2022A&A...666A.150M

Context. For the past decade, it has been suggested that intermediate polars (IPs), a subclass of magnetic cataclysmic variables (CVs), are one of the main contributors to the hard diffuse X-ray emission from the Galactic center (GC) and Galactic ridge.
Aims. In our ongoing XMM-Newton survey of the central region of the Galactic disk (20° ×2°), we detected a persistent IP candidate, 1.7° away from the GC. In this work, we better characterize the behavior of this source by looking at the new and archival XMM-Newton data.
Methods. We performed a detailed X-ray spectral modeling of the source. Furthermore, we searched for X-ray pulsations in the light curve as well as its counterpart at other wavelengths.
Results. The XMM-Newton spectrum (0.8-10 keV) of the source is described by a partial covering collisionally ionized diffuse gas with plasma temperature $ kT=15.7^{+20.9}_{-3.6} $ keV. In addition, the spectrum shows the presence of iron lines at E = 6.44, 6.65, and 6.92 keV with equivalent widths of $ 194^{+89}_{-70} $, $ 115^{+79}_{-75} $, and $ 98^{+93}_{-74} $ eV, respectively. The X-ray light curve shows a coherent modulation with a period of P = 432.44 ± 0.36 s, which we infer is the spin period of the white dwarf. The white dwarf mass estimated from fitting a physical model to the spectrum results in $ M_{\mathrm{WD}}=1.05^{+0.16}_{-0.21}\,M_{\odot} $. We were able to find a likely optical counterpart in the Gaia catalog with a G magnitude of 19.26, and the distance to the source derived from the measured Gaia parallax is ∼4.3 kpc.
Conclusions. We provide an improved source localization with subarcsec accuracy. The spectral modeling of the source indicates the presence of intervening circumstellar gas, which absorbs the soft X-ray photons. The measured equivalent width of the iron lines and the detection of the spin period in the light curve are consistent with those from IPs.