Publications
of the
MPIfR
Optical & Infrared
Interferometry Group
F. Yuan:
Luminous hot accretion disks
MNRAS 324, 119-127 (2001)
Abstract.
We find a new two-temperature hot branch of equilibrium solutions for
stationary accretion discs around black holes. In units of Eddington
accretion rate defined as 10LEddc2, the accretion
rates to which these solutions correspond are within the range Mȯ1<~Mȯ<~1,
where Mȯ1 is the critical rate of advection-dominated
accretion flow (ADAF). In these solutions, the energy loss rate of the
ions by Coulomb energy transfer between the ions and electrons is
larger than the viscously heating rate and it is the advective heating
together with the viscous dissipation that balances the Coulomb cooling
of ions. When Mȯ1<~Mȯ<~ Mȯ2,
where Mȯ2~5Mȯ1<1, the accretion flow remains
hot throughout the disc. When Mȯ2<~Mȯ<~1,
Coulomb interaction will cool the inner region of the disc within a
certain radius (rtr~several tens of Schwarzschild radii or
larger depending on the accretion rate and the outer boundary
condition) and the disc will collapse on to the equatorial plane and
form an optically thick cold annulus. Compared with ADAF, these hot
solutions are much more luminous because of the high accretion rate and
efficiency; therefore, we call them luminous hot accretion discs.
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