\begin{table}%t3
\caption{90\% upper limits on the ACIS-I count rates ($CR$),
0.5--10~fluxes ($F$), and 1~keV flux density ($S_{\nu}$)
across the NGC~6251 jet regions
(following their definition in Birkinshaw \& Worrall 1993).
The distance $d$ is defined from the inner-outer border of
each region to the core.
Fluxes are calculated assuming a power-law spectrum, with
$\Gamma=2$ and photoelectric absorption
column density $N_{\rm H} = 5.7 \times 10^{20}$~cm$^{-2}$.\label{tab2}}
%\begin{center}
{\begin{tabular}{lccccc} 
\hline \hline
Region & $d$ & Area & $CR$ & $F$ & $S_{\nu}$ \\
& (arcsec) & (arcsec$^2$) & ($10^{-4}$) & $^a$ & (nJy) \\ \hline
A & 10--40 & 46.8 & 2.8 & 2.3 & 0.34 \\
B & 40--126 & 140.6 & 2.2 & 1.8 & 0.26 \\
C & 126--178 & 78.1 & 2.9 &  2.4 & 0.36 \\
D & 178--264 & 124.9 & 1.9 & 1.6 & 0.24 \\
 \hline 
\end{tabular}}
\parbox{7cm}{
$^a$ In the 0.5--10~keV band, in units of $10^{-15}$~erg~cm$^{-2}$~s$^{-1}$.}
%\end{center}
\par
\end{table}