\begin{table}%t3
\caption{\label{tab_release}Summary of the releases of the XRT post-launch RMFs.}
\small%\centerline
 {
\begin{tabular}{cclc}
\hline \hline
%&&& \\[-8pt]
Release number$^\dagger$  & Release date  & Main improvements in the RMFs & Text section
number\\
\hline
07  & 2005 April 5  &  {\bf Line shoulder:} ad-hoc increase of threshold to favour & 3.3.3  \\
    &    &  sub-threshold losses in PC \& WT mode & \\
\hline
08  &  2006 April 24  &  {\bf Low-energy response:} change in the description
    the  & 3.3.1 \\
    &    &  surface loss function in PC \& WT mode  &    \\
\hline
%&&& \\[-8pt]
09$^\ddagger$  & 2007 May 31  &  {\bf Line shoulder:} New description of the charge
    cloud in & 3.3.3\\
    &    &  the field-free region for high-energy photons ($E > 2$ keV) &\\
    &    &  in PC mode &\\
    &    &  {\bf Shelf:} Rescaling of the shelf in both PC \& WT mode & 3.3.2\\
\hline
11$^*$  & 2008 June 25 & {\bf Loss function:} New description of the surface loss function & 3.3.4\\
      &            & in the 1-2 keV energy range in WT mode & \\
\hline
\end{tabular}}
\medskip
$^\dagger$ The v006 response files correspond to the pre-launch response files. \\
$^\ddagger$ The v009 response files were renamed as v010 response files when the substrate voltage was raised from 0 to 6~V on 2007~August~30 (see Sect.~4.3) following an update of the ground software. \\
$^*$ \url{http://swift.gsfc.nasa.gov/docs/heasarc/caldb/swift/docs/xrt/SWIFT-XRT-CALDB-09_v11.pdf}
 (Godet et~al. \cite{Gode08}).
\end{table}