Luminous binary supersoft X-ray sources: Optical colors and absolute magnitudes*
Astronomical Institute, Academy of Sciences of the Czech Republic, 251 65 Ondřejov, Czech Republic
Corresponding author: email@example.com
Accepted: 15 April 2003
An analysis of the color indices and absolute magnitudes 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 of the individual objects is very large, from to , most systems having . The objects with the orbital period days tend to possess brighter with the increasing Porb. The same trend is apparent also for . There is no systematic difference between the classical SSXBs and the VSs, as regards their and . The soft X-ray phase of the novae V 1974 Cyg and V 382 Vel occurred at significantly brighter than those of most other SSXBs while of the recurrent nova U Sco was comparable to the SSXBs of the comparable Porb. We showed that the luminosity of the reprocessing medium in the symbiotic SSXBs does not increase much with Porb, 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 or of all kinds of the SSXBs is rather weak, but resolvable, and is more prominent for . The implications for the reprocessing medium are discussed.
Key words: stars: binaries: close / stars: binaries: general / stars: circumstellar matter / stars: novae, cataclysmic variables
© ESO, 2003