AAS Meeting #194 - Chicago, Illinois, May/June 1999
Session 84. Studying the Anatomy of the Milky Way
Display, Thursday, June 3, 1999, 9:20am-4:00pm, Southwest Exhibit Hall

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[84.02] Stellar Orbits and Variability in the Central 1"x1" of the Milky Way

A. M. Ghez, M. Morris, E. E. Becklin, A. Tanner (UCLA)

Four years ago, we initiated a proper motion study of the Galaxy's central stellar cluster using diffraction-limited K[2.2 micron]-band images obtained with the W.M. Keck I 10-m telscope. With relative positional accuracies of 2 milliarcsec, we have been able to measure stars moving at velocities up to 1400 km s-1 at projected distances from the apparent radio counterpart of the black hole, Sgr A*, down to 0.004 pc (0.1"). These measurements have not only provided us with direct dynamical evidence for a supermassive central black hole (Ghez et al. 1998), but have also permitted us to begin to constrain the orbits of these stars for the first time ever. We will present a detailed analysis of stars observed in the central 1"x1", including (1) constraints on the orbital parameters, (2) limits on the flux from Sgr A*, and (3) a discussion of S3, an intriguing variable source located a mere 70 milliarcsec away from the nominal position of Sgr A*.

This work is supported by the NSF and the Packard Foundation.

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