\begin{table}%t1
\caption{Blue edge in terms of $\log T_{\rm eff}$ of the $g$-mode instability strip for our sdB models$^a$.
\label{blue edge}}
%\centerline
{
\begin{tabular}{llllllll}
\hline\hline
\vspace{-0.25cm}\\
Fe&  Ni & H/He-&opacity &\multicolumn{4}{c}{$l$}\\
 & &diffusion & & 1 & 2 & 3 & 4  \\
\vspace{-0.25cm}\\
\hline
\vspace{-0.25cm}\\
yes & yes &  yes &OPAL  & 4.34  & 4.38 & 4.41 & 4.43    \\
yes & yes &  yes & OP      & 4.41 & 4.45 & 4.47 & 4.48  \\
yes & yes &  no &  OP      & 4.38  & 4.43 & 4.45 & 4.47   \\
yes & no &  yes &   OP    & 4.35  & 4.39 & 4.42 & 4.44  \\
\hline
\end{tabular}}
\medskip
$^a$The results for the first three assumptions are also shown in Fig.~\ref{istrip}.
\end{table}