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

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6. Conclusions

Following the model of vdH we find a reasonable fit for the visual light curve of CAL 87 including the secondary, the disk and an extended spray region. This extended region presumably created by the material impinging on the disk acts like a screen for the radiation from the hot white dwarf and provides the high amount of optical light, which cannot originate in a thin disk (Meyer & Meyer-Hofmeister 1995). This results in a permanently hidden white dwarf, covered by the spray, supported by the low observed X-ray luminosity on the order of 1-10% of other LMXBs and supersoft sources, (Pakull et al. 1988, Greiner 1995, private communication). We found that thin hot spot descriptions resulting in a direct view toward the white dwarf were not successful.

Including energy transport of the irradiated flux to non-illuminated parts on the secondary surface yields slightly better results around primary eclipse. It increases the visual light from the secondary because of lower bolometric corrections. Therefore, one obtains a high stellar contribution to the light curve using a reasonable efficiency parameter of radiation reprocessing, even if the irradiated surface area is small because of the large disk shadow.

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© European Southern Observatory (ESO) 1997

Online publication: July 8, 1998