2000ApJ...529..675B

We have conducted a variability study of several radio/millimeter sources that are possible counterparts of high-energy gamma-ray sources detected by EGRET. Some sources were possibly variable during this period. The radio source with the highest spectral and temporal coverage, PMN J0850-1213, behaves in a manner consistent with the shocked-jet models for extragalactic radio sources proposed in the literature. In addition, GB 105536.5+564424 is an X-ray-selected BL Lac object, and, if the identification with the EGRET source is correct, it would be the most distant such object detected at energies >100 MeV (z=0.41). A future detection in the TeV range, as well, could provide an important constraint on absorption of very high energy gamma rays by the intergalactic infrared photon field. We also discuss the possibility that this object is a gravitationally microlensed active galactic nucleus, with the foreground lensing object at z=0.144.