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Astron. Astrophys. 353, 646-654 (2000)

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

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

1 MPI für Astrophysik, Karl-Schwarzschild-Strasse 1, 85740 Garching, Germany
2 Universitäts-Sternwarte, Geismarlandstrasse 11, 37083 Göttingen, Germany
3 MPI für Extraterrestrische Physik, Giessenbachstrasse 6, 85740 Garching, Germany
4 Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482 Potsdam Germany

Received 7 September 1999 / Accepted 5 November 1999

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 [FORMULA], for its distance we get [FORMULA] 200 pc.

Key words: stars: novae, cataclysmic variables – stars: magnetic fields – stars: individual: RX J1313.2 – 3259 – stars: binaries: close – X-rays: stars – accretion, accretion disks

* Based in part on observations collected at the European Southern Observatory, La Silla, Chile with the ESO/MPI 2.2m telescope in MPI time and with various telescopes in ESO time (ESO Nos. 50.6-017, 50.6-021, 54.D-0698, 55.D-0383, 56.D-0552, 56.D-0561, 61.D-0415).

Send offprint requests to: H.-C. Thomas (hcthomas@mpa-garching.mpg.de)

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© European Southern Observatory (ESO) 2000

Online publication: December 17, 1999
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