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S. Gezari, A.M. Ghez, E.E. Becklin, J. Larkin, I. McLean, M. Morris (UCLA)
We present initial results from a spectroscopic study of the SgrA* (IR) Cluster, a concentration of faint stars (K ~ 14 - 16 mag) within ~ 0."5 of SgrA*, the compact radio source associated with the central 2.6x106 M\sun black hole. High spatial resolution (\thetares ~ 0."07) and Strehl ratios of ~ 0.2 achieved with adaptive optics allows us to measure the spectra of these stars individually, from which the spectral types and radial velocities of the stars can be determined. Here we show moderate spectral resolution (R ~ 2000) K-band (2.0 - 2.4 \mum) spectra obtained with NIRSPEC+AO on the Keck II telescope of five sources in the central cluster. CO bandhead absorption, indicative of late type stars, is detected in a proper motion star 0."037 West and 0."443 South of SgrA*. The deepest CO bandhead in the spectrum, CO (2-0) at 2.29 \mum, has an equivalent width of ~ 10 Å. The absolute K magnitude and CO absorption line strength of this star is consistent with an early K giant. The blueshift of the CO bandhead corresponds to a radial velocity for the star of ~ - 300 km s-1. The other sources observed lack CO bandhead absorption, ruling out the possibility that they are late-type stars, and suggesting from their absolute K magnitudes that they are late O/early B main sequence stars.