Astron. Astrophys. 326, 419-426
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Optics near Kerr black holes:
spectra of advection dominated accretion flows
M. Jaroszyski and A. Kurpiewski
Warsaw University Observatory, Al. Ujazdowskie 4,
PL-00478 Warsaw, Poland
Received 11 March 1997 / Accepted 25 March 1997
We investigate advection dominated accretion flows of matter in the vicinity
of black holes, using the fully relativistic description in the frame of
disk approximation. We also include some effects of the quasi-sphericity
of the flow.
We are interested in the spectra emitted by such flows and
specifically, in the relativistic effects accompanying propagation of light.
Using the ray shooting method in the Kerr metric we calculate the
spectra of three different accretion flows. We also calculate the shape
of a -ray line which could be formed in the flow, assuming that
it has a natural Doppler profile.
We find that effects of relativistic optics may influence the isotropy
of the radiation and that observers close to the equatorial plane would
measure a higher source luminosity.
The line is strongly broadened, but the fact that the flow is
quasi-spherical removes two-peak shape of the line characteristic for
the spectra emitted from thin, Keplerian disks.
The kinematics of the advection dominated flows is not unique (as
opposed to Keplerian disks or spherical free-fall) and it would be
probably difficult to find strong limits on source models using the
Key words: accretion processes - radiation mechanisms: non-thermal
© European Southern Observatory (ESO) 1997
Online publication: September 9, 1997
Last change: April 20, 1998