\begin{table}%t4 \par \caption{\label{om}Optical Monitor parameters and source fluxes for the three \xmm~observations.} \small%\centering \par \begin{tabular}{lcccccc} \hline \hline \noalign{\smallskip} Filter & $\lambda_{\rm e}$\tablefootmark{a} & $A_{\lambda_{\rm e}}/A_{\rm V}$\tablefootmark{b} & $F_{\rm conv}$\tablefootmark{c} & $F_{4/10}$\tablefootmark{d} & $F_{26/9}$\tablefootmark{d} & $F_{28/9}$\tablefootmark{d} \\ \hline \noalign{\smallskip} $V$ & 5430 & 1.016 &$2.49 \times 10^{-16}$ & 11.84 & 14.51 & 14.42 \\ $B$ & 4500 & 1.293 &$1.29 \times 10^{-16}$ & 9.64 & 12.08 & 12.09 \\ $U$ & 3440 & 1.634 &$1.94 \times 10^{-16}$ & 7.48 & 9.79 & 9.78 \\ $UVW1$ & 2910 & 1.870 &$4.76 \times 10^{-16}$ & 6.12 & 8.27 & 8.14 \\ $UVM2$ & 2310 & 2.827 &$2.20 \times 10^{-15}$ & 5.57 & 7.74 & 7.71 \\ $UVW2$ & 2120 & 3.167 &$5.71 \times 10^{-15}$ & -- & -- & 7.08 \\ \hline \end{tabular} \tablefoot{\tablefoottext{a}{The effective wavelength of the filter in \AA.} \tablefoottext{b}{The ratio of $A_{\lambda_{\rm e}}$, i.e. the extinction in magnitudes at the effective wavelength of the filter $\lambda_{\rm e}$, to $A_{V}$ (5500~\AA) obtained from the interstellar reddening curve given by \citet{ccm} and updated by \citet{odonnell}.} \tablefoottext{c}{The conversion factor from rate (Counts~s$^{-1}$) to flux (erg~cm$^{-2}$~s$^{-1}$\AA$^{-1}$) from the OM in-orbit calibration (see SAS watch-out page).} \tablefoottext{d}{The flux of PKS~2005$-$489, corrected for galactic extinction, measured in the three epochs (Oct. 4, 2005; Sept. 26 and 28, 2005). The units are mJy.}} \end{table}