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Paper: Variable Hard X-Ray Emission from the Sgr B2 Molecular Cloud
Volume: 439, The Galactic Center: a Window to the Nuclear Environment of Disk Galaxies
Page: 442
Authors: Terrier, R.; Ponti, G.; Bélanger, G.; Decourchelle, A.; Tatischeff, V.; Goldwurm, A.; Trap, G.
Abstract: The 4 million solar masses black hole at the Galactic centre (GC) is remarkably quiet today. The molecular cloud Sgr B2, among others, emits strong Fe Kα photons as well as hard X-rays up to 100 keV. This has been interpreted as the result of the illumination of the cloud by a past high luminosity period of Sgr A*. This interpretation is still controversial since irradiation by subrelativistic cosmic rays might also account for the observed spectra. We present here the results of 7 years of INTEGRAL monitoring of Sgr B2 and show that its hard X-ray (20–60 keV) flux has decreased by nearly 40% during that period. This cannot be accounted for by cosmic ray interpretations and support the idea that Sgr A* was more active in the past and has been quiescent since about 100 years.
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