RXJ0531.5-4624: a new ROSAT-discovered AM Herculis binary in the "period gap".
Abstract
We report the discovery of a new AM Herculis system (polar) identified as the optical counterpart of the bright, soft, high-galactic latitude X-ray source RXJ0531.5-4624 detected during the ROSAT All-Sky Survey. Optical spectroscopy of the V approximately 17 mag object shows systematic radial velocity variations of the emission lines with an orbital period of 133.5 min, placing the object well within the period gap of cataclysmic variables. The X-ray flux is approximately 80% modulated with the same period and has two maxima per orbital cycle. Optically, the system varies by approximately 1 mag around the orbit. The morphology of the light curve has, however, changed significantly within a few months. From cyclotron harmonics seen in the red wavelength range of a low-resolution spectrum, we derive a magnetic field strength in the accretion region of B aproximately 19 MG. The relative intensity of the spectral features of the secondary star implies a distance of d approximately 300 pc.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- November 1994
- Bibcode:
- 1994A&A...291L..27R
- Keywords:
-
- Astronomical Spectroscopy;
- Cataclysmic Variables;
- Hercules Nova;
- Stellar Mass Ejection;
- Stellar Orbits;
- X Ray Astronomy;
- X Ray Binaries;
- Light Curve;
- Radial Velocity;
- Rosat Mission;
- Sky Surveys (Astronomy);
- Stellar Magnetic Fields;
- Variations;
- Astronomy;
- ACCRETION;
- STARS: BINARIES: CLOSE;
- STARS: BINARIES: SPECTROSCOPIC;
- STARS: INDIVIDUAL (RXJ0531.5-4624);
- STARS: NOVAE;
- CATACLYSMIC VARIABLES;
- X-RAYS: STARS