A DeepExtremeUltravioletExplorerObservation of the Extreme Ultraviolet Transient RE J1255+266

Abstract

We report on the analysis of a deep Extreme Ultraviolet Explorer (EUVE) observation made with the Deep Survey and Spectrometer telescope, which included in the field the remarkable bright extreme ultraviolet (EUV) transient source RE J1255+266, discovered in 1994 June by the ROSAT Wide Field Camera (WFC). A careful analysis of the resulting Deep Survey (DS) Lexan/B (67-178 A) image, whose aggregated exposure time is 137 ks, has not revealed any trace of the source but has yielded a quite stringent formal upper limit on the quiescent EUVE DS count rate of 0.003 counts s-1 (3 σ) and a visual upper limit of 0.002 counts s-1. An analysis based on blackbody spectra, pure hydrogen DA white dwarf models, and optically thin plasma model spectra has provided constraints on the source counterpart. The observed count rate upper limit is consistent with the optical identification proposed by 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 rate 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.