Issue |
A&A
Volume 672, April 2023
|
|
---|---|---|
Article Number | A188 | |
Number of page(s) | 10 | |
Section | Stellar structure and evolution | |
DOI | https://doi.org/10.1051/0004-6361/202345966 | |
Published online | 21 April 2023 |
Serendipitous discovery of the magnetic cataclysmic variable SRGE J075818−612027
1
Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany
e-mail: sok@aip.de
2
Department of Astronomy & Space Sciences, Faculty of Science, University of Ege, 35100 Bornova, Izmir, Turkey
3
South African Astronomical Observatory, PO Box 9 Observatory Road, Observatory, 7935 Cape Town, South Africa
4
Department of Astronomy, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa
5
Department of Physics, University of the Free State, PO Box 339 Bloemfontein 9300, South Africa
Received:
20
January
2023
Accepted:
24
February
2023
We report the discovery of SRGE J075818−612027, a deep stream-eclipsing magnetic cataclysmic variable found serendipitously in SRG/eROSITA calibration and performance verification phase (CalPV) observations of the open cluster NGC 2516 as an unrelated X-ray source. An X-ray timing and spectral analysis of the eROSITA data is presented and supplemented by an analysis of TESS photometry and SALT spectroscopy. X-ray photometry reveals two pronounced dips repeating with a period of 106.144(1) min. The 14-month TESS data reveal the same unique period. A low-resolution identification spectrum obtained with SALT displays hydrogen Balmer emission lines on a fairly blue continuum. The spectrum and the stability of the photometric signal led to the classification of the new object as a polar-type cataclysmic variable. In this context, the dips in the X-ray light curve are explained by absorption in the intervening accretion stream and by a self-eclipse of the main accretion region. The object displays large magnitude differences on long timescales (months) both at optical and X-ray wavelengths, which are interpreted as high and low states and thus support its identification as a polar. The bright phase X-ray spectrum can be reflected with single temperature thermal emission with 9.7 keV and bolometric X-ray luminosity LX ≃ 8 × 1032 erg s−1 at a distance of about 2.7 kpc. The X-ray spectrum lacks the pronounced soft X-ray emission component prominently found in ROSAT-discovered polars.
Key words: novae / cataclysmic variables / binaries: close / X-rays: binaries / stars: individual: SRGE J075818−612027 / stars: fundamental parameters
© The Authors 2023
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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