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تسجيل مستخدم جديدKeck Observations of the Galactic Center Source G2: Gas Cloud or Star?
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We present new observations and analysis of G2 - the intriguing red emission-line object which is quickly approaching the Galaxys central black hole. The observations were obtained with the laser guide star adaptive optics systems on the W. M. Keck I and II telescopes and include spectroscopy (R ~ 3600) centered on the Hydrogen Br-gamma line as well as K (2.1 micrometer) and L (3.8 micrometer) imaging. Analysis of these observations shows the Br-gamma line emission has a positional offset from the L continuum. This offset is likely due to background source confusion at L. We therefore present the first orbital solution derived from Br-gamma line astrometry, which when coupled with radial velocity measurements, results in a later time of closest approach (2014.21 +/- 0.14), closer periastron (130 AU, 1900Rs), and higher eccentricity (0.9814 +/- 0.0060) compared to a solution using L astrometry. The new orbit casts doubt on previous associations of G2 and a low surface brightness tail. It is shown that G2 has no K counterpart down to K ~ 20 mag. G2s L continuum and the Br-gamma line-emission is unresolved in almost all epochs; however it is marginally extended in our highest quality Br-gamma data set from 2006 and exhibits a clear velocity gradient at that time. While the observations altogether suggest that G2 has a gaseous component which is tidally interacting with the central black hole, there is likely a central star providing the self-gravity necessary to sustain the compact nature of this object.
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In 2011, we discovered a compact gas cloud (G2) with roughly three Earth masses that is falling on a near-radial orbit toward the massive black hole in the Galactic Center. The orbit is well constrained and pericenter passage is predicted for early 2
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