ar X iv : a st ro - p h / 03 11 14 7 v 1 6 N ov 2 00 3 INTEGRAL detection of hard X - ray emission from the Galactic nuclear region 1

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 ′ (FWHM). We report on the discovery of a source, IGR J17456-2901, coincident with the Galactic Nucleus Sgr A * to within 0 ′ .9. Located at R.A.(J2000.0) = 17 h 45 m 38 s .5, 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) × 10 35 ergs s −1. 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 ′ of the Galaxy and a contribution from the galactic supermassive black hole itself cannot be excluded. Subject headings: hard x-rays: observations — galactic center: supermassive black hole — galactic center: x-ray transients — galactic center 1 Based on observations with INTEGRAL, an ESA project with instruments and science data centre funded by ESA member states (especially the and with the participation of Russia and the USA.