\begin{table}%t3
%\centering
\par
%\renewcommand{\arraystretch}{1.1}
\caption{Summary of optical and ultraviolet observations. All data but the
point in the $R$ band were measured by \Swift-UVOT. The {$R$-band}
observations is by \citet{Tristram05}. All measurements were corrected for the
Galactic extinction \citep[$A_{\rm V} = 0.123$~mag;][]{Schlegel98}, assuming the
Milky Way extinction curve by \citet{Pei92}. The optical-to-X-ray spectral
index is $\beta_{\rm OX} = \log(F_\nu^{\rm opt}/F_\nu^{\rm X}) / \log(\nu_{\rm
X}/\nu_{\rm opt})$. The X-ray frequency was set to $\nu_{\rm X} = 1.5$~keV, the
logarithmic mean of the XRT observing range. The X-ray flux was computed by
interpolating the XRT light curve { to} the time of the optical limit. The
last column reports the ratio of the extrapolated X-ray flux to the optical one
(assuming no spectral breaks between the two bands; see
Fig.~\ref{fg:SED}).\label{tab:optical}}
\small
%\centering
\begin{tabular}{lllllllll} \hline\hline
\noalign{\smallskip}
  Time since burst &Filter & Wavelength  & Exposure time & Extinction & Magnitude &  Flux density &$\beta_\mathbf{OX}$ &   X-ray/optical ratio\\
(s)                  &           &(\AA) 	  &(s)  	     & (mag)         &              &($\mu$Jy)       &		&                    \\ \hline
\noalign{\smallskip}
3300                 &{\it UVW2}       &1930  	  &10		     &0.29           &${>} 17.41$     &${<} 99.11$	     &${<} 0.52$  &$\rm {>} 23^{+8.9}_{-6.4}$\\[2mm]
3306                 &$V$        &5460  	  &100  	     &0.12           &${>} 18.66$     &${<} 107.5$	     &${<} 0.45$  &$\rm {>} 65 ^{+31}_{-21}$ \\[1mm]
3350                 &{\it UVM2}       &2220  	  &100  	     &0.36           &${>} 18.54$     &${<} 34.17$	     &${<} 0.32$  &$\rm {>} 75 ^{+30}_{-21}$ \\[1mm]
3470                 &{\it UVW1}       &2600  	  &100  	     &0.27           &${>} 18.75$     &${<} 27.80$	     &${<} 0.29$  &$\rm {>} 103^{+43}_{-30}$ \\[1mm]
5219                 &$U$        &3450  	  &750  	     &0.20           &${>} 19.65$     &${<} 11.00$	     &${<} 0.24$  &$\rm {>} 176^{+77}_{-54}$ \\[1mm]
9390                 &$B$        &4350  	  &714  	     &0.16           &${>} 20.87$     &${<} 17.47$	     &${<} 0.46$  &$\rm {>} 52 ^{+24}_{-16}$ \\ \hline
\noalign{\smallskip}
24~840             &$R_{\rm MOA}$ &6399  	  &600  	     &0.10           &${>} 20.20$     &${<} 25.70$	     &${<} 0.74$  &$\rm {>} 10^{+5.0}_{-3.4}$\\
 \hline
\end{tabular}
\end{table}