Speaker
Description
The source 1A 0538-66, located in the Large Magellanic Cloud, contains the fastest-spinning neutron star in an accreting X-ray binary and shows a combination of extreme properties unmatched in other NS/Be systems.
It is characterized by extraordinary multiwavelength variability, including sporadic episodes of seconds-long X-ray flares with a dynamic range >1000 and peak luminosities exceeding 10$^{38}$ erg/s, which are correlated with bright, fast optical flares. The fast pulsations (69 ms), discovered in the 80's during a super-Eddington outburst and never reobserved for almost 40 yrs, were recently detected at a much lower luminosity level, challenging our understanding of accretion physics. In 2025, 1A 0538-66 displayed a new outburst reaching super-Eddington luminosities typical of ultraluminous X-ray sources.
I will present the results of recent observations of this binary system and discuss how they constrain the physical mechanisms, such as magnetic field geometry and accretion flow dynamics, responsible for its unique variability.