EDP Sciences
Free access
Issue
A&A
Volume 407, Number 1, August III 2003
Page(s) L17 - L20
Section Letters
DOI http://dx.doi.org/10.1051/0004-6361:20030983


A&A 407, L17-L20 (2003)
DOI: 10.1051/0004-6361:20030983

Letter

XMM-Newton observation of the brightest X-ray flare detected so far from Sgr A*

D. Porquet1, P. Predehl1, B. Aschenbach1, N. Grosso2, A. Goldwurm3, P. Goldoni3, R. S. Warwick4 and A. Decourchelle3

1  Max-Planck-Institut für extraterrestrische Physik, PO Box 1312, Garching bei München 85741, Germany
2  Laboratoire d'Astrophysique de Grenoble, Université Joseph-Fourier, BP 53, 38041 Grenoble Cedex 9, France
3  CEA, DSM, DAPNIA, Service d'Astrophysique, C.E. Saclay, 91191 Gif-Sur-Yvette Cedex, France
4  Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UK

(Received 26 May 2003 / Accepted 26 June 2003 )

Abstract
We report the high S/N observation on October 3, 2002 with XMM-Newton of the brightest X-ray flare detected so far from Sgr A* with a duration shorter than one hour (~2.7 ks). The light curve is almost symmetrical with respect to the peak flare, and no significant difference between the soft and hard X-ray range is detected. The overall flare spectrum is well represented by an absorbed power-law with a soft photon spectral index of $\Gamma =2.5 \pm0.3$, and a peak 2-10 keV luminosity of 3.6 $^{+0.3}_{-0.4}\times 10 ^{35}$ erg s -1, i.e. a factor 160 higher than the Sgr A* quiescent value. No significant spectral change during the flare is observed. This X-ray flare is very different from other bright flares reported so far: it is much brighter and softer. The present accurate determination of the flare characteristics challenge the current interpretation of the physical processes occuring inside the very close environment of Sgr A* by bringing very strong constraints for the theoretical flare models.


Key words: Galaxy: center -- X-rays: individuals: Sgr A* -- X-rays: general -- radiation mechanisms: general

Offprint request: D. Porquet, dporquet@mpe.mpg.de

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