\begin{table}%t2
\caption{\label{tab:Rfit}Reference load target temperature.} % title of Table
%\centering
                          % used for centering table
\begin{tabular}{l c c}        % centered columns (4 columns)
\hline\hline 
\noalign{\smallskip}
   & \multicolumn{2}{c}{\tt RCA27} \\
%\hline                 % inserts double horizontal lines
   & M & S \\   
\hline
$a$	& $5.7\pm	0.2$ & $2.5\pm	0.1$  \\
$b$	& $0.58\pm	0.02$ & $0.81\pm	0.01$  \\
$c$	& $0.00686\pm 5.8\times 10^{-4}$ & $0.00322\pm	3.2\times 10^{-4}$ \\
\hline                                  %inserts single line
   &\multicolumn{2}{c}{\tt RCA28} \\
  & M & S \\   
\hline
$a$	& $2.47\pm	0.05$ & $5.50\pm	0.09$ \\
$b$	& $0.799\pm	0.007$ & $0.57\pm	0.01$ \\
$c$ &	$0.00407\pm 2.5\times 10^{-4}$ & $0.00831\pm 4.1\times 10^{-4}$ \\
\hline
\end{tabular}
\tablefoot{Quadratic fit coefficients.}
\end{table}