EUVE J0425.6-5714: A Newly Discovered AM Herculis Star

J. P. Halpern, K. M. Leighly, H. L. Marshall, M. Eracleous, T. Storchi-Bergmann

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6 Scopus citations


We detected a new AM Her star serendipitously in a 25 day observation with the EUVE satellite. A coherent period of 85.82 minutes is present in the EUVE Deep Survey imager light curve of this source. A spectroscopic optical identification is made with a 19th magnitude blue star that has H and He emission lines, and broad cyclotron humps typical of a magnetic cataclysmic variable. A lower limit to the polar magnetic field of 50 MG is estimated from the spacing of the cyclotron harmonics. EUVE J0425.6-5714 is also detected in archival ROSAT HRI observations spanning 2 months, and its stable and highly structured light curve permits us to fit a coherent ephemeris linking the ROSAT and EUVE data over a 1.3 yr gap. The derived period is 85.82107 ± 0.00020 minutes, and the ephemeris should be accurate to 0.1 cycles until the year 2005. A narrow but partial X-ray eclipse suggests that this object belongs to the group of AM Her stars whose viewing geometry is such that the accretion stream periodically occults the soft X-ray emitting accretion spot on the surface of the white dwarf. A nondetection of hard X-rays from ASCA observations that are contemporaneous with the ROSAT HRI shows that the soft X-rays must dominate by at least an order of magnitude, which is consistent with a known trend among AM Her stars with large magnetic fields. This object should not be confused with the Seyfert galaxy 1H 0419-577 (= LB 1727), another X-ray/EUV source that lies only 3′.95 away and that was the principal target of these monitoring observations.

Original languageEnglish (US)
Pages (from-to)1394-1399
Number of pages6
JournalPublications of the Astronomical Society of the Pacific
Issue number754
StatePublished - Dec 1998

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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