Issue |
A&A
Volume 455, Number 2, August IV 2006
|
|
---|---|---|
Page(s) | 679 - 684 | |
Section | Stellar atmospheres | |
DOI | https://doi.org/10.1051/0004-6361:20065102 | |
Published online | 04 August 2006 |
On the relevance of Compton scattering for the soft X-ray spectra of hot DA white dwarfs
1
Institut für Astronomie und Astrophysik, Universität Tübingen, Sand 1, 72076 Tübingen, Germany e-mail: suleimanov@astro.uni-tuebingen.de
2
Kazan State University, Kremlevskaja str., 18, Kazan 420008, Russia
3
Kazan Branch of Isaac Newton Institute, Santiago, Chile
4
Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warsaw, Poland
5
Smithsonian Astrophysical Observatory, MS-3, 60 Garden Street, Cambridge, MA 02138, USA
Received:
27
February
2006
Accepted:
7
May
2006
Aims.We re-examine the effects of Compton scattering on the
emergent spectra of hot DA white dwarfs in the soft X-ray range.
Earlier studies
have implied that sensitive X-ray observations at
wavelengths Å might be capable of probing the flux
deficits predicted by the redistribution of electron-scattered X-ray
photons toward longer wavelengths.
Methods.We adopt two independent numerical approaches to the inclusion of
Compton scattering in the computation of pure hydrogen atmospheres in
hydrostatic equilibrium. One employs the Kompaneets diffusion
approximation formalism,
while the other uses the cross-sections and redistribution functions
of Guilbert. Models and emergent spectra are computed for stellar
parameters representative of HZ 43 and Sirius B, and for models with an
effective temperature K.
Results.The
differences between emergent spectra computed for Compton and Thomson
scattering cases are completely negligible in the case of both HZ 43
and Sirius B models, and are also negligible
for all practical purposes for models
with temperatures as high as K.
Models of the soft X-ray flux from these stars
are instead dominated by uncertainties in their fundamental
parameters.
Key words: radiative transfer / scattering / methods: numerical / stars: white dwarfs / stars: atmospheres / X-rays: stars
© ESO, 2006
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