THE EUV TRANSIENT RE JI255+266

We have identified the optical counterpart of the EUV transient source RE J1255+266 with an similar to 18 mag blue star which has an unusual optical spectrum showing a blue continuum and broad Balmer absorption lines characteristic of a DA white dwarf, together with intense narro w H Balmer and He I lines in emission. Subsequent optical spectroscopy and photometry, together with near-IR photometry, demonstrate that th is system is most likely a cataclysmic variable (CV) system with a hig h-mass white dwarf and very low-mass companion viewed almost pole-on ( i.e. inclination i <5 degrees). At the time of our observations the sy stem appears to be in its quiescent state with very little continuum e mission from the disc, Fitting of the broad Balmer absorption lines yi elds temperature and gravity estimates for the white dwarf. These meas urements provide a means of estimating the distance to RE J1255+266; w e find d=1801(-55)(+80) pc. At this distance the outburst EUV luminosi ty of REJ1255+266 is L(EUV) >10(34) erg s(-1). The large observed EUV luminosity of the outburst may be due to the viewing geometry of this system which favours a direct and unobscured view of the EUV/soft X-ra y emission region in the boundary layer between the white dwarf and th e inner accretion disc.