The International Workshop on
Quark Phase Transition in Compact Objects and Multimessenger Astronomy:
Neutrino Signals, Supernovae and Gamma-Ray Bursts

7-14 October 2015

Super-Eddington accretion disks in Ultraluminous X-ray sources Fabrika S., Vinokurov A., Atapin K., Sholukhova O.

Abstract

      The origin of Ultraluminous X-ray sources (ULXs) in external galaxies whose X-ray luminosities exceed those of the brightest black holes in our Galaxy hundreds and thousands times is mysterious. The most popular models for the ULXs involve either intermediate mass black holes (IMBHs) or stellar-mass black holes accreting at super-Eddington rates. Here we review the ULX properties, their X-ray spectra indicate the presence of hot winds in their accretion disks supposing the supercritical accretion. However, the strongest evidences come from optical spectroscopy. The spectra of the ULX counterparts are very similar to that of SS433, the only known supercritical accretor in our Galaxy. The spectra are apparently of WNL type (late nitrogen Wolf-Rayet stars) or LBV (luminous blue variables) in their hot state, which are very scarce stellar objects. We find that the spectra do not originate from WNL/LBV type donors but from very hot winds from the accretion disks, whose physical conditions are similar to those in stellar winds from these stars. The results suggest that bona-fide ULXs must constitute a homogeneous class of objects, which most likely have supercritical accretion disks.

Reference:
Fabrika S., Vinokurov A., Atapin K., Sholukhova O., "Super-Eddington accretion disks in Ultraluminous X-ray sources", in "Proceedings of the International Workshop on Quark Phase Transition in Compact Objects and Multimessenger Astronomy: Neutrino Signals, Supernovae and Gamma-Ray Bursts", Russia, Nizhnij Arkhyz (SAO RAS), Terskol (BNO INR RAS), October, 7 - 14, 2015, Publishing house "Sneg", Pyatigorsk, 2016, ISBN 978-5-903129-85-0, pp. 37-42.
DOI: 10.26119/SAO.2020.1.51244
Download .pdf