\begin{table}%t5
%\centering
\par
\caption{Upper limits to the BD X-ray luminosities. The hydrogen column
density in unit of $10^{21}$~cm$^{-2}$ given in Col.~(3) is obtained
from the optical extinction using the relation $N_{\rm H,21} =  1.6
\times A_{\rm V}$~cm$^{-2}$~mag$^{-1}$ \citep{vuong03,cardelli89}. Exposure times in
Col.~(4) are for summed EPIC (pn+M1+M2) data, in units equivalent for
a pn-on-axis observation. Columns~(5) and (6) give the upper limits at
the 95\% confidence level for net counts in the 0.5--2~keV energy
range and the X-ray luminosity in the 0.5--8~keV energy range
corrected for absorption, respectively. The upper limit to the
X-ray fractional luminosity, $\eta=\log (L_{\rm X}/L_*)$, is given in
the last column.
\label{table:ul}}
\begin{tabular}{@{}lcccccc@{}}
\hline\hline
\multicolumn{1}{c}{BD name} & XEST & $N_{\rm H,21}$ & Exp. & $N$ &
$L_{\rm X,27}$ & $\eta$ \\
& \# &  ~cm$^{-2}$ & ks & cnts & erg~s$^{-1}$\\
\multicolumn{1}{c}{(1)}     & (2)      & (3) & (4) & (5) & (6) & (7)\\
\hline
2MASS~J0414    & 20  &  1.1  &  44.7   &  115.5  &  15.8 & --3.6\\
2MASS~J0421    & 11  &  4.8  &  38.4   &  19.5   &  6.1  & --3.3\\
KPNO-Tau~2     &23+24&  0.6  &  22.1   &  30.2   &   6.0 & --3.6\\
KPNO-Tau~4     & 02  &  3.9  &  51.8   &  25.8   &   5.0 & --3.5\\
KPNO-Tau~6     & 14  &  0.1  &  26.8   &  31.1   &   6.4 & --3.3\\
KPNO-Tau~7     & 14  &  0.1  &  25.6   &  16.9   &   2.5 & --3.8\\
KPNO-Tau~9     &08+09&  0.1  &  51.5   &  37.9   &   2.8 & --3.1\\
CFHT-BD-Tau~2  & 08  &  0.1  &  33.9   &  25.5   &   2.9 & --4.0\\
\hline
\end{tabular}
\end{table}