\begin{table}%t1
\caption{\label{top}Overview of the nine most frequent burster sources in the
Galactic center region. They are ordered in decreasing number of
bursts observed per source with the WFC.  For each source a factor
(conv.) in erg/count is derived to convert photon flux to energy flux
in 2$-$28~keV . We also show the net exposure for each individual source
and the distance as quoted in the literature. For each distance
estimate we assume an error of~30\%. The distances are derived from:
[1]~Galloway et~al. (\cite{gpc+02}), [2]~Muno et~al. (\cite{Muno2000}), [3]~in~'t~Zand
et~al. (\cite{Zand1999}), [4]~Lutovinov et~al. (\cite{2001}), [5]~Muno et~al. (\cite{Muno2001}), [6]~Gottwald et~al. (\cite{Gotthelf1989}), [7]~Augusteijn et~al. (\cite{ahj+98}), [8]~Kuulkers \& van~der~Klis (\cite{Kuulkers2000}), [9]~Heasley et~al. (\cite{hjz+00}).}
%\centerline
{
\begin{tabular}{lccccl}
\hline
\hline
Source & \#bursts & Exp. time & Conv. & $d$ & Ref.\\
       & WFC      &  (Ms) & ($10^{-8}$)  & (kpc) &\\
\hline
GX~354-0    & 423 & 7.4 & 1.9 & 5.4 & [1]\\
KS~1731-260 & 339 & 6.7 & 1.5 & 7.0 & [2]\\
GS~1826-24  & 260 & 6.5 & 1.9 & 8.0 & [3]\\
A~1742-294  & 178 & 7.0 & 2.2 & 8.5 & [4]\\
4U~1702-429 & 104 & 8.9 & 1.7 & 6.7 & [5]\\
4U~1705-44  &  66 & 8.7 & 1.8 & 8.9 & a\\
4U~1636-536 &  61 & 4.7 & 1.5 & 5.9 & [7]\\
GX~3$+$1      &  61 & 6.9 & 1.6 & 4.5 & [8]\\
4U~1820-30  &  49 & 7.1 & 1.6 & 7.6 & [9]\\
\hline
\end{tabular}}
\smallskip
a: Distance estimated from [6].
\end{table}