Further COS-B evidence for gamma-ray emission from 3C273

The results of a third observation of the Virgo region of the sky by the ESA gamma-ray satellite COS-B are reported. The gamma-ray source (CG291 plus 65) was again seen, and the combined data are analyzed to improve on the position and time-averaged energy spectrum of the source. During the observation, the number of photons from the instrumental background (owing to interactions of cosmic-ray particles with matter in front of the telescope) was minimal since the observation was near the solar maximum. The total number of accepted photons was relatively low, approximately 700 (effective field of view, about 20 deg radius; energies, greater than 50 MeV).