A new cataclysmic variable RX J0757.0+6306: candidate for the shortest period intermediate polar

A new cataclysmic variable is identified as the optical counterpart of the faint and hard X-ray source RX J0757.0+6306 discovered during the ROSAT all-sky survey. Strong double-peaked emission lines bear evidence of an accretion disc via an S-wave which varies with a period of 81+/- 5 min. We identify this period as the orbital period of the binary system. CCD photometry reveals an additional period of 8.52+/- 0.15 min. which was stable over four nights. We suggest that RX J0757.0+6306 is possibly an intermediate polar, but we cannot exclude the possibility that it is a member of the SU UMa group of dwarf novae.