\begin{table}%t1 
\caption{\label{tab_amcvn}The known AM~CVn systems.}
%\centerline
{ 
\small\begin{tabular}{lcl}
\hline\hline
System & $P_{\rm orb}$ (s) & Type\\
\hline
      RX~J0806.3+1527   &  321.52911(2)  &  ultra-short, pulsed X-ray    \\  
      V407~Vul &  569.4  &  ultra-short, pulsed X-ray    \\  \hline
      %\noalign{\smallskip}\hline\noalign{\smallskip}
      ES~Cet   &  621  & high-state\\
      AM~CVn   &  1028.73  & high-state\\
      HP~Lib   &  1103  & high-state\\  \hline
      %\noalign{\smallskip}\hline\noalign{\smallskip}
      CR~Boo   &  1471  & outbursting\\
      KL~Dra   &  1500  & outbursting\\
      V803~Cen &  1596  & outbursting\\
      SDSS~J0926+3642 &  1699  & outbursting\\
      CP~Eri   &  1701  & outbursting\\
      2003aw (V406~Hya)   &  2028  & outbursting\\
      2QZ~J1427-01 & 2194 (?) &  outbursting\\\hline
      %\noalign{\smallskip}\hline\noalign{\smallskip}
      SDSS~J1240-0159   &  2242  & low-state\\
      GP~Com   &  2794  & low-state\\
      CE~315 (V396~Hya)  &  3906  & low-state\\
\hline
      SDSS~J1411+4812 & 2760  &  emission lines\\
      SDSS~J1552+3201 & 3376.3(3) &  emission lines\\
      SDSS~J0129+3842 & --- &  emission lines\\
      SDSS~J1208+3550 & --- & emission lines\\
      SDSS~J2047+0008 & --- & absorption lines\\
      SNF~20060524-042 & --- & ---\\
      %\noalign{\smallskip}
      \hline
    \end{tabular}}
 \smallskip
\par
    Data taken from \citet{bild2006} and references therein,
    \citet{roel2007a,roel2007b}, \citet{and2005,and2008}, and the
    website of G. Nelemans (\url{http://www.astro.ru.nl/\textasciitilde nelemans/}).
\end{table}