EDP Sciences
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Volume 379, Number 1, November III 2001
Page(s) L13 - L16
Section Letters
DOI http://dx.doi.org/10.1051/0004-6361:20011346

A&A 379, L13-L16 (2001)
DOI: 10.1051/0004-6361:20011346

The Nature of the 10 kilosecond X-ray flare in Sgr A*

S. Markoff, H. Falcke, F. Yuan and P. L. Biermann

Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany

(Received 6 September 2001 / Accepted 26 September 2001)

The X-ray mission Chandra has observed a dramatic X-ray flare -a brightening by a factor of 50 for only three hours -from Sgr A*, the Galactic Center supermassive black hole. Sgr A* has never shown variability of this amplitude in the radio and we therefore argue that a jump of this order in the accretion rate does not seem the likely cause. Based on our model for jet-dominated emission in the quiescent state of Sgr A*, we suggest that the flare is a consequence of extra electron heating near the black hole. This can either lead to direct heating of thermal electrons to $T_{\rm
e}\sim6\times 10^{11}$ K and significantly increased synchrotron-self Compton emission, or result from non-thermal particle acceleration with increased synchrotron radiation and electron Lorentz factors up to $\gamma_{\rm e}\ga10^{5}$. While the former scenario is currently favored by the data, simultaneous VLBI, submm, mid-infrared and X-ray observations should ultimately be able to distinguish between the two cases.

Key words: galaxy: center -- galaxies: jets -- X-rays: galaxies -- radiation mechanisms: non-thermal -- accretion, accretion disks -- black hole physics

Offprint request: S. Markoff, smarkoff@mpifr-bonn.mpg.de

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