parameters on the
opacity distribution functions, in particular that with increasing
line density and increasing Delta the ODF becomes narrower and its
maximum is shifted to larger extinction values.
Title: The new cosmos : an introduction to astronomy and astrophysics
Authors: Unsoeld, Albrecht; Baschek, Bodo
Bibcode: 2001ncia.book.....U
Altcode:
No abstract at ADS
Title: The diffusion of radiation in moving media. II. Limits for
large and small velocity gradients for deterministic lines
Authors: Wehrse, R.; Baschek, B.; von Waldenfels, W.
Bibcode: 2000A&A...359..788W
Altcode:
The general formulae for radiative quantities in the diffusion limit
for a differentially moving 3D medium which have been derived in Paper
I of this series, are evaluated for the limiting cases of very large
and very small velocity gradients | w | . The extinction coefficient
is specified by the continuum and the contribution of spectral lines
which is formulated deterministically. For large w all radiative
quantities can conveniently be calculated in terms of the spectral
thickness, i.e. of the wavelength-integrated extinction coefficient,
which can be well approximated by a piecewise linear function. For
small w the radiative quantities are developed to the second order
in w. The coefficients are essentially determined by the first
two wavelength derivatives of the mean free path of the photons,
i.e. of the reciprocal extinction coefficient. Since these depend
on temperature, density and chemical composition only, they can be
precalculated resulting in convenient expressions for hydrodynamic
calculations. Examples are given for selected extinction coefficients
such as a power-law continuum, a spectral edge, a single narrow line,
and many, isolated as well as overlapping lines. In the non-overlapping
case the lines contribute only in second order of w and the motions
always lead to a decrease of the total flux whereas the radiative
acceleration is unaffected. On the other hand, the effect of overlapping
lines can only be determined by a detailed calculation for any specific
extinction distribution. Furthermore, it is shown that the flux vector
has components perpendicular to the temperature gradient if the latter
is not parallel to the velocity vector.
Title: The diffusion of radiation in moving media. I. Basic
assumptions and formulae
Authors: Wehrse, R.; Baschek, B.; von Waldenfels, W.
Bibcode: 2000A&A...359..780W
Altcode:
The 3D radiative transfer equation for differentially moving media is
derived upon the assumption that the motions are sufficiently slow. Its
solution is then applied to the limiting case of large optical depths,
i.e. to the diffusion approximation. Although the effective extinction
for static 1D media has been derived by Rosseland already in 1924,
it is for the first time in this Paper that for moving 3D media with
many spectral lines general expressions for radiative quantities are
derived in a rigorous way. Given are simple to use monochromatic
as well as wavelength-integrated expressions for the flux and the
radiative acceleration, and a generalized version of the Rosseland
mean opacity. The essential effects of the motions upon the radiative
flux are discussed for the simple case of a single spectral line on
a continuum.
Title: Diffusion of radiation in moving media
Authors: Baschek, B.; Wehrse, R.; Waldenfels, W. V.
Bibcode: 2000nuas.conf....1B
Altcode:
No abstract at ADS
Title: Radiation fields in moving media: new analytical and numerical
solutions of the transfer equation.
Authors: Wehrse, R.; Baschek, B.
Bibcode: 1999PhR...311..187W
Altcode:
Significant progress has been achieved in the solution of the radiative
transfer equation for various geometries, velocities, scattering modes
etc. In particular, it has been become possible for the first time
to derive an orthogonal system of functions that solves the transfer
equation for plane media, to model numerically radiation fields in
arbitrarily shaped 3D configurations with a prescribed accuracy, and
to obtain general quadrature solutions for spheres with relativistic
velocities. The latter are of special importance since they lead
to accurate and convenient expressions for the diffusion limit in
moving media. In this contribution the new techniques are reviewed
and the consequences for our understanding of radiation fields briefly
discussed.
Title: Radiation fields in moving media: effects of many spectral
lines in AGN accretion disks.
Authors: Baschek, B.; Wehrse, R.
Bibcode: 1999PhR...311..201B
Altcode:
Analytical solutions of the radiative transfer equation derived
for differentially moving media allow the efficient inclusion of an
arbitrarily large number of spectral lines both in a deterministic
and in a stochastic way. For a deterministic line set and not too
small velocities, a high computational speed-up is achieved if the
solution is expressed not in terms of the extinction coefficient
but by its much smoother wavelength integral. The assumption of a
Poisson point process for the number of lines, combined with suitable
distributions for the line positions and other line parameters,
is a flexible presentation of the wavelength dependence of the line
extinction coefficient which well describes deterministic "real" lines
and requires only few parameters. The intricate connection between
line properties and the emergent intensity can then be evaluated to a
large part analytically. Assuming Lorentz profiles and a power law for
the line strength distribution, the authors discuss the effect of many
spectral lines on the radiation field of a typical AGN accretion disk,
in particular, on the emerging radiation and on its diffusion limit
holding in the interior.
Title: Der neue Kosmos. Einführung in die Astronomie und Astrophysik.
Authors: Unsöld, A.; Baschek, B.
Bibcode: 1999dnke.book.....U
Altcode:
I. Klassische Astronomie und das Planetensystem: klassische
Astronomie; physikalische Beschaffenheit der Körper im
Planetensystem. II. Strahlung, Instrumente und Beobachtungsverfahren:
Strahlung und Materie; astronomische und astrophysikalische
Instrumente. III. Sonne und Sterne - Astrophysik des einzelnen Sterns:
Entfernungen und Zustandsgrößen der Sterne; Spektren und Atmosphären
der Sterne; Aufbau und Entwicklung der Sterne. IV. Sternsysteme,
Kosmologie und Kosmogonie: Sternhaufen; interstellare Materie und
Sternentstehung; Aufbau und Dynamik des Milchstraßensystems; Galaxien
und Galaxienhaufen; Kosmologie - der Kosmos als Ganzes; Kosmogonie
des Sonnensystems.
Title: Der neue Kosmos
Authors: Unsöld, Albrecht; Baschek, Bodo
Bibcode: 1999neko.book.....U
Altcode:
Astronomie, Astrophysik und Weltraumforschung haben innerhalb weniger
Jahrzehnte eine geradezu explosive Entwicklung genommen. Die neuen
Beobachtungsmöglichkeiten durch die Raumfahrt, die Entwicklung
hochempfindlicher Computer haben uns neuartige Aspekte in der
faszinierenden Welt der Galaxien und Quasare, der Sterne und Planeten
erschlossen. Die vorliegende 6., völlig überarbeitete Auflage des
Neuen Kosmos, trägt dieser stürmischen Entwicklung Rechnung. In
überschaubarem Umfang wird - bei bescheidenen Ansprüchen an
die mathematisch-naturwissenschaftliche Vorbildung des Lesers eine
zusammenhängende Einführung in das Gesamtgebiet der Astronomie und
Astrophysik gegeben, welche die Beobachtungen und die Grundgedanken
ihrer theoretischen Deutung in gleicher Weise berücksichtigt. Auch
mit der 6. Auflage wird Der neue Kosmos den Studenten und Forschern
in Bereichen der Astronomie, Physik und Geowissenschaften sowie einem
weiten Kreis ernsthaft interessierter Amateure viel Neues und viel
Freude bringen.
Title: Differentially moving media with many spectral lines:
stochastic approach.
Authors: Wehrse, R.; von Waldenfels, W.; Baschek, B.
Bibcode: 1998JQSRT..60..963W
Altcode:
Based upon the analytical solution of the radiative transfer equation
for a given source function and a new approach to account for very
many spectral lines contributing to the extinction, the connection
between line properties and the emergent intensity is derived under the
assumption that the wavelengths of the line centers follow a Poisson
point process, whereas the other line parameters may have arbitrary
distribution functions. A comparison with the widely used list of Kurucz
(1994) shows that the Poisson distribution well describes deterministic
"real" lines. The presentation by a Poisson point process requires only
a modest number of parameters and is very flexible. It allows most
operations to be carried out analytically and hence is very suitable
to study the intricate influence of many lines on radiation fields
in differentially moving media. The authors consider a simplified
case of the solution of the radiative transfer equation in order to
demonstrate the basic effects of the velocity field upon the emerging
radiation field. Expressions for the expectation value of the intensity
are derived, and examples are given for Lorentz line profiles and
infinitely sharp lines, in particular as functions of the velocity
gradient and the mean line density.
Title: Radiation hydrodynamics with many spectral lines. Analytical
expressions for a differentially moving slab.
Authors: Baschek, B.; Grueber, C.; von Waldenfels, W.; Wehrse, R.
Bibcode: 1997A&A...320..920B
Altcode:
An analytical solution of the comoving frame radiative transfer
equation for a differentially moving slab is obtained and written
in terms of the wavelength-integrated extinction coefficient ψ,
the spectral thickness. It is shown that ψ is much smoother than
the extinction coefficient χ(λ) itself and that it can be well
approximated e.g. by a simple piecewise linear function. Compared to
conventional algorithms it allows speed-ups of factors >=10^5^ in
the calculation of wavelength-integrated quantities such as e.g. the
total flux, the radiative force, or the energy balance with an accuracy
of <=1%. The total number of lines which can be taken into account
is essentially unlimited. A simple expression for the total flux in
the diffusion limit is derived and the dependencies on the velocity
gradient are discussed.
Title: Spectroscopic data for linear molecules.
Authors: Suvernev, A.; Baschek, B.; Wehrse, R.; Goodson, D.
Bibcode: 1997AGAb...13...30S
Altcode:
No abstract at ADS
Title: Radiative transfer in moving spherical
atmospheres. II. Analytical solution for fully relativistic radial
motions.
Authors: Baschek, B.; Efimov, G. V.; von Waldenfels, W.; Wehrse, R.
Bibcode: 1997A&A...317..630B
Altcode:
Based on the well known solution of the time-independent radiative
transfer equation along a ray and on suitable point transformations,
general quadrature solutions of the monochromatic transfer equation
for plane-parallel, spherically-symmetric and arbitrarily shaped
3D configurations with differential motion are derived for the
observer's and the comoving frame. The source function is assumed
to be given; however, the scattering case requires only a simple
iteration in addition. Since complete Lorentz transformations are
used, the velocities are not restricted. It is shown that in many
cases the explicit form of the transfer equation - which often is
quite complicated - is not required for the determination of the
specific intensities.
Title: Institut für Theoretische Astrophysik der Universität
Heidelberg. Jahresbericht für 1996.
Authors: Baschek, B.
Bibcode: 1997MitAG..80..317B
Altcode:
No abstract at ADS
Title: Differentially moving media with many spectral lines:
stochastical approach.
Authors: Baschek, B.; von Waldenfels, W.; Wehrse, R.
Bibcode: 1997AGAb...13..150B
Altcode:
No abstract at ADS
Title: Radiative transfer: new light on old problems.
Authors: Baschek, B.
Bibcode: 1996AGAb...12..145B
Altcode:
No abstract at ADS
Title: In memoriam Albrecht Unsöld, 20 April 1905 - 23 September
1995.
Authors: Baschek, B.
Bibcode: 1996PhyBl..52..890B
Altcode: 1996PhB....52..890B
No abstract at ADS
Title: Albrecht Unsöld (20. April 1905 - 23. September 1995).
