Emission lines from X-ray illuminated accretion disc in black hole binaries

TL;DR

This paper models emission lines from X-ray illuminated accretion discs in black hole binaries, exploring how different parameters affect observable features like Fe line strength, aligning with real observations.

Contribution

It introduces a comprehensive model of emission lines considering various accretion flow parameters and their impact on observable spectral features.

Findings

Fe line equivalent width decreases with higher accretion rates.

Fe line equivalent width increases with gas column density.

Model results agree with observational data.

Abstract

X-ray flux from the inner hot region around central compact object in a binary system illuminates the upper surface of an accretion disc and it behaves like a corona. This region can be photoionised by the illuminating radiation, thus can emit different emission lines. We study those line spectra in black hole X-ray binaries for different accretion flow parameters including its geometry. The varying range of model parameters captures maximum possible observational features. We also put light on the routinely observed Fe line emission properties based on different model parameters, ionization rate, and Fe abundances. We find that the Fe line equivalent width $W_{\rm E}$ decreases with increasing disc accretion rate and increases with the column density of the illuminated gas. Our estimated line properties are in agreement with observational signatures.