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F. Yuan (Harvard-Smithsonian CfA), E. Quataert (UC Berkeley), R. Narayan (Harvard-Smithsonian CfA)
We investigate accretion models for Sgr A*, the supermassive black hole in our Galactic Center, in light of new observational constraints. Confirmation of linear polarization in the submm emission argues for very low accretion rates, much less than the Bondi rate. We calculate the spectra produced by a hybrid electron population, consisting of both thermal and power-law particles, in such models. The observed radio spectrum can be explained if roughly 2% of the electron thermal energy resides in a power-law tail, with the remaining electrons being thermal. The submm-bump is due to the thermal population. In the innermost region of the accretion flow, transient events such as magnetic reconnection may occasionally accelerate some fraction of the electrons into a power-law tail. The synchrotron emission from those electrons, or the Compton up-scattering of submm photons by those electrons, may account for the X-ray flares observed by Chandra.
F.Y. and R.N. were supported in part by NASA grant NAG5-10780 and NSF grant AST 9820686, E.Q. was supported in part by NASA grant NAG5-12043.
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Bulletin of the American Astronomical Society,
© 2003. The American Astronomical Soceity.