Ad. Schwope et al., Zeeman lines and a single cyclotron line in the low-accretion rate polar 1RXS J012851.9-233931 (RBS0206), ASTRON ASTR, 348(3), 1999, pp. 861-867
We present a low-resolution discovery spectrum and CCD-photometry of the br
ight X-ray source 1RXS J0 12851.9-233931 found in the ROSAT All-Sky Survey.
These first observations suggest that the source is an AM Herculis star (p
olar) accreting at a low rate. The optical spectrum is dominated by Zeeman
absorption features from the white dwarf, indicating a mean photospheric ma
gnetic field of 36 +/- 1MG. Only weak Balmer line emission was observed. In
the near infra-red, a single intense cyclotron hump was observed. The infe
rred magnetic field strength in the accretion plama is 45 +/- 1 MG, the tem
perature in the plasma is below 2keV. Likely orbital periods are similar to
90 min or similar to 146 min, the latter inside the cataclysmic variable p
eriod gap. The system is an ideal target for further detailed investigation
s of the field structure on a magnetic white dwarf by phase-resolved spectr
opolarimetry.