The Observed Galactic Annihilation Line: Possible Signature of Accreting Small‐Mass Black Holes in the Galactic Center

Compton Gamma Ray Observatory, OSSE, SMM, TGRS, balloon and recent INTEGRALdata reveal a feature of the 0.511 MeV annihilation radiation of the GalacticCenter with a flux of approximately 5x 10^{-4}~0.511 MeV photons cm^{-2}s^{-1}. We argue that e+e- pairs can be generated when the X-ray radiationphotons and ~10-30 MeV photons interact with each other in the compact regionin the proximity of the Galactic Center black hole. In fact, disks formed nearblack holes of 10^{17} g mass should emit the ~ 10 MeV temperature blackbodyradiation. If positron e+ sources are producing about 10^{42} e+ s^{-1} nearthe Galactic Center they would annihilate on the way out and result in 0.511MeV emission. We suggest that the annihilation radiation can be anobservational consequence of the interaction of the accretion disk radiation ofthe SMall Mass Black Holes (SMMBHs) with X-ray radiation in the GalacticCenter. This is probably the only way to identify and observe these SMMBHs.Comment: 21 pages, 1 figure, to appear in the ApJ, 10 March 2006, v 639 2 issu