1998A&A...338..465S

We present the first detailed multi-wavelength study of the ROSAT-discovered AM Herculis binary RX J0203.8+2959 comprising extended CCD and photoelectric photometry, phase-resolved spectroscopy with high and low spectral resolution and pointed ROSAT observations with the PSPC and the HRI. Between 1992 and 1997 the system displayed states of high and low accretion with mean brightness levels of V=15.5^m and 18^m, respectively. A timing analysis revealed that the binary is rotating synchronously with a period of 4.6hr and is thus one of the longest-period polars known. The emission lines are structured showing narrow and broad components. We could distinguish between line emission arising from the heated side of the secondary star and the accretion stream. Velocity information derived for a narrow emission line with suspected origin on the heated side of the companion star allowed us to constrain its orbital velocity and to phase its inferior conjunction. In addition the photospheric spectrum of the secondary star could be detected in the near-infrared. The strength of the TiO-bands was used to determine its spectral type as dM 2.5, which is consistent with a Roche lobe filling main sequence star, and to estimate the distance of the system to be ∼600pc. Definite confirmation of its magnetic nature is given by the detection of cyclotron harmonics implying a field strength of B=38±2MG. The accretion geometry could not be fixed unequivocally. The morphology of the optical light curves is suggestive of one active accretion region which undergoes no selfeclipse. A corresponding simple light curve pattern is not seen at X-ray wavelengths, it's time signature is dominated by instationary accretion of discrete blobs. We report on the occasional occurence of phase- and colour-dependent quasi-periodic oscillations at periods of ∼7 and ∼14min.