Masaaki Kusunose, Fumio Takahara
Recent observations of Sgr A$^*$ by Fermi and HESS have detected steady
gamma-ray emission in the GeV and TeV bands. We present a new model to explain
the GeV gamma-ray emission by inverse Compton scattering by nonthermal
electrons supplied by the NIR/X-ray flares of Sgr A$^*$. The escaping electrons
from the flare regions accumulate in a region with a size of $\sim 10^{18}$ cm
and magnetic fields of $\lesssim 10^{-4}$ G. Those electrons produce gamma-rays
by inverse Compton scattering off soft photons emitted by stars and dust around
the central black hole. By fitting the GeV spectrum, we find constraints on the
magnetic field and the energy density of optical-UV radiation in the central 1
pc region around the supermassive black hole. While the GeV spectrum is well
fitted by our model, the TeV $\gamma$-rays, whose spectral index is different
from that of the GeV emission, may be from different sources such as pulsar
wind nebulae.
View original:
http://arxiv.org/abs/1201.5438
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