Abstract for Proposal 084423

Fast multi-wavelength variability from a BH: speed, size and geometry of a jet

Correlated fast multi-wavelength variability is quickly becoming a key tool for studying the physics of accretion/ejection of relativistic jets. Using X-ray/IR simultaneous data we have recently discovered vibrations from a relativistic jet down to 62.5 ms time scale, which allowed us to estimate the jet speed and size. Our results from further data also show that the jet properties depend on the spectral state of the BH. Here, we propose to monitor the outburst evolution of a BH transient with XMM, simultaneously with ground-based OIR facilities, in order to apply the same technique to different states. We will monitor the energetic and geometrical changes in the jet, and its relation with the accretion disk. We propose to perform up to 12 short XMM observations.



Details on Observing Strategy and Trigger Criteria
We will activate our program as soon as a (known or new) BH is reported in outburst by any ground- or space-based facility, including MAXI, Swift, NuSTAR, XMM itself. Reaction time: as we aim at monitoring the full outburst, we do not require fast reaction time. We can live with observations scheduled one week or more after the trigger, depending on the XMM schedule complexity and/or on the VLT Service-Mode nights. Observing strategy: we are very flexible on this as well. The observing strategy will depend mostly on the SM nights at VLT. We will agree on a provisional strategy upon trigger, and we will then follow closely the source evolution and in case modify the strategy as needed. As for the trigger, we will do this with more than one week notice.