Detection of hard X-ray emission from the Galactic nuclear region with INTEGRAL

Abstract

This letter presents the first results of an observational campaign to study the Galactic Centre with INTEGRAL. The mosaicked images obtained with the IBIS/ISGRI coded aperture instrument in the energy ranges 20-40 and 40-100 keV, give a yet unseen view of the high-energy sources of this region in hard X- and gamma-rays with an angular resolution of 12 arcmin (FWHM). We report on the discovery of a source, IGR J17456-2901, coincident with the Galactic Nucleus SgrA* to within 0.9 arcmin. Located at R.A.(J2000.0) = 17h45m38.5s, Dec.(J2000.0) = -29:01:15, the source is visible up to about 100 keV with a 20-100 keV luminosity at 8 kpc of (2.89 +/- 0.41) x 10^35 ergs/s. Although the new INTEGRAL source cannot unequivocally be associated to the Galactic Nucleus, this is the first report of significant hard X-ray emission from within the inner 10 arcmin of the Galaxy and a contribution from the galactic supermassive black hole itself cannot be excluded.