RE J1255+266—Detection of an Extremely Bright EUV Transient

• Published in: International Astronomical Union Colloquium
• Main Author: Dahlem, Michael
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 1996
• Subjects: North Pole
• Online Access: http://dx.doi.org/10.1017/s025292110003640x; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S025292110003640X

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 ~ 89°. Its observed EUV flux (62-110 eV) at the time of the detection was of order 7 × 10 −9 ergs s −1 cm −2 , 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 0.86 days. With respect to earlier non-detections, the source brightened by a factor of > 7000. Such a behavior has not been observed before. Thus, it is unclear what type of source RE J1255+266 might be. The most likely optical counterpart is a faint ( V ~ 18.5 mag) object with a blue spectrum (taken from an objective-prism Schmidt plate). For more details on the optical identification see the paper by J. Pye (this conference). Simultaneous observations with CGRO/BATSE resulted in non-detections of the source in the 8-50 keV energy range.