Authors: Baschek, B.
Bibcode: 1996MitAG..79...11B
Altcode:
No abstract at ADS
Title: Landolt-Börnstein: Numerical Data and Functional Relationships
in Science and Technology - New Series " Gruppe/Group 6 Astronomy and
Astrophysics " Volume 3 Voigt: Astronomy and Astrophysics. Extension
and Supplement to Volume 2 " Stars and Star Clusters
Authors: Aller, L. H.; Appenzeller, I.; Baschek, B.; Butler, K.;
De Loore, C.; Duerbeck, H. W.; El Eid, M. F.; Fink, H. H.; Herczeg,
T.; Richtler, T.; Schneider, H.; Scholz, M.; Seggewiss, W.; Seitter,
W. C.; Trümper, J.; Ulmenschneider, P.; Wehrse, R.; Weidemann, V.
Bibcode: 1996lbor.book.....A
Altcode:
Astronomy and Astrophysics were first treated in volume III of the
6th edition of Landolt-Börnstein in 1952, then in volumes VI/1 and
VI/2 of the New Series, 1965 and 1981/82 respectively. The present
volume VI/3 is a further supplementation of volume VI/1. The decimal
classification scheme of the first supplement volumes, VI/2, has been
maintained, fields without significant new developments are clearly
indicated. A synoptic list of contents over all three volumes provides
an excellent overview for the user as well as a Comprehensive Index
in the forthcoming last subvolume of VI/3.
Title: Institut für Theoretische Astrophysik der Universität
Heidelberg. Jahresbericht für 1995.
Authors: Baschek, B.
Bibcode: 1996MitAG..79..343B
Altcode:
No abstract at ADS
Title: Radiative transfer in moving spherical
atmospheres. I. Analytical perturbation solution for the gray case.
Authors: Baschek, B.; Hafner, M.; Wehrse, R.
Bibcode: 1995A&A...301..511B
Altcode:
Analytical expressions for the frequency-integrated mean intensity and
the total flux are obtained for expanding or collapsing spherical gray
configurations in radiative equilibrium. Such radiation fields (and
the corresponding temperature distributions) could up to now only be
obtained by means of purely numerical work. Our formulae are based on
the first two moment equations of the radiative transfer equation and a
closure relation that decomposes the radiation field into an isotropic
and an outward-peaked contribution and that assures consistency of the
definitions of the moments and the corresponding transfer equations. The
expressions are exact to first order in v/c and are therefore applicable
to a wide variety of objects. The depth dependence of the opacity may
be arbitrary, the important cases of power and exponential laws are
considered in detail and found to result in formulae that can easily
be handled. The previously known relations for static spherical and
plane-parallel media are contained as special cases.
Title: Summary and Outlook, Future Needs for Atomic Data
Authors: Baschek, B.
Bibcode: 1995ASPC...78..527B
Altcode: 1995aapn.conf..527B
No abstract at ADS
Title: The galactic abundance gradients traced by B-type stars.
Authors: Kaufer, A.; Szeifert, Th.; Krenzin, R.; Baschek, B.; Wolf, B.
Bibcode: 1994A&A...289..740K
Altcode:
We obtained high S/N, high resolution spectra of 16 B-type main sequence
stars in young open clusters and in HII regions with galactocentric
distances between 7 and 16 kpc. Chemical abundances for this sample were
derived using line-blanketed LTE model atmospheres and line formation
in LTE. Our analyses together with published data from similar analyses
of B-type stars result in flat gradients or even no gradients at all
for oxygen and nitrogen in the outer part of the galactic disk. It
is conjectured that the larger metallicity gradients cited for HII
regions are essentially due to a steepening within the inner 6 kpc
towards the galactic center.
Title: Photospheric Supernova Spectra - Quantification of the
Information Content
Authors: Hafner, M.; Baschek, B.; Wehrse, R.
Bibcode: 1994MNRAS.269..764H
Altcode:
Spectroscopic diagnostics of expanding supernova photospheres (in their
coasting phase) require determination of at least six parameters
which characterize the state of the emitting layers (effective
temperature, photo spheric radius, density exponent, expansion velocity,
microturbulence, and element abundances), i.e. two more than for a
compact stellar atmosphere in hydrostatic equilibrium. Besides the
larger set of parameters, the expansion process itself complicates
the unambiguous interpretation of the spectrum considerably: the
broadening and blending of lines correspond to a lower spectral
resolution, and, in addition, the relativistic Doppler boosting inside
the differentially expanding envelope mimics changes in the effective
temperature. The effects of the expansion on the information content
are quantified by calculating the apparent spectral information (ASI)
of synthetic supernova spectra. We address the problem of the extent
to which parameters can be determined from an observed spectrum (with
prescribed AS I). Key words: line: profiles - methods: data analysis -
supernovae: general.
Title: VizieR Online Data Catalog: Galactic abundance gradients
(Kaufer+, 1994)
Authors: Kaufer, A.; Szeifert, T.; Krenzin, R.; Baschek, B.; Wolf, B.
Bibcode: 1994yCat..32890740K
Altcode:
Not Available (4 data files).
Title: Vertical Structure and Spectra of Accretion Disks
Authors: Wehrse, R.; Baschek, B.; Shaviv, G.
Bibcode: 1994ASPC...56...35W
Altcode: 1994ibs..conf...35W
No abstract at ADS
Title: New Aspects of Magellanic Cloud Research
Authors: Baschek, B.; Klare, G.; Lequeux, J.
Bibcode: 1993LNP...416.....B
Altcode: 1993namc.meet.....B
The proceedings of the Second European Meeting on "New Aspects of
Magellanic Cloud Research" review the most recent progress in the
study of the LMC and SMC. The activities within the ground-based ESO
key programme "Coordinated Investigations of Selected Regions in the
Magellanic Clouds", as well as new exciting observations from space
missions (ROSAT, IUE, ISO, IRAS) result in a more profound insight into
the structure, kinematics, populations (stars, clusters, interstellar
medium), and the chemical composition and evolution of the Magellanic
Cloud system. The book addresses researchers and graduate students
in astrophysics.
Title: The chemical composition of B-type giants in the Magellanic
Clouds.
Authors: Jüttner, A.; Wolf, B.; Baschek, B.
Bibcode: 1993AGAb....9...30J
Altcode:
No abstract at ADS
Title: New Abundance Analyses of B-Type Giants in the Magellanic
Clouds
Authors: Juttner, A.; Stahl, O.; Wolf, B.; Baschek, B.
Bibcode: 1993LNP...416..337J
Altcode: 1993namc.meet..337J
We made observations to derive chemical abundances for the elements He,
C, N, O, Mg, Al, Si, S, and Fe in B-type giants in the Magellanic Clouds
(MCs). The abundance determinations were carried out differentially
to the galactic B-type giant HR 2618 which shows intermediate
atmospheric parameters relative to the coolest and hottest stars
of our sample. Model atmosphere parameters of the target stars
were aslo determined with low resolution IUE spectrophotometry. The
model atmospheres were also used in conjuction with IUE data to stud
interstellar reddening n the MCs.
Title: The galactic abundance gradient.
Authors: Kaufer, A.; Krenzin, R.; Szeifert, T.; Wolf, B.; Baschek, B.
Bibcode: 1993AGAb....9..165K
Altcode:
No abstract at ADS
Title: Introduction
Authors: Baschek, B.
Bibcode: 1993LNP...416....1B
Altcode: 1993namc.meet....1B
No abstract at ADS
Title: Line Formation in Accretion Disks
Authors: Baschek, B.; Papkalla, R.; Wehrse, R.
Bibcode: 1993AnIPS..10..176B
Altcode:
No abstract at ADS
Title: Billiardenmal heller als die Sonne.
Authors: Baschek, B.; Wehrse, R.
Bibcode: 1993ruca....1.....B
Altcode:
No abstract at ADS
Title: Book-Review - the New Cosmos - ED.4
Authors: Unsold, A.; Baschek, B.
Bibcode: 1992JBAA..102..109U
Altcode:
No abstract at ADS
Title: The Effects of Lines on the Mean Opacities in Novae,
Supernovae, and Accretion Disks
Authors: Wehrse, R.; Baschek, B.; Shaviv, G.
Bibcode: 1992RMxAA..23..247W
Altcode:
For the solution of the hydrodynamic equations in differentially
moving media the calculation of the radiation fiux, the gradient of
the radiation pressure, and the energy balance is required. After a
brief discussion of the shortcomings of the approximations which are
frequently made, we suggest a fast method for the accurate calculation
of these quantities by means of three mean opacity coefficients which
replace the Rosseland mean of the static case. This method allows a
consistent inclusion of the important contribution of spectral lines
to the radiation field. Key words: ACCRETION - OPACITIES - STARS:
NOVAE - STARS: SUPERNOVAE
Title: The New Cosmos - ED.4
Authors: Unsold, A.; Baschek, B.
Bibcode: 1992Sci...255.1757U
Altcode:
No abstract at ADS
Title: Lambda Bootis stars
Authors: Baschek, Bodo
Bibcode: 1992LNP...401..224B
Altcode: 1992aets.conf..224B
A brief discussion of the properties, in particular of the abundance
pattern, and of the origin of the λ Bootis stars is given.
Title: Trouble in the Magellanic Clouds - First results from the
Key Programme on coordinated investigations of selected regions in
the Magellanic Clouds
Authors: de Boer, K. S.; Spite, F.; Francois, P.; Cayrel, R.; Spite,
M.; Baschek, B.; Koeppen, J.; Wolf, B.; Stahl, O.; Juettner, A.;
Seggeweiss, W.; Bomans, D. J.; Grebel, E. K.; Geyer, E. H.; Richtler,
T.; Vallenari, A.; Koornneef, J.; Israel, F. P.; Molaro, P.; Monai,
S.; Vladilo, G.; D'Odorico, S.; Leisy, R.; Dennefeld, M.; Ferlet,
R.; Vidal-Madjar, A.; Stasinska, G.; Azzopardi, M.; Meyssonnier, N.;
Muratorio, G.; Rebeirot, E.; Lequeux, J.
Bibcode: 1991Msngr..66...14D
Altcode: 1991Mgr....66...14D
Results of coordinated subprojects on selected regions in Magellanic
Clouds performed in the framework of the Key Program are briefly
reviewed. The subprojects include spectroscopic survey with EFOSC
(Marseille, Paris, Uppsala), CCD photometry of small field within
the regions (Bonn), IRAC photometry of small fields within the
regions (Baltimore, Leiden), stellar spectroscopy for studying
element abundances in the hot and cool stars (Heidelberg and Meudon,
respectively), the interstellar absorption lines (Trieste, Paris),
and the spectra of emission nebulae (Paris).
Title: The parameters R and Teff in stellar models and observations.
Authors: Baschek, B.; Scholz, M.; Wehrse, R.
Bibcode: 1991A&A...246..374B
Altcode:
Different definitions of radii and effective temperatures in
extended-atmosphere stars (protostars, red giants, central stars
of planetary nebulae, Wolf-Rayet stars, (novae, and supernovae)
are reviewed and clarified. Their properties, their interrelations
and their meaning for interior models, for atmospheric models and
for the interpretation of flux and of angular diameter measurements
are discussed.
