\begin{table}%t1
%\centering
\par
\caption{\label{tabella}Parameters for the BL~Lac sources discussed in the text. }
\small \begin{tabular}{ccccc}
\hline\hline
Source name & $\delta$ & $\gamma_{\rm p}$ & $L_{r}$ & $L_{T}$\\
\hline\noalign{\smallskip}
S5 0716+714 (low) & 12 & $9.1\times{10}^{2}$ & $4.2\times{10}^{44}$ & $1.3\times{10}^{45}$\\
S5 0716+714 (high) & 19 & $2.8\times{10}^{3}$ & $1.5\times{10}^{45}$ & $3.1\times{10}^{45}$\\
Mrk 501 (low)  & 15 & $1.4\times{10}^{5}$ & $4.9\times{10}^{42}$ & $1.2\times{10}^{43}$\\
Mrk 501 (high) & 15 &$1.9\times{10}^{5}$ & $2.3\times{10}^{43}$ & $3.1\times{10}^{43}$\\
Mrk 421 (2000, low)  & 20 &$5.2\times{10}^{4}$ & $4.0\times{10}^{42}$ & $1.9\times{10}^{43}$\\
Mrk 421 (2000, high) & 20 &  $6.1\times{10}^{4}$ & $8.1\times{10}^{42}$ & $3.1\times{10}^{43}$\\
Mrk 421 (2008, low)  & 20 & $2.5\times{10}^{4}$ & $1.6\times{10}^{43}$ & $4.1\times{10}^{43}$\\
Mrk 421 (2008, high) & 20 & $3.4 \times{10}^{4}$ & $2.1\times{10}^{43}$ & $4.6\times{10}^{43}$\\
\hline\\[-2mm]
\end{tabular}
\smallskip
The redshifts are $z = 0.031$ for S5~0716+714, $z=0.034$ for Mrk~501 and $z=0.030$ for Mrk~412; $L_{\rm r}$ and $L_{\rm T}$ are given in~erg~s$^{-1}$.
\end{table}