Discovery of the bright eclipsing polar RXJ 2107.9-0518.
Abstract
We report the discovery of a new eclipsing AM Herculis variable (polar) as optical counterpart of the X-ray bright, soft, high-galactic latitude X-ray source RXJ2107.9-0518 detected during the ROSAT All Sky Survey (henceforth designated to as RX21). With V ≃ 15m.3 in its high accretion state RX21 is the brightest among 5 known eclipsing systems. The eclipse lasts 9.75 minutes and was detected at optical and X-ray wavelengths. The optical eclipse lightcurve is structured due to subsequently vanishing and reappearing light sources (the white dwarf and the accretion stream). The morphology of the X-ray lightcurve is suggestive of only one active pole. The orbital period is 125 min, close to the lower edge of the CV period gap, implying either an unusual binary evolution or a massive white dwarf. A low-resolution spectrum obtained in a state of reduced accretion displays cyclotron lines as well as spectral features of the secondary star. The implied field strength in the accretion region is B ∼ 37 MG, the distance to RX21 is d ∼ 250pc.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- April 1993
- Bibcode:
- 1993A&A...271L..25S
- Keywords:
-
- cataclysmic variables;
- AM Herculis binaries;
- stars: individual (RXJ2107.9-0518);
- Binaries: eclipsing;
- X-rays