On the hysteresis effect in transitions between accretion and propeller regimes by Sercan Çıkıntoğlu et al. on Thursday 24 November

Some observations and numerical simulations of disc-magnetosphere interaction

show that accretion can proceed in the propeller regime. When the Alfv\'en

radius is beyond the corotation radius, matter climbs up to the high latitudes

where the Alfv\'en surface is inside the equilibrium surface and can accrete.

We calculate the fraction of the mass flux in the disc that can accrete onto

the neutron star depending on the fastness parameter and the inclination angle

between rotation and magnetic axis. We find that, for a narrow range of the

fastness parameter, the Alfv\'en and the equilibrium surfaces intersect at two

different critical latitudes. While the system is transiting from the propeller

to the accretion regime (the initial rise of an outburst), accretion proceeds

from the region above the higher critical latitude. In transitions from the

accretion to the propeller regime (decay of the outburst), accretion of matter

can proceed from the disc midplane. As a result, the transition from the

propeller to the accretion regime occurs at a luminosity higher than the

transition from the accretion to the propeller regime. We discuss the

implications of our results for spectral transitions exhibited by low-mass

X-ray binaries.

arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.12945v1