EGRET GAMMA-RAY SOURCES: GRO J0744 + 54 AND GRO J0957 + 65 ( = BL LACERTAE OBJECT 0954 + 658)

摘要

EGRET detected an unidentified source, GRO J0744 + 54, at a significance of 6.5 σ, during its observations from 1993 June 28 to July 12. The source was seen again in the following 2 week viewing period and was weakly evident in the earlier phase 1 of the EGRET observations. Considering the variability of its gamma-ray flux, and its location at high Galactic latitude, GRO J0744 + 54 is likely to be a previously undetected blazar. Its most likely identification is with the radio source 87GB 073840.5 + 545138. A second source, GRO J0957 + 65, was seen by EGRET during the same two viewing periods at a combined significance of 5.7 σ. The most probable counterpart of GRO J0957 + 65 is the BL Lacertae object 0954 + 658. The spectra, time variability, and positions of the two sources are presented. Multiwavelength observations of 0954 + 658 are also presented.