\begin{table}%t3
\caption{X-ray flux limits for H$_2$O maser sources without good X-ray spectra, observed and corrected for galactic absorption (see Sect.~4.2). With the exception of the kilomaser galaxy NGC~4293, all sources host megamasers.}\label{limit}
%\centerline
{
\begin{tabular}{lcc}
\hline\hline
Source  &    Observed &   Corrected  \\
        &    upper    &   upper      \\
        &    limit    &   limit      \\
        & \multicolumn{2}{c}{(10$^{-13}$~erg~cm$^{-2}$~s$^{-1}$)} \\
\hline
NGC~235A$^{a}$         & 2.91 &  4.50  \\
NGC~449$^{b}$	     & 3.07 &  6.55  \\
NGC~591$^{b}$	     & 3.73 &  7.63  \\
NGC~613$^{a}$	     & 2.14 &  3.38  \\
IC~184$^{a}$     & 2.51 &  4.19  \\
UGC~3255$^{a}$         & 3.66 & 10.34  \\
VII~ ZW 73$^{a}$       & 4.02 &  9.35  \\
Mrk~78$^{a}$           & 5.88 & 11.55  \\
J0804+3607$^{a}$        & 2.06 &  3.19  \\
NGC~2824$^{a}$	     & 3.02 &  5.50  \\
NGC~2960$^{a}$	     & 3.41 &  6.51  \\
NGC~2979$^{a}$	     & 2.93 &  5.75  \\
Mrk~34$^{b}$           & 1.60 &  2.16  \\
NGC~3735$^{a}$	     & 1.64 &  2.52  \\
NGC~4293$^{a}$	     & 2.74 &  4.78  \\
NGC~5495$^{a}$	     & 4.58 &  9.22  \\
NGC5793$^{b}$           & 9.41 &  22.8  \\
NGC~6323$^{a}$         & 1.61 &  2.67  \\
IRAS F19370--0131$^{a}$ & 5.11 & 15.00  \\
NGC~6926$^{a}$         & 3.20 &  7.49  \\
AM2158-380NED02$^{a}$   & 2.77 &  4.20  \\
TXS~2226-184$^{b}$     & 4.31 &  7.84  \\
IC~1481$^{b}$          & 3.61 &  7.73  \\ 
\hline
\end{tabular}}
\medskip
$^a$ Upper limits to 0.1--2.4~keV fluxes, obtained from the {\it ROSAT} X-Ray All-Sky Survey with HEASARC (High Energy Astrophysics Science Archive Research Center). \\
$^b$ Tentative or negative detections by {\it ASCA} (0.3--12~keV) from TARTARUS version~3.0 at formal 3.19, 9.34, 4.72, 7.36, 0.12, and 2.89$\sigma$ levels for NGC~449, NGC~591 Mrk~34, NGC~5793, \mbox{TXS~2226-184} and IC~1481, respectively. For the way the given flux limits were derived, see also footnote~$a$. 
\end{table}