Title: Limitations of Stellar Abundance Determinations
Authors: Baschek, B.
Bibcode: 1991IAUS..145...39B
Altcode:
No abstract at ADS
Title: Concluding Remarks (i)
Authors: Baschek, B.
Bibcode: 1991IAUS..145..447B
Altcode:
No abstract at ADS
Title: Der neue Kosmos
Authors: Unsöld, Albrecht; Baschek, Bodo
Bibcode: 1991neko.book.....U
Altcode:
Astronomie, Astrophysik und Weltraumforschung haben innerhalb weniger
Jahrzehnte eine geradezu explosive Entwicklung genommen. Die neuen
Beobachtungsmöglichkeiten durch die Raumfahrt, die Entwicklung
hochempfindlicher Computer haben uns neuartige Aspekte in der
faszinierenden Welt der Galaxien und Quasare, der Sterne und
Planeten erschlossen. Die vorliegende fünfte, erweiterte Auflage
des Neuen Kosmos, die bereits knapp drei Jahre nach der vierten,
völlig neubearbeiteten Auflage erscheint, trägt dieser stürmischen
Entwicklung Rechnung. In überschaubarem Umfang wird - bei bescheidenen
Ansprüchen an die mathematisch-naturwissenschaftliche Vorbildung
des Lesers - eine zusammenhängende Einführung in das Gesamtgebiet
der Astronomie und Astrophysik gegeben, welche die Beobachtungen
und die Grundgedanken ihrer theoretischen Deutung in gleicher Weise
berücksichtigt. Auch mit der 5. Auflage wird Der Neue Kosmos den
Studenten und Forschern in Bereichen der Astronomie, Physik und
Geowissenschaften sowie einem weiten Kreis ernsthaft interessierter
Amateure viel Neues und viel Freude bringen.
Title: Element Abundances from B Stars in the Magellanic Clouds
Authors: Jüttner, A.; Stahl, O.; Wolf, B.; Baschek, B.
Bibcode: 1991IAUS..148..388J
Altcode:
No abstract at ADS
Title: The New Cosmos
Authors: Unsöld, Albrecht; Baschek, Bodo; Brewer, W. D.
Bibcode: 1991neco.book.....U
Altcode: 1991QB43.2.U5713...
Astronomy, astrophysics and space research have developed extensively
and rapidly in the last few decades. The new opportunities
for observation afforded by space travel, the development of
high-sensitivity light detectors and the use of powerful computers
have revealed new aspects of the fascinating world of galaxies and
quasars, stars and planets. The fourth, completely revised edition
of The New Cosmos bears witness to this explosive development. It
provides a comprehensive but concise introduction to all of astronomy
and astrophysics. It stresses observations and theoretical principles
equally, requiring of the reader only basic mathematical and scientific
background knowledge. Like its predecessors, this edition of The New
Cosmos will be welcomed by students and researchers in the fields of
astronomy, physics and earth sciences, as well as by serious amateur
astronomers.
Title: Der neue Kosmos.
Authors: Unsöld, A.; Baschek, B.
Bibcode: 1991dnk..book.....U
Altcode:
Contents: 1. Einführung. 2. Klassische Astronomie. Das
Planetensystem. 3. Astronomische and astrophysikalische
Instrumente. 4. Sonne und Sterne. Astrophysik des einzelnen
Sterns. 5. Sternsysteme: Milchstraße und Galaxien. Kosmogonie und
Kosmologie. 6. Entstehung des Planetensystems. Entwicklung der Erde
und des Lebens. For the English translation of this fifth, revised
and enlarged German edition see 003.001.
Title: Book-Review - the New Cosmos
Authors: Unsold, A.; Baschek, B.; Priebe, A.
Bibcode: 1990AN....311..370U
Altcode:
No abstract at ADS
Title: Abundances from B stars of the Magellanic Clouds.
Authors: Reitermann, A.; Baschek, B.; Stahl, O.; Wolf, B.
Bibcode: 1990A&A...234..109R
Altcode:
Model atmosphere analyses of two B giants, NGC 1818/D 12 and NGC
330/3, which are probably members of blue globular clusters of the
LMC and SMC, respectively, are carried out. The analyses are based
on CASPEC spectrograms (resolution ~20.000 S/N >/~ 50), on IUE low
dispersion spectrograms (both SWP and LWP) and on UBVRI photometry. The
analysis is carried out differentially with respect to the galactic
star HR 3663 (B3III) which has been observed with the same instruments
(CASPEC and IUE). The observations are best fitted by model atmospheres
with effective temperatures (T_eff_) and surface gravities (log g) of
17,900 / 2.85 and 18,700 / 3.00 for the LMC and SMC star, respectively,
and a microturbulent velocity of ξ = 10 km s^-1^ for both stars. A
deficiency of the metals (without CNO) of {DELTA} log ɛ, = -0.8
and -1.1 is derived for the LMC and SMC star, respectively. The CNO
pattern is surprising; whereas C behaves like the rest of the metals,
N is considerably and O significantly overabundant. The abundances
are compared with data of H II regions and of late type stars of the
field and in clusters, found in the literature. From the comparatively
well known distances and hence luminosities and the model parameters,
the radius and the mass of both stars are derived. We obtain R = 22.8
R_sun_ and M = 15 M, for NGC 1818/D12 and R = 23.9 R_sun_ and M =
19 M_sun_ for NGC 330/3. These values agree within the uncertainties
of our analyses with the values estimated from evolutionary tracks.
Title: Line radiation from media with random source functions.
Authors: Baschek, B.; Wehrse, R.
Bibcode: 1990JQSRT..44..159B
Altcode:
Frequently, the runs of temperature and density in line emitting
media are not smooth but show statistical fluctuations. Consequently,
the emergent intensities are no longer deterministic but have to
be described by statistical distribution functions w. The authors
derive closed expressions for w, for lines from two-level atoms. They
are exact if the Planck function has a stochastic depth dependence
and other quantities are deterministic, and in the general case,
are correct to first order in the statistical perturbations. The
depth dependences of the extinction coefficient, the de-excitation
parameter and the redistribution function may be chosen arbitrarily,
but must be prescribed.
Title: Fe II lines from laboratory and astrophysical sources.
Authors: Baschek, B.; Johansson, S.
Bibcode: 1990JQSRT..44..215B
Altcode:
No abstract at ADS
Title: Element abundances in the blue globular cluster NGC 2004
(LMC) derived from B Stars.
Authors: Baschek, B.; Jüttner, A.; Scholz, M.; Stahl, O.; Szeifert,
T.; Wolf, B.
Bibcode: 1990AGAb....4...31B
Altcode:
No abstract at ADS
Title: Chemical abundances in early B-type stars.
Authors: Szeifert, T.; Jüttner, A.; Stahl, O.; Wolf, B.; Baschek, B.
Bibcode: 1990AGAb....4...32S
Altcode:
No abstract at ADS
Title: Accuracy of abundances from stars in near-by galaxies
Authors: Baschek, B.
Bibcode: 1990LNP...356...91B
Altcode: 1990aeas.conf...91B
Abundance determinations in near-by galaxies are discussed on the basis
of analyses of individual stars. Accurate abundances for a large number
of elements require highresolution spectra with . Reasonable results can
still be obtained with R - 103. At these resolutions, confusion by other
stars in the aperture is not a serious problem. Compared to supergiants,
near-main sequence B stars have the advantage that their analysis is
not severely affected by NLTE effects and that their surface composition
is not contaminated by processed matter. At present, these stars can be
reached with R 104 in the Magellanic Clouds. The very large telescopes
of the 1990's will make them accessible in M31 with high resolution. As
an illustration, spectra of two near-main sequence B stars in the LMC
and SMC with m v - 14 mag , obtained with CASPEC at the 3.6 m telescope
of ESO are presented, and preliminary abundance results are reported.
Title: How many lines make a model atmosphere?
Authors: Baschek, B.
Bibcode: 1990asos.conf...33B
Altcode:
No abstract at ADS
Title: Element abunances in the Magellanic Clouds
Authors: Baschek, B.
Bibcode: 1990nuas.symp...49B
Altcode:
No abstract at ADS
Title: Book-Review - the New Cosmos
Authors: Unsold, A.; Baschek, B.; Kasimenko, T. V.
Bibcode: 1989SvA....33..568U
Altcode:
No abstract at ADS
Title: Coordinated investigation of selected regions in the Magellanic
Clouds.
Authors: de Boer, K. S.; Azzopardi, M.; Baschek, B.; Dennefeld, M.;
Israel, F. P.; Molaro, P.; Seggewiss, W.; Spite, F.; Westerlund, B. E.
Bibcode: 1989Msngr..57...27D
Altcode: 1989Mgr....57...27D
The greatly enhanced observational Possibilities for research in the
Magellanic Clouds, such as bigger telescopes and the CCD as detector,
has led the way to studies hitherto unimagined. The possibility to
reach 60 kpc distant stars of fifth absolute magnitude (i. e. down to
main-sequence stars fainter than the Sun) or to obtain stellar spectra
to do a fine-analysis of atmospheric temperature and composition
has mightily raised the importance of the astrophysical laboratory
called Magellanic Clouds. In particular the study of the intricately
interwoven processes of formation of stars from progenitor gas clouds
and the evolution of stellar complexes can in our times superbly be
investigated by observing the Magellanic Cloud constituents.
Title: Chemical Abundances from B-Stars in the Magellanic Clouds
Authors: Reitermann, A.; Stahl, O.; Wolf, B.; Baschek, B.
Bibcode: 1989Ap&SS.156..113R
Altcode:
We observed near-Main-Sequence B-stars in the Magellanic Clouds with
the 3.6 m telescope and CASPEC at La Silla. We obtained spectra of
high resolution and high S/N-ratio. The stars are members of the blue
globular clusters NGC 1818 (LMC) and NGC 330 (SMC). The spectra are
used for differential abundance analyses using ι HER as galactic
reference star. Apart from CNO the metals are underabundant by about
a factor of three and four for the LMC and SMC star, respectively. The
CNO pattern is interesting since in both stars oxygen is considerably
more abundant than carbon.
Title: Element abundances in the Magellanic Clouds
Authors: Baschek, B.
Bibcode: 1989nuas.conf...49B
Altcode:
The author reports on the analysis of high-resolution spectra (λ/Δλ
= 2×104) of two near-mainsequence B stars of mv
≅ 14 mag with the CASPEC echelle spectrograph at the 3.6 m telescope
of ESO with a signal-to-noise ratio ≥50. These stars, No. D 12 in NGC
1818 of the LMC and No. 3 in NGC 330 of the SMC, are members of blue
globular cluster. Since they are not much evolved their composition is
expected to resemble that of the gas. The observable elements bridge
the abundance information for lighter elements accessible from H II
regions and planetary nebulae on the one hand, and for the heavier
elements from the cooler supergiants on the other hand.
Title: Institut für Theoretische Astrophysik. Jahresbericht für
1988.
Authors: Tscharnuter, W. M.; Baschek, B.
Bibcode: 1989MitAG..72..149T
Altcode:
No abstract at ADS
Title: Element abundances in the Magellanic clouds from B stars.
