Reflection in neutron star and black hole binaries

Abstract

X-ray spectra of black hole and neutron star binaries in the hard spectral state are dominated by the Comptonized emission generated in the optically thin plasma in the vicinity of the compact object and a reflected component whose origin is related to the reflection of the primary Comptonized emission from the optically thick accretion disk. It has been demonstrated that there is a significant correlation between the strength of the reflected component and the Comptonization parameter in black hole systems. This correlation have led to important conclusion regarding the source of the soft seed photons for Comptonization and the overall geometry of the accretion flow in X-ray binaries. In this work we study relation between these two parameters in an accreting neutron star 4U1608-52 and demonstrate that it significantly differs from the correlation observed in black hole systems. We interpret this result in terms of the difference in the properties of the compact object in BH and NS systems.