RX J1313.2-3259, a long-period Polar discovered with ROSAT

Astronomy & Astrophysics in press

Contact: aschwope@aip.de

Preprint of paper

H.-C. Thomas [1], K. Beuermann [2], V. Burwitz [3], K. Reinsch [2], A.D. Schwope [4]



  1. Max-Planck-Institut f¨r Astrophysik, Karl-Schwarzschild-Strasse 1, D-85748 Garching, Germany
  2. Universitätssternwarte Göttingen, Geismarlandstrasse 11, D--37083 Göttingen, Germany
  3. Max-Planck-Institut f¨r Extraterrestrische Physik, Karl-Schwarzschild-Strasse 1, D-85748 Garching, Germany
  4. Astrophysikalisches Institut Potsdam, An der Sternwarte 16, D-14482 Potsdam, Germany

Abstract:

We report observations of a new AM Herculis binary identified as the optical counterpart of the X-ray source RX J1313.2-3259, detected during the ROSAT All-Sky Survey (RASS). It has an orbital period of 251 min and is strongly modulated at optical wavelengths. The long-term behavior is characterized by a pronounced variation in X-rays between the RASS and two subsequent pointings (decrease by a factor 40 in count rate) and by moderate changes in the optical brightness (up to a factor 5). The X-ray spectrum is dominated by a soft quasi-blackbody component, with a smaller contribution from thermal bremsstrahlung. Measurements of high circular polarization confirm its classification as a Polar with a magnetic field strength of 56 MG. The average visual magnitude of RX J1313.2-3259 is V = 16m, for its distance we get 200 pc.