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Astron. Astrophys. 318, 73-80 (1997)

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Visual light from the eclipsing supersoft X-ray source CAL 87

S. Schandl *, E. Meyer-Hofmeister and F. Meyer

Max-Planck-Institut für Astrophysik, Karl Schwarzschildstr. 1, D-85740 Garching, Germany

Received 3 January 1996 / Accepted 18 June 1996


We calculate the visual light curve of CAL 87 based on the assumption that an accreting steadily burning white dwarf irradiates the accretion disk and the secondary star, as suggested by van den Heuvel et al. (1992). We find a reasonable fit including the following sources of visual light: 1. the secondary star where the energy from irradiation is spread out over the surface, 2. the accretion disk with an optically thick, cold, clumpy spray presumably caused by an accretion stream of high mass flow rate impinging on the disk (hot spot). This spray moving around the disk can account for the asymmetry in the light curve and the depth of the secondary minimum. This supports the assumption that the white dwarf is permanently hidden by the disk.

Key words: accretion disks – binaries: eclipsing – stars: CAL 87 (LMC) – X-rays: stars

* email: suh@mpa-garching.mpg.de

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© European Southern Observatory (ESO) 1997

Online publication: July 8, 1998