18 février 2020Ultraluminous X-ray sources: what have we learned recently?

Fabien GRISE
University of Iowa, USA

After a decade of intense studies using the latest X-ray and optical telescopes, the nature of ultraluminous X-ray sources (ULXs) is still largely unknown. No definitive answer has emerged on the question of the mass of the black hole powering these objects (intermediate-mass or supercritical stellar-mass?). Further, we lack even basic knowledge about the binary systems and the companion stars. I will summarize the outstanding issues in the field and review recent important results. In a second part, I will focus on more recent work including a study of a persistent ULX that shows long-term X-ray behavior consistent with some Galactic X-ray binaries, which includes the detection of superorbital periodicities and recurrent X-ray dipping.