http://arxiv.org/abs/2002.04652
We have derived a method yielding very strong constraints on the inner radii of accretion disks in black-hole X-ray binaries based on the Stefan-Boltzmann law. It follows from considering the irradiating flux and the effective temperature of inner parts of the disk. Then, the presence of a quasi-thermal component with a color temperature higher than the effective one is required whenever Fe K fluorescence and reflection features are observed. The observed absence of such quasi-thermal components with the color temperature of $\sim$1 keV rules out a disk extending close to the innermost stable circular orbit in high-luminosity hard states and requires it to be truncated, favoring the presence of a hot flow inside the disk truncation radius in those states. We have also derived a method based on comparing the disk densities fitted (by other authors) using high-density reflection codes with those calculated by us from the fitted ionization parameter, the source luminosity and the disk inner radius. However, we have found a very large scatter of the density ratios, preventing us from obtaining significant constraints as yet.
A. Zdziarski and B. Marco
Thu, 13 Feb 20
9/54
Comments: submitted to ApJ, comments are welcome
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