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The discovery of weak coherent pulsations in the ultraluminous X-ray source NGC 1313 X-2

Sathyaprakash, R. and Roberts, T. P. and Walton, D. J. and Fuerst, F. and Bachetti, M. and Pinto, C. and Alston, W. N. and Earnshaw, H. P. and Fabian, A. C. and Middleton, M. J. and Soria, R. (2019) The discovery of weak coherent pulsations in the ultraluminous X-ray source NGC 1313 X-2. Monthly Notices of the Royal Astronomical Society: Letters, 488 (1). L35-L40. ISSN 1745-3925. doi:10.1093/mnrasl/slz086.

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We report the detection of weak pulsations from the archetypal ultraluminous X-ray source (ULX) NGC 1313 X-2. Acceleration searches reveal sinusoidal pulsations in segments of two out of six new deep observations of this object, with a period of ∼1.5 s and a pulsed fraction of ∼5 per cent⁠. We use Monte Carlo simulations to demonstrate that the individual detections are unlikely to originate in false Poisson noise detections given their very close frequencies; their strong similarity to other pulsations detected from ULXs also argues they are real. The presence of a large bubble nebula surrounding NGC 1313 X-2 implies an age of order 1 Myr for the accreting phase of the ULX, which implies that the neutron star’s (NS) magnetic field has not been suppressed over time by accreted material, nor has the NS collapsed into a black hole, despite an average energy output into the nebula two orders of magnitude above Eddington. This argues that most of the accreted material has been expelled over the lifetime of the ULX, favouring physical models including strong winds and/or jets for NS ULXs.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Sathyaprakash, R.0000-0002-5254-3969
Roberts, T. P.0000-0001-8252-6337
Walton, D. J.0000-0001-5819-3552
Fuerst, F.0000-0003-0388-0560
Bachetti, M.0000-0002-4576-9337
Pinto, C.0000-0003-2532-7379
Alston, W. N.0000-0003-2658-6559
Earnshaw, H. P.0000-0001-5857-5622
Fabian, A. C.0000-0002-9378-4072
Middleton, M. J.0000-0002-8183-2970
Soria, R.0000-0002-4622-796X
Additional Information:© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2019 May 30. Received 2019 May 28; in original form 2019 April 11. Published: 02 July 2019. The authors wish to thank the referee for their useful comments that helped improve this paper. RS is grateful for the studentship from the STFC (ST/N50404X/1). TPR was funded as part of the STFC consolidated grant ST/K000861/1. HPE acknowledges support under NASA contract NNG08FD60C. CP is thankful for an ESA Research Fellowship, and DJW acknowledges support from an STFC ERF. This work is based on observations obtained with XMM–Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA.
Group:Space Radiation Laboratory
Funding AgencyGrant Number
Science and Technology Facilities Council (STFC)ST/N50404X/1
Science and Technology Facilities Council (STFC)ST/K000861/1
European Space Agency (ESA)UNSPECIFIED
Subject Keywords:accretion, accretion discs – X-rays: binaries
Issue or Number:1
Record Number:CaltechAUTHORS:20190809-141259403
Persistent URL:
Official Citation:R Sathyaprakash, T P Roberts, D J Walton, F Fuerst, M Bachetti, C Pinto, W N Alston, H P Earnshaw, A C Fabian, M J Middleton, R Soria, The discovery of weak coherent pulsations in the ultraluminous X-ray source NGC 1313 X-2, Monthly Notices of the Royal Astronomical Society: Letters, Volume 488, Issue 1, September 2019, Pages L35–L40,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:97725
Deposited By: Tony Diaz
Deposited On:09 Aug 2019 21:20
Last Modified:16 Nov 2021 17:33

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