Article

On the orbital period of the new cataclysmic variable EUVE J2115-586

We have obtained phase-resolved spectroscopy (3660-6040 A) of the recently discovered cataclysmic variable EUVE J21 15-586 using the 74-inch telescope at Mount Stromlo Observatory. The radial velocity is modulated over a period of 110.8 min with a possible one-cycle-per-day alias of 102.8 min, and a semiamplitude of ?270 km s-1 at H? and ?390 km s-1 at He II ?4686. The spectroscopic appearance (H I Balmer, Ca II, He I, He II emission lines), the orbital period, and the velocity amplitude indicate that this cataclysmic variable is probably an AM Her type; the absence of cyclotron humps indicates a low intensity magnetic field (B<20 MG). Extreme ultraviolet emission phased at the orbital period shows evidence of variability, but additional EUV/soft x-ray observations are recommended.

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