Bulletin of the American Physical Society
2005 APS April Meeting
Saturday–Tuesday, April 16–19, 2005; Tampa, FL
Session X3: Galactic Center |
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Sponsoring Units: DAP Chair: Steven Boggs, University of California-Berkeley Room: Marriott Tampa Waterside Grand Salon A/B |
Tuesday, April 19, 2005 10:45AM - 11:21AM |
X3.00001: A Detailed X-ray View of High-Energy Activity in the Galactic Center Invited Speaker: Over the past six years, the Chandra X-ray Observatory has repeatedly observed Sagittarius (Sgr) A*, the compact nonthermal radio source and supermassive black hole at the dynamical center of our Milky Way Galaxy. The combined deep exposure coupled with Chandra's 0.5-arcsecond resolution have produced the most sensitive X-ray image of our Galactic center, allowing us to study the central black hole and its environment in unprecedented detail. Sgr~A* is extremely faint in X-rays, radiating about 11 orders of magnitude below the Eddington limit, despite the abundant supply of fuel provided by the strong winds emanating from a cluster of young, massive stars in the central parsec. The properties of this X-ray emission will be discussed, along with the emission from surrounding stars, supernovae, and other structures in the central parsecs of the Galaxy, including the recent discovery of an overabundance of X-ray transients within the central parsec that provides evidence for the existence of a swarm of stellar-mass black hole and neutron star X-ray binaries surrounding the supermassive black hole. In October 2000, Chandra discovered a rapid, large-amplitude X-ray flare from Sgr~A*. This extreme activity was totally unexpected. Chandra and XMM-Newton have since shown that Sgr~A* flares in X-rays on a daily basis. NIR flares have been discovered within the last year at about three times the rate of the X-ray flares, raising the question of whether the X-ray and NIR flares are produced by the same or different processes. I will present results from the first simultaneous detection of an X-ray and NIR flare from Sgr~A*. At least in this case, the X-rays and NIR photons appear to arise from the same electron population. [Preview Abstract] |
Tuesday, April 19, 2005 11:21AM - 11:57AM |
X3.00002: 511 keV emission from the Galactic Center Invited Speaker: |
Tuesday, April 19, 2005 11:57AM - 12:33PM |
X3.00003: The Galactic Center: The Nearest Laboratory for Studying Supermassive Black Holes Invited Speaker: Because of its proximity the Center of the Milky Way is a unique laboratory for studying supermassive black holes. Measurements of stellar velocities and partial orbits from speckle interferometric and adaptive optics imaging in the period 1992 - 2003 have established a compelling case that this dark mass concentration is a massive black hole of about 3 to 4 Million solar masses. Since then several spectacular results have emerged from the latest generation of instruments and telescopes: The discovery, time resolved photometry, and spectral characterisation of infrared emission from the flaring black hole give insight to the physical properties just a few light minutes from the event horizon. The spectral classification of about a dozen stars in the central few light weeks reveals the paradox of youth of the stellar population. And the measurement of the radial velocities for these stars allows a full three dimensional characterisation of the orbits, as well as a geometric determination of the distance to the Center of our Galaxy. [Preview Abstract] |
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