The Galactic Centre Region
14 September 2005
In an article to be published in the Astrophysical Journal, Bélanger et al. present the results of a detailed analysis of approximately 1900 hours of observations of the galactic centre, obtained with Integral since the launch of the spacecraft in October 2002.The IBIS/ISGRI imager on the Integral observatory detected for the first time a hard X-ray source, IGRJ17456–2901, located within 1 arcminute of Sagittarius A* (Sgr A* - the black hole residing at the centre of our Galaxy) over the energy range 20–100 keV.
Two years and an effective exposure of 4.7×106 s have allowed for obtaining more stringent positional constraints on this high-energy source and the construction of its spectrum in the energy range 20–400 keV.
This central source near Sgr A* appears not te be a point source as previously thought, but likely is a diffuse, but compact, source. The observations by Bélanger et al. also show that the source is faint, but persistent with no detected variability.
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The galactic centre as observed with IBIS/ISGRI onboard INTEGRAL. The image covers a region of about 2.5° x 1.5°. Credits: G. Bélanger (CEA Saclay) et al. |
By combining the ISGRI spectrum together with the total X-ray spectrum corresponding to the same physical region around Sgr A* from XMM-Newton data, and collected during part of the gamma-ray observations, Bélanger et al. have also constructed the first accurate wide band high-energy spectrum for the central arcminutes of the Galaxy. These findings are also presented in the upcoming publication (see also 'Bélanger et al. 2005').
