MASTER OT J072007.30+451611.6: A polar with strong optical variability and suppressed He ii emission
Bobakov A.V. Zharikov S.V. Karpova A.V. Zyuzin D.A. Kirichenko A.Y. Shibanov Y.A. Karimov R. Vaidman N.L. Nurmakhametova S.T. Gilfanov M.R. Michel R.
1 August 2025Oxford University Press
Monthly Notices of the Royal Astronomical Society
2025#541Issue 43468 - 3478 pp.
The transient optical source MASTER OT J072007.30+451611.6 has been recently discovered and proposed as a peculiar polar with an unusually high amplitude of the orbital brightness variation in the optical of 3 mag. To clarify its nature, we performed multiband time-series optical photometry with 1.5-m class telescopes and spectroscopy with the 10.4-m Gran Telescopio Canarias. We also analysed archival data of different optical surveys and detected the source in X-rays with the Spectrum-RG/eROSITA telescope (extended ROentgen Survey with an Imaging Telescope Array on board Spectrum Roentgen Gamma observatory). We confirm the orbital period of 1.5 h with the high amplitude of the brightness modulation. Compiling survey data, covering 19 yr, we find high and low-brightness states of the object at time-scales of years, likely explained by different accretion rates. Our data were obtained in the high-brightness state. Optical spectra with hydrogen and helium emission lines, consisting of broad and narrow components, indicate the presence of an accretion stream without disc. The Doppler tomography shows that the narrow component is mainly emitted from the Lagrangian L point, while the broad component is from the region where the accretion stream interacts with the white dwarf magnetosphere. The ratio of equivalent widths of He ii 4686 and H emission lines is
binaries: close , novae, cataclysmic variables , stars: individual: MASTER OT J072007.30+451611
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Ioffe Institute, 26 Politekhnicheskaya, St. Petersburg, 194021, Russian Federation
Instituto de Astronomía, Universidad Nacional Autónoma de México, Apdo. Postal 106, Ensenada, Baja California, 22860, Mexico
Ulugh Beg Astronomical Institute, Uzbekistan Academy of Sciences, Tashkent, 100052, Uzbekistan
Faculty of Physics and Technology, Al-Farabi Kazakh National University, Al-Farabi Ave., 71, Almaty, 050040, Kazakhstan
Fesenkov Astrophysical Institute, Observatory, 23, Almaty, 050020, Kazakhstan
Space Research Institute, Russian Academy of Sciences, Profsoyuznaya Str 84/32, Moscow, 117997, Russian Federation
Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, Garching, D-85741, Germany
Ioffe Institute
Instituto de Astronomía
Ulugh Beg Astronomical Institute
Faculty of Physics and Technology
Fesenkov Astrophysical Institute
Space Research Institute
Max-Planck-Institut für Astrophysik
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