2015ApJ...810...20W -
Astrophys. J., 810, 20 (2015/September-1)
Nature of the extreme ultraluminous X-ray sources.
WIKTOROWICZ G., SOBOLEWSKA M., SADOWSKI A. and BELCZYNSKI K.
Abstract (from CDS):
In this proof-of-concept study we demonstrate that in a binary system mass can be transferred toward an accreting compact object at an extremely high rate. If the transferred mass is efficiently converted to X-ray luminosity (with disregard of the classical Eddington limit) or if the X-rays are focused into a narrow beam, then binaries can form extreme ultraluminous X-ray (ULX) sources with an X-ray luminosity of. For example, Lasota and King argued that the brightest known ULX (HLX-1) is a regular binary system with a rather low-mass compact object (a stellar-origin black hole (BH) or a neutron star (NS)). The predicted formation efficiencies and lifetimes of binaries with the very high mass transfer rates are large enough to explain all observed systems with extreme X-ray luminosities. These systems are not only limited to binaries with stellar-origin BH accretors. Notably, we have also identified such objects with NSs. Typically, a BH is fed by a massive () Hertzsprung gap donor with Roche lobe overflow (RLOF) rate of). For NS systems the typical donors are evolved low-mass () helium stars with RLOF rate of. Our study does not prove that any particular extreme ULX is a regular binary system, but it demonstrates that any ULX, including the most luminous ones, may potentially be a short-lived phase in the life of a binary star.
Abstract Copyright:
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Journal keyword(s):
stars: black holes - stars: neutron - X-rays: binaries
Simbad objects:
9
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