Hard X-ray view of the past activity of Sgr A* in a natural Compton mirror
Abstract
We report the association of the recently discovered hard X-ray source IGR J17475-2822 with the giant molecular cloud Sgr B2 in the Galactic Center region. The broad band (3-200 keV) spectrum of the source constructed from data of different observatories strongly supports the idea that the X-ray emission of Sgr B2 is Compton scattered and reprocessed radiation emitted in the past by the Sgr A* source. We conclude that 300-400 years ago Sgr A* was a low luminosity (L≈ 1.5× 1039 erg s-1 at 2-200 keV) AGN with a characteristic hard X-ray spectrum (photon index Γ≈ 1.8). We estimate the mass and iron abundance of the Sgr B2 scattering gas at 2× 106 M⊙(r/10 pc)2 and 1.9 solar, respectively (where r is the radius of the cloud).
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- October 2004
- DOI:
- 10.1051/0004-6361:200400064
- arXiv:
- arXiv:astro-ph/0408190
- Bibcode:
- 2004A&A...425L..49R
- Keywords:
-
- Galaxy: center;
- ISM: clouds: individual: Sgr B2;
- X-rays: ISM;
- Astrophysics
- E-Print:
- 5 pages, 3 fugures. Submmitted to A&