Abstract:

X-ray pulsars (XRPs) are accreting strongly magnetised neutron stars (NSs) in close binary systems. The magnetic field strength at the NS surface here can exceed 1.e12 G. Such a strong field shapes the geometry of accretion flow and heavily influences elementary processes of particle interaction. Because of the extremely strong magnetic field and wide range of observed luminosity (more than eight orders of magnitude), XRPs can be considered as unique labs to study physics under various extreme conditions. Observational studies in recent years have yielded many surprising results. In particular, it was recognised that XRPs can be incredibly bright and exceed the Eddington luminosity limit by a factor of hundreds. Recent pioneering observations of polarisation in the X-ray energy band have shown unexpected results that are poorly explained by current theoretical models. We have to admit that despite a more or less clear general picture of physical processes, there is much we do not understand in detail.

In my talk, I will give an overview of the theory of accretion onto strongly magnetised NSs and focus your attention on some theoretical problems and open questions that concern plasma physics in a strong magnetic field.