EUVE_J1429--38.0: A New Magnetic Cataclysmic Variable

The source EUVE_J1429--38.0 was discovered serendipitously by the Extreme Ultraviolet Explorer (EUVE ) satellite on 1993 March 5. Optical spectroscopy confirms a cataclysmic-variable--type optical counterpart for the source, showing Balmer, He i, and Ca emission, as well as strong He ii emission. The optical spectrum, the apparent high/low state behavior, and possible weak cyclotron humps visible in the spectrum indicate that this star is likely to be an AM Herculis system, but the possibility of being a DQ Her, or an unlocked AM Her system cannot be excluded. Analysis of the highly modulated EUVE photometry yields a period of 2() h22() m, which we conclude is the binary orbital period. In addition, a 57() m period is also present. Thus, we conclude that EUVE_J1429--38.0 is a newly discovered magnetic cataclysmic variable with a likely orbital period of 142() m. The detection of cyclotron radiation (with optical polarimetry) and phase-resolved optical spectroscopy is needed to unequivocally establish this star as an AM Her system and remove any ambiguity as to its periods. An orbital period of 2fh36 would make EUVE_J1429--38.0 only the third known AM Her system within the cataclysmic variable period gap, all three of which were discovered through EUV observations. This work has been supported by NASA contracts NAS5-30180 and NAS5-29298, and NASA grant NAG5-2902 to SBH.