Variability in the cycle length of the supersoft source RX J0513.9-6951
Max-Planck-Institut für extraterrestische Physik, PO Box 1312, 85741 Garching, Germany e-mail: email@example.com
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
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