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 \textit{Swift} Deep Galactic Plane Survey (DGPS). The source X-ray spectrum (\textit{Swift} and \textit{NuSTAR}) is described by thermal bremsstrahlung radiation with a temperature of kT=10.1±1.2 keV, yielding an X-ray (0.3−10 keV) luminosity LX=(6.5±0.8)×1031 erg s−1 at a \textit{Gaia} distance of 460 pc. Spectroscopy with the Southern African Large Telescope (SALT) revealed a flat continuum dominated by emission features, demonstrating an inverse Balmer decrement, the λ4640 Bowen blend, almost a dozen HeI lines, and HeII λ4541, λ4686 and λ5411. Our high-speed photometry demonstrates a preponderance of flickering and flaring episodes, and revealed the orbital period of the system, Porb=2.87 hr, which fell well within the cataclysmic variable (CV) period gap between 2−3 hr. These features classify 1RXS J165424.6-433758 as a nearby polar magnetic CV.
@article{arxiv.2306.05576,
title = {Identification of 1RXS J165424.6-433758 as a polar cataclysmic variable},
author = {B. O'Connor and J. Brink and D. A. H. Buckley and K. Mukai and C. Kouveliotou and E. Gogus and S. B. Potter and P. Woudt and A. Lien and A. Levan and O. Kargaltsev and M. G. Baring and E. Bellm and S. B. Cenko and P. A. Evans and J. Granot and C. Hailey and F. Harrison and D. Hartmann and A. J. van der Horst and D. Huppenkothen and L. Kaper and J. A. Kennea and P. O. Slane and D. Stern and E. Troja and R. A. M. J. Wijers and G. Younes},
journal= {arXiv preprint arXiv:2306.05576},
year = {2023}
}