Astron. Astrophys. 338, 465-478 (1998)

The new long-period AM Herculis system RX J0203.8+2959

R. Schwarz ¹, A.D. Schwope ^{* 1}, K. Beuermann ^{2, 3}, V. Burwitz, ^{2, 3}, J.-U. Fischer ¹, R. Fried ⁴, I. Lehmann ¹, K.-H. Mantel, ⁵, S. Mengel ¹, A. Metzner ¹, K. Misselt ⁶, P. Notni ¹, K. Reinsch, ², A. Shafter ⁷ and H.-C. Thomas <sup>8

1</sup> Astrophysikalisches Institut Potsdam, An der Sternwarte 16, D-14482 Potsdam, Germany
² Universitätssternwarte Göttingen, Geismarlandstrasse 11, D-37083 Göttingen, Germany
³ Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse, D-85740 Garching, Germany
⁴ Braeside Observatory, Flagstaff, AZ 86002, USA
⁵ Universitätssternwarte München, Scheinerstrasse 1, D-81679 München, Germany
⁶ Department of Physics and Astronomy, Lousiana State University, Baton Rouge, LA 70803-4001, USA
⁷ Department of Astronomy and Mount Laguna Observatory, San Diego State University, San Diego, CA 92182, USA
⁸ Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Strasse 1, D-85740 Garching, Germany

Received 26 March 1998 / Accepted 15 June 1998

Abstract

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 and , respectively. A timing analysis revealed that the binary is rotating synchronously with a period of 4.6 hr 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 600 pc. Definite confirmation of its magnetic nature is given by the detection of cyclotron harmonics implying a field strength of  MG.

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 14 min.

Key words: accretion, accretion disks binaries: close stars: individual: RX J0203.8+2959 stars: magnetic fields novae, cataclysmic variables

* Visiting astronomer, German-Spanish Astronomical Center, Calar Alto, operated by the Max-Planck-Institut für Astronomie, Heidelberg, jointly with the Spanish National Commission for Astronomy.

Send offprint requests to: R. Schwarz

© European Southern Observatory (ESO) 1998

Online publication: September 14, 1998

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