0420062

We propose to carry out an INTEGRAL observation of Sgr A* simultaneously with an approved XMM-Newton large project (200 ks exposure) and the associated multiwavelength campaign planned for spring 2007. The primary aim of this program is the study of the combined X-ray/Gamma-ray flaring activity of SgrA* the radiative manifestation of the supermassive black hole at the galactic center.The discovery of several bright and hard X-ray flares from Sgr A* with Chandra and XMM-Newton have opened new perspectives in understanding the processes at work in the accreting supermassive black hole of the galactic center. The deep INTEGRAL monitoring of the Galactic Center performed in 2003-2004 led to the discovery of emission at energies >20 keV in the direction of the Sgr A complex (the source IGR J1745.6-2901). This excess appears to be constant and it is possibly not associated with the activity of SgrA* but it is still essential to carefully check this hypothesis by searching for IGR J1745.6-2901 gamma-ray variability at the times when Sgr A* is seen to flare in X-rays.The previous coordinated XMM-INTEGRAL campaign aimed to carry out this program failed in resolving this issue because quite unluckily both the bright X-ray flares seen with XMM occurred when INTEGRAL was in the radiation belts. A new campaign with XMM-Newton and HST has been planned for spring 2007 and we propose to perform again coordinated INTEGRAL - XMM observations to search for gamma-ray variability correlated to the X-ray flares. Simultaneous detection of Sgr A* X-ray flares with INTEGRAL even more if coupled to simultaneous infrared and sub-mm observations will be invaluable in assessing the emission models at work in this source. [truncated! Please see actual data for full text]