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Superdisks in Supersoft X-Ray Sources

2001; Oxford University Press; Volume: 53; Issue: 1 Linguagem: Inglês

10.1093/pasj/53.1.111

2053-051X

Jun Fukue, Katsura Matsumoto,

Astrophysics and Cosmic Phenomena

In supersoft X-ray sources the mass accretion rate is roughly equal to the Eddington rate, and traditional standard disks cannot be adequate. We thus propose a supercritical accretion disk (superdisk) for supersoft X-ray sources. We have found that superdisks exhibit various distinct features, compared with standard thin disks. The continuous spectra of superdisks generally become flat ($ \nu S_\nu \sim \nu^0$), which are greatly different from those of disk-blackbody spectra, as expected in the usual accretion disk systems. This flat nature is not so prominent in supersoft X-ray sources, compared with that in the superdisk around a black hole, since the radial extension of the disk is much smaller. Moreover, irradiation becomes important for a smaller accretion rate system. The superdisk picture was applied to RX J0019.8+2156, and reproduced its spectra and optical light curves well.