Abstract:
The spacetime metric around astrophysical black holes is thought to be well approximated by the Kerr solution of general relativity, but macroscopic deviations from standard predictions are possible in a number of scenarios beyond Einstein’s gravity. The study of the reflection spectrum of thin accretion disks is potentially a powerful tool to probe the metric around astrophysical black holes and confirm the Kerr paradigm. Recently, we have extended the RELXILL model to non-Kerr background. In this talk, I will present some preliminary constraints on possible deviations from the Kerr metric from the analysis of the reflection spectrum of the black hole binary GX 339-4.