Discovery of an EUV-bright polar in the period gap from the ROSAT Wide Field Camera sky survey

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Abstract
We report the discovery of a new polar found during the all-sky survey of extreme-UV sources conducted by the UK Wide Field Camera on board ROSAT. The V ~ 16 object is the brightest EUV polar observed by this instrument during the survey. These and subsequent optical observations show that the orbital period of the system is 2.33 h, placing it well inside the cataclysmic variable ‘period gap’. Results from preliminary optical photometry, spectroscopy and polarimetry are presented, and compared to other known polars. The ROSAT results indicate that the system exhibits a soft X-ray excess, by at least a factor of ~ 2 over the hard bremsstrahlung component. We discuss the likely evolutionary status of this ‘period gap’ polar, and conclude that it was probably born in the gap, rather than evolving through it from a longer period. Finally, we discuss the probable accretion geometry of the system.

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