Bayesian X-ray Spectral Analysis of Black Hole Spins in Seyfert I AGN

X-ray spectra emitted from the innermost regions around spinning supermassive black holes (SMBH), where they are impacted by general-relativistic frame-dragging effects geometrically described by the Kerr metric, could provide valuable information about the SMBH spins. Typically, radio-quiet Seyfert I active galactic nuclei (AGN) have low inclinations with respect to the line of sight, so their X-ray spectra from the innermost regions are not obscured by the surrounding dusty doughnut-shaped tori of AGN. We recently employed a sophisticated Markov chain Monte Carlo (MCMC) Bayesian statistical program (pyBLoCXS) to simultaneously fit an inclination-dependent relativistic ray-tracing reflection model (relxill) to the relativistically broadened fluorescent iron line (6.4 keV rest frame) and Compton reflection hump (> 10 keV) in XMM-Newton and NuSTAR archival X-ray observations of some Seyfert I AGN (NGC 3783, MCG-6-30-15, and NGC 4593). Our MCMC-based Bayesian spectral analysis puts robust constraints on the relxill model parameters such as the black hole spin, inclination angle, iron abundance, and reflection fraction. Further studies of a large sample of Seyfert I AGN are necessary to get a broader picture of the implications of SMBH spins for AGN feedback and host galaxies.