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Multi-wavelength study of accretion onto black holes and its evolution during cosmic times

Final Report Summary - HIGH-Z & MULTI-λ (Multi-wavelength study of accretion onto black holes and its evolution during cosmic times)

The Universe observed with human eyes is dominated by stars and Galaxies surrounding us. X-ray astronomy opened a new window to explore the Cosmo and showed that the X-ray Universe is dominated by the radiation from accreting compact objects (e.g. black holes and neutron stars).
During the Marie Curie fellowship we investigated the supermassive black hole residing at the center of the Milky Way and we lead the European effort to monitor its X-ray activity. We investigated the X-ray emission from the central degree of the Galaxy, discovering new features produced by past events of accretion onto the black hole (Ponti et al. sub.1). We have been leading several multi-wavelength campaigns to monitor the pericenter passage of a small cloud in a collision course with the supermassive black hole, discovering variations in its typical properties (Ponti et al. sub.2). We have been awarded long monitoring programs to observe with the best European X-ray telescope ever made. Dr. Ponti has been invited to be part of the science team (for the Galactic center) of the new hard X-ray focussing telescope lead by Caltech. The connection between the soft X-ray data from the European telescope XMM-Newton with the ones from NuSTAR allowed us to perform a revolution in our understanding of the Galactic center (Mori et al. in prep.; Shuo et al. in prep.).

It is observationally established that outflows are associated to accreting sources. We recently discovered (during the previous Marie Curie fellowship) that stellar mass accreting black holes show powerful winds only during some moments of their life (Ponti et al. 2012). During this fellowship we demonstrated that this behaviour is not a peculiarity accreting black holes, but it extends to accreting neutron stars too (Ponti et al. 2014; 2015). In particular, the same wind properties and phenomenology is observed in the two best studied accreting neutron stars. This has strong implications for the entire field of accretion physics. One strong implication (prediction) of this study is that the same wind should be present in every accreting source. We have also discovered a new cosmological distance measure, using AGN variability (Ponti et al. 2012; La Franca et al. 2014). Thanks to this discovery and to this fellowship, I have been in the position to take a leading role in the study of accretion onto supermassive black holes within the eROSITA collaboration. eROSITA is the next X-ray satellite that will be launched by an European country (designed and build at the host institution).

This European fellowship allowed me to take an leading role in the proposal of new European missions. We successfully proposed the Athena mission that is now an approved cornerstone in the European Space Agency (ESA) vision. Athena will be the next generation large area X-ray observatory. This fellowship has been instrumental to become the chair of one of the science panels (Science Working Group 2.3: Feedback in local AGN and star forming galaxies) appointed by the Athena Science Study Team and ESA.