Bibcode
Pakull, Manfred W.; Grisé, Fabien; Motch, Christian
Bibliographical reference
Populations of High Energy Sources in Galaxies Proceedings of the 230th Symposium of the International Astronomical Union, Held in Dublin, Ireland 15-19 August 2005, Edited by E. J. A. Meurs; G. Fabbiano. Cambridge: Cambridge University Press, 2006., pp.293-297
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0
2006
Citations
76
Refereed citations
71
Description
Optical studies of ultraluminous X-ray sources (ULX) in nearby galaxies
have turned out to be instrumental in discriminating between various
models including the much advertised intermediate mass black hole
hypothesis and various beaming scenarios. Here we report on ESO VLT and
SUBARU observations of ULX that have revealed the parent stellar
clusters with ages of some 60 million years in two cases. Thus we are
able to derive upper limits of about 8 M&sun; for the mass
donors in these systems. The optical counterparts are dominated by X-ray
heated accretion disks, and the discovery of the He II γ4686
emission line now allows to derive dynamical masses in these systems.
Apparent radial velocity variations of 300 km/s have been detected in
NGC 1313 X-2 which, if confirmed by further observations, would exclude
the presence of IMBH in these systems.