Please use this identifier to cite or link to this item:
Title: Masses, beaming and eddington ratios in ultraluminous X-ray sources
Authors: King, A. R.
First Published: 1-Feb-2009
Publisher: Royal Astronomical Society (RAS)
Citation: Monthly Notices of the Royal Astronomical Society: LETTERS, 2009, 393 (1)
Abstract: I suggest that the beaming factor in bright ultraluminous X-ray sources (ULXs) varies as Graphic, where Graphic is the Eddington ratio for accretion. This is required by the observed universal Lsoft∝T−4 relation between soft-excess luminosity and temperature, and is reasonable on general physical grounds. The beam scaling means that all observable properties of bright ULXs depend essentially only on the Eddington ratio Graphic, and that these systems vary mainly because the beaming is sensitive to the Eddington ratio. This suggests that bright ULXs are stellar-mass systems accreting at Eddington ratios of the order of 10–30, with beaming factors b≳ 0.1. Lower luminosity ULXs follow bolometric (not soft-excess) L∼T4 correlations and probably represent sub-Eddington accretion on to black holes with masses ∼10M⊙. High-mass X-ray binaries containing black holes or neutron stars and undergoing rapid thermal- or nuclear-time-scale mass transfer are excellent candidates for explaining both types. If the Graphic scaling for bright ULXs can be extrapolated to the Eddington ratios found in SS433, some objects currently identified as active galactic nuclei at modest redshifts might actually be ULXs (‘pseudo-blazars’). This may explain cases where the active source does not coincide with the centre of the host galaxy.
DOI Link: 10.1111/j.1745-3933.2008.00594.x
ISSN: 1745-3933
Version: Publisher Version
Status: Peer-reviewed
Type: Journal Article
Rights: This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2009 the authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. 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

Files in This Item:
File Description SizeFormat 
MNRAS-2009-King-L41-4.pdfPublished (publisher PDF) 473.26 kBAdobe PDFView/Open

Items in LRA are protected by copyright, with all rights reserved, unless otherwise indicated.