AAS 200th meeting, Albuquerque, NM, June 2002
Session 44. The Milky Way: Center and Halo
Display, Tuesday, June 4, 2002, 10:00am-6:30pm, SW Exhibit Hall

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[44.02] Short Term Variability of Sagittarius A* in the Near-Infrared

S.D. Hornstein, A.M. Ghez, A.M. Tanner (UCLA), S. Gezari (Columbia University), M. Morris, E.E. Becklin (UCLA), P. Wizinowich (Keck Observatory)

The recent detection of a 10 ksec (~3 hr) X-ray flare by the Chandra Observatory has raised the possibility of enhanced emission over a broad range of wavelengths from Sagittarius A*, the putative 2.6 x 106 Msolar black hole at the Galactic Center, during a flaring event. We have therefore reconstructed 3 hr data sets from 2 micron speckle and adaptive optics images (\thetares = 50 - 100 mas) obtained with the W. M. Keck 10-m Telescopes between 1995 and 2001 for a dynamical study of the Galactic Center (Ghez et al. 1998, 2000). In 27 separate observations, no evidence of any significant emission associated with Sgr A* was detected, with limits ranging from 32.4 to 2.6 mJy (dereddened) and a median value of 5.4 mJy. While the lowest limit is consistent with previously published values, the coverage of our data set provides strong constraints on the duty cycle for any random flaring event that would raise the emission above current near-infrared detection limits. At the 99.7% confidence level, no detections in 27 observations implies a duty cycle of <18%. Including the Chandra observations in this calculation, the duty cycle is further restricted to 0.04%<(duty cycle)<15%. However, the joint probability distribution for the above hypothesis peaks at a duty cycle of 2.7% with a probability of 7.7%. This low probability suggests that the model favored by Markoff et al. (2001), in which the flare is produced through local heating of relativistic particles in an accretion disk or jet around Sgr A* (e.g. a sudden magnetic reconnection event), is unlikely because it predicts peak 2 micron emission of ~300 mJy, well above our detection limit.

This work is supported by the National Science Foundation.

The author(s) of this abstract have provided an email address for comments about the abstract: seth+aas@astro.ucla.edu

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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.