Bottom: Calculated spectral energy distributions of BL Lac objects for various values of the normalized accretion rate $\dot{m}$. Inset (top center): Dependence of the acceleration timescale t_acc on $\dot{m}$, showing the nearly linear scaling required to explain BL Lac sources. The colored points correspond to the SED curves, indicating that higher $\dot{m}$ produces more luminous sources.