CGRO observations of BL Lac objects and other blazars

Among the 68 blazars detected by EGRET with high confidence, roughly 25-30% are classified as BL Lac objects. Although most are of the LBL (RBL) subspecies, 4 HBLs (XBLs) have now been detected convincingly. In general, the BL Lacs appear to have slightly harder spectra than the other blazars, and to be somewhat less variable. On average, the LBLs are substantially less luminous in gamma rays than are the EGRET-detected quasars, and the gamma luminosity of the EGRET-detected HBLs is lower than that of the quasars by a factor of at least 10(2) - 10(4). One BL Lac object, BL Lacertae itself, received exceptionally good optical coverage during an EGRET target-of-opportunity hare observation in 1997 July. During a I-day miniflare in the middle of the EGRET observation, the optical and gamma-ray fluxes appeared to peak very close in time. For the only other blazar flare with comparable optical coverage, that of 3C 279 in 1996 Feb, there is little evidence for 1-day-scale gamma/optical correlation, although it was bright in both of those bands.