Identification of 1RXS J165424.6-433758 as a Polar Cataclysmic Variable
Mukai, K.; Troja, E.; Cenko, S. B.; Lien, A.; Hailey, C.; Harrison, F.; Stern, D.; Kouveliotou, C.; Kaper, L.; Wijers, R. A. M. J.; Baring, M. G.; van der Horst, A. J.; Kennea, J. A.; Buckley, D. A. H.; Evans, P. A.; O'Connor, B.; Levan, A.; Hartmann, D.; Kargaltsev, O.; Potter, S. B.; Bellm, E.; Woudt, P.; Younes, G.; Göğüş, E.; Granot, J.; Huppenkothen, D.; Brink, J.; Slane, P. O.
United States, South Africa, Turkey, Netherlands, United Kingdom, Israel, Italy
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 II λ4541, 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.