A&A 401, 1009-1015 (2003)
DOI: 10.1051/0004-6361:20030159
High efficiency of soft X-ray radiation reprocessing in supersoft X-ray sources due to multiple scattering
V. Suleimanov1, 2, F. Meyer3 and E. Meyer-Hofmeister31 Department of Astronomy, Kazan State University, Kremlevskaya 18, Kazan 8, 420008, Russia
2 Kazan Branch of Isaac Newton Institute, Santiago, Chile
3 Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Straße 1, 85740 Garching, Germany
(Received 14 August 2002 / Accepted 30 January 2003 )
Abstract
Detailed analysis of the lightcurve of CAL 87 clearly has shown
that the high optical luminosity comes from the accretion disc rim
and can only be explained by a severe thickening of the disc rim
near the location where the accretion stream impinges. This area
is irradiated by the X-rays where it faces the white dwarf.
Only if the reprocessing rate of X-rays to optical light is high
a luminosity as high as observed can be understood. But a recent detailed study
of the soft X-ray radiation reprocessing in supersoft X-ray sources
has shown that the efficiency is not high enough.
We here propose a solution for this problem. As already discussed in
the earlier lightcurve analysis the impact of the
accretion stream at the outer disc rim produces a "spray",
consisting of a large number of individual gas blobs imbedded in a
surrounding corona. For the high mass flow rate this constitutes an
optically thick vertically extended screen at the rim of the accretion disc.
We analyse the optical properties of this irradiated spray and find that
the multiple scattering between these gas blobs leads to an effective
reprocessing of soft X-rays to optical light as required by the observations.
Key words: accretion, accretion disks -- radiative transfer -- scattering -- stars: novae, cataclysmic variables -- stars: circumstellar matter -- X-rays: stars
Offprint request: V. Suleimanov, vals@ksu.ru
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