Discovery of eRASSt J192932.9-560346: a bright, two-pole accreting, eclipsing polar

Abstract

We report the discovery of a bright (V ~ 15), eclipsing, two-pole accreting magnetic cataclysmic variable (CV), a polar, as counterpart of the eROSITA and Gaia transients eRASSt 192932.9-560346 and Gaia21bxo. Frequent large amplitude changes of its brightness at X-ray and optical wavelengths by more than 4 magnitudes was indicative of a CV nature of the source. Identification spectra obtained with the 10m SALT telescope revealed the typical features of a magnetic CV, strong, broad HeI, HeII and hydrogen Balmer emission lines superposed on a blue continuum. Time-resolved photoelectric polarimetry revealed circular polarization to vary from -20% to +20%, and linear polarization from 0% to 10% confirming the system to be magnetic CV of the polar subclass. High cadence photometry revealed deep, structured eclipses, indicating that the system is a two pole accretor. The orbital period determined from the eclipse times is 92.5094 +- 0.0002 min. The X-ray spectrum is thermal only and the implied luminosity is L_X=2.2 x 10^(31) erg/s at the Gaia-determined distance of 376 pc.

Submitted to A&A for the Special Issue: The Early Data Release of eROSITA and Mikhail Pavlinsky ART-XC on the SRG Mission. 5 pages, 7 figures

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• Discrete sources as the origin of the Galactic X-ray ridge emission
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• Serendipitous discovery of the magnetic cataclysmic variable SRGE J075818-612027
• Discovery of the magnetic cataclysmic variable XMM J152737.4-205305.9 with a deep eclipse-like feature
• The eROSITA DR1 variability catalogue
• Cataclysmic Variable Candidates Identified in eROSITA-DE DR1,XMM-Newton, Swift, and ROSAT Catalogs
• Confirmation of SRGt 062340.2-265751 as a nova-like cataclysmic variable with a possible magnetic nature