SDSS J085414.02+390537.3 -- a new asynchronous polar

Abstract

The asynchrony of the polar SDSS~J085414.02+390537.3 was revealed using the data of ZTF photometric survey. The light curves show a beat period $P_{beat} = 24.6 \pm 0.1$~days. During this period the system changes its brightness by $\sim 3^m$. The periodograms show power peaks at the white dwarf's rotation period $P_{spin} = 113.197 \pm 0.001$~min and orbital period $P_{orb} = 113.560 \pm 0.001$~min with the corresponding polar asynchrony $1-P_{orb}/P_{spin} = 0.3\%$. The photometric behavior of the polar indicates a change of the main accreting pole during the beat period. Based on the Zeeman splitting of the H$\beta$ line, an estimate of the mean magnetic field strength of the white dwarf is found to be $B = 28.5\pm 1.5$~MG. The magnetic field strength $B \approx 34$~MG near the magnetic pole was found by modeling cyclotron spectra. Doppler tomograms in the H$\beta$ line demonstrate the distribution of emission sources typical for polars.