Authors: Baschek, B.; Juttner, A.; Reitermnn, A.; Scholz, M.; Stahl,
O.; Wolf, B.
Bibcode: 1989AGAb....3..114B
Altcode: 1989AGAb....3..116B; 1989MitAG...3..116B
No abstract at ADS
Title: The chemical composition of the lambda Bootis stars.
Authors: Baschek, B.; Slettebak, A.
Bibcode: 1988A&A...207..112B
Altcode:
Measurements of the equivalent widhts of 24 UV lines from IUE spectra of
10 λ Bootis or suspected λ Bootis stars and 19 normal standard stars
of spectral types B8-A7 are compared with line strengths calculated
from model atmospheres. The light elements (C, N, and O) in the λ Boo
stars are in the range slightly overabundant relative to the standard
(solar composition) stars. On the other hand, the heavier elements (Mg,
Al, Si, S, Mn, Fe, and Ni) are moderately deficient (≅0.5 dex) in the
λ Boo stars compared to the standard stars. The results are difficult
to understand in terms of nucleosynthesis, nor is an explanation based
on a possible low-abundance fluctuation in the interstellar medium
at the time of star formation very satisfactory. A model based on the
diffusion hypothesis has attractive features, but the rapid rotation
of the λ Boo stars may present difficulties.
Title: The analysis of spectra of novae taken near maximum.
Authors: Stryker, L. L.; Hestand, J.; Starrfield, S.; Wehrse, R.;
Hauschildt, P.; Spies, W.; Baschek, B.; Shaviv, G.
Bibcode: 1988ESASP.281a.149S
Altcode: 1988IUES....1..149S; 1988IUE88...1..149S; 1988uvai....1..149S
A project to analyze ultraviolet spectra of novae obtained at or near
maximum optical light is presented. These spectra are characterized
by a relatively cool continuum with superimposed permitted emission
lines from ions such as Fe II, Mg II, and Si II. Spectra obtained
late in the outburst show only emission lines from highly ionized
species and in many cases these are forbidden lines. The ultraviolet
data will be used with calculations of spherical, expanding, stellar
atmospheres for novae to determine elemental abundances by spectral
line synthesis. This method is extremely sensitive to the abundances
and completely independent of the nebular analyses usually used to
obtain novae abundances.
Title: Line radiation from accretion discs: Spatially resolved
distribution
Authors: Baschek, B.; Adam, J.; Plate, R.; Stoerzer, H.; Wehrse, R.
Bibcode: 1988AdSpR...8b.315B
Altcode: 1988AdSpR...8..315B
Detailed geometrically thin α-disc models are constructed and their
spatially resolved emerging line spectrum is calculated by solving
the equation of radiative transport along a large number of lines of
sight. Application to the Hα emission of the cataclysmic system Z Cha
shows that - in contrast to black body or model atmosphere approaches
- the observed emission line characteristics of white dwarf discs are
well described.
Title: General introduction to the 'Fe II problem'
Authors: Baschek, B.
Bibcode: 1988ASSL..138....1B
Altcode: 1988IAUCo..94....1B; 1988pffl.proc....1B
A brief historical introduction is given to selected problems
regarding observations and interpretations of iron lines in
astronomical objects. The results of early spectroscopy of the sun
and of early quantitative stellar analyses using quantum mechanics
are reviewed. Early quantitative analyses of Fe emission lines are
summarized, and the development of the 'iron problem' of the 1960s is
described. Some present-day Fe II problems are discussed.
Title: Chemical Abundances from Main Sequence B Stars in the
Magellanic Clouds
Authors: Baschek, B.
Bibcode: 1988iue..prop.3274B
Altcode:
No abstract at ADS
Title: Doubly Excited Feii Lines in the A-Star 21-PEGASI
Authors: Adam, J.; Baschek, B.; Brage, T.; Nilsson, A. E.; Johansson,
S.
Bibcode: 1988ASSL..138..243A
Altcode: 1988IAUCo..94..243A; 1988pffl.proc..243A
The majority of about 120 ultraviolet iron lines, among them strong
lines around 1850 Å, which have recently been identified as transitions
from doubly excited levels in Fe II during a new investigation of the
hollow-cathode spectrum of iron, coincide with absorption lines in the
high-resolution IUE spectrum of the sharp-lined A star 21 Pegasi. Model
atmosphere calculations of the line strengths confirm the identification
for about one third of the lines.
Title: Der neue Kosmos
Authors: Unsold, Albrecht; Baschek, B.
Bibcode: 1988dnk..book.....U
Altcode: 1988QB43.2.U57.....
No abstract at ADS
Title: Accidental Degeneracy Between Doubly Excited States in Feii
Authors: Brage, T.; Nilsson, A. E.; Johansson, S.; Baschek, B.;
Adams, J.
Bibcode: 1988ASSL..138...63B
Altcode: 1988IAUCo..94...63B; 1988pffl.proc...63B
No abstract at ADS
Title: New laboratory recordings of Fe II in the IUE region
Authors: Baschek, Bodo; Johansson, Sveneric
Bibcode: 1988ASSL..138...35B
Altcode: 1988pffl.proc...35B; 1988IAUCo..94...35B
An investigation of the laboratory spectrum of Fe II in the wavelength
region 1300 - 3250 Å is in progress. The authors present here a
preliminary report on the 1700 - 3250 Å range, where high-resolution
spectra from a hollow-cathode lamp contain some 11500 lines of Fe I
and Fe II. The authors plan to extend the term analysis of Fe II and
present all identified lines in an updated multiplet table.
Title: Der neue Kosmos
Authors: Unsöld, Albrecht; Baschek, Bodo
Bibcode: 1988neko.book.....U
Altcode:
Astronomie, Astrophysik und Weltraumforschung haben innerhalb weniger
Jahrzehnte eine geradezu explosive Entwicklung genommen. Die neuen
Beobachtungsmöglichkeiten durch die Raumfahrt, die Entwicklung
hochempfindlicher Lichtdetektoren und der Einsatz leistungsstarker
Computer haben uns neuartige Aspekte in der faszinierenden Welt der
Galaxien und Quasare, der Sterne und Planeten erschlossen. Nachdem die
dritte Auflage vergriffen ist, trägt die vorliegende vierte, völlig
neubearbeitete Auflage des NEUEN KOSMOS dieser stürmischen Entwicklung
Rechnung. In überschaubarem Umfang wird - bei bescheidenen Ansprüchen
an die mathematisch-naturwissenschaftliche Vorbildung des Lesers -
eine zusammenhängende Einführung in das Gesamtgebiet der Astronomie
und Astrophysik gegeben, welche die Beobachtungen und die Grundgedanken
ihrer theoretischen Deutung in gleicher Weise berücksichtigt. Auch in
seiner neuen Gestalt wird der NEUE KOSMOS den Studenten und Forschern
in Bereichen der Astronomie, Physik und Geowissenschaften sowie einem
weiten Kreis ernsthaft interessierter Amateure viel Neues und viel
Freude bringen.
Title: Ultraviolet Doubly Excited Fe II Lines in the Laboratory and
in the A-Type Star 21 Pegasi
Authors: Adam, J.; Baschek, B.; Johansson, S.; Nilsson, A. E.;
Brage, T.
Bibcode: 1987ApJ...312..337A
Altcode:
During a new investigation of the UV hollow-cathode spectrum of iron,
some 120 lines were identified, among them strong lines around 1850 A,
as transitions from doubly excited levels in Fe II. A combination of
selective population by charge-transfer processes in the laboratory
source and of a strong configuration interaction is probably the cause
of unexpectedly large intensities of a great number of lines. The
new energy levels and calculated oscillator strengths for the newly
identified transitions are presented. Most of the new lines coincide
with absorption lines in the high-resolution IUE spectrum of the
sharp-lined A star 21 Pegasi. For about one-third of them, located
mostly in the region 1750-1900 A, the identifications are confirmed
by modal atmosphere calculations. For the remaining coincidences the
stellar line is probably blended with another contributor.
Title: Abundance Patterns in Some Old Stars
Authors: Baschek, Bodo
Bibcode: 1987LNP...287..174B
Altcode: 1987nuas.proc..174B
The abundance patterns in old, extremely metal-poor stars are
discussed. Particular emphasis is placed on the dwarf carbon star
G 77-61, which has the lowest iron abundance found in a near-main
sequence star up to now. The abundance characteristics of this star
are interpreted in terms of contamination by mass transfer from an
evolved primary.
Title: Fifteen Years of Sonderforschungsbereich in Heidelberg -
Research on Circumstellar Matter
Authors: Baschek, B.
Bibcode: 1987IAUS..122....1B
Altcode:
No abstract at ADS
Title: Synthetic Spectra for Supernovae II
Authors: Spies, W.; Hauschildt, P.; Wehrse, R.; Baschek, B.; Shaviv, G.
Bibcode: 1987LNP...287..316S
Altcode: 1987nuas.proc..316S
The results of an attempt to study the spectra of supernova photospheres
using detailed photospheric models are reported. The photosphere is
calculated assuming a spherical configuration, a density following
a power law with exponent 10, the existence of LTE and radiative
equilibrium, and expansion velocity increasing proportionally to the
radius. The calculated spectra and effective temperature agree well
with the observed spectrum of SN 1980 K. Interesting correspondences
are found between the UV fluxes of SN 1987 A and the energy distribution
of a blanketed model with T(eff) = 8000 K and v(exp) = 15,000 km/s.
Title: Observation of lambda lambda 1600 and 3040 features in the
spectra of field horizontal branch stars.
Authors: Jaschek, M.; Baschek, B.; Jaschek, C.; Heck, A.
Bibcode: 1985A&A...152..439J
Altcode:
Low-resolution IUE spectra reveal broad flux depressions at λλ1600
and 3040 Å in several horizontal-branch stars. These features have
previously been found in the λ Boo stars, which are peculiar stars
of a different population but share the property of metal-weakness
with the horizontal-branch stars.
Title: Book-Review - the New Cosmos
Authors: Unsold, A.; Baschek, B.
Bibcode: 1984Sci...223.1096U
Altcode:
No abstract at ADS
Title: The ultraviolet (IUE) spectra of the lambda Bootis stars.
Authors: Baschek, B.; Koeppen, J.; Scholz, M.; Wehrse, R.; Heck, A.;
Jaschek, C.; Jaschek, M.
Bibcode: 1984A&A...131..378B
Altcode:
Ultraviolet spectra of several λ Boo stars and λ Boo candidates have
been obtained with the IUE satellite in low- and in high-resolution. It
is possible to discriminate the λ Boo stars from the normal A stars on
low resolution spectra by their strong absorption features at λλ1600,
1657(C I), 1931(C I), and 3040 Å. The λ1600 feature, about 80 Å
wide and not resolved into lines in the high-resolution mode, and
the λ3040 feature remain unidentified. The well-developed spectrum
of neutral carbon in λ Boo suggests that C (and possibly also N)
may not share the underabundances of the heavier elements.
Title: Book-Review - the New Cosmos - ED.3
Authors: Unsold, A.; Baschek, B.
Bibcode: 1984S&T....67..428U
Altcode:
No abstract at ADS
Title: The role of oscillator strengths in modelling and analysing
stellar spectra.
