Black hole formation in X-ray binaries: The case of GRO J1655-40

In recent years proper motion measurements have been added to the set of observational constraints on the current properties of Galactic X-ray binaries. We develop an analysis that allows us to consider all this available information and reconstruct the full evolutionary history of X-ray binaries back to the time of core collapse and compact object formation. Here we present our analysis and results for GRO J1655-40. We find that a symmetric black hole (BH) formation event cannot be formally excluded, but that the associated system parameters are only marginally consistent with the currently observed binary properties. BH formation mechanisms involving an asymmetric supernova explosion with associated BH kick velocities of a few tens of km s ^-1, on the other hand, satisfy the constraints much more comfortably. We also derive an upper limit on the BH kick magnitude of ≃ 210km s ^-1.