Implementation of a radial disk ionization profile in the RELXILL_NK model

Understand

Very steep reflection emissivity profiles in the inner part of accretion disks are commonly found in the analysis of X-ray observations of black hole binaries and AGN, but there is some debate about their exact origin.

• While steep reflection emissivity profiles can be naturally produced by compact coronae close to black holes, the measured radial emissivity parameter can be further increased by the radial disk ionization profile when the theoretical model assumes a disk with constant ionization.
• In this paper, we implement the possibility of a radial disk ionization profile in the reflection model RELXILL_NK, which is a package designed to calculate reflection spectra of "deformed" Kerr black holes.
• We analyze a NuSTAR observation of the black hole binary EXO 1846-031, which was previously found to have a very high inner emissivity index.