Volume 393, Number 3, October III 2002
|Page(s)||913 - 920|
|Section||Interstellar and circumstellar matter|
|Published online||01 October 2002|
XMM-Newton observations of MR Vel/RX J0925.7-4758
Observatoire Astronomique, UA 1280 CNRS, 11 rue de l'Université, 67000 Strasbourg, France
2 Astronomical Institute, Utrecht University, PO Box 80000, 3508 TA Utrecht, The Netherlands
3 Terschelling 120, 3524 AZ Utrecht, The Netherlands
4 Sterrenkundig Instituut Anton Pannekoek, Kruislaan 403, 1098 SJ Amsterdam, The Netherlands
Corresponding author: C. Motch, firstname.lastname@example.org
Accepted: 27 June 2002
We report on XMM-Newton observations of the galactic supersoft X-ray source RX J0925.7-4758. The RGS spectrum exhibits a wealth of spectral features from iron and oxygen. XMM-Newton data confirm the finding of previous Chandra HETGS/MEG observations that NLTE models of hot white dwarf atmospheres fail to represent the complex spectrum. There are clear evidences for P Cygni profiles with wind velocities of up to 2000 km s-1. Small flux variations with time scales larger than 1000 s are present. The strongest power is at ~0.21 d, a period close to that seen in V band optical light curves. A detailed analysis of the associated changes in the RGS and EPIC pn spectra hint at a mostly grey mechanism suggesting a variation of the visibility of the white dwarf due to occulting material in the accretion disk. Finally, we detect radial velocity changes of 173 ± 47 km s-1 between two RGS observations obtained half an orbital cycle apart. The amplitude of the RGS velocity shift is consistent with that of the optical λ 4686 and thus supports the idea that most of the optical line emission arises from the accretion disk.
Key words: X-rays: binaries / X-rays: individual: RX J0925.7-4758 / stars: individual: MR Vel / stars: mass-loss / techniques: radial velocities
© ESO, 2002
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