Abstract
We report here the identification of the soft X-ray source H0139–68 with a star at RA = 01h 39 min 37.5 s, dec = −68° 08′ 32″ (1950). Time-resolved spectrophotometry of the star over 3 h shows a V magnitude variation between 14.9 and 16.4 with a period of∼110 min. The spectra are dominated by emission lines of neutral hydrogen, neutral helium and singly ionized helium throughout the period. The line ratios of the Balmer lines Hγ/Hβ and the He I lines are flatter relative to case B recombination values, while the He II ratios are consistent with optically thin recombination. The mean radial velocity of the emission lines varies with the photometric period roughly sinusoidally from 340 to −150 km s−1. The continuum is very red at maximum light, flat at minimum and shows strong polarization. These optical characteristics of the candidate star are similar to those of the magnetic cataclysmic variable AM Herculis.
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Visvanathan, N., Pickles, A. Optical identification of X-ray source H0139 – 68 with an AM Herculis-type system. Nature 298, 41–44 (1982). https://doi.org/10.1038/298041a0
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DOI: https://doi.org/10.1038/298041a0
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