Sgr A, located at the dynamical center of the Milky Way, is closest supermassive black hole. Surrounding Sgr A at about 30", the torus of neutral gas named the CircumNuclear Disk (CND) was detected in X-rays for the first time. We deduced that the CND rather acts as a barrier for the Galactic Centre plasma. Despite its very low luminosity, Sgr A experiences a flaring activity that can be observed in infrared, X-ray, and submillimeter wavelengths. However, the origin of such flares is still debated. Recently, we have conducted a study of the X-ray flaring activity of Sgr A considering the overall flares observed with XMM-Newton, Chandra and Swift telescopes since 1999. We have shown that the activity of the supermassive black hole has changed since 2013 whereas it was constant since 1999: the flaring rate of the brightest flares increased while the flaring rate of the less luminous flares decreased. This change in the flaring activity could be explained by a change in the mass-accretino rate or a change in the distribution of relativist electrons.
|Choix de session parallèle||1.1 Les diverses facettes du centre galactique : des abords du trou noir à son environnement plus lointain.|