1995A&A...295L..13D

During a pointed ROSAT observation in the direction of the Coma cluster of galaxies an exceptionally bright EUV source, RE J1255+266, was detected serendipitously. The source is located close to the Galactic North pole, at b_II~=89deg. Its observed EUV flux (62-110eV) at the time of the detection was of order 7x10-9ergs/s/cm2, making RE J1255+266 temporarily one of the brightest EUV sources on the sky. The EUV flare of RE J1255+266 has a light curve with a decay time of about 0.86days. With respect to earlier non-detections, the source brightened by a factor of ∼7000. Such a behaviour has not been observed before. Thus, it is unclear what type of source RE J1255+266 might be. Up to now no positive identification with any known source could be obtained. Emission at the position of the source was previously only detected in the 1987 Green Bank radio continuum survey. Simultaneous observations with CGRO/BATSE resulted in non-detections of the source in the 8-50keV energy range.