Authors: Baschek, B.
Bibcode: 1984PhST....8...21B
Altcode: 1984PhyS....8...21B
In order to elucidate the needs for atomic data, in particular for
oscillator stengths, an overview is given over the role of line
absorption in the quantitative analysis of high-resolution stellar
spectra.
Title: Lambda Bootis Stars
Authors: Baschek, B.
Bibcode: 1983iue..prop.1611B
Altcode:
No abstract at ADS
Title: The new cosmos
Authors: Unsold, Albrecht; Baschek, B.
Bibcode: 1983neco.book.....U
Altcode: 1983QB43.2.U5713...
No abstract at ADS
Title: High-Resolution Spectrosopy of Blue Halo Stars
Authors: Baschek, B.
Bibcode: 1983iue..prop.1579B
Altcode:
No abstract at ADS
Title: Needs for atomic data for quantitative analysis of stellar
spectra.
Authors: Baschek, B.
Bibcode: 1983HiA.....6..781B
Altcode:
Emphasis is placed on the needs for atomic data arising from ultraviolet
spectra. The treatment is restricted to the photospheric parts of
stellar spectra, characterized by a continuum with absorption lines. It
is noted that typical temperatures range from a few thousand K to almost
100,000 K, with densities exceeding 10 to the 11th/cu cm. Figures are
included giving three examples of parts of solar and stellar spectra in
the ultraviolet; these serve as illustrations of the type and quality
of the observational material now available for ultraviolet spectrum
analyses. The discussion covers stellar absorption coefficients,
the completeness of line identification, and the specific needs for
atomic data.
Title: Miscellaneous remarks on theoretical aspects of UV stellar
classification
Authors: Baschek, B.
Bibcode: 1982ESASP.182..115B
Altcode: 1982uvsc.conf..115B
Stellar atmosphere parameters and the importance of spectral resolution
for stellar classification are discussed and analyses of blue halo
stars are summarized. A UV classification scheme, involving effective
temperature, surface gravity, an abundance parameter (given variations
in He, CNO, or metal abundance) and peculiarity affixes similar to
the MK system, is advocated. Spectral resolution of 1 A at 1500 A can
be achieved, using high dispersion IUE spectra. Analysis of the OB
subdwarf HD 149382 shows the importance of high dispersion spectra
compared with the 6A low dispersion observations. Anomalies such as
silicon underabundance by a factor 40,000, are clearly revealed. Lack
of atomic data (line identification lists, oscillator strengths)
limits line identification, so quantitative calibration, especially
at low reduction, is difficult unless the classification features are
dominated by a very few, very strong, lines.
Title: The OB subdwarf Feige 66, a chemical-composition twin to
HD 149382.
Authors: Baschek, B.; Hoeflich, P.; Scholz, M.
Bibcode: 1982A&A...112...76B
Altcode:
The ultraviolet (1160 to 3230 A) and the blue spectrum of the OB
subdwarf, Feige 66, is analyzed differentially to HD 149382. The
effective temperature, the surface gravity and the helium abundance
of Feige 66 deviate only very little from those of HD 149382. The line
spectra are almost identical, and the same strange abundance pattern as
in HD 149382 is found in Feige 66. In particular, silicon is extremely
deficient relative to a solar mixture. A sulfur enrichment in Feige
66 is the only significant heavy element abundance difference between
the two stars.
Title: Analysis of Feige 66, another extremly silicon-deficient
OB subdwarf.
Authors: Baschek, B.; Hoflich, P.; Scholz, M.
Bibcode: 1982ESASP.176..309B
Altcode: 1982IUE3r......309B; 1982iue..conf..309B
A high resolution IUE spectrum from 1160 to 3230 A of Feige 66 was
analyzed by model atmosphere techniques differentially to OB subdwarf
HD 149382. The stars have similar effective temperatures and surface
gravities, and exhibit remarkably similar abundance patterns.
Title: Angle-Averaged Redistribution Function in the Laboratory Frame
Authors: Seitz, M.; Baschek, B.; Wehrse, R.
Bibcode: 1982A&A...109...10S
Altcode:
Laboratory frame angle-averaged redistribution functions are calculated
for the case that upper and lower level are broadened by elastic
and inelastic collisions as well as by radiative processes. The
computations are based on the atomic-frame redistribution functions
derived by Cooper and Ballagh (1978) in the framework of the density
matrix formalism. The results are interpreted as a superposition of
complete redistribution functions involving Gauss and Lorentz profiles
and of δ-functions representing Rayleigh scattering.
Title: On the spectrum of the Herbig Be-Star HD 200775.
Authors: Baschek, B.; Beltrametti, M.; Koeppen, J.; Traving, G.
Bibcode: 1982IAUS...98..499B
Altcode:
No abstract at ADS
Title: Spectral analysis of the OB subdwarf HD 149382.
Authors: Baschek, B.; Kudritzki, R. P.; Scholz, M.; Simon, K. P.
Bibcode: 1982A&A...108..387B
Altcode:
The ultraviolet and blue spectrum of the OB subdwarf HD 149 382 is
analyzed in an investigation of the star's evolutionary status. An
effective temperature of 35,000 + or - 2000 K is derived from fitting
the observed continuum, hydrogen lines and helium lines to fluxes
of unblanketed non-LTE models. LTE analyses of heavy-element lines
yield deficiencies of carbon and oxygen and normal nitrogen abundance
compared to the sun, which indicates the CNO cycle's possession of the
material. Calcium is overabundant, phosphorus and sulfur are normal,
and aluminum and silicon are deficient. A tentative explanation of the
abundance pattern in terms of the diffusion hypothesis is proposed,
and the C/N/O abundance ratios indicate that the CNO cycle operated
on a mixture which originally may have been poorer in the heavier
elements than the solar mixture.
Title: Book-Review - the New Cosmos 3ED.ENL.
Authors: Unsold, A.; Baschek, B.; Bruck, H. A.
Bibcode: 1982Obs...102...17U
Altcode:
No abstract at ADS
Title: On the spectrum of the Herbig Be star HD 200775.
Authors: Baschek, B.; Beltramitti, M.; Koppen, J.; Traving, G.
Bibcode: 1982A&A...105..300B
Altcode:
On the basis of high-dispersion spectra and other observational
material, HD 200775 is reanalyzed using ι Her as a comparison star. By
comparing the depths in the wings of Hγ and Hδ and the equivalent
widths of He I lines with predictions from model atmospheres we find
Teff =17000±1000 K (in the scale of Kurucz' 1979 models)
and log g [cm-2] = 3.6±0.3 corresponding to a spectral type
of B 3 V. This is consistent with the continuum energy distribution if
one allows for some circumstellar emission The interstellar absorption
features at 4430 and 2200 Å are of unusual weakness. The strength of
the Hα emission requires a substantial rate of photoionization from
the first excited level (n =2) of hydrogen which probably arises from
a compact envelope. This is in accord with the finding that the radio
emission at λ2 cm is less than 3 mJy.
Title: Book-Review - the New Cosmos
Authors: Unsold, A.; Baschek, B.; Frohlich, H. E.
Bibcode: 1982AN....303..104U
Altcode:
No abstract at ADS
Title: Landolt-Börnstein: Numerical Data and Functional Relationships
in Science and Technology - New Series " Gruppe/Group 6 Astronomy and
Astrophysics " Volume 2 Schaifers/Voigt: Astronomy and Astrophysics
/ Astronomie und Astrophysik " Stars and Star Clusters / Sterne
und Sternhaufen
Authors: Aller, L. H.; Appenzeller, I.; Baschek, B.; Duerbeck, H. W.;
Herczeg, T.; Lamla, E.; Meyer-Hofmeister, E.; Schmidt-Kaler, T.;
Scholz, M.; Seggewiss, W.; Seitter, W. C.; Weidemann, V.
Bibcode: 1982lbg6.conf.....A
Altcode:
No abstract at ADS
Title: Lambda Bootis Stars
Authors: Baschek, B.
Bibcode: 1982iue..prop.1277B
Altcode:
No abstract at ADS
Title: Institut für Theoretische Astrophysik. Jahresbericht für
1981.
Authors: Baschek, B.; Traving, G.
Bibcode: 1982MitAG..56..177B
Altcode:
No abstract at ADS
Title: On the stimulated emission terms in partial redistribution
calculations
Authors: Baschek, B.; Oxenius, J.; Mihalas, D.
Bibcode: 1981A&A....97...43B
Altcode:
It is shown that the formulation given by Mihalas (1978) of the
stimulated emission term in partial redistribution calculations is
incorrect. It is noted that in the solar and stellar computations
presented thus far in the literature this error is of no importance
because the stimulated emission terms were negligible. However,
for computations for lines in which h-nu/kT is not large compared
with unity, the error could have serious consequences and the correct
formulation should therefore be used. To this end, corrected, albeit
approximate, equations are given for the various cases of interest.
Title: Der neue Kosmos
Authors: Unsöld, A.; Baschek, B.
Bibcode: 1981neko.bookR....U
Altcode:
No abstract at ADS
Title: Strange abundances in an OB-subdwarf based on IUE observations.
Authors: Baschek, B.; Kudritzki, R. P.; Scholz, M.; Simon, K. P.
Bibcode: 1981Lie81.R....451B
Altcode:
No abstract at ADS
Title: O- and B-type subdwarfs.
Authors: Baschek, B.
Bibcode: 1981ebds.conf....3B
Altcode:
No abstract at ADS
Title: High-Resolution Spectroscopy of Blue Halo Stars
Authors: Baschek, B.
Bibcode: 1981iue..prop..885B
Altcode:
No abstract at ADS
Title: Der neue Kosmos
Authors: Unsöld, A.; Baschek, B.
Bibcode: 1981neko.bookQ....U
Altcode:
No abstract at ADS
Title: High-Resolution Spectroscopy of Blue Halo Stars
Authors: Baschek, B.
Bibcode: 1981iue..prop..990B
Altcode:
No abstract at ADS
Title: Strange Abundances in an Ob-Subdwarf from IUE Observations
Authors: Baschek, B.; Kudritzki, R. P.; Scholz, M.; Simon, K. P.
Bibcode: 1981LIACo..23..451B
Altcode: 1981cpsu.conf..451B
No abstract at ADS
Title: Institut für Theoretische Astrophysik. Jahresbericht für
1980.
Authors: Baschek, B.; Traving, G.
Bibcode: 1981MitAG..53..167B
Altcode:
No abstract at ADS
Title: Der neue Kosmos
Authors: Unsold, Albrecht; Baschek, B.
Bibcode: 1981dnk..book.....U
Altcode: 1981QB43.2.U57.....
No abstract at ADS
Title: Observations with the International Ultraviolet Explorer -
Need for Atomic Data in Astrophysics
Authors: Baschek, B.
Bibcode: 1981ecap.conf...46B
Altcode:
No abstract at ADS
Title: Charge transfer in the reversible C + H/+/ yields C/+/ +
H reaction and the C I lambda1101 absorption edge in A stars
Authors: Che, A.; Baschek, B.
