The brightest Ultra Luminous X-ray Sources : evidence for super-Eddington accretion and intermediate mass black holes

Séminaire IPAG de Natalie Webb (IRAP), jeudi 8 janvier 2015 à 11h00, IPAG seminar room

Ultra Luminous X-ray (ULX) sources are defined as off-nuclear point-like X-ray sources with X-ray luminosities that exceed the Eddington limit for a 10 solar mass black hole. Their nature is still unclear, but it has been proposed that these objects may be stellar mass black holes accreting above the Eddington limit, although a mechanism is yet to be identified for exceeding this theoretical limit. Alternatively, they may be the much sought after intermediate mass black holes, that are thought to be the building blocks of the supermassive black holes present in the centres of the most massive galaxies. During this seminar I will present recent advances in our understanding of ULXs. I will include our recent discovery that the bright ULX M 82 X-2, appears to be a neutron star accreting at 100 times the Eddington limit and the evidence that ESO 243-49 HLX-1 is an intermediate mass black hole. I will also discuss what the implications of these findings.