1RXS J020929.0+283243 is a polar cataclysmic variable

ATel #666; P. Rodriguez-Gil (IAC), J. Casares (IAC), C. Zurita (IAC), M. A. P. Torres (CfA), D. Steeghs (CfA), R. I. Hynes (Lousiana)
on 30 Nov 2005; 10:11 UT
Credential Certification: P. Rodriguez-Gil (prguez@ll.iac.es)

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We present simultaneous time-resolved photometry and spectroscopy of the eclipsing cataclysmic variable 1RXS J020929.0+283243 (ATel #652). Our data indicate that it is a new AM Herculis (i.e. polar) system. Unfiltered photometry (25-sec time resolution) was performed on 2005 November 8 UT at the 2.56-m Nordic Optical Telescope on La Palma. The light curve covers 2.4 orbital cycles and displays two eclipses. Combination of our mid-eclipse times (HJD=2453683.5966(1) and HJD=2453683.6633(1)) with the ephemeris previously reported in ATel #652 enables us to refine the ephemeris to T0(HJD)=2453666.5484(1) + 0.0668554(5) * E. The optical light curve shows a bright phase lasting for about 0.6 cycle, which has a double-humped structure with broad intensity peaks at phases ~0.75 and ~0.2, the eclipse of the white dwarf being right in the middle. The eclipse lasts for ~6 min. The shape of the light curve is very similar to that of the polar EP Draconis (Schwope & Mengel 1997, Astr. Nachr. 318, 25) and can be interpreted as strong cyclotron beaming from magnetic accretion structures on the surface of the white dwarf. Simultaneous spectroscopy (410-sec time resolution) at the 4.2-m William Herschel Telescope also on La Palma shows that the optical spectrum of 1RXS J020929.0+283243 is dominated by intense, single-peaked Balmer and HeI emission lines. The spectrum also exhibits a strong HeII 4686 emission line, characteristic of magnetic accretion. The Halpha, Hbeta, and HeII 4686 trailed spectrograms are typical of an AM Herculis system with the lines consisting of at least two different components: a narrow emission with a relatively low radial velocity amplitude and origin on the irradiated face of the donor star, and a broad emission component with radial velocity peaking at about +/-1000 km/s at orbital phase 0/0.5, likely originating in the gas stream. All the above indicates that 1RXS J020929.0+283243 is actually an AM Her star and not a disc-accreting system as it was suggested by Denisenko et al. in ATel #652. Time-resolved X-ray observations and optical circular and linear polarimetry of this new AM Her cataclysmic variable are encouraged.