HST observations of some QSOs show a strong, abrupt increase in polarization
at rest wavelength about 750 A, suggestive of a connection with the Lyman edge
of hydrogen. Blaes and Agol (1996) have proposed an explanation in terms of
stellar atmosphere effects in an accretion disk around a supermassive black
hole. We have computed the polarized spectrum of a such a disk, including the
effects of the relativistic transfer function. Relativistic effects add an
additional blueshift of the polarization rise sufficient that the model cannot
explain the observations.
A good fit results if the emitted radiation is assumed to have a sharp
increase in polarized flux at the Lyman edge in the rest frame of the orbiting
gas. Relativistic effects then cause the observed polarization to rise sharply
at a wavelength substantially less than 912 A. The blueshift depends on the
angular momentum of the black hole and the inclination of the disk. A good fit
to PG 1630+377 results from a simple model with a dimensionless angular
momentum a = 0.5 and an observer viewing angle cos theta = 0.1. An intermediate
value of a might result from coallescing black holes, successive accretion
events, or electromagnetic extraction of angular momentum from the hole.Comment: 24 pages incl. 9 PostScript figures. Uses aaspp4.sty and flshrt.sty.
To be published in The Astrophysical Journal, Vol. 496 (1988 April 1
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.