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We report the association of the recently discovered hard X-ray source IGRJ17475-2822 with the giant molecular cloud Sgr B2 in the Galactic Centerregion. The broad band (3-200 keV) spectrum of the source constructed from dataof different observatories strongly supports the idea that the X-ray emissionof Sgr B2 is Compton scattered and reprocessed radiation emitted in the past bythe Sgr A* source. We conclude that 300-400 years ago Sgr A* was a lowluminosity (L ~ 1.5e39 erg/s at 2-200 keV) AGN with a characteristic hard X-rayspectrum (photon index Gamma ~ 1.8). We estimate the mass and iron abundance ofthe Sgr B2 scattering gas at 2e6 Msun (r/10pc)^2 and 1.9 solar, respectively(where r is the radius of the cloud).

Hard X-ray view of the past activity of Sgr A$^{\star}$ in a natural Compton mirror