\begin{table}%T5
%\centering
\small
  \caption{Candidate and confirmed astrometric binaries in the \hipp{} catalogue. For each subgroup we list the number $N_\star$ of known members, the number of stochastic (X); orbital (O); acceleration (G); component (C); and suspected (S) binaries in the \hipp{} catalogue. For each (S)~binary we list between brackets how many of these are also (X)-flagged. The last three columns list the "astrometric binary fraction'' -- including the (X), (O), (G) binaries -- without the (S) binaries and with the (S)~binaries included, and the \hipp{} "visual'' binary fraction, for the (C)~binaries only. (V) binaries are not present in \sco{}.
 \label{table: hipparcos_observations} }
  \begin{tabular}{lr ccccc lll}
    \hline
    \hline\\[-3.2mm]
    Subgroup& $N_\star$&(X)& (O) &(G) & (C)& (S)             & $\tilde{F}_{M,\rm ~XOG}$ & $\tilde{F}_{M,\rm ~XOGS}$ & $\tilde{F}_{M,\rm ~C}$ \\
    \hline
    US      & 120   & 1 & 0   & 4  & 15 & 8  (1)  & $4.2 \pm 1.5\%$      &  $10.0\pm 2.1\%$      & $ 12.5\pm 3.0\%$    \\
    UCL     & 221   & 0 & 1   & 9  & 36 & 7  (0)  & $4.5 \pm 1.5\%$      &  $\ 7.7\pm 1.9\%$      & $ 16.3\pm 3.0\%$   \\
    LCC     & 180   & 2 & 0   & 6  & 28 & 11  (2)  & $4.4 \pm 1.6\%$      &  $\ 9.4\pm 2.4\%$      & $ 15.6\pm 3.0\%$    \\
    \hline
    \sco{} & 521 & 3 & 1   & 19 & 79 & 26  (3)  & $4.4 \pm 1.0\%$      &  $\ 8.8\pm 1.4\%$      & $ 15.2\pm 1.8\%$   \\
    \hline
  \end{tabular}
\end{table}