Identification of 1RXS J165424.6-433758 as a Polar Cataclysmic Variable

Creators: O'Connor, B.^{1, 2, 3}; Brink, J.^{4, 5}; Buckley, D. A. H.^{4, 5, 6, 7}; Mukai, K.^{3, 8}; Kouveliotou, C.¹; Göğüş, E.⁹; Potter, S. B.^{5, 10}; Woudt, P.⁴; Lien, A.¹¹; Levan, A.¹²; Kargaltsev, O.¹; Baring, M. G.¹³; Bellm, E.¹⁴; Cenko, S. B.^{2, 3}; Evans, P. A.¹⁵; Granot, J.^{1, 16}; Hailey, C.¹⁷; Harrison, F.¹⁸; Hartmann, D.¹⁹; van der Horst, A. J.¹; Huppenkothen, D.²⁰; Kaper, L.²¹; Kennea, J. A.²²; Slane, P. O.²³; Stern, D.²⁴; Troja, E.²⁵; Wijers, R. A. M. J.^{1, 21}; Younes, G.¹

1. George Washington University
2. University of Maryland, College Park
3. Goddard Space Flight Center
4. University of Cape Town
5. South African Radio Astronomy Observatory
6. Southern African Large Telescope
7. University of the Free State
8. University of Maryland, Baltimore County
9. Sabancı University
10. University of Johannesburg
11. University of Tampa
12. Radboud University Nijmegen
13. Rice University
14. University of Washington
15. University of Leicester
16. Open University of Israel
17. Columbia University
18. California Institute of Technology
19. Clemson University
20. Netherlands Institute for Space Research
21. University of Amsterdam
22. Pennsylvania State University
23. Harvard-Smithsonian Center for Astrophysics
24. Jet Propulsion Lab
25. University of Rome Tor Vergata

Abstract

We present the results of our X-ray, ultraviolet, and optical follow-up campaigns of 1RXS J165424.6-433758, an X-ray source detected with the Swift Deep Galactic Plane Survey. The source X-ray spectrum (Swift and NuSTAR) is described by thermal bremsstrahlung radiation with a temperature of kT = 10.1 ± 1.2 keV, yielding an X-ray (0.3–10 keV8) luminosity L_X = (6.5 ± 0.8) × 10³¹ erg s⁻¹ at a Gaia distance of 460 pc. Spectroscopy with the Southern African Large Telescope revealed a flat continuum dominated by emission features, demonstrating an inverse Balmer decrement, the λ4640 Bowen blend, almost a dozen He i lines, and He iiλ4541, λ4686, and λ5411. Our high-speed photometry demonstrates a preponderance of flickering and flaring episodes, and revealed the orbital period of the system, P_orb = 2.87 hr, which fell well within the cataclysmic variable (CV) period gap between 2 and 3 hr. These features classify 1RXS J165424.6-433758 as a nearby polar magnetic CV.

Copyright and License

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.

Acknowledgement

The authors thank the anonymous referee for their careful review and constructive feedback. B.O. would like to acknowledge the significant contribution of Nicholas Gorgone to DGPS operations and analyses during his dissertation research. B.O. acknowledges useful discussions with Jeremy Hare. B.O. and C.K. acknowledge support from NASA grant 80NSSC20K0389.

This work is based on observations obtained with the Southern African Large Telescope under program 2021-2-LSP-001. 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 work made use of data from the NuSTAR mission, a project led by the California Institute of Technology, managed by the Jet Propulsion Laboratory, and funded by the National Aeronautics and Space Administration. 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 data obtained from the 4XMM XMM-Newton serendipitous stacked source catalog 4XMM-DR11s compiled by the institutes of the XMM-Newton Survey Science Centre selected by ESA.

Facilities

Swift - , NuSTAR - The NuSTAR (Nuclear Spectroscopic Telescope Array) mission, XMM - , SALT - Southern African Large Telescope, Elizabeth -

Software References

HEASoft 6.29c, XRTDAS, NuSTARDAS, SAS, XSPEC (Arnaud 1996), IRAF (Tody 1986), Astropy (Astropy Collaboration et al. 2013), ARIADNE (Vines & Jenkins 2022), and dynesty (Speagle 2020).

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