\begin{table}%t1
%%\centering
\par
\caption{JEM--X main characteristics. 
(Quoted sensitivities are actual values for two JEM--X units.)}\label{tab1}
\begin{tabular}{ll}
\hline\hline
Mask diameter & 535 mm \\
\hline
Detector diameter & 250 mm \\
\hline
Mask--detector distance & 3~401 mm \\
\hline
Energy--range & 3--35 keV \\
\hline
&\\[-4mm]
Energy resolution & {$ \frac{\Delta E}{E} = 0.40\times{\left(\frac{1}{E[{\rm keV}]} + \frac{1}{60}\right)}^{1/2} $}\\[-4mm]
&\\
\hline
Angular resolution & $3.35'$ \\
\hline
Field of view (diameter) & 4.8$^\circ$ Fully coded \\
                         & 7.5$^\circ$ Half response\\
                         & 13.2$^\circ$ Zero response\\
\hline
Point source location & $15''$ (for a 10$\sigma$ source)\\
\hline
Narrow line detection sensitivity & $1.9\times 10^{-5}$~phot~cm$^{-2}$~s$^{-1}$ @ 6 keV \\
Isolated on--axis source & $8.5\times 10^{-5}$~phot~cm$^{-2}$~s$^{-1}$ @ 30 keV \\
For a 3$\sigma$ detection in a 10$^6$~s observation & \\
\hline
Continuum sensitivity & $1.2\times 10^{-5}$~phot~cm$^{-2}$~s$^{-1}$~keV$^{-1}$@ 6 keV \\
Isolated on--axis source & $1.3\times 10^{-5}$~phot~cm$^{-2}$~s$^{-1}$~keV$^{-1}$ @ 30 keV \\
For a 3$\sigma$ detection in a 10$^6$~s observation & \\
\hline
Time resolution & 122 $\mu$s\\
\hline
\end{tabular}
\end{table}