Μάθημα : Ενημέρωση φοιτητών κατεύθυνσης Αστροφυσικής

Abstract:  X-ray pulsars, predominantly found in Be X-ray binaries (BeXRBs), are powered by accretion processes.  These systems are powered by the transfer of matter from a massive companion to a rapidly rotating neutron star (NS), resulting in highly variable X-ray emission. BeXRBs exhibit recurrent outbursts that offer crucial windows into the physics of accretion and radiation by highly magnetized NSs. 

Interest in these systems has surged with the discovery of pulsating ultra-luminous X-ray sources (PULXs), where NSs accrete at rates exceeding the classical Eddington limit. These sources challenge our understanding of accretion physics, revealing that under certain conditions, stable, super-Eddington accretion onto NSs is not only possible, but sustained. Accompanying outflows may contribute to collimated or beamed emission, enhancing their apparent luminosity.

In this talk, I will introduce the key observational signatures of PULXs and their implications for high-energy astrophysics. The focus, however, will be on BeXRBs that have shown super-Eddington outbursts in the past decade. These events offer rare opportunities to apply spin-torque models, allowing us to infer fundamental properties such as the magnetic field strength of NSs and the orbital parameters of their systems. I will also highlight the interplay between X-ray and optical variability during these outbursts, probing a new way of studying super-Eddington accretion.