Astron. Astrophys. 321, 245-253 (1997)

The structure of the accretion disk rim in supersoft X-ray sources

E. Meyer-Hofmeister ^*, S. Schandl and F. Meyer

Max-Planck-Institut für Astrophysik, Karl Schwarzschildstr. 1, D-85740 Garching, Germany

Received 16 August 1996 / Accepted 2 October 1996

Abstract

Supersoft X-ray sources are characterized by the radiation of a white dwarf with a temperature of some K. The compact star is surrounded by an irradiated accretion disk which provides the high optical luminosity. For CAL 87 (Schandl et al. 1996a, 1996b) it could be shown, that this disk has an elevated rim at the outer edge. The impact of the accretion stream from the companion on the disk is important for the rim structure.

More optical observations have recently become available for supersoft sources. Detailed features became known, as short-time variations of the shape of the orbital light curve of RX J0019 (Will & Barwig 1996), the long-term variations of RX J0019 (Greiner & Wenzel 1995) and the changes of RX J0513 between a high and a low state (Alcock et al. 1996). We use our simulation of the orbital light curves (developed for CAL 87) to analyse the disk rim structure of these two other sources in comparison with the observations. We find that a high rim gives good agreement and allows to explain the observations. For the modelling of the high state of RX J0513 the irradiation of disk and secondary by an extended white dwarf is included. The consistent appearance of a high rim feature raises interesting dynamical problems for the stream disk interaction.

Key words: accretion disks binaries: eclipsing stars: CAL 87, RX J0019.8, RX J0513.9 X-rays: stars

* email: emm@mpa-garching.mpg.de

SIMBAD Objects

Contents

• 1. Introduction
• 2. The structure of the accretion disk
  • 2.1. The bulge of the accretion disk in LMXRBs
  • 2.2. The modelling of the disk in SSS
• 3. The source CAL 87
• 4. The source RX J0019.8+2156
  • 4.1. The orbital light curve
  • 4.2. Short-time changes of the shape of the orbital light curve
    • 4.2.1. The light curve near the secondary minimum
    • 4.2.2. The light curve at phases of high brightness
    • 4.2.3. The light curve near the primary minimum
  • 4.3. Long-term variations of the optical brightness
• 5. The source RX J0513.9-6951
  • 5.1. Observations
  • 5.2. The modelling of the low state
  • 5.3. The modelling of the high state
• 6. Relation between mass overflow rate and disk rim height
• 7. Conclusions
• Acknowledgements
• References

© European Southern Observatory (ESO) 1997

Online publication: June 30, 1998
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