\begin{table}
\caption{Absolute flux calibration for the various photometric bands used in
this paper.}\label{absflux}
\begin{tabular}{lcc}
\hline\hline
phot.\ band & 0-mag flux & reference \\
            & W~m$^{-2}$~$\mu$m$^{-1}$ \\
\hline\noalign{\smallskip}
2MASS $J$      & 3.129\xt{-9}  & \cite{cohen03} \\
2MASS $H$      & 1.133\xt{-9}  &  '' \\
2MASS $K_{\rm s}$  & 4.283\xt{-10} &  '' \\
Cousins $I_{\rm C}$& 1.196\xt{-8}  & \cite{lamla82} \\
DENIS Gunn-$i$ & 1.20\xt{-8}   & \cite{fouque00} \\
DENIS $J$      & 3.17\xt{-9}   &  '' \\
DENIS $K_{\rm s}$  & 4.34\xt{-10}  &  '' \\
Geneva $U$     & 5.754\xt{-8}  & \cite{rufener88} \\
Geneva $B$     & 2.884\xt{-8}  &  '' \\
Geneva $V$     & 3.736\xt{-8}  &  '' \\
Johnson $B$    & 7.20\xt{-8}   & \cite{johnson65, johnson66} \\
Johnson $V$    & 3.92\xt{-8}   &  '' \\
Johnson $R$    & 1.76\xt{-8}   &  '' \\
Johnson $J$    & 3.4\xt{-9}    &  '' \\
Johnson $H$    & 1.26\xt{-9}   &  '' \\
Johnson $K$    & 3.9\xt{-10}   &  '' \\
MSSO $J$       & 3.03\xt{-9}   & \cite{thomas73} \\
MSSO $H$       & 1.17\xt{-9}   &  '' \\
MSSO $K$      & 4.02\xt{-10}  &  '' \\
MSSO $L$       & 6.18\xt{-11}  &  '' \\
\hline
\end{tabular}
\end{table}