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F.K. Baganoff, M.W. Bautz, G.R. Ricker (MIT), M. Morris, E.E. Becklin, A.M. Ghez, S.D. Hornstein, A.M. Tanner (UCLA), W.N. Brandt, G. Chartas, E.D. Feigelson, G.P. Garmire (PSU), A.S. Cotera, P.M. Hinz, W.F. Hoffmann, M.R. Meyer (Steward Obs.), A. Eckart (U. Cologne), R. Genzel (MPE), J.-H. Zhao, R.M. Herrnstein, J.L. Hora (CfA), J.-P. Macquart (U. Groningen), Y. Maeda (ISAS), R.J. Sault (ATNF), G.B. Taylor (NRAO), F. Walter (Caltech)
Sgr A* was observed with the ACIS-I instrument on the Chandra X-Ray Observatory for 0.5 Ms during the period 22 May 2002 to 4 June 2002. Three X-ray flares with amplitudes in excess of a factor of 10 and several flares of lower amplitude were detected. The flare durations ranged from half an hour to several hours with rise and fall times of a few hundred seconds, similar to the original X-ray flare discovered with Chandra in 2000. These observations confirm that rapid X-ray flaring of Sgr A* is common. Averaging over all Chandra observations from 1999-2002, a total of 0.6 Ms, the mean rate of factor-of-10 flares is 0.6 +\- 0.3 per day. During the Chandra observations, a network of ground-based telescopes were employed for simultaneous observations for varying amounts of time and at various wavelengths: the Keck-I Telescope at 2 and 10 microns; the VLT at 2 to 5 microns; the Magellan-Baade Telescope at 10 microns; the SMA at 1 mm; the ATCA and the Owens Valley Millimeter Array at 3 mm; the VLBA at 7 mm; and the VLA at 0.7, 1.3 and 2 cm. We compare the variability properties in the X-ray and longer wavelength bands to assess models for the origin of the X-ray flares from Sgr A*.
This research was supported by NASA grant NAS8-39073.
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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.