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Searching for the Donor Stars of ULX Pulsars

Heida, M. and Harrison, F. A. and Brightman, M. and Fürst, F. and Stern, D. and Walton, D. J. (2019) Searching for the Donor Stars of ULX Pulsars. Astrophysical Journal, 871 (2). Art. No. 231. ISSN 1538-4357. doi:10.3847/1538-4357/aafa77.

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We report on our search for the optical counterparts of two ultraluminous X-ray pulsars with known orbital periods, M82 X-2 and NGC 5907 X-1, in new and archival Hubble Space Telescope observations, in an effort to characterize the donor stars in these systems. We detect five near-infrared sources consistent with the position of M82 X-2 that are too bright to be single stars. We also detect seven sources in the WFC3/UVIS F336W image whose photometry matches that of 10–15 M ⊙ stars turning off the main sequence. Such stars have densities consistent with the properties of the donor star of M82 X-2 as inferred from X-ray timing analysis, although it is also possible that the donor is a lower-mass star below our detection limit or that there is a significant contribution from the accretion disk to the optical emission. We detect three candidate counterparts to NGC 5907 X-1 in the near-infrared. All of these are too bright to be the donor star of the ultraluminous X-ray source (ULX), which, based on its orbital period, is a red giant. The high background at the location of NGC 5907 X-1 precludes us from detecting this expected donor star. The recently discovered NGC 5907 ULX-2 also falls within the field of view of the near-infrared imaging; we detect four sources in the error circle, with photometry that matches asymptotic giant branch stars. The star suggested to be the counterpart of NGC 5907 ULX-2 by Pintore et al. falls outside our 2σ error circle.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Heida, M.0000-0002-1082-7496
Harrison, F. A.0000-0003-2992-8024
Brightman, M.0000-0002-8147-2602
Fürst, F.0000-0003-0388-0560
Stern, D.0000-0003-2686-9241
Walton, D. J.0000-0001-5819-3552
Additional Information:© 2019 The American Astronomical Society. Received 2018 October 2; revised 2018 December 18; accepted 2018 December 19; published 2019 February 4. We would like to thank the anonymous referee whose comments helped to significantly improve the paper. This work is based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program 15074. Support for Program number 15074 was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS 5-26555. The scientific results reported in this article are based in part on data obtained from the Chandra Data Archive. This work has made use of data from the European Space Agency (ESA) mission Gaia (, processed by the Gaia Data Processing and Analysis Consortium (DPAC, Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. The work of DS was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. Facilities: HST (WFPC2 and WFC3) - , Chandra (ACIS) - , Gaia - . Software: astropy (Astropy Collaboration et al. 2013), DOLPHOT (Dolphin 2000), MESA (Paxton et al. 2011, 2013, 2015), CIAO (Fruscione et al. 2006).
Group:Space Radiation Laboratory, Astronomy Department
Funding AgencyGrant Number
NASANAS 5-26555
Gaia Multilateral AgreementUNSPECIFIED
Subject Keywords:infrared: stars – stars: neutron – X-rays: individual (M82 X-2, NGC 5907 X-1, NGC 5907 ULX-2)
Issue or Number:2
Record Number:CaltechAUTHORS:20190204-095332991
Persistent URL:
Official Citation:M. Heida et al 2019 ApJ 871 231
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:92620
Deposited By: Tony Diaz
Deposited On:04 Feb 2019 18:05
Last Modified:16 Nov 2021 03:52

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