\begin{table}%T4
%\centering
\par
\caption{Best-fit parameters of the power-law plus two Gaussians
model reproducing the [21$-$22]~\AA~ Mkn~421 spectra taken by the \mbox{RGS-1}.
The errorbars refer to the 90\% confidence intervals.}
\label{2122-tab}
\begin{tabular}{cccc}\hline\hline
\multicolumn{4}{c}{RGS-1 [21$-$22.2]~\AA}\\
\hline
Feature & $\lambda$ & {\it FWHM}  & $k$  \\
number  &  (\AA)    & (m\AA) & (cts cm$^{-2}$ s$^{-1}$~\AA$^{-1}$)\\
\hline
\multicolumn{4}{c}{ToO spectrum}\\
\hline
7 & $21.5915\pm0.013$ & $\rm 78^{+28}_{-25}$ & $-0.0025\pm0.0007$ \\
8 & $21.801\pm0.0005$ & $7\pm1$ & $-0.018\pm0.005$ \\
\hline
\multicolumn{4}{c}{Archival data}\\
\hline
7 & $21.612\pm0.010$ & $\rm 68^{+19}_{-16}$ & $-0.012\pm0.002$ \\
8 & $21.819\pm0.001$ & $12\pm2$ & $-0.342\pm0.068$ \\
\hline
\multicolumn{4}{c}{Total}\\
\hline
7 & $21.603\pm0.008$ & $\rm 81^{+17}_{-15}$ & $-0.109\pm0.019$ \\
8 & $21.823\pm0.001$ & $6\pm2$ & $-0.277\pm0.059$ \\
\hline 
\end{tabular}
\end{table}