Bibcode: 1980A&A....86L...7C
Altcode:
The paper examines the simplified non-LTE calculations of the C I
lambda1101 absorption edge performed for model atmospheres of effective
temperatures of 10,000 and 11,000 K and a surface gravity of 10,000
cm/s, including the charge transfer reaction C + H(+) reversibly
yields C(+) + H + 2.34 eV. The rate coefficient suggested by Steigman
(1975) in an analysis of the hot intercloud medium is adopted; the
neutral carbon atom is approximated by three levels plus continuum. The
ionization equilibrium C I/C II in early A-type stellar atmospheres is
significantly influenced by the charge transfer reaction; the effect
decreases with the increasing effective temperature.
Title: The far ultraviolet spectrum of the B-type subdwarf HD 205805.
Authors: Baschek, B.; Kudritzki, R. P.; Scholz, M.
Bibcode: 1980ESASP.157..319B
Altcode: 1980iue..conf..319B; 1980IUE2n......319B
High resolution International Ultraviolet Explorer spectra of HD 205 805
(sdB, mv = 10.2, Teff = 26500 K, g = 100.00 cm
s to the minus 2d power) were obtained in the range 1170-3230 A. Some
1150 absorption lines with central depths equal to or greater than 0.2
were measured. A radial velocity of -80 km sec permitted a distinction
to be made between stellar and interstellar lines. The stellar spectrum
exhibits many lines of doubly ionized elements, especially of C, Si,
S, Ti, Cr, Mn and Fe. Preliminary estimates of selected abundances
are given by comparison with the normal B star gamma Peg.
Title: The far ultraviolet spectrum of the OB-type subdwarf HD 149382.
Authors: Baschek, B.; Kudritzki, R. P.; Scholz, M.
Bibcode: 1980ESASP.157..315B
Altcode: 1980iue..conf..315B; 1980IUE2n......315B
High resolution International Ultraviolet Explorer spectra of the
OB-type subdwarf HD 149 382 were obtained from lambda = 1160 to 3230
A. The stellar spectrum, which only shows hydrogen, helium and sulfur
lines in the blue, exhibits more than 1500 absorption features with
central depths greater than 0.2 in the far ultraviolet. He II 1640
is the only helium line found in this spectral region. The spectrum
is dominated by the doubly and triply ionized stages of carbon,
nitrogen and twelve heavier elements which are certainly or probably
present. Oxygen and eleven other elements are possibly present. The
Si IV resonance doublet at 1394 and 1403 A was not found. Preliminary
atmospheric parameters teff = 35000 K, g = 10 to the 5.5
power cm s to the -2 power, log NHe/N sub H = -1.4 were
derived.
Title: Institut für Theoretische Astrophysik. Jahresbericht für
1979.
Authors: Baschek, B.; Traving, G.
Bibcode: 1980MitAG..49..163B
Altcode:
No abstract at ADS
Title: Anomale Spektren von Roten Riesen. Kernreaktionen und
Mischungsprozesse bei der Sternentwicklung.
Authors: Baschek, B.
Bibcode: 1979S&W....18...82B
Altcode:
Analysis of various anomalous spectra of developed cool stars shows
that these spectra can largely be accounted for by anomalous chemical
compositions of the atmospheres of the stars. The means of transport of
burning products to the outer layers is still undetermined. Abundance
anomalies in S-stars and cool C-stars can be attributed to the operating
of neutron processes corresponding to the Ne-22 mechanism.
Title: Institut für Theoretische Astrophysik. Jahresbericht für
1978.
Authors: Baschek, B.; Traving, G.
Bibcode: 1979MitAG..46..146B
Altcode:
No abstract at ADS
Title: Abundances in evolved stars - Introductory report
Authors: Baschek, B.
Bibcode: 1979LIACo..22..327B
Altcode: 1979eiu..conf..327B; 1979eisu.conf..327B
After a brief outline of some problems in connection with the abundance
determination from stellar spectra, the chemical compositions of
post-mainsequence stars are discussed. Considered are those stars
whose abundances indicate that products of interior nuclear reactions
have been brought to the surface. Anomalies of He, CNO, C-12/C-13,
Li and heavy s-elements indicate the operation of hydrogen and helium
burning and of slow-neutron processes associated with helium shell
flashes, and provide information on mixing and mass loss mechanisms
in various evolutionary stages. Of particular interest are OBCN stars,
Wolf-Rayet-stars, helium stars, horizontal-branch stars, and the various
types of peculiar red giants and subgiants such as weak-G-band stars,
barium stars, carbon (C, CH, CH-like) stars and S stars. The observed
abundances suggest that transport of processed matter to the surface has
to be more efficient than indicated by current stellar evolution theory.
Title: B-Type Halo Stars
Authors: Baschek, B.
Bibcode: 1979iue..prop..324B
Altcode:
No abstract at ADS
Title: Institut für Theoretische Astrophysik. Jahresbericht für
1977.
Authors: Baschek, B.; Traving, G.
Bibcode: 1978MitAG..44..115B
Altcode: 1978MitAG..44..115.
No abstract at ADS
Title: The temperature probability function and infrared emissivity
of dust heated by randomly distributed stars.
Authors: Baschek, B.; Gampper, G.; Traving, G.
Bibcode: 1978A&A....62..223B
Altcode:
Summary. The temperature probability function of interstellar dust
grains which are heated by randomly distributed stars is calculated
upon the assumption of (i) uniformly distributed dust of uniform size
and optical properties, and (ii) stars of uniform luminosity. The
absorption of the heating stellar radiation by the interstellar medium
is taken into account by introducing a shielding distance r . The
probability distribution depends essentially on , the number of stars
within . The infrared emission of dust is calculated assuming different
power laws for the dust absorption coefficient, and the applicability
to astronomical objects is briefly discussed. Key words: heated dust -
infrared emission
Title: Comments on the Paper by A. E. Rydgren "T Tauri Stars and the
(J-H), (H-K) Diagram"
Authors: Baschek, B.; Wehrse, R.
Bibcode: 1977PASP...89..345B
Altcode:
The theoretical (J - H) and (H - K) color indices, calculated by Rydgren
(1976) for a hydrogen envelope of about 20,000 K surrounding T Tauri
stars, are noticeably changed when line radiation is taken into account
in addition to bound-free and free-free continuum emission. Key words:
T Tauri stars-infrared photometry
Title: Non-LTE analysis of neutral oxygen lines in A-type stars.
Authors: Baschek, B.; Scholz, M.; Sedlmayr, E.
Bibcode: 1977A&A....55..375B
Altcode:
Not Availablen-LTE calculations of neutral oxygen lines in A-type
stars sare performed by simultaneously solving the rate equations and
the sequations of radiative transfer and particle conservation, using
the smethod of complete linearisation. Oxygen is treated as a trace
element swith an abundance of loge0 =8.6 in Balmer line-blanketed model
satmospheres (in hydrostatic and radiative equilibrium) of effective
stemperatures Teff=17S0O, 10000 and 7500 K, surface gravities logg
=4.0, s2.5 and 1.0, and microturbulent velocities =0 and 5 km s- . For
the 7500 sK, logg =2.5 model an oxygen underabundance of a factor of
10 is also sconsidered in view of application to horizontal-branch
stars. The sneutral oxygen atom is approximated by the ground state,
the continuum sand seven excited levels of the quintet system,
comprising the stransitions 11302, 9265, 7771-5, 6465, 6158, 3947 and
1355 A. sTheoretical line profiles of the infrared triplet 7771- 5,
equivalent swidths of all lines, and level occupations are given for
the models sconsidered. Some additional details (e.g. transition rates)
are spresented for the 10000 K, logg =4 model. The dependence of the
non-LTE seffects on various parameters is briefly discussed. Pronounced
non-LTE seffects occur even in main- sequence models, e.g. strong
overpopulations sof the 3s 5S0 and 4p5P levels in the upper atmospheres
and substantial sstrengthening, compared to LTE values, of the infrared
11302, 9265 and s7771-5 lines. LTE abundance determinations based on
the 7771-5 triplet stherefore result in a significant overestimate of
the oxygen abundance s(by a factor of 10 to 100). Key words: Non-LTE
analysis oxygen - A stars sabundances
Title: Institut für Theoretische Astrophysik. Report for 1976.
Authors: Baschek, B.; Traving, G.
Bibcode: 1977MitAG..41..114B
Altcode:
No abstract at ADS
Title: Heidelberg-Königstuhl, Landessternwarte. Report for 1976.
Authors: Appenzeller, I.; Baschek, B.
Bibcode: 1977MitAG..41..116A
Altcode:
No abstract at ADS
Title: The chemical composition of the horizontal-branch star
Feige 86.
Authors: Baschek, B.; Sargent, A. I.
Bibcode: 1976A&A....53...47B
Altcode:
Summary. A model atmosphere abundance analysis based on blue high
dispersion spectrograms is carried out for the horizontal-branch B
star Feige 86. An effective temperature of Teff = 17500+ 1500 0K (on
the temperature scale f unblanketed models) and a surface gravity of
log g =4.2+0.2 are derived. It transpires that, with the exception of
carbon, which is more deficient in Feige 86, the abundance anomalies
are strikingly similar to those in the peculiar, Population I, B-type
"phosphorus star" 3 Cen A. Key words: Feige 86 horizontal branch stars
stellar abundance anomalies
Title: Der Ausbruch von V1057 Cygni.
Authors: Baschek, B.
Bibcode: 1976S&W....15..281B
Altcode:
The behavior of the variable star V 1057 Cyg, which increased its
brightness during an interval of a few months by almost six stellar
magnitudes, is similar to that of the star FU Ori in 1936/37. It
is known that V 1057 Cyg was a T Tauri star before the outburst. An
analysis of the characteristics of the outburst of V 1057 Cyg provides,
therefore, important information for a study of T Tauri stars and the
theory of stellar development. Attention is given to details concerning
the discovery of V 1057 Cyg, its study, the behavior of V 1057 Cyg
before the outburst, models of the photosphere, infrared observations,
the stellar mass, and an interpretation of the observed phenomena
Title: T-Tauri Sterne - Überblick über Beobachtungen und
Deutungsversuche.
Authors: Baschek, B.
Bibcode: 1976S&W....15..151B
Altcode:
The stars considered were first defined with respect to their
characteristics as members of a special group by Joy (1945,
1949). They are found in regions which exhibit intense dust absorption
properties. Their space density is relatively high. The stars must be
considered as young. Their study can, therefore, provide important
information concerning the early phases of stellar development. The
general characteristics of the stars are discussed, taking into account
stellar classification, spectral properties, and an interpretation of
the spectra. Attention is also given to details regarding the stage
of development reached by the stars.
Title: (invited Lecture)
Authors: Baschek, B.
Bibcode: 1976IAUS...72....3B
Altcode:
No abstract at ADS
Title: Lehrstuhl für Theoretische Astrophysik. Report 1975.
Authors: Baschek, B.; Traving, G.
Bibcode: 1976MitAG..39...97B
Altcode:
No abstract at ADS
Title: Strahlung staubgefüllter H II-Regionen
Authors: Baschek, B.; Wehrse, R.
Bibcode: 1976MitAG..38Q..77B
Altcode:
No abstract at ADS
Title: Radiation from inhomogeneous dusty Strömgren spheres.
Authors: Baschek, B.; Wehrse, R.
