\begin{table}%t1
\caption{\label{table_fluxes}Overview of the properties$^1$ of the observed flashes discussed in this paper.}
%\centerline
 {\small \begin{tabular}{cc@{}cl@{}c@{}c@{}c@{}c@{}c@{}c@{}c@{}}
\hline \hline\noalign{\smallskip}
\multicolumn{1}{c}{Source} &
\multicolumn{1}{c}{$F_{\rm bb,peak}$ (10$^{-8}$} &
\multicolumn{1}{c}{} &
\multicolumn{1}{c}{$F_{\rm pers}$} &
\multicolumn{1}{c}{} &
\multicolumn{1}{c}{$F_{\rm pers,bol}/F_{\rm bb,peak}$} &
\multicolumn{1}{c}{$L_{\rm x,bol}$ (10$^{36}$} &
\multicolumn{1}{c}{$\Delta t_{\rm last}$} &
\multicolumn{1}{c}{} &
\multicolumn{1}{c}{$\Delta t_{\rm next}$} &
\multicolumn{1}{c}{} \\
\multicolumn{1}{c}{} &
\multicolumn{1}{c}{erg~cm$^{-2}$~s$^{-1}$)} &
\multicolumn{1}{c}{} &
\multicolumn{1}{c}{(10$^{-10}$~erg~cm$^{-2}$~s$^{-1}$)} &
\multicolumn{1}{c}{} &
\multicolumn{1}{c}{$\equiv${}$L_{\rm x,bol}/L_{\rm Edd}$} &
\multicolumn{1}{c}{erg~s$^{-1}$)} &
\multicolumn{1}{c}{(days)} &
\multicolumn{1}{c}{} &
\multicolumn{1}{c}{(days)} &
\multicolumn{1}{c}{} \\
\hline
\object{Cen~X-4} & $\sim$120 & [1] & $<$20$^a$ (2--10~keV) & [1] & $\lesssim$0.0033 & $\lesssim$0.7 & $>$40 & [1,2] & $\simeq$2 & [1,3] \\
\object{2S~1711$-$339} & $3.0 \pm 1.0^b$ & [4] & $<$0.7 (2--28~keV) & [4] & $\lesssim$0.0047 & $\lesssim$1 & $\sim$340 & [4] & $\simeq$1440 & [5] \\
\object{GRS~1747$-$312} & $\simeq$2.5$^c$ & [6] & $<$0.6 (0.1--200~keV) & [6] & $\lesssim$0.0024 & $\lesssim$0.5 & $\simeq$26 & [6] & $\simeq$28 & [6] \\
\object{IGR~J17473$-$2721} & $\simeq$11$^d$ & [7] & $<$1.7 (2--10~keV) & [8] & $\lesssim$0.0031 & $\lesssim$0.4 & $\sim$960 & [9,10] & $\simeq$2 & [8,11] \\
\object{2S~1803$-$245} & $3.1 \pm 0.7$ & [12] & $<$2$^e$ (2--28~keV) & [4] & $\lesssim$0.013 & $\lesssim$3 &  $\sim$7990 & [13] & $\simeq$7 & [12] \\
\object{SAX~J1808.4$-$3658} & $25 \pm 2^c$ & [14] & $<$3 (2--28~keV) & [14] & $\lesssim$0.0024 & $\lesssim$0.5 & $\simeq$17 & [14] & $\simeq$543 & [15] \\
\hline
\end{tabular}}
\medskip
$^a$~{\it Vela 5B} 56~h upper limit; $^b$~highest peak flux among the flash sample in [4]; $^c$~photospheric radius-expansion flash; $^d$~peak flux observed during another flash reported by~[7]; $^e$~no limits are quoted in [12]; we, therefore, assume the highest {\it BeppoSAX}/WFC flux upper limit from~[4].\\
{\it Note~1.} In the first two columns we give the observed flash bolometric
peak fluxes ($F_{\rm bb,peak}$) and the 3$\sigma$ upper limits on the flux around the flashes ($F_{\rm pers}$). From these we infer the flash peak luminosities in terms of the Eddington luminosity ($L_{\rm Edd}$), assuming  $L_{\rm x,bol}/L_{\rm Edd} \equiv F_{\rm pers,bol}/F_{\rm bb,peak}$ 
(see Sect.~3), where $F_{\rm pers,bol}$ and $L_{\rm x,bol}$ are the
bolometric pre-flash source flux and luminosity, respectively.
Assuming $L_{\rm Edd} = 2 \times 10^{38}$~erg~s (see Sect.~2) we
derive an upper limit on $L_{\rm x,bol}$. In the last two columns
we provide the time since the last and to the next detected \mbox{X-ray} outburst with respect to the time of the flash, $\Delta t_{\rm last}$ and $\Delta t_{\rm next}$, respectively. References are given in brackets:  [1]~this paper; [2]~Conner et~al. (\cite{Conner1969}); [3]~Belian et~al.  (\cite{Belian1972}); [4]~Cornelisse et~al. (\cite{Cornelisse2002}a); 
[5]~Markwardt \& Swank (2004); [6]~\mbox{in 't Zand} et~al. (2003b); 
[7]~Altamirano et~al.  (\cite{Altamirano2008}); [8]~Markwardt et~al. (\cite{Markwardt2008});  [9]~Grebenev et~al.  (\cite{Grebenev2005}); [10]~Markwardt \&\ Swank (\cite{Markwardt2005}); [11]~Del Monte et~al.  (\cite{Delmonte2008}); [12]~Cornelisse et~al. (\cite{Cornelisse2007});  [13]~Jernigan (\cite{Jernigan1976}); [14]~\mbox{in 't Zand} et~al.  (\cite{Zand2001}); [15]~Marshall (\cite{Marshall1998}).
\end{table}