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Astron. Astrophys. 318, 134-139 (1997)

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1. Introduction

Cataclysmic variables are binary stars at a late stage of their evolution. They consist of a white dwarf primary which accretes matter from its Roche-lobe-filling, late-type companion. If the primary has little or no magnetic field, then accretion proceeds via a disk. If the white dwarf has a strong magnetic field, then it may synchronize its rotation with the orbital rotation and accretion proceeds via a magnetically focused accretion stream directly from the L1 point to the surface of the white dwarf at the magnetic pole nearest to the secondary. Emission from the accretion hot spot is observed in the EUV and soft X-ray regimes. In the intermediate polars (IPs), the magnetic field is less strong and a partial disk may form which is disrupted at its inner radii by the magnetosphere of the white dwarf.

The X-ray satellite ROSAT has brought to light a number of new cataclysmic variables, the majority of them polars (eg. Beuermann & Burwitz, 1995). The IPs found by ROSAT, although small in number, may be divided into two classes, separated by their X-ray spectra: the hard and soft IPs (Haberl & Motch 1995, Motch & Haberl 1995).

Extensive reviews of the properties of cataclysmic variables can be found in la Dous (1993, 1994) and Warner (1995). See Cropper (1990) for a comprehensive review of the properties of polars.

We present here the identification of the ROSAT soft X-ray source RX J2353.0-3852 as a cataclysmic variable, most likely nonmagnetic with a low mass transfer rate but possibly an intermediate polar with a very long white dwarf spin period.

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© European Southern Observatory (ESO) 1997

Online publication: July 8, 1998
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