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A new transient ultraluminous X-ray source in NGC 7090

Walton, D. J. and Heida, M. and Bachetti, M. and Fürst, F. and Brightman, M. and Earnshaw, H. and Evans, P. A. and Fabian, A. C. and Grefenstette, B. W. and Harrison, F. A. and Israel, G. L. and Lansbury, G. B. and Middleton, M. J. and Pike, S. and Rana, V. and Roberts, T. P. and Rodriguez Castillo, G. A. and Salvaterra, R. and Song, X. and Stern, D. (2021) A new transient ultraluminous X-ray source in NGC 7090. Monthly Notices of the Royal Astronomical Society, 501 (1). pp. 1002-1012. ISSN 0035-8711. doi:10.1093/mnras/staa3666.

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We report on the discovery of a new, transient ultraluminous X-ray source (ULX) in the galaxy NGC 7090. This new ULX, which we refer to as NGC 7090 ULX3, was discovered via monitoring with Swift during 2019–2020, and to date has exhibited a peak luminosity of L_X ∼ 6 × 10³⁹ erg s⁻¹. Archival searches show that, prior to its recent transition into the ULX regime, ULX3 appeared to exhibit a fairly stable luminosity of L_X ∼ 10³⁸ erg s⁻¹. Such strong long-time-scale variability may be reminiscent of the small population of known ULX pulsars, although deep follow-up observations with XMM–Newton and NuSTAR do not reveal any robust X-ray pulsation signals. Pulsations similar to those seen from known ULX pulsars cannot be completely excluded, however, as the limit on the pulsed fraction of any signal that remains undetected in these data is ≲20 per cent. The broad-band spectrum from these observations is well modelled with a simple thin disc model, consistent with sub-Eddington accretion, which may instead imply a moderately large black hole accretor (M_(BH) ∼ 40 M⊙). Similarly, though, more complex models consistent with the super-Eddington spectra seen in other ULXs (and the known ULX pulsars) cannot be excluded given the limited signal-to-noise ratio of the available broad-band data. The nature of the accretor powering this new ULX therefore remains uncertain.

Item Type:Article
Related URLs:
URLURL TypeDescription ItemESA XMM–Newton Science Archive
https://heasarc.gsfc.nasa.govRelated ItemNASA HEASARC Archive ItemNASA Chandra Data Archive Paper
Walton, D. J.0000-0001-5819-3552
Heida, M.0000-0002-1082-7496
Bachetti, M.0000-0002-4576-9337
Fürst, F.0000-0003-0388-0560
Brightman, M.0000-0002-8147-2602
Earnshaw, H.0000-0001-5857-5622
Evans, P. A.0000-0002-8465-3353
Fabian, A. C.0000-0002-9378-4072
Grefenstette, B. W.0000-0002-1984-2932
Harrison, F. A.0000-0003-2992-8024
Israel, G. L.0000-0001-5480-6438
Lansbury, G. B.0000-0002-5328-9827
Middleton, M. J.0000-0002-8183-2970
Pike, S.0000-0002-8403-0041
Rana, V.0000-0003-1703-8796
Roberts, T. P.0000-0001-8252-6337
Salvaterra, R.0000-0002-9393-8078
Song, X.0000-0003-4924-0550
Stern, D.0000-0003-2686-9241
Additional Information:© 2020 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2020 November 18. Received 2020 November 17; in original form 2020 October 9. Published: 25 November 2020. The authors would like to thank the reviewer for their positive feedback, which helped to improve the final version of the manuscript. DJW and MJM acknowledge support from the Science and Technology Facilities Council (STFC) in the form of Ernest Rutherford Fellowships. PAE acknowledges UK Space Agency (UKSA) support. This research has made use of data obtained with NuSTAR, a project led by Caltech, funded by NASA and managed by the NASA Jet Propulsion Laboratory (JPL), and has utilized the NUSTARDAS software package, jointly developed by the Space Science Data Centre (SSDC; Italy) and Caltech (USA). This research has also made use of data obtained with XMM–Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States, as well as public data from the Swift data archive. Finally, this work has also made use of data obtained from the Chandra Source Catalog, provided by the Chandra X-ray Center (CXC) as part of the Chandra Data Archive, as well as data obtained from the 4XMM XMM-Newton serendipitous source catalogue, compiled by the 10 institutes of the XMM-Newton Survey Science Centre (SSC) selected by ESA. Data Availability: All of the data underlying this article are either already publicly available from ESA’s XMM–Newton Science Archive (, NASA’s HEASARC archive (, and NASA’s Chandra Data Archive (, or will be from 2021 May.
Group:Astronomy Department, Space Radiation Laboratory, NuSTAR
Funding AgencyGrant Number
Science and Technology Facilities Council (STFC)UNSPECIFIED
United Kingdom Space Agency (UKSA)UNSPECIFIED
Subject Keywords:stars: black holes – stars: neutron – X-rays: binaries – X-rays: individual (NGC 7090 ULX3)
Issue or Number:1
Record Number:CaltechAUTHORS:20210201-140020702
Persistent URL:
Official Citation:D J Walton, M Heida, M Bachetti, F Fürst, M Brightman, H Earnshaw, P A Evans, A C Fabian, B W Grefenstette, F A Harrison, G L Israel, G B Lansbury, M J Middleton, S Pike, V Rana, T P Roberts, G A Rodriguez Castillo, R Salvaterra, X Song, D Stern, A new transient ultraluminous X-ray source in NGC 7090, Monthly Notices of the Royal Astronomical Society, Volume 501, Issue 1, February 2021, Pages 1002–1012,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:107840
Deposited By: Tony Diaz
Deposited On:01 Feb 2021 22:50
Last Modified:16 Nov 2021 19:06

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