High Energy at MPA: Discovery of a superluminal Fe K echo at the Galactic Center: The in-glorious past of Sgr A* betrayed by molecular clouds

by Gabriele Ponti (University of Southampton)

Lecture Hall (MPA, Garching)

Lecture Hall

MPA, Garching

The study of the 8 years XMM-Newton monitoring of the Galactic Centre Molecular Clouds (MC), within 15 arcmin from SgrA*, will be presented. The emission from the X-ray bright MC shows all the features characteristic of reflection. The long baseline monitoring allows the characterisation of the temporal evolution of the MC emission, showing a complex pattern of significant variations. In particular, we observe an apparent super-luminal motion of a light front illuminating a Molecular nebula. This might be due to a source outside the MC (such as SgrA* or a bright and long outburst of a X-ray binary), while it can not be due to low energy cosmic rays or a source located inside the cloud. We also observe a decrease of the X-ray emission from G0.11-0.11, behaviour similar to the one of SgrB2 (for which we measured a fading of the hard X-ray emission in the last 7 years, thanks to the INTEGRAL monitoring of the GC). The line intensities, clouds dimensions, columns densities and positions with respect to SgrA*, are consistent with being produced by the same SgrA* flare. We will infer the past activity of Sgr A* showing that its luminosity has been less than 10^36 erg s-1 since the World War II, that it ended a period of activity (with L~10^39 erg s-1) about 100 years ago and most probably never reached luminosity higher than 10^41 erg s-1 (~2*10^-4 Eddington) since the end of the Roman Empire.