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Searching for propeller-phase ULXs in the XMM-Newton Serendipitous Source Catalogue

Earnshaw, H.P.; Roberts, T.P.; Sathyaprakash, R.

Searching for propeller-phase ULXs in the XMM-Newton Serendipitous Source Catalogue Thumbnail


Authors

H.P. Earnshaw

R. Sathyaprakash



Abstract

We search for transient sources in a sample of ULXs from the 3XMM-DR4 release of the XMM-Newton Serendipitous Source Catalogue in order to find candidate neutron star ULXs alternating between an accreting state and the propeller regime, in which the luminosity drops dramatically. By examining their fluxes and flux upper limits, we identify five ULXs that demonstrate long-term variability of over an order of magnitude. Using Chandra and Swift data to further characterise their light curves, we find that two of these sources are detected only once and could be X-ray binaries in outburst that only briefly reach ULX luminosities. Two others are consistent with being super-Eddington accreting sources with high levels of inter-observation variability. One source, M51 ULX-4, demonstrates apparent bimodal flux behaviour that could indicate the propeller regime. It has a hard X-ray spectrum, but no significant pulsations in its timing data, although with an upper limit of 10% of the signal pulsed at ∼1.5 Hz a pulsating ULX cannot be excluded, particularly if the pulsations are transient. By simulating XMM-Newton observations of a population of pulsating ULXs, we predict that there could be approximately 200 other bimodal ULXs that have not been observed sufficiently well by XMM-Newton to be identified as transient.

Citation

Earnshaw, H., Roberts, T., & Sathyaprakash, R. (2018). Searching for propeller-phase ULXs in the XMM-Newton Serendipitous Source Catalogue. Monthly Notices of the Royal Astronomical Society, 476(3), 4272-4277. https://doi.org/10.1093/mnras/sty501

Journal Article Type Article
Acceptance Date Feb 21, 2018
Online Publication Date Feb 23, 2018
Publication Date May 21, 2018
Deposit Date Feb 23, 2018
Publicly Available Date Feb 28, 2018
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 476
Issue 3
Pages 4272-4277
DOI https://doi.org/10.1093/mnras/sty501
Related Public URLs https://arxiv.org/pdf/1802.07753.pdf

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Accepted Journal Article (384 Kb)
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Copyright Statement
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society © 2018 The Authors.
Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.






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