Wien Fireball Model of Relativistic Outflows in Active Galactic Nuclei

We study steady and spherically symmetric outflows of pure electron-positron pair plasma as a possible acceleration mechanism of relativistic jets up to the bulk Lorentz factor of greater than 10. These outflows are initiated by the ``Wien fireball'', which is optically thick to Compton scattering but thin to absorption and in a Wien equilibrium state between pairs and photons at a relativistic temperature.