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"High mass accretion rate black holes: a new spectral state for ULX and 
the highest mass accretion rate AGN?"

Prof. Chris Done
University of Durham, U.K.
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When: Tuesday, 29th of September of 2009 at 2:00 pm
Where: 2nd Floor Seminar Room

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Abstract:

Black hole binaries show how the accretion flow varies up to luminosities 
around Eddington. At these high luminosities the spectrum can either be 
dominated by the disc, or can be increasingly strongly comptonised. In the 
most extreme Comptonisation states, the corona becomes optically thick and 
cool, distorting the view of the inner disc. The only black hole binary to 
spend significant amounts of time above Eddington is the pathologically 
variable source GRS1915+105, where the corona has even higher optical depth 
and is cooler. Such cool, optically thick comptonised spectra are also a good 
description of the spectra seen from ULX and from the highest mass accretion 
rate AGN such as the X-ray QPO source REJ1034+396. We speculate that these 
objects are showing a new 'ultraluminous' spectral state above the Eddington 
limit, where mass loss through winds becomes increasingly important, 
enveloping the inner disc in optically thick material.
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