\begin{table}%t2
     \caption{\label{ages}Ages (in logarithmic scale) of the debris discs detected at the
       millimetre wavelength, with IRAM (this work), SEST and OVRO (from C05). 
       They have been derived using different techniques: the strength of the 
       CaII~H and K ($R'_{\rm HK}$) and Lithium (Li) emission, X-ray activity
       ($X$-$ray$), and the rotational period-age ($p_{\rm rot}$) relation 
       (L. Hillenbrand, private communication). The ages are averaged and the
       standard deviation is adopted as error.}
\par
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\par
     %\centering
\par
     \begin{tabular}{rrrrr}
       \hline
       \hline
       Method&	HD~377	& HD~8907&	HD~104860&	HD~107146\\
       \hline
       $R'_{\rm HK}$	& 8.34	& 8.78 & 8.44	& 8.09 \\
       $v \sin i$	        & 7.99	& 8.1  &  --	& 8.89  \\
       $p_{\rm rot}$	& --	& --    &  7.62	&    --  \\
       $X$-$ray$	        & 7.9	& 7.88 & 8.06	&   --   \\
        Li 	        & 7.8	& 9.28 & 8.08	& 8.1  \\
       average		& 8.01	& 8.51 & 8.05	& 8.36 \\
       stdev		& 0.23	& 0.64 & 0.34	& 0.46 \\ 
       \hline
     \end{tabular} 
   \end{table}