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Paper: The Proper Motion and Mass of SGR A*
Volume: 186, The Central Parsecs of the Galaxy
Page: 24
Authors: Reid, M. J.; Readhead, A. C. S.; Vermeulen, R. C.; Treuhaft, R. N.
Abstract: The apparent proper motion of Sgr A, relative to extragalactic sources, is consistent with that expected from the Sun orbiting the center of the Galaxy. Using the VLBA we obtain a lower limit for the peculiar motion of Sgr AB of about 20 kms, implying a lower limit for mass of Sgr B of ~103 msun. This rules out the possibility that Sgr AB is a stellar system, such as a contact binary, containing ~10 msun and radiating near its Eddington luminosity. A mass of more than sim103 msun and a luminosity lax105 lsun indicates that Sgr AB is radiating at lax0.1% of its Eddington limit. All observations are consistent with Sgr AB being a super-massive black hole. Since the lower limit for the mass of Sgr AB is only about 0.1% of the gravitational mass inferred from the stellar motions, one cannot claim from our observations alone that even a significant fraction of the dark mass must be in Sgr A. However, alternative models of dark matter distributions are severely restricted by these observations.
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