The gloriuos past of the supermassive black hole at the galactic center unveiled with XMM and Integral
Abstract
The 8 year XMM-Newton monitoring of the Galactic Centre, along with Integral long surveys and coupled to several correlated multiwavelength (MWL)campaigns, has provided crucial mea-surements of the present and past activity of Sgr A*, the supermassive black hole (SMBH) at the galactic center. With the MWL studies of the hour-long Sgr A* X-ray, infrared and sub-mm flares, we were able to set important new constraints on the emission mechanism and on the physical conditions of the emitting plasma close to the SMBH horizon during these events. With the long term surveys we discovered the decrease over the years of the hard X-ray emis-sion from the Sgr B2 giant molecular cloud and a superluminal propagation of the neutral iron Kα emission at 6.4 keV line through the molecular clouds (MC) located close, in projection, to Sgr A*. These variabilities and spectral measurements trace the recent history of Sgr A*, since they are likely due to reflection and fluorescence excitation of cold molecular material by high-energy radiation emitted by the central SMBH in the past. The MC emission vari-ations, besides to exclude alternative models for the 6.4 keV line emission based on particles interactions, can indeed be explained assuming that Sgr A* underwent a single outburst that rose its luminosity at a level of 1039 erg s-1 (106 times higher than its present luminosity but still 10-5 times its Eddington limit) about 400 year ago, stayed luminous till about 100 years ago and then decayed to the present level of very weak activity. These results allow us for the first time to more precisely compare Sgr A* to the AGN behavior because they show that Sgr A* activity was, only 100 years back, comparable to the one of the typical quiescence state of low-luminosity AGNs.
- Publication:
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38th COSPAR Scientific Assembly
- Pub Date:
- 2010
- Bibcode:
- 2010cosp...38.2251G