Bibcode: 1975A&A....43...29B
Altcode:
The characteristic behavior of the center-to-limb variation and the
integrated spectrum of dusty Stroemgren spheres is discussed on the
basis of simplified models with constant gas-to-dust ratios. It is
assumed that the ionization of the gas and the heating of the dust is
due to a central star (of type O 6 V). The density distribution is
assumed to be Gaussian. The spectral region considered, ranges from
radio frequencies to the near infrared (to about 0.8 micron), including
the region in which internal dust absorption becomes important.
Title: The OB-type subdwarf HD 149382 and the nature of the subdwarf
B stars.
Authors: Baschek, B.; Norris, J.
Bibcode: 1975ApJ...199..694B
Altcode:
Results are reported for analysis of high-dispersion spectra and
monochromatic emission measures of the OB-type subdwarf HD 149382. An
effective temperature of 40,000 K is determined together with a
surface gravity (log g) of 5.8. It is found that helium is deficient
by a factor of 10 as compared with Population I stars, sulfur is
overabundant by a factor of 10, and all other heavy elements are
probably underabundant. This star is shown to be an intermediate
case between the O and B subdwarf classes. Suggestions are made as
to the nature of Bp stars, B-type subdwarfs, and DA white dwarfs. The
evolutionary status of B subdwarfs is considered.
Title: Supernovae
Authors: Baschek, B.
Bibcode: 1975MitAG..36...33B
Altcode:
The characteristics of the various types of supernovae in galaxies
and the frequency of their appearance are discussed. Supernovae
in our Galaxy are considered along with the spectra of supernovae,
an interpretation of the light curves, and models for supernovae of
type I and type II. Attention is given to the processes of hydrostatic
carbon burning and explosive carbon burning. Light curves of several
supernovae are presented in graphs and the importance of a consideration
of statistical data in a discussion of the various models of supernovae
of type II is pointed out.
Title: Abundance anomalies in early-type stars.
Authors: Baschek, B.
Bibcode: 1975psae.book..101B
Altcode:
A summary is presented of the quantitative abundance data for some
selected groups of peculiar early-type stars. Problems related to
the determination of abundance anomalies are examined, taking into
account a definition of abundances, relative and normal abundances,
and model atmospheres of peculiar stars compared to normal stars. The
population I peculiar B stars are considered along with the CNO stars,
and the population II B stars. The origin of the Ap phenomenon is
discussed, giving attention to nuclear processes, nonnuclear processes,
the removal of surface abundance anomalies, and inferences from the
early-type peculiar stars.
Title: Problems in stellar atmospheres and envelopes
Authors: Baschek, B.; Kegel, W. H.; Traving, G.
Bibcode: 1975psae.book.....B
Altcode: 1975QB809.P76......
The energy flux of the sun is considered along with model stellar
atmospheres and heavy element abundances, the problems and properties
of helium stars, abundance anomalies in early-type stars, and A-type
horizontal-branch stars. Attention is also given to white dwarfs
and their place in galactic evolution, Herbig-Haro objects and T
Tauri Nebulae, circumstellar envelopes and mass loss of red giant
stars, cosmic masers, radio emission from stellar and circumstellar
atmospheres, and line formation in turbulent media. Individual items
are announced in this issue.
Title: Lehrstuhl für Theoretische Astrophysik. Report 1974.
Authors: Baschek, B.; Traving, G.
Bibcode: 1975MitAG..37...89B
Altcode:
No abstract at ADS
Title: Infrared emission of dust heated by randomly distributed stars
Authors: Baschek, B.; Traving, G.; Wehrse, R.
Bibcode: 1974A&A....36..147B
Altcode:
Summary. Theoretical infrared spectra of dust heated by the radiation
of randomly distributed stars are discussed, using the nearest star
approximation in order to calculate mean intensities. These spectra are
considerably flatter than emission with a uniform dust temperature. Key
words: infrared emission - heated dust
Title: A search for neutral iron lines in a Centauri.
Authors: Norris, J.; Baschek, B.
Bibcode: 1974ApJ...193..133N
Altcode:
A search for neutral iron lines, which were reported by Underhill and
Klinglesmith, in the helium spectrum variable a Cen has been carried
out on spectra taken in 1968/69. No lines of Fe i have been found around
the phase, 0.22, at which the lines were previously reported to be most
prominent. Subject headings: line identifications - spectrum variables -
star, individual
Title: Detectability and nature of CNO anomalies in early-type
main-sequence stars.
Authors: Baschek, B.; Scholz, M.
Bibcode: 1974A&A....30..395B
Altcode:
Summary. Using model atmosphere techniques, we calculate selected
spectral features in near-main-sequence stars in the range 0 B 5 for
eight different element mixtures which are chosen to characterize the
anomalous CNO line strengths discovered by Walborn. We discuss when
CNO abundance anomalies can be detected at classification dispersion
through anomalous line strengths or through inconsistencies from
different classification criteria. A comparison of our results with
the predictions by Paczynski (1973) does not give much support to
the hypothesis that meridional circulation causes the N type anomaly
in hot main-sequence stars. Key words: OB stars - Walborn's stars -
CNO anomalies
Title: On the detectability of Bp-type abundance anomalies in early
main-sequence stars.
Authors: Baschek, B.; Kodaira, K.; Scholz, M.
Bibcode: 1974A&A....34....1B
Altcode:
Summary. With model atmosphere techniques, we calculate selected
spectral features in near-main-sequence stars in the range from 0 9
to B 5 using anomalous element abundances which are typically found
in middle to late Bp type stars. We discuss whether these abundance
anomalies can be detected at classification dispersion in stars
earlier than about B 3. The observed absence of weak-helium-line
stars of the Si- and the -type implies the absence of anomalies of
these groups in early B stars. Anomalies typical of weakhelium-line
stars of the Ti-Sr-type and of manganese stars may escape detection
in classification work. Key words: Ap stars Bp stars abundance anomalies
Title: Lehrstuhl für Theoretische Astrophysik. Report 1973.
Authors: Baschek, B.; Traving, G.
Bibcode: 1974MitAG..35...91B
Altcode:
No abstract at ADS
Title: On the chemical abundances in the weak-helium-line star
alpha Sculptoris.
Authors: Baschek, B.
Bibcode: 1973A&A....25..333B
Altcode:
Summary. A brief discussion and comparison of the recent abundance
determinations in cc Scl by Schmitt (1972) and Vilhu (1972) is
given. Key words. cc Sculptoris - weak-helium4ine stars - abundances
Title: Ap-Sterne und Supernovae
Authors: Baschek, B.; Kegel, W. H.
Bibcode: 1973MitAG..34...84B
Altcode:
No abstract at ADS
Title: Lehrstuhl für Theoretische Astrophysik. Report 1972.
Authors: Baschek, B.; Traving, G.
Bibcode: 1973MitAG..33...88B
Altcode:
No abstract at ADS
Title: A model for the helium spectrum variable a Centauri.
Authors: Norris, J.; Baschek, B.
Bibcode: 1972A&A....21..385N
Altcode:
Summary. We propose an empirical model to explain the observed
variations of the helium spectrum variable a Centauri. The model
consists of a rotating star, the surface of which consists of a
small helium rich region (spot), and a large helium deficient region
(non-spot). The non-spot resembles a weak-helium-line star with Te
=210000, logg =4.2 and y = N(He)/[N(He) + N(H)] =0.004. Assuming
that gravity remains constant over the surface, the observations of
continuum, helium and hydrogen line strengths are used to determine
the parameters of the two region model: the area of the spot, A =0.3 in
units of hemispheres, the difference in helium abundance A y = y(spot)
- y(non-spot) =0.8; and the difference in effective temperature A Te
= 16000. The variations of metallic lines and radial velocities can
then be explained with this model. In particular, we can simply obtain
the observed constancy of Si II lines and the variability of the Si
in lines. Because of differences in scale heights between the helium
rich and the helium poor regions we suggest that a magnetic field (
500 Gauss) may provide the restraining force necessary to maintain the
identity of the two regions. We speculate that the formation of the a
Centauri phenomenon requires a two stage process involving a transfer
of helium rich material from an evolving companion, together with the
process (whatever it may be) at work in the weak-helium-line stars. Key
words: a Centauri - helium spectrum variables - we ak-helium-line stars
Title: Abundance Anomalies in the ON Type Star HD 188209
Authors: Baschek, B.; Kodaira, K.; Scholz, M.
Bibcode: 1972ApL....12..227B
Altcode:
No abstract at ADS
Title: The Chemical Composition of the B-Type Subdwarf HD 4539
Authors: Baschek, Bodo; Sargent, Wallace L. W.; Searle, Leonard
Bibcode: 1972ApJ...173..611B
Altcode:
HD 4539 is one of the brightest known members of the class of early-type
high-latitude stars with very weak helinm lines Its spectrum is compared
to that of the standard main-sequence star L Her (which has already
been studied by others in detail), and a differential model-atmosphere
abundance analysis is reported. The He/H ratio is found to be 16
times smaller in the subdwarf than it is in normal B stars of the
solar neighborhood. The abundance peculiarities of this star are not
confined to helium. The N/H ratio is higher than normal by a factor
of 3 and the 0/H ratio is lower than normal by a factor exceeding 10
while the C/H ratio is normal. `i,T speculate concerning the origins
of this remarkable composition, but have no convincing hypothesis to
put forward. Ve argue that the helium deficiency in this star cannot
be regarded as evidence for a low primordial helium abundance.
Title: Lehrstuhl für Theoretische Astrophysik. Report 1971.
Authors: Baschek, B.; Traving, G.
Bibcode: 1972MitAG..31..312B
Altcode:
No abstract at ADS
Title: The spectrum of zeta Puppis (O5f).
Authors: Baschek, B.; Scholz, M.
Bibcode: 1971A&A....15..285B
Altcode:
We present new observations of the line spectrum of Pup (0 5 f) from
3150 to A 8600. The absorption spectrum is similar to that of 9 Sgr
(0 5). There are, however, features which poilit to a later and others
which point to an earlier spectral type than 9 Sgr. The emission
spectrum shows deviations from typical Of type spectra, e. g. C rn
5696 is absent, and C Iv 5802 12 appears in emission. The existence
of a much fainter secondary WoIf-Rayet component cannot completely
be ruled out. The effective temperature derived from the absorption
line spectrum, Tvff 500000, is considerably higher than Tvff = 31000 +
25000 deduced from the interferometric diameter measurement of Davis
et al. (1970). It is suggested that this discrepancy is reduced if
effects of rapid rotation and, possibly, of interstellar absorption
are taken into consideration. Key words: Puppis - Of stars
Title: Erratum; The Absolute Magnitude of Y Velorum
Authors: Baschek, B.
Bibcode: 1971A&A....12R.322B
Altcode:
No abstract at ADS
Title: Erratum; The Composite Spectrum of y2 Velorum
Authors: Baschek, B.; Scholz, M.
Bibcode: 1971A&A....12Q.322B
Altcode:
No abstract at ADS
Title: The composite spectrum of gamma 2 Velorum.
Authors: Baschek, B.; Scholz, M.
