THE ECLIPSING AM HERCULIS BINARY V2301 OPHIUCHI .1. ROSAT AND IUE OBSERVATIONS

We present X-ray and UV observations of the unique eclipsing cataclysm ic variable V2301 Oph (1H1752+081). The X-ray eclipse of the primary s tar is total and corresponds in phase with the optical eclipse of the white dwarf. The X-ray light curve shows a quasi-sinusoidal orbital '' hump'' typical of AM Her systems. The orbital phase at which the hump has its peak has remained at similar to 0.9 in all ROSAT observations taken over several years. We can rule out a 100% modulated spin-pulse signal with a period shorter than P-orb. Thus, it is very unlikely tha t there is either a non-synchronously rotating white dwarf or an accre tion disk in V2301 Oph. The relatively hard X-ray spectrum of this wea kly-magnetic system does not change its shape during the orbit or arou nd the eclipse and is consistent with that expected from a hot accreti on column on a weakly magnetized white dwarf. The interstellar absorbi ng column density of similar to 4.10(20) H-atoms cm(-2) required by th e X-ray spectral fits is capable of hiding any weak soft X-ray compone nt. The lower limit to the relative contributions of a hard bremsstrah lung and a soft blackbody component is consistent with both the empiri cal relation for AM Hers and the theoretical expectations for a system with a low magnetic field strength. The irregular ''dips'' present in the light curve around phases 0.85-0.92 with depths up to 80% are not accompanied by significant changes in the hardness ratios and must be due to partial covering by a structured and blobby accretion stream w hich has been lifted out of the orbital plane by the magnetic field of the primary. The close agreement between the phasing of the dips and the peak of the X-ray light curves is expected in a synchronous magnet ic accretor. The relative strengths of the NV, CIV, and Hell UV emissi on lines are typical for AM Her stars. Thus, the X-ray orbital light c urves and the X-ray and UV spectra clearly identify V2301 Oph as an AM Her system.