The X-ray hardness ratio variation in low-mass X-ray binaries

Abstract

The behaviour of the hardness ratio in low-mass X-ray binaries (LMXRB) indicates that at some value of mass accretion rate\(\dot M\), the X-ray intensity decreases with increasing\(\dot M\). It is suggested here that, at some\(\dot M\), wind from the accretion disk becomes appreciable and depletes the mass accretion on to the neutron star and thus reduces the X-ray intensity. This explains the behaviour of the hardness ratio in LMXRB. Possible implications of this on quasi-periodic oscillations are discussed.