On the Origin of Rapid Flares in TeV Blazars

Abstract

The rapid variability of the VHE emission reported for some TeV blazars implies Doppler factors well in excess of those inferred from superluminal motions and unification schemes. We propose that those extreme flares may result from radiative deceleration of blobs on scales where local dissipation occurs. The minimum jet power estimated from the resolved synchrotron emission on VLBI scales appears to be consistent with this model. It is shown that if the energy distribution of nonthermal electrons accelerated locally in the blob is reasonably flat, then a background radiation field having a luminosity in the range 10$^{41}-10^{42}$ erg s$^{-1}$ can give rise to a substantial deceleration of the blob, but still be transparent enough to allow the TeV $γ$-rays thereby produced to escape the system.