Two new ROSAT discovered high field polars: RX J2022.6-3954 in Sagittarius and RX J0132.7-6554 in Hydrus.
Abstract
We report the discovery of two new AM Herculis systems (polars), identified as the optical V~19mag and V~20mag counterparts of the soft X-ray sources RXJ2022.6-3954 and RXJ0132.7-6554 detected during the ROSAT All-Sky Survey and present the results of our optical and X-ray follow-up observations. From the cyclotron emission lines detected in the optical spectra we determine magnetic field strengths in the accretion region of B=67(2)MG for RXJ2022.6-3954 and B=68(2)MG for RXJ0132.7-6554. With P_orb_=78.0176(4)min for RXJ2022.6-3954 and P_orb_=77.831(8)min for RXJ0132.7-6554 both objects have orbital periods which lie at the lower limit of the period distribution of CVs. RXJ0132.7-6554 is the shortest period polar yet detected. Both objects show no eclipse by the secondary stars, and, therefore must have orbital inclinations of i<~85°. As RXJ2022.6-3954 shows a dip due to the accretion stream crossing our line-of-sight and the accretion region on the white dwarf is partially self-eclipsed we can further constrain the orbital inclination and co-latitude of the magnetic pole to be 45°<i<85° and 45°>δ>5°. From the absence of M-star features in the faint phase spectra of both objects we obtain a lower limit for the distance to RXJ2022.6-3954 of d>190pc and to RXJ0132.7-6554 of d>300pc . The high magnetic fields and short orbital periods make both objects highly interesting in the context of the evolution of accreting close-binary systems.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- November 1997
- Bibcode:
- 1997A&A...327..183B
- Keywords:
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- ACCRETION;
- ACCRETION DISKS;
- STARS: INDIVIDUAL (RX J2022.6-3954);
- STARS: INDIVIDUAL (RX J0132.7-6554);
- STARS: NOVAE;
- CATACLYSMIC VARIABLES;
- STARS: MAGNETIC X-RAYS: STARS