Constraints on the Physical Parameters of TeV Blazars

We consider the constraints on the physical parameters of a homogeneous SSCmodel that can be derived from the spectral shape and variability of TeVblazars. Assuming that the relativistic electron spectrum is a broken powerlaw, where the break energy $\gamma_b$ is a free parameter, we write theanalytical formulae that allow to connect the physical parameters of the modelto observable quantities. The constraints can be summarized in a plane wherethe coordinates are the Doppler factor and the magnetic field. The consistencybetween the break energy and the balance between cooling and escape and theinterpretation of the soft photon lags measured in some sources as radiativecooling times are treated as additional independent constraints. We apply themethod to the case of three well known blazars, PKS 2155-304, Mrk421 and Mrk 501.Comment: 36 pages, incl. 6 figures in PS format, AAS LaTeX, to be published in ApJ, Dec 199