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 SRG/eROSITA and Gaia transients eRASSt J192932.9-560346 and Gaia21bxo. Frequent large-amplitude changes of its brightness at X-ray and optical wavelengths by more than four magnitudes are 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 that the circular polarization varies from −20 to +20% and the linear polarization varies from 0 to 10%, confirming the system to be a 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 LX = 2.2 × 1031 erg s−1 at the Gaia-determined distance of 376 pc.
- Publication:
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Astronomy and Astrophysics
- Pub Date:
- May 2022
- DOI:
- arXiv:
- arXiv:2106.14540
- Bibcode:
- 2022A&A...661A..43S
- Keywords:
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- stars: individual: eRASSt 192932.9-560346;
- X-rays: stars;
- novae;
- cataclysmic variables;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- Submitted to A&