The Fastest Relativistic Jets: VLBA Observations of Blazars with Apparent Speeds Exceeding 25c

We have measured peak apparent speeds of 25.6c ± 7.0c, 25.6c ± 4.4c, and 28.2c ± 6.6c in the jets of 0235+164, 0827+243, and 1406-076, respectively, based on six epochs of high-sensitivity VLBA observations at 22 and 43 GHz during 2002 and 2003 (H0 = 71 km s-1 Mpc-1, Ωm = 0.27, and ΩΛ = 0.73). These blazars had been identified as potentially having apparent speeds exceeding 40c in an earlier VLBA survey of EGRET blazars by Jorstad and coworkers. We therefore confirm (with high confidence in 0827+243, and lower confidence in 0235+164 and 1406-076) the presence of highly relativistic pattern speeds in these three jets, although not at the >40c levels reported by Jorstad and coworkers. The lower limit to the bulk Lorentz factor implied by the observed apparent speeds is Γ ≳ 25-30 in these three sources, if the pattern speeds are equal to or slower than the bulk flow speed.