Probing the reach of the Intermediate Polar Cataclysmic Variable Population with Swift J183920.1-045350

Abstract

We report on the Swift/XRT Deep Galactic Plane Survey discovery and multi-wavelength follow-up observations of a new intermediate polar Cataclysmic Variable, Swift J183920.1-045350. A 449.7 s spin period is found in Xmm-Newton and NuSTAR data, accompanied by a 459.9 s optical period that is most likely the synodic, or beat period, produced from a 5.6 h orbital period. The orbital period is seen with moderate significance in independent long-baseline optical photometry observations with ZTF and SAAO. We find that the source X-ray pulsed fraction decreases with increasing energy. The X-ray spectra are consistent with the presence of an Fe emission line complex with both local and interstellar absorption. In the optical spectra, strong Hα, H I, He I and He II emission lines are observed, all common features in magnetic CVs. The source properties are thus typical of known intermediate polars, with the exception of its estimated distance of 2.26⁺¹˙⁹³₋₀.₈₃ kpc, which is larger than typical, extending the reach of the CV population in our Galaxy.