Swift Deep Galactic Plane Survey Classification of Swift J170800-402551.8 as a Candidate Intermediate Polar Cataclysmic Variable

Abstract

Here, we present the results of our multi-wavelength campaign aimed at classifying Swift J170800−402551.8 as part of the Swift Deep Galactic Plane Survey (DGPS). We utilized Target of Opportunity (ToO) observations with Neil Gehrels Swift, Observatory, Chandra X-ray Observatory and the Southern African Large Telescope (SALT), as well as multi-wavelength archival observations from Gaia, VPHAS, and Hα. The source displays a periodicity of 784 s in our XMM–Newton observation.The X-ray spectrum (XMM–Newton and NuSTAR) can be described by thermal bremsstrahlung radiation with a temperature of kT ≈ 30 keV. The phase-folded X-ray light curve displays a double-peaked, energy-dependent pulse profile. We used Chandra to precisely localize the source, allowing us to identify and study the multiwavelength counterpart. Spectroscopy with SALT identified a Balmer H α line, and potential He I lines, from the optical counterpart. The faintness of the counterpart (r ≈ 21 AB mag) favours a low-mass donor star. Based on these criteria, we classify Swift J170800−402551.8 as a candidate intermediate polar cataclysmic variable, where the spin period of the white dwarf is 784 s.