Astron. Astrophys. 358, 993-1000 (2000)

Turmoil on the accretion disk of GRO J1655-40

E. Kuulkers ^1,2, J.J.M. in't Zand ¹, R. Cornelisse ^1,2, J. Heise ¹, A.K.H. Kong ³, P.A. Charles ^3,4, A. Bazzano ⁵, M. Cocchi ⁵, L. Natalucci ⁵ and P. Ubertini <sup>5

1</sup> Space Research Organization Netherlands, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands (E.Kuulkers@sron.nl)
² Astronomical Institute, Utrecht University, P.O. Box 80000, 3508 TA Utrecht, The Netherlands
³ Department of Astrophysics, Nuclear and Astrophysics Laboratory, Keble Road, Oxford OX1 3RH, UK
⁴ Department of Physics and Astronomy, University of Southampton, Southampton, SO17 1BJ, UK
⁵ Istituto di Astrofisica Spaziale (CNR), Area Ricerca Roma Tor Vergata, Via del Fosso del Cavaliere, 00133 Roma, Italy

Received 10 February 2000 / Accepted 10 April 2000

Abstract

During the 1996/1997 outburst of the X-ray transient GRO J1655-40 the Wide Field Cameras onboard BeppoSAX observed the system with nearly continuous coverage during some stages of this outburst. On two occasions we find clear evidence for frequent dipping behaviour, characterized by several absorption dips occurring within one binary orbit. However, during preceding and following binary orbits there is no sign of such dips at the same range of orbital phases. We also collected light curves of absorption dips as seen with other X-ray instruments. Although the 65 dips that were collected occur preferably between orbital phases 0.68 and 0.92, there is evidence that the morphology of the material causing the dips is changing over just one binary orbit. The short duration (minutes) and phasing of the dips are discussed in the framework of models where the stream from the companion star encounters a hot outer rim on the accretion disk.

Key words: accretion, accretion disks stars: binaries: close stars: individual: GRO J1655-40 X-rays: stars

Send offprint requests to: E. Kuulkers

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Contents

• 1. Introduction
• 2. Observations and analysis
• 3. Results
  • 3.1. The quest for X-ray dips
  • 3.2. From binary orbit to binary orbit
• 4. Discussion
  • 4.1. Orbital phase dependence
  • 4.2. Stream-disk interaction
• Acknowledgements
• References

© European Southern Observatory (ESO) 2000

Online publication: June 20, 2000
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