On the limit of brightness temperature in nonstationary radio sources

Observations imply that extragalactic radio sources must be in nonstationary states. One possible way to interpret a observed high brightness temperature which exceeds the inverse Compton limit is by means of a nonstationary condition (Kellerman and Pauliny-Toth 1969, Slysh 1992). This paper investigates the maximum brightness temperature of nonstationary radio sources by incorporating the continuity equation for the electron number density and the radiative transfer equation. In radio sources with a high enough magnetic field, synchrotron losses should be considered and the maximum brightness temperature will not achieve the maximum value suggested by Slysh (1992). Strong acceleration canonly shorten the time to achieve the brightness temperature limit and doesnot violate the KPT limit.