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Accretion rates and beaming in ultraluminous X-ray sources

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journal contribution
posted on 24.10.2012, 09:15 by A. R. King
I show that extreme beaming factors b are not needed to explain ultraluminous X-ray sources (ULXs) as stellar-mass binaries. For neutron-star accretors, one typically requires b∼ 0.13, and for black holes almost no beaming (b∼ 0.8). The main reason for the high apparent luminosity is the logarithmic increase in the limiting luminosity for super-Eddington accretion. The required accretion rates are explicable in terms of thermal-time-scale mass transfer from donor stars of mass 6–10 M⊙, or possibly transient outbursts. Beaming factors ≲0.1 would be needed to explain luminosities significantly above 1040L40 erg s−1, but these requirements are relaxed somewhat if the accreting matter has low hydrogen content.

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Citation

Monthly Notices of the Royal Astronomical Society: LETTERS, 2008, 385 (1)

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VoR (Version of Record)

Published in

Monthly Notices of the Royal Astronomical Society: LETTERS

Publisher

Royal Astronomical Society (RAS)

issn

1745-3933

Copyright date

2008

Available date

24/10/2012

Publisher version

http://mnrasl.oxfordjournals.org/content/385/1/L113

Language

en

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