Astron. Astrophys. 333, 540-546 (1998)

Optical and X-ray study of MS1603+2600 ^*

P.J. Hakala ^{1, 2}, D.H. Chaytor ⁴, O. Vilhu ¹, V. Piirola ³, S.L.Morris ⁴ and P. Muhli <sup>1

1</sup> Observatory and Astrophysics Laboratory, P.O. Box 14, FIN-00014 University of Helsinki, Finland
² Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking RH5 6NT, Surrey, UK
³ Tuorla Observatory, FIN-21500 Piikkio, Finland
⁴ Dominion Astrophysical Observatory, National Research Council, 5071 West Saanich Road, Victoria, B.C., V8X 4M6, Canada

Received 23 June 1997 / Accepted 21 November 1997

Abstract

We present results from years of optical monitoring of an unusual interacting compact binary MS1603+2600 together with the results of ROSAT observations. Our CCD-photometry confirms the erratic behaviour of the optical light curve shape reported by Morris et al. (1990). The ROSAT-PSPC observations suggest that MS1603 might be a short period soft X-ray transient (SXT) never seen in outburst. This would probably require, that the compact object in MS1603 is a black hole rather than a neutron star. In addition to optical photometry and ROSAT data, we present first circular polarimetric observations of the source and discuss the nature and origin of MS1603+2600.

Key words: stars: individual: MS1603+2600 stars: binaries, close accretion

* Based on optical observations made at the Nordic Optical Telescope, La Palma

Send offprint requests to: P.J. Hakala

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Contents

• 1. Introduction
• 2. Optical CCD-photometry and circular polarimetry
  • 2.1. Results from optical monitoring
• 3. ROSAT-PSPC observations
  • 3.1. Periodogram analysis
  • 3.2. The phased light curve
• 4. Discussion
  • 4.1. Cataclysmic variable?
  • 4.2. Low mass X-ray binary?
  • 4.3. Transient LMXB in quiescence?
• 5. Conclusions
• Acknowledgements
• References

© European Southern Observatory (ESO) 1998

Online publication: April 20, 1998
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