Spectroscopic observations of the eclipsing Polar MN Hya (RX J0929--24)

Abstract

We present low--medium resolution optical spectroscopy of the eclipsing AM Her system MN Hya (RX J0929--24). We determine the magnetic field strength at the primary accretion region of the white dwarf to be 42MG from the spacing of cyclotron features visible during ~0.4--0.7. From spectra taken during the eclipse we find that the secondary has a M3--4 spectral type. Combined with the eclipse photometry of Sekiguchi, Nakada & Bassett and an estimate of the interstellar extinction we find a distance of ~300--700pc. We find unusual line variations at phase ~0.9: Halpha is seen in absorption and emission. This is at the same point in the orbital phase that a prominent absorption dip is seen in soft X-rays.