CRTS J035010.7+323230, a new eclipsing polar in the cataclysmic variable period gap

Abstract

We report the discovery of a new eclipsing polar, CRTS J035010.7+323230 (hereafter CRTS J0350+3232). We identified this cataclysmic variable (CV) candidate as a possible polar from its multi-year Catalina Real-Time Transient Survey (CRTS) optical light curve. Photometric monitoring of 22 eclipses in 2015 and 2017 was performed with the 2.1-m Otto Struve Telescope at McDonald Observatory. We derive an unambiguous high-precision ephemeris. Strong evidence that CRTS J0350+3232 is a polar comes from optical spectroscopy obtained over a complete orbital cycle using the Apache Point Observatory 3.5-m telescope. High velocity Balmer and He II $\lambda$4686Å emission line equivalent width ratios, structures, and variations are typical of polars and are modulated at the same period, 2.37-hrs (142.3-min), as the eclipse to within uncertainties. The spectral energy distribution and luminosity is found to be comparable to that of AM Herculis. Pre-eclipse dips in the light curve show evidence for stream accretion. We derive the following tentative binary and stellar parameters assuming a helium composition white dwarf and a companion mass of 0.2 M${}_{\odot }$: inclination i = 74.68${}^o$ $\pm$ 0.03${}^o$, semi-major axis a = 0.942 $\pm$ 0.024 R${}_{\odot }$, and masses and radii of the white dwarf and companion respectively: M${}_1$ = 0.948 ${}_{-0.012}^{+0.006}$ M${}_{\odot }$, R${}_1$ = 0.00830 ${}_{-0.00006}^{+0.00012}$ R${}_{\odot }$, R${}_2$ = 0.249 $\pm$ 0.002 R${}_{\odot }$. As a relatively bright (V $\sim$ 17-19 mag), eclipsing, period-gap polar, CRTS J0350+3232 will remain an important laboratory for the study of accretion and angular momentum evolution in polars.

11 pages, 15 figures

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