EDP Sciences
Free access
Volume 406, Number 2, August I 2003
Page(s) 613 - 621
Section Stellar atmospheres
DOI http://dx.doi.org/10.1051/0004-6361:20030655

A&A 406, 613-621 (2003)
DOI: 10.1051/0004-6361:20030655

Luminous binary supersoft X-ray sources: Optical colors and absolute magnitudes

V. Simon

Astronomical Institute, Academy of Sciences of the Czech Republic, 251 65 Ondrejov, Czech Republic
(Received 27 September 2002 / Accepted 15 April 2003 )

An analysis of the color indices and absolute magnitudes MV0 of the "classical" supersoft X-ray binary sources (SSXBs), the V Sge-type stars (VSs), the symbiotic SSXBs, and the classical novae in the soft X-ray phase is presented. This approach can help comparing the properties and configuration of the reprocessing medium in the individual systems. The range of MV0 of the individual objects is very large, from MV0=8.5 to MV0=-4, most systems having MV0<2. The objects with the orbital period $P_{\rm orb}<4$ days tend to possess brighter MV0 with the increasing $P_{\rm orb}$. The same trend is apparent also for MU0. There is no systematic difference between the classical SSXBs and the VSs, as regards their MV0 and MU0. The soft X-ray phase of the novae V 1974 Cyg and V 382 Vel occurred at significantly brighter MV0 than those of most other SSXBs while MV0 of the recurrent nova U Sco was comparable to the SSXBs of the comparable $P_{\rm orb}$. We showed that the luminosity of the reprocessing medium in the symbiotic SSXBs does not increase much with $P_{\rm orb}$, when compared with the luminosity of the classical SSXBs and VSs; this speaks against large disks in these symbiotics. The classical SSXBs and the VSs have colors very similar each to other and form closed groups in the color-color diagrams. A Balmer jump occurs frequently in emission as inferred from the colors. The correlation between the bolometric luminosity, determined from the X-ray spectra and MV0 or MU0 of all kinds of the SSXBs is rather weak, but resolvable, and is more prominent for MU0. The implications for the reprocessing medium are discussed.

Key words: stars: binaries: close  -- stars: binaries: general  -- stars: circumstellar matter  -- stars: novae, cataclysmic variables

SIMBAD Objects

© ESO 2003