Swift Deep Galactic Plane Survey classification of Swift J170800−402551.8 as a candidate intermediate polar cataclysmic variable

Here, we present the results of our multiwavelength 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 the Neil Gehrels Swift Observatory, Chandra X-ray Observatory, Neutron star Interior Composition Explorer (NICER), X-ray Multi-Mirror Mission (XMM-Newton), Nuclear Spectroscopic Telescope Array (NuSTAR), and the Southern African Large Telescope (SALT), as well as multiwavelength archival observations from Gaia, VST Photometric H$ Survey, and VISTA Variables in the Via Lactea. 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.