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

Correlated fast multiwavelength variability is quickly becoming a key tool for studying thephysics of accretion/ejection of relativistic jets. Using Xray/IR simultaneousdata we have recently discovered vibrations from a relativistic jet down to 62.5ms time scale, which allowed us to estimate the jet speed and size. Our resultsfrom further data also show that the jet properties depend on the spectral stateof the BH. Here, we propose to monitor the outburst evolution of a BH transientwith XMM, simultaneously with groundbased OIR facilities, in order to apply thesame technique to different states. We will monitor the energetic andgeometrical changes in the jet, and its relation with the accretion disk. We propose to perform up to 10 short XMM observations. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]