Astron. Astrophys. 336, 626-636 (1998)

Soft X-ray emission of VY Sculptoris stars during optical high state

J. Greiner

Astropysikalisches Institut Potsdam, An der Sternwarte 16, D-14482 Potsdam, Germany

Received 27 April 1998 / Accepted 13 May 1998

Abstract

I have collected all available ROSAT observations of VY Scl stars including those during the all-sky survey to investigate the presence, strength and spectrum of soft X-ray emission (0.1-2.4 keV) of this group of nova-like variables. A total of 9 out of the 14 VY Scl stars are detected with ROSAT, mostly during optical high states. Interestingly, all detections during the optical high state have very similar X-ray spectral characteristics. I find that a simple blackbody model gives a reasonably good fit in all cases, with temperatures falling in the narrow range between 0.25-0.5 keV. Possible emission mechanisms are discussed.

Key words: accretion, accretion disks instabilities X-rays: stars stars: novae, cataclysmic variables

Send offprint requests to: J. Greiner, (jgreiner@aip.de)

SIMBAD Objects

Contents

• 1. Introduction
• 2. Observations
  • 2.1. ROSAT all-sky survey and pointed observations
  • 2.2. Optical data
• 3. Results
  • 3.1. X-ray spectral analysis
  • 3.2. X-ray temporal analysis
  • 3.3. Notes on individual objects
• 4. Discussion
  • 4.1. Comparison between VY Scl stars and dwarf novae
  • 4.2. Is a blackbody model reasonable?
  • 4.3. The classical boundary layer picture
  • 4.4. Heavily absorbed classical boundary layer emission
  • 4.5. X-ray emission from an optically thick wind
  • 4.6. Coronal region above the accretion disk
  • 4.7. Coronal emission of the late-type companion star
  • 4.8. Evaporation of the accretion disk
  • 4.9. Stream impact region
• 5. Conclusions
• Acknowledgements
• References

© European Southern Observatory (ESO) 1998

Online publication: July 20, 1998
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