3EG J2016+3657: Confirming an EGRET blazar behind the Galactic plane

We recently identified the blazar-like radio source G74.87+1.22 (B2013+370) as the counterpart of the high-energy gamma -ray source 3EG J2016+3657 in the Galactic plane. However, since most blazar identifications of EGRET sou rces are only probabilistic in quality even at high Galactic latitude, and since there also exists a population of unidentified Galactic EGRET sources , we sought to obtain additional evidence to support our assertion that 3EG J2016+3657 is a blazar. These new observations consist of a complete set o f classifications for the 14 brightest ROSAT X-ray sources in the error cir cle, of which B2013+370 remains the most likely source of the c-rays. We al so obtained further optical photometry of B2013+370 itself which shows that it is variable, providing additional evidence of its blazar nature. Intere stingly, this field contains, in addition to the blazar, the Crab-like supe rnova remnant CTB 87, which is too distant to be the EGRET source, and thre e newly discovered cataclysmic variables, all five of these X-ray sources f alling within 16' of each other. This illustrates the daunting problem of o btaining complete identifications of EGRET sources in the Galactic plane.