Astronomy & Astrophysics

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Issue		A&A Volume 410, Number 2, November I 2003
Page(s)		L5 - L8
Section		Letters
DOI		10.1051/0004-6361:20031355

A&A 410, L5-L8 (2003)
DOI: 10.1051/0004-6361:20031355

Letter

Faint hard X-ray sources in the Galactic Center region: Supernova ejecta fragments population

A. M. Bykov

AF Ioffe Institute for Physics and Technology, St. Petersburg 194021, Russia
(Received 2 May 2003 / Accepted 3 September 2003 )

Abstract
Long Chandra observations of $17 \hbox{$^\prime$ }\times 17 \hbox{$^\prime$ }$ field in the Galactic Center (GC) region reported by Muno et al. (2003) have revealed a population of about 2000 hard faint X-ray sources limited by luminosities $L_{\rm x} \geq 10^~ \rm ~erg~s^$ . We show that fast moving knots (FMKs) of supernovae ejecta could comprise a sizeable fraction of the sources. Each supernova event can produce hundreds of FMKs. The presence of ~3 supernova remnants of age $\sim$ 10³ ${\rm years}$ in the GC region could provide the required number of the FMKs. Simulated X-ray spectra of the FMKs contain both thermal and nonthermal components. The nonthermal spectra are power-laws with hard photon indexes $0 \leq \Gamma \leq 1.5$ and prominent lines of some metals (e.g. Fe). The ${\rm log}\,N$ - ${\rm log}\,S$ distribution and the hardness ratios of the FMKs in the GC region are consistent with the Chandra findings. Spatial distribution of the FMKs in the GC region should appear as an ensemble of coherent shell and jet-like structures of a few arcmin-scale.

Key words: acceleration of particles -- radiation mechanisms: non-thermal -- ISM -- clouds -- ISM: individual object: Galactic Center -- ISM: supernova remnants -- X-rays: diffuse background

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