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

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 <sup>3

1</sup> 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 19 mag and V 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 P_orb  = 78.0176(4) min for RX J2022.6-3954 and P_orb  = 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 . 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 and . 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  pc and to RX J0132.7-6554 of  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 48.6-002, 51.7-045, 55.D-0383).

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

SIMBAD Objects

Contents

• 1. Introduction
• 2. Observations
  • 2.1. Optical observations
  • 2.2. X-ray observations
• 3. Results
  • 3.1. RX J2022.6-3954
    • 3.1.1. Orbital period and modulations
    • 3.1.2. Magnetic field strength
    • 3.1.3. Distance estimate
  • 3.2. RX J0132.7-6554
    • 3.2.1. Orbital period and modulations
    • 3.2.2. Magnetic field strength
    • 3.2.3. Distance estimate
  • 3.3. X-ray spectra
• 4. Discussion and conclusions
• Acknowledgements
• References

© European Southern Observatory (ESO) 1997

Online publication: April 8, 1998
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