Speaker
Description
Be X-ray binaries (BeXRBs) consist of a Be star (a massive star with a circumstellar disk) and a neutron star. They constitute a prominent subclass within the category of high-mass X-ray binaries, characterized by their transient nature. These binaries intermittently exhibit X-ray outbursts, whereas the rest of the time they remain quiescent. On the transition between these two X-ray activity states, it is believed that a BeXRB enters a quiescent state when accretion onto the neutron star is impeded by its rapidly rotating magnetosphere. However, the observational support for this centrifugal inhibition of accretion, often referred to as the propeller mechanism, comes only from a couple of systems with a neutron star with a relatively short spin period. The applicability of this mechanism in other BeXRBs, particularly those housing slowly rotating neutron stars, remains uncertain. In this presentation, we explore a possibility that in misaligned BeXRBs, the wind of the Be star can strongly suppress accretion, dispersing the accreting gas by its large ram pressure. Employing analytical models for both the wind and accretion disk, we compare the wind ram pressure with the gas pressures of the accretion flow for a number of systems with well determined/constrained parameters. We find that in some systems the state transition from the X-ray outburst to the quiescence is likely attributed to the inhibition of accretion by the stellar wind. In order to better understand how this mechanism works, we discuss the interaction between the stellar wind and the accretion flow in more detail, on the basis of the results from 3D hydrodynamic simulations.
