A DEEP EXTREME-ULTRAVIOLET EXPLORER OBSERVATION OF THE EXTREME-ULTRAVIOLET TRANSIENT RE J1255+266

We report on the analysis of a deep Extreme Ultraviolet Explorer (EUVE ) observation made with the Deep Survey and Spectrometer telescope, wh ich included in the field the remarkable bright extreme ultraviolet (E UV) transient source RE J1255+266, discovered in 1994 June by the ROSA T Wide Field Camera (WFC). A careful analysis of the resulting Deep Su rvey (DS) Lexan/B (67-178 Angstrom) image, whose aggregated exposure t ime is 137 ks, has not revealed any trace of the source but has yielde d a quite stringent formal upper limit on the quiescent EUVE DS count rate of 0.003 counts s(-1) (3 sigma) and a ''visual'' upper limit of 0 .002 counts s(-1). An analysis based on blackbody spectra, pure hydrog en DA white dwarf models, and optically thin plasma model spectra has provided constraints on the source counterpart. The observed count rat e upper limit is consistent with the optical identification proposed b y Watson et al. in which a DA white dwarf is the primary component of a CV-like system involving a very low mass M dwarf secondary star. Our upper limit to the EUVE DS count rate, when compared with the count r ate observed with the ROSAT WFC at the peak of the outburst, implies a brightening of the EUV source flux relative to quiescence by a factor of greater than 54,000.