Bibcode: 1971A&A....11...83B
Altcode:
Equivalent widths of absorption lines of the 0 component of the
spectroscopic binary 8 Vel (WC 8 + 08) are measured on high-dispersion
spectrograms. By comparison with seven OB spectra, the 0 star is
classified as 08, and its visual continuum is found to be 1 to 1.8
magnitudes brighter than that of the WoIf-Rayet star. From the absolute
magnitude, Mv( 8 Vel) = - 5.6 + 0A, of the binary, one obtains Mv (WC
8) = (- 3.6... - 4.2) + 0.4 for the Woll-Rayet component. Key words:
WoIf-Rayet stars
Title: Lehrstuhl für Theoretische Astrophysik. Report 1970.
Authors: Baschek, B.; Traving, G.
Bibcode: 1971MitAG..29...76B
Altcode:
No abstract at ADS
Title: Supernovae.
Authors: Baschek, B.
Bibcode: 1971S&W....10..189B
Altcode:
No abstract at ADS
Title: Aufbau und Entwicklung von Sternen.
Authors: Baschek, B.
Bibcode: 1971S&W....10..117B
Altcode:
No abstract at ADS
Title: The absolute magnitude of gamma Velorum.
Authors: Baschek, B.
Bibcode: 1970A&A.....7..318B
Altcode:
A spectroscopic determination of the absolute magnitude of the early
B star y1 Vel (HR 3206) is given by analyzing the spectrum relative
to y Peg, Her and Hya. Assuming Mr = - 3.5 for T Sco, Mr (yi Vel) = -
3.2 + 0.4 is derived. Depending on the choice of the absolute magnitude
of the 0 type component, the absolute niagnitude of the Wolf-Rayet
component of y8 Vel (HR 3207) is Mr(WC 8) = ....... - 5.3. Key words:
absolute magnitude - B stars - Wolf-Rayet stars
Title: Experimental Oscillator Strengths of Fe II Lines and the
Solar Iron Abundance.
Authors: Baschek, B.; Garz, T.; Holweger, H.; Richter, J.
Bibcode: 1970A&A.....4..229B
Altcode:
Experimental Oscfflator Strengths of Fe II Lines and the Solar Iron
Abundance The wall-stabilized arc burning in argon with a small
admixture of iron chloride used by Garz and Kock (1969) to measure
oscffiator strengths of Fe I lines also allows the determination of
oscillator strengths of Fe U lines. We present oscffiator strengths
of 14 Fe U lines based on the absolute scale of Garz and Kock for Fe I
lines. A solar abundance log s (Fe) = 7.63 + 0.20, normalized to log S
(H) = 12.00, is derived out of ionized iron lines. A comparison with
previous experimental and stellar oscfflator strengths of Fe U lines
is carried out and some implications on analyses of stellar spectra
are discussed. Key words: oscillator strengths - solar abundance
Title: Neutral-Helium Line Strengths. II. The B-Type Subdwarf
HD 205805
Authors: Baschek, Bodo; Norris, John
Bibcode: 1970ApJS...19..327B
Altcode:
Spectra and continuum colors have been obtained for the B-type subdwarf
HD 205805. On the assumption of LTE, an analysis of the helium line
strengths leads to the conclusion that the atmospherichelium abundance
of HD 205805 is smaller by a factor of 10 than that of the Population I
star Peg. The helium singlet-triplet anomaly is explained by both the
higher gravity and the lower helium abundance of the subdwarf. There
is no evidence for departures from LTE. An analysis, using the data
of Sargent and Searle, of three other sdB stars, Feige 11, 36, and
65, shows that the helium deficiency is a common property of these
stars. Compared with HD 205805, Feige 11 and 65 are deficient by a
factor of 4. Feige 36 has an abundance similar to that of HD 205805.
Title: Neutral-Helium Line Strengths. I. Line Profiles for a Grid
of Approximate Line-Blanketed Model Atmospheres
Authors: Norris, John; Baschek, Bodo
Bibcode: 1970ApJS...19..305N
Altcode:
Line profiles of neutral helium are presented for a grid of approximate
line-blanketed model atmospheres. The isolated lines are computed with
the line-broadening theory of Griem, Baranger, Koib, and Oertel. The
wings (long-wavelength halves) of the strong lines of the series are
obtained from the quasi-static of Pfennig and Trefftz; the cores are
computed from an adiabatic-impact treatment following Traving.
Title: On the microturbulence in A and F stars.
Authors: Baschek, B.; Reimers, D.
Bibcode: 1969A&A.....2..240B
Altcode:
For reciprocal effective temperatures 0.57 0 0 71 the observed
microturbulent yelocities of main- sequence stars are noticeably larger
than outside this temperature range. Values up to nearly sound velocity
are found for normal stars as well as for metaffic-line stars. This
large scatter of microturbulent velocities, however, does not explain
that observed for the m1 indices among late A-type stars. Key words:
microturbulence - normal stars - metaffic-line stars - m1 index Die
beobachteten Mikroturbulenzgeschwindigkeiten von Hauptsequenzsternen
sind im Bereich 0.57 0 0.71 erheblich als auBerhaib. Man findet Werte
bis aunaherud Schallgeschwindigkeit, und zwar fur normale Sterne
und auch Metalliniensterne. Trotzdem reicht dieser Bereich in den
Turbulenzgeschwindigkeiten nicht aus, um die beobachtete Streuung in
den Str5mgrenschen -Indizes bei spa ten A-Sternen zu erkiar. en.
Title: The Chemical Composition of the Lambda Bootis Stars
Authors: Baschek, Bodo; Searle, Leonard
Bibcode: 1969ApJ...155..537B
Altcode:
A curve-of-growth abundance analysis has been carried out of X Boo, 29
Cyg, `zr1 On, 0 Hya, and y Aqr and of the comparison stars $ An, p Peg,
a Lyr, and HD 161817. It is found that only X Boo, 29 Cyg, and ii-' On
form a distinct group from the composition point of view. These stars
are young main-sequence A stars of low turbulent velocities with metal
deficiencies of a factor of `-~-`3. Oxygen abundances are normal. In
X Boo itself, Ca and Mg are deficient with respect to iron. It is
suggested that these stars constitute a type of Ap star and that their
composition does not reflect that of the materialfrom which theyformed
Title: Center-to-Limb Analysis of the Solar Oxygen Lines
Authors: Müller, Edith A.; Baschek, Bodo; Holweger, Hartmut
Bibcode: 1968SoPh....3..125M
Altcode:
Several lines of neutral oxygen observed at various positions on the
solar disk were used to study the influence of (1) the temperature
distribution, (2) the velocity field, and (3) the damping on the line
profiles and the abundance of oxygen in the photosphere. Theoretical
profiles were calculated on the basis of four different model
atmospheres in LTE. It was found that the model proposed by HOLWEGER
(1967) best reproduced the center-to-limb observations of the lines
studied. The weighted mean of the oxygen abundance turned out to be
log ɛO = 8.83 on the basis of log ɛH = 12.00.
Title: Probleme der Spektralanalyse von Sternen der Population II
Authors: Baschek, B.
Bibcode: 1967MitAG..23...58B
Altcode:
No abstract at ADS
Title: Quantitative Analyse des Spektrums des F8 V-Sterns Beta
Virginis
Authors: Baschek, B. H.; Holweger, H.; Namba, O.; Traving, G.
Bibcode: 1967ZA.....65..418B
Altcode:
No abstract at ADS
Title: CI- und CH-Linien im Sonnenspektrum
Authors: Baschek, B.; Holweger, H.
Bibcode: 1967ZA.....67..143B
Altcode:
No abstract at ADS
Title: Ein ALGOL-Programm fur die quantitative Analyse von
Sternspektren
Authors: Baschek, B.; Holweger, H.; Traving, G.
Bibcode: 1966AAHam...8...26B
Altcode:
No abstract at ADS
Title: Tabellen fur die Berechnung von Zustandssummen
Authors: Traving, G.; Baschek, B.; Holweger, H.
Bibcode: 1966AAHam...8....1T
Altcode:
No abstract at ADS
Title: On the influence of surface gravity on UBV colours OG G-type
stars
Authors: Baschek, B.
Bibcode: 1966JQSRT...6..701B
Altcode:
No abstract at ADS
Title: Effective Temperatures and Gravities of ap, Am, and Normal
A-Type Stars.
Authors: Baschek, Bodo; Oke, J. B.
Bibcode: 1965ApJ...141.1404B
Altcode:
Effective temperatures and gravities are determined for selected Ap,
Am, and normal A-type stars and it is found that the colors are modified
substantially by the presence of abnormally strong metallic lines. The
gravities of all stars, with one exception, are those expected of
main-sequence stars. The Am stars in the Hyades are systematically
hotter than the corresponding normal stars.
Title: Quantitative Analyse des Spektrums des Schnelläufers Wilson
10367 (LPM 661). Mit 3 Textabbildungen
Authors: Baschek, B.
Bibcode: 1965ZA.....61...27B
Altcode:
No abstract at ADS
Title: Quantitative Interpretation of Stellar Spectra Using Model
Atmospheres
Authors: Baschek, B.
Bibcode: 1964SAOSR.167..254B
Altcode:
No abstract at ADS
Title: The Near Infrared Spectrum of Nova Herculis 1963
Authors: Baschek, Bodo
Bibcode: 1964PASP...76...22B
Altcode:
No abstract at ADS
Title: Differentielle Wachstumstumskurven. Mit 2 Textabbildungen
Authors: Baschek, B.; Traving, G.
Bibcode: 1964ZA.....59..276B
Altcode:
No abstract at ADS
Title: Häufigkeiten von Na und Mg in Metallinien- und Ap-Sternen. Mit
2 Textabbildungen
Authors: Baschek, B.
Bibcode: 1964ZA.....60...76B
Altcode:
No abstract at ADS
Title: Solare bzw. stellare Oszillatorenstärken des Fe II
Authors: Baschek, B.; Kegel, W. H.; Traving, G.
Bibcode: 1963ZA.....56..282B
Altcode:
No abstract at ADS
Title: Häufigkeitsbestimmung für Kohlenstoff aus CH-Banden im
Subdwarf HD 140283 und in der Sonne. Mit 3 Textabbildungen
Authors: Baschek, B.
Bibcode: 1963ZA.....56..207B
Altcode: 1962ZA.....56..207B
No abstract at ADS
Title: Abhängigkeit des Strömgrenschen Index m und der Farbindizes
U-B, B-V von der Metallhäufigkeit bei sonnenähnlichen Sternen. Mit
3 Textabbildungen
Authors: Baschek, B.
Bibcode: 1960ZA.....50..296B
Altcode:
No abstract at ADS
Title: Aufbau und chemische Zusammensetzung der Atmosphäre des
Subdwarfs HD 140283. Mit 10 Textabbildungen
Authors: Baschek, B.
Bibcode: 1959ZA.....48...95B
Altcode:
No abstract at ADS
Title: Aufbau und chemische Zusammensetzung der Atmosphäre des
Subdwarfs HD 140283 Title: Aufbau und chemische Zusammensetzung der
Atmosphäre des Subdwarfs HD 140283 Title: Structure and chemical
composition of the atmosphere of the sub-dwarf HD 140283;
Authors: Baschek, Bodo
Bibcode: 1959PhDT........69B
Altcode:
No abstract at ADS