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

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 photoionized by the illuminating radiation, and 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 WE 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.