EDP Sciences
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Volume 481, Number 1, April I 2008
Page(s) 193 - 198
Section Stellar structure and evolution
DOI http://dx.doi.org/10.1051/0004-6361:20067010
Published online 04 February 2008

A&A 481, 193-198 (2008)
DOI: 10.1051/0004-6361:20067010

Variability in the cycle length of the supersoft source RX J0513.9-6951

V. Burwitz1, K. Reinsch2, J. Greiner1, E. Meyer-Hofmeister3, F. Meyer3, F. M. Walter4, and R. E. Mennickent5

1  Max-Planck-Institut für extraterrestische Physik, PO Box 1312, 85741 Garching, Germany
    e-mail: burwitz@mpe.mpg.de
2  Institut für Astrophysik, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
3  Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, 85740 Garching, Germany
4  Department of Physics and Astronomy, State University of New York at Stony Brook, Stony Brook, NY 11794-3800, USA
5  Departamento de Física, Universidad de Concepción, Casilla 160-C, Concepción, Chile

(Received 22 December 2006 / Accepted 28 January 2008)

Context.The supersoft X-ray binary RX J0513.9-6951 shows cyclic changes between optical-low / X-ray-on states and optical-high / X-ray-off states. It is supposed to be accreting close to the Eddington-critical limit and driven by "accretion wind evolution".
Aims.We seek to derive the variations in the characteristic time scales of the long-term optical light curve and to determine the implications for the physical parameters of the system.
Methods.We used existing and new optical monitoring observations covering a total time span of 14 years and compared the durations of the low and high states with the model calculations of Hachisu & Kato.
Results.The cycle lengths and especially the durations of the optical high states show a longterm modulation with variations that, according to the accretion wind evolution model, would imply variations in the mass transfer rate by a factor of 5 on timescales of years.

Key words: stars: individual: RX J0513.9-6951 -- stars: binaries: close -- stars: white dwarfs -- accretion, accretion disks -- X-rays: stars -- galaxies: individual: Large Magellanic Cloud

© ESO 2008