Identification of an X-Ray Pulsar in the BeXRB System IGR J18219−1347

Creators: O'Connor, B.; Göğüş, E.; Huppenkothen, D.; Kouveliotou, C.; Gorgone, N.; Townsend, L. J.; Calamida, A.; Fruchter, A.; Buckley, D. A. H.; Baring, M. G.; Kennea, J. A.; Younes, G.; Arzoumanian, Z.; Bellm, E.; Cenko, S. B.; Gendreau, K.; Granot, J.; Hailey, C.; Harrison, F.; Hartmann, D.; Kaper, L.; Kutyrev, A.; Slane, P. O.; Stern, D.; Troja, E.; van der Horst, A. J.; Wijers, R. A. M. J.; Woudt, P.

Abstract

We report on observations of the candidate Be/X-ray binary (BeXRB) IGR J18219−1347 with the Swift/X-ray Telescope, the Nuclear Spectroscopic Telescope ARray, and the Neutron Star Interior Composition Explorer during Type-I outbursts in 2020 March and June. Our timing analysis revealed the spin period of a neutron star with P_(spin) = 52.46 s. This periodicity, combined with the known orbital period of 72.4 days, indicates that the system is a BeXRB. Furthermore, by comparing the spectral energy distribution of the infrared counterpart to that of known BeXRBs, we confirm this classification and set a distance of approximately 10–15 kpc for the source. The broadband X-ray spectrum (1.5–50 keV) of the source is described by an absorbed power law with a photon index Γ ∼ 0.5 and a cutoff energy at ∼13 keV.

Additional Information

© 2022 The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 2021 November 24; revised 2022 January 21; accepted 2022 January 24; published 2022 March 10. The authors acknowledge useful discussions with Matteo Bachetti, Tomaso Belloni, and Oleg Kargaltsev. B.O., C.K., and N.G. acknowledge supported under NASA Grants 80NSSC20K0389 and 80NSSC19K091. L.J.T. is supported by the South African National Research Foundation. J.G. acknowledges support by the ISF-NSFC joint research program (grant No. 3296/19). This work made use of data supplied by the UK Swift Science Data Centre at the University of Leicester. This research has made use of the XRT Data Analysis Software (XRTDAS) developed under the responsibility of the ASI Science Data Center (ASDC), Italy. This research has made use of the NuSTAR Data Analysis Software (NuSTARDAS) jointly developed by the ASI Space Science Data Center (SSDC, Italy) and the California Institute of Technology (Caltech, USA). This research has made use of data and/or software provided by the High Energy Astrophysics Science Archive Research Center (HEASARC), which is a service of the Astrophysics Science Division at NASA/GSFC. The scientific results reported in this article are based on observations made by the Chandra X-ray Observatory. This research has made use of software provided by the Chandra X-ray Center (CXC) in the application package CIAO. These results also made use of Lowell Observatory's Lowell Discovery Telescope (LDT), formerly the Discovery Channel Telescope. Lowell operates the LDT in partnership with Boston University, Northern Arizona University, the University of Maryland, and the University of Toledo. Partial support of the LDT was provided by Discovery Communications. LMI was built by Lowell Observatory using funds from the National Science Foundation (AST-1005313). Some of the observations reported in this paper were obtained with the Southern African Large Telescope (SALT) under program 2018-2-LSP-001. We additionally made use of Astropy, a community-developed core Python package for Astronomy (Astropy Collaboration et al. 2013). Facilities: Swift - Swift Gamma-Ray Burst Mission, NuSTAR - , NICER - , SALT - , LDT - , UKIRT - , ZTF - , PS1. - Software: HEASoft v6.27.2, XRTDAS, NuSTARDAS v1.9.2, NICERDAS v7a, XSPEC v12.11.0 (Arnaud 1996), IRAF (Tody 1986), DAOPHOT (Stetson 1987), SExtractor (Bertin & Arnouts 1996), Swarp (Bertin 2010), SCAMP (Bertin 2006), astrometry.net (Lang et al. 2010), Stingray (Huppenkothen et al. 2019), Astropy (Astropy Collaboration et al. 2013).

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