Discovery of the magnetic cataclysmic variable XMM J152737.4–205305.9 with a deep eclipse-like feature

Abstract

We report the identification and subsequent examination of a polar-type cataclysmic variable named XMM J152737.4−205305.9 newly discovered with the X-ray Multi-Mirror Mission (XMM-Newton). This discovery was made by matching the XMM-Newton data archive with the cataclysmic variable candidate catalog provided by Gaia Data Release 3 (DR3). The use of X-ray photometry led to the identification of two distinct dips that exhibit a recurring pattern with a precise period of 112.4 (1) min in two XMM-Newton observations made one year apart. The data obtained from photometry provided by the Zwicky Transient Facility (ZTF) and the Asteroid Terrestrial-impact Last Alert System (ATLAS) survey consistently indicate the presence of mass-accretion states that differ by up to 2 mag. Following the optical data, the Spectrum Roentgen Gamma(SRG)/eROSITA All Sky Survey observed the system at two different X-ray levels, which may imply different accretion states. Following these observations, the low-resolution spectrum obtained using SALT spectroscopy exposes the prominent hydrogen Balmer and helium emission lines, strongly supporting the categorization of this system as a polar-type magnetic cataclysmic variable. The XMM-Newton observations conducted at various X-ray levels reveal a consistent pattern of a deep dip-like feature with a width of ≈9.1 min. This feature implies the presence of an eclipse in both observations. According to Gaia data, the object is located at a distance of 1156−339+720 pc, and its X-ray luminosity lies within the LX = (3 − 6)×1031 erg s−1 range.