A Method for Black Hole Mass Determination in Accretion-powered X-Ray Sources

We describe a method for the determination of black hole masses based on information inferred from high-energy spectra. It is required that the spectral energy distribution consist of thermal and Comptonized components. One can then, in principle, infer the depth of the gravitational potential well for sources of known distance. The thermal component is inferred by the integration of a blackbody spectral form over the disk. We assume that the color temperature distribution in the disk has a specific shape given by the Shakura-Sunyaev disk model that goes to zero at the inner disk radius and at infinity and has a maximum at 4.2 RS. In this formulation there is only one parameter, the so-called color correction factor, relating the apparent temperature to effective temperature, which characterizes the thermal emission component. We have made use of improved Galactic black hole binary dynamical mass determinations to derive, in effect, an empirical calibration of this factor. We then present our analysis of observational data for representative objects of several classes: Galactic black hole X-ray binaries, narrow-line Seyfert galaxies (NLS1s), and "ultraluminous" extragalactic X-ray sources (ULXs). We then apply our mass determination calculation and present our results. We argue that this approach can potentially fill a void in the current knowledge of NLS1 and ULX properties and discuss how a deeper understanding of both classes has relevance to the broader issues of how cosmic black holes, beyond the stellar-mass realm, are formed and what is their overall mass distribution.