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Zeeman lines and a single cyclotron line in the low-accretion rate polar 1RXS J012851.9-233931 (RBS0206)

A. D. Schwope·R. Schwarz·J. Greiner
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Abstract

We present a low-resolution discovery spectrum and CCD-photometry of the bright X-ray source 1RXS J012851.9-233931 found in the ROSAT All-Sky Survey. These first observations suggest that the source is an AM Herculis star (polar) accreting at a low rate. The optical spectrum is dominated by Zeeman absorption features from the white dwarf, indicating a mean photospheric magnetic field of 36 +- 1 MG. Only weak Balmer line emission was observed. In the near infra-red, a single intense cyclotron hump was observed. The inferred magnetic field strength in the accretion plama is 45 +- 1 MG, the temperature in the plasma is below 2 keV. Likely orbital periods are ~90 min or ~146 min, the latter inside the cataclysmic variable period gap. The system is an ideal target for further detailed investigations of the field structure on a magnetic white dwarf by phase-resolved spectropolarimetry.

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A. D. Schwope, R. Schwarz, J. Greiner. 1999-05-31. Zeeman lines and a single cyclotron line in the low-accretion rate polar 1RXS J012851.9-233931 (RBS0206). https://arxiv.org/abs/astro-ph/9905392

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