Spectra of Puffy Accretion Discs: the kynbb Fit

TL;DR

This study evaluates the effectiveness of existing spectral models in interpreting synthetic spectra of puffy accretion discs from simulations, revealing their limitations and the need for more accurate models based on numerical results.

Contribution

It demonstrates that current spectral models like kerrbb and kynbb fail to accurately recover key parameters of puffy accretion discs, highlighting the necessity for new models grounded in simulations.

Findings

kerrbb and kynbb models do not accurately recover black hole spin and accretion rate

current models are inadequate for luminous, mildly sub-Eddington accretion regimes

new models should be developed based on numerical simulation data

Abstract

Puffy disc is a numerical model, expected to capture the properties of the accretion flow in X-ray black hole binaries in the luminous, mildly sub-Eddington state. We fit the kerrbb and kynbb spectral models in XSPEC to synthetic spectra of puffy accretion discs, obtained in general relativistic radiative magnetohydrodynamic simulations, to see if they correctly recover the black hole spin and mass accretion rate assumed in the numerical simulation. We conclude that neither of the two models is capable of correctly interpreting the puffy disc parameters, which highlights a necessity to develop new, more accurate, spectral models for the luminous regime of accretion in X-ray black hole binaries. We propose that such spectral models should be based on the results of numerical simulations of accretion.