\begin{table}%t7
\caption{\label{compare_table}Comparison of the ionisation parameters, hydrogen column densities and outflow velocities of the NGC~3516 warm absorber phases~found in recent observations, shown in increasing order of~$\xi$.}
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\begin{tabular}{l l l  |l l l | l l l l  |l l l l}
\hline
\hline 
\multicolumn{3}{c|}{\citet{Tur05}\tablefootmark{a}} & \multicolumn{3}{c|}{\citet{Mar08}\tablefootmark{b}} & \multicolumn{4}{c|}{\citet{Tur08}\tablefootmark{c}} & \multicolumn{4}{c}{Present work\tablefootmark{d} } \\
$\log\ \xi$\tablefootmark{e} $\sim$ & $\NH$\tablefootmark{f}  $\sim$ & $v$\tablefootmark{g}  $\sim$ & $\log\ \xi$\tablefootmark{e} $\sim$ & $\NH$\tablefootmark{f} $\sim$ & $v$\tablefootmark{g} $\sim$ & $\log\ \xi$\tablefootmark{e} $\sim$ & $\NH$\tablefootmark{f} $\sim$ & $v$\tablefootmark{g} $\sim$ & zone & $\log\ \xi$\tablefootmark{e} $\sim$ & $\NH$\tablefootmark{f} $\sim$ & $v$\tablefootmark{g} $\sim$ & phase \\
\hline
-- & -- & -- & -- & -- & -- & $-2.4$ & $0.2$ & ? & $1$ & -- & -- & -- & --\\
$-0.5$ & $0.5$ & $-200$ & $0.3$ & $5.5$ & ? & $0.25$ & $0.05$ & ? & $2$ & $0.9$ & $0.4$ & $-100$ & A \\
$2.5$  & $25$ & $-1100$ & -- & -- & -- & $2.2$ & $20$ & $-1600$ & $3$ & $2.4$ & 2 & $-1500$ & B \\
$3.0$ & $2$ & $-1100$ & $3.7$ & $4$ & $-1100$\tablefootmark{h}  & $4.3$ & $26$ & $-1000$ & $4$ & $3.0$ & $1$ & $-900$ & C \\
\hline
\end{tabular}
\tablefoot {\tablefoottext{a}{From the Apr. and Nov. 2001 \xmm\ \mbox{EPIC-pn} spectra. The values of the ionisation parameter in $\xi$ form are given in \citet{Tur08};}
\tablefoottext{b}{from the Oct. 2005 {\it Suzaku} XIS and HXD spectra;}
\tablefoottext{c}{from the Oct. 2006 \xmm\ \mbox{EPIC-pn} and {\it Chandra} HETG spectra;}
\tablefoottext{d}{from the Oct. 2006 \xmm\ \mbox{EPIC-pn} and RGS~spectra;}
\tablefoottext{e}{${\rm erg\ cm\ }{\rm s}^{-1}$;}
\tablefoottext{f}{$10^{22}$ ${\rm cm}^{-2}$;}
\tablefoottext{g}{flow velocity in~\kms;}
\tablefoottext{h}{based on the velocity obtained in \cite{Tur05}.}}
\end{table}