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Accretion onto stellar mass black holes

By Patrick Deegan


I present work on the accretion onto stellar mass black holes in several scenarios.\ud Due to dynamical friction stellar mass black holes are expected to form high density\ud cusps in the inner parsec of our Galaxy. These compact remnants may be accreting cold\ud dense gas present there, and give rise to potentially observable X-ray emission. I build a\ud simple but detailed time-dependent model of such emission. Future observations of the\ud distribution and orbits of the gas in the inner parsec of Sgr A* will put tighter constraints\ud on the cusp of compact remnants.\ud GRS 1915+105 is an LMXB, whose large orbital period implies a very large accretion\ud disc and explains the extraordinary duration of its current outburst. I present\ud smoothed particle hydrodynamic simulations of the accretion disc. The models includes\ud the thermo-viscous instability, irradiation from the central object and wind loss. I find\ud that the outburst of GRS 1915+105 should last a minimum of 20 years and up to ∼ 100\ud years if the irradiation is playing a significant role in this system. The predicted recurrence\ud times are of the order of 10^4 years, making the duty cycle of GRS 1915+105 to be\ud a few 0.1%.\ud I present a simple analytical method to describe the observable behaviour of long period\ud black hole LMXBs, similar to GRS 1915+105. Constructing two simple models for\ud the surface density in the disc, outburst and quiescence times are calculated as a function\ud of orbital period. LMXBs are an important constituent of the X-ray light function (XLF)\ud of giant elliptical galaxies. I find that the duty cycle can vary considerably with orbital\ud period, with implications for modelling the XLF

Publisher: University of Leicester
Year: 2009
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