A comprehensive, Bayesian analysis of black hole LMXB X-ray spectra using XMM-Newton

In principle, the X-ray spectra of accreting black holes LMXBs contain information about the geometry of the accretion flow and potentially the spacetime near the black hole, determined by its mass and spin. In practice, the inferences about spin and inner flow remain controversial despite big improvements in signal to noise and resolution of the data since the first attempts to infer spin from X-ray spectra. Rather than attempt to “measure” the spin or the inner flow size from the spectral model with variable spin or R_in, we attempt a comprehensive spectral analysis using a zero spin (and R_in=6r_g) model - the “vanilla” model - in an attempt to understand under what conditions, if at all, the model can be made to reproduce the data for various LMXB systems. We adopt a fully Bayesian approach with the best available prior information on BH mass and distance, making use of the latest and most self-consistent combination of various emission components and the most accurate models of interstellar absorption, using XMM-Newton RGS data. With a sample of over 35 black hole XRBs and upwards of 100 observations, this marks the largest and most self-consistent analysis of its nature, allowing for detailed exploration of the geometric properties and changes these systems experience throughout outburst.