APT3 - Observations from High Energy Astrophysics Satellites |
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Speaker |
Soria, Robert |
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Talk Title |
Accretion states in stellar-mass black holes and ultraluminous X-ray sources |
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Abstract |
The canonical accretion states of stellar-mass black holes are a low/hard state (radiatively inefficient, dominated by inverse-Compton emission and steady jets), a high/soft state (radiatively efficient standard disk) and, on rare occasions, a very-high-state (with both a steep power law and a disk component). This simple scheme was also applied to AGN. But X-ray studies of ULXs over the past decade have revealed a more complex state structure. Some ULXs may be in the very high state or slim-disk state. Others (especially the most luminous sources, at L > 1E40 erg/s) have a hard power-law spectrum, a "high/hard" state unknown in Galactic black holes. And most ULXs never seem to switch to the disk-dominated high/soft state. I will discuss possible interpretations of these findings in terms of black hole masses and accretion rates. |
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