Astronomy and Astrophysics – Astrophysics
Scientific paper
1995-08-03
Astrophys.J. 457 (1996) 821
Astronomy and Astrophysics
Astrophysics
32 Pages, 6 Figures included, Compressed Postscript, To Appear in Astrophysical Journal
Scientific paper
10.1086/176777
We present models of the soft X-ray transients, A0620-00, V404 Cyg, and X-ray Nova Mus 1991, in quiescence. In each source, we postulate that there is an outer region, extending outward from about 3000 Schwarzschild radii, where the accretion flow is in the form of a standard thin disk. The outer disk produces most of the radiation we observe in the infrared, optical and UV bands. We propose that the disk undergoes an instability at its inner edge, perhaps by the mechanism described recently by Meyer \& Meyer-Hofmeister for cataclysmic variables. The accreting gas is thereby converted into a hot corona which flows into the black hole as a nearly virial two-temperature flow. We describe the hot inner flow by means of a recently discovered stable solution of optically thin advection-dominated accretion. In this flow, most of the thermal energy released by viscous dissipation is advected into the black hole and only a small fraction, $\sim10^{-4}-10^{-3}$, of the energy is radiated. The radiation is in the form of Comptonized synchrotron and bremsstrahlung emission, and has a broad spectrum extending from optical to soft gamma-rays. The models we present are consistent with all the available data in the three sources. In particular, the X-ray emission from the hot inner flow fits the observed flux and spectral index of A0620-00. We derive a mass accretion rate of $\sim10^{-11}\msyr$ in A0620-00 and Nova Mus, and $\sim{\rm few}\times10^{-10}\msyr$ in V404 Cyg. The best fit to the data is obtained for a viscosity parameter $\alpha\sim0.1-0.3$ in the hot flow. The models predict that all three sources must have substantial flux in hard X-rays and soft $\gamma$-rays. This prediction is testable in the case of V404 Cyg with current instruments. A necessary feature of our proposal is that most of the viscous
McClintock Jeffrey E.
Narayan Ramesh
Yi Insu
No associations
LandOfFree
A New Model for Black Hole Soft X-ray Transients in Quiescence does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with A New Model for Black Hole Soft X-ray Transients in Quiescence, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and A New Model for Black Hole Soft X-ray Transients in Quiescence will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-469025