\begin{table}%t2
%\centering
\par
\caption{Best-fit parameters and results for the analysis of the
nuclear spectra of NGC~6251. Model legenda: PL~=~power-law; TH~=~thermal
component ({\tt mekal} implementation in X{\sc spec})
with solar abundances; GA~=~Gaussian
emission line; BKPL~=~broken power-law.\label{tab1}}
\begin{tabular}{lcccccccc} 
\hline \hline
Model & $N_{\rm H}$ & $\Gamma$ & $kT_1$/$\Gamma_{{\rm soft}}$ & $kT_2$/$E_{{\rm break}}$ & $E_{\rm c}$ & $I_{\rm c}$ & $EW$ & $\chi^2/$~d.o.f. \\
Mission & ($10^{21}$~cm$^{-2}$) & & (keV)/ & (keV) & (keV) & ($10^{-6}$~ph~cm$^{-2}$~s$^{-1}$) & (eV) & \\ \hline
\multicolumn{7}{l}{{\it BeppoSAX}} \\
PL & $0.8 \pm^{0.6}_{0.3}$ & $1.79 \pm^{0.06}_{0.07}$ & ... & ... & ... & ... & ... & 96.7/92 \\
PL+TH & $1.0 \pm^{0.12}_{0.05}$ & $1.70 \pm^{0.12}_{0.16}$ & $1.4 \pm^{0.9}_{0.7}$ & ... & 6.4$^{\dag}$ & $<$8.0 & $<$160 & 92.3/90 \\
 & &  & & ... & 6.59$^{\dag}$ & $<$4.5 & $<$80 &  \\
 & &  & & ... & 6.7$^{\dag}$ & $<$3.0 & $<$60 &  \\
 & &  & & ... & 6.96$^{\dag}$ & $<$2.1 & $<$50 &  \\  
\multicolumn{7}{l}{{\it ASCA}} \\ 
PL & $0.9 \pm^{0.4}_{0.3}$ & $2.06 \pm^{0.08}_{0.07}$ & ... & ... & ... & ... & ... &  259.7/225 \\
PL+TH & $1.6 \pm^{0.7}_{0.8}$ & $2.00 \pm^{0.08}_{0.07}$ & $0.85 \pm^{0.34}_{0.15}$ & ... & ... & ... & ... &  240.6/223 \\
PL+2$\times$TH & $1.6 \pm^{2.1}_{0.8}$ & $2.3 \pm 0.4$ & $0.8 \pm^{0.3}_{0.2}$ & $6 \pm^6_2$ & ... & ... & ... &  231.8/221 \\
PL+TH+GA & $1.7 \pm^{0.5}_{0.4}$ & $2.05 \pm^{0.11}_{0.10}$ & $0.84 \pm^{0.27}_{0.18}$ & & $6.59 \pm 0.16$ & $8 \pm 4$ &  $500 \pm 200$ & 228.1/221 \\
BKPL+GA & $4.0 \pm^{1.8}_{1.5}$ & $2.28 \pm^{0.17}_{0.14}$ & $3.7 \pm^{1.2}_{0.9}$ & $1.38 \pm^{0.15}_{0.09}$ & $6.62 \pm^{0.12}_{0.18}$ & $10 \pm4 $ & $800 \pm 300$ & 245.0/226 \\ \hline \end{tabular} 
\par
\smallskip
\noindent
$^{\dag}$~Gaussian emission profiles added to the best-fit continuum. Centroid energies $E_{\rm c}$ are fixed. Upper limits are at the~90\% confidence level.
\end{table}