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|Title:||Ultraluminous X-ray sources in external galaxies|
|Authors:||King, Andrew R.|
Davies, Melvyn B.
|Citation:||Astrophysical Journal, 2001, 552 (2), pp.L109-L112|
|Abstract:||We investigate models for the class of ultraluminous nonnuclear X-ray sources (i.e., ultraluminous compact X-ray sources [ULXs]) seen in a number of galaxies and probably associated with star-forming regions. Models in which the X-ray emission is assumed to be isotropic run into several difficulties. In particular, the formation of sufficient numbers of the required ultramassive black hole X-ray binaries is problematic, and the likely transient behavior of the resulting systems is not in good accord with observation. The assumption of mild X-ray beaming suggests instead that ULXs may represent a short-lived but extremely common stage in the evolution of a wide class of X-ray binaries. The best candidate for this is the phase of thermal-timescale mass transfer that is inevitable in many intermediate- and high-mass X-ray binaries. This in turn suggests a link with the Galactic microquasars. The short lifetimes of high-mass X-ray binaries would explain the association of ULXs with episodes of star formation. These considerations still allow the possibility that individual ULXs may contain extremely massive black holes.|
|Rights:||Copyright © 2001, The American Astronomical Society. Deposited with reference to the publisher’s archiving policy available on the SHERPA/RoMEO website.|
|Appears in Collections:||Published Articles, Dept. of Physics and Astronomy|
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|10.1086_320343.pdf||Post-review (final submitted)||55 kB||Adobe PDF||View/Open|
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