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Astron. Astrophys. 327, 183-190 (1997)

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Two new ROSAT discovered high field polars: RX J2022.6-3954 in Sagittarius and RX J0132.7-6554 in Hydrus *

V. Burwitz 1, K. Reinsch 1, K. Beuermann 1, 2 and H.-C. Thomas 3

1 Universitäts-Sternwarte Göttingen, Geismarlandstr. 11, D-37083 Göttingen, Germany
2 MPI für Extraterrestrische Physik, Giessenbachstr. 1, D-85740 Garching, Germany
3 MPI für Astrophysik, Karl-Schwarzschild-Str. 1, D-85740 Garching, Germany

Received 21 April 1997 / Accepted 16 June 1997

Abstract

We report the discovery of two new AM Herculis systems (polars), identified as the optical V [FORMULA] 19 mag and V [FORMULA] 20 mag counterparts of the soft X-ray sources RX J2022.6-3954 and RX J0132.7-6554 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 RX J2022.6-3954 and B  = 68(2) MG for RX J0132.7-6554 . With Porb  = 78.0176(4) min for RX J2022.6-3954 and Porb  = 77.831(8) min for RX J0132.7-6554 both objects have orbital periods which lie at the lower limit of the period distribution of CVs. RX J0132.7-6554 is the shortest period polar yet detected. Both objects show no eclipse by the secondary stars, and, therefore must have orbital inclinations of [FORMULA]. As RX J2022.6-3954 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 [FORMULA] and [FORMULA]. From the absence of M-star features in the faint phase spectra of both objects we obtain a lower limit for the distance to RX J2022.6-3954 of [FORMULA]  pc and to RX J0132.7-6554 of [FORMULA]  pc. The high magnetic fields and short orbital periods make both objects highly interesting in the context of the evolution of accreting close-binary systems.

Key words: accretion, accretion disks – stars: individual (RX J2022.6 – 3954) – stars: individual (RX J0132.7 – 6554) – stars: novae, cataclysmic variables – stars: magnetic X-rays: stars

* Based on observations collected at the European Southern Observatory, La Silla, Chile with the 2.2-m telescope of the Max-Planck-Society in MPI time and with various telescopes in ESO time (ESO [FORMULA] 48.6-002, 51.7-045, 55.D-0383).

Send offprint requests to: burwitz@uni-sw.gwdg.de

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© European Southern Observatory (ESO) 1997

Online publication: April 8, 1998
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