Issue |
A&A
Volume 374, Number 1, July IV 2001
|
|
---|---|---|
Page(s) | 265 - 279 | |
Section | Stellar structure and evolution | |
DOI | https://doi.org/10.1051/0004-6361:20010735 | |
Published online | 15 July 2001 |
LTE spectrum synthesis in magnetic stellar atmospheres
The interagreement of three independent polarised radiative transfer codes
1
Département de Physique, Université de Montréal, CP 6128 succ. Centre-Ville, Montréal, QC, Canada H3C 3J7
2
Institut für Astronomie, Universität Wien, Türkenschanzstr. 17, 1180 Wien, Austria
3
European Southern Observatory, Casilla 19001, Santiago 19, Chile
4
Uppsala Astronomical Observatory, Box 515, 751 20 Uppsala, Sweden
5
Physics & Astronomy Department, University of Western Ontario, London, Ontario, Canada N6A 3K7
Corresponding author: G. A. Wade, wade@astro.umontreal.ca
Received:
10
November
2000
Accepted:
22
May
2001
With the aim of establishing a benchmark for the detailed calculation
of the polarised line profiles of magnetic stars, we describe an
intercomparison of LTE Stokes profiles calculated using three
independent, state-of-the-art magnetic spectrum synthesis codes: Cossam,
ı10 and Zeeman2. We find, upon establishing a homogeneous basis for the
calculations (identical definitions of the Stokes parameters and the
magnetic and stellar reference frames, identical input model stellar
atmosphere, identical input atomic data, and identical chemical element abundances and
magnetic field distributions), that local and disc-integrated Stokes IQUV
profiles of Fe calculated using the three codes agree very
well. For the illustrative case of disc-integrated profiles
calculated for abundance
, dipole
magnetic field intensity
kG, and projected rotational
velocity
km s-1, Stokes I profiles (depth ∼40% of
the continuum flux Ic) agree to within about 0.05% rms of Ic,
Stokes V profiles (full amplitude ∼10% ) to within about 0.02% rms of
Ic, and Stokes Q and U profiles (full amplitudes ∼2% ) at the
sub-0.01% rms level. These differences are sufficiently small so as to allow
for congruent interpretation of the best spectropolarimetric data
available, as well as for any data likely to become available during the
near future. This indicates that uncertainties in modeling Stokes profiles
result overwhelmingly from uncertainties in input atomic and physical data,
especially the state and structure of model stellar atmospheres.
Key words: line: profiles / polarisation / stars: magnetic fields / stars: atmospheres
© ESO, 2001
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