Unraveling the Puzzle of the Eclipsing Polar SDSS J015543.40+002807.2 with XMM and Optical Photometry/Spectropolarimetry

Abstract

The cataclysmic variable SDSS J015543.40+002807.2 is confirmed to be a magnetic system of the AM Herculis type. With an orbital period of 87.13 minutes, it is also the shortest period eclipsing Polar known. Monitoring with XMM-Newton finds a high-state light curve dominated by a single X-ray-emitting accretion pole located slightly prograde of the secondary star. The hard X-ray spectrum is typical of radial shocks on magnetic white dwarfs (kT~10 keV), and there is evidence for a soft X-ray component consistent with reprocessing from the stellar surface. The optical circular polarization is weak (v