AAS 205th Meeting, 9-13 January 2005
Session 24 Galactic Center
Poster, Monday, January 10, 2005, 9:20am-6:30pm, Exhibit Hall

## [24.04] Infrared Monitoring of the Supermassive Black Hole at the Galactic Center

S.D. Hornstein, A.M. Ghez, M. Morris (UCLA), K Matthews (Caltech), J Lu (UCLA), D. Thompson (Caltech), E.E. Becklin (UCLA), B.T. Soifer (Caltech), F.K. Baganoff (MIT)

We present the results of a dedicated monitoring program aimed at studying the intensity variations of the near-infrared emission associated with the supermassive black hole at the Galactic center (Sgr A*-IR.) This effort was carried out during the summer of 2004 with the W. M. Keck 10-meter telescope's adaptive optics system and covered seven nights, two of which were coordinated with several observatories, including the Chandra X-ray Telescope. Variability on a range of time scales, from minutes to months, was seen. These variations, which typically had an amplitude of a factor of no more than two, extended through observations made in concert with Chandra, which showed no X-ray variations, although the timescales for variations were similar. Comparisons of near-simultaneous data obtained in the K' (2.1 \mum)- and L' (3.8 \mum)- bandpasses suggest that Sgr A*-IR has an observed K'-L' of 2.6 mag, which is more than a magnitude redder than the surrounding stellar sources and consistent with synchrotron models for the emission.

Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.