\begin{table}%t1
\caption{\label{history}\grs~flux history.}
%\centerline
{ 
\tiny \begin{tabular}{lccc}
\hline \hline\noalign{\smallskip}
Date & Instrument   & Flux$^a$   & Ref.$^b$ \\
~ & ~ & [$10^{-11}$ \ergperseccm] & ~  \\
\hline\noalign{\smallskip}
1990--2002 & \dotfill& \dots& [1] \\	
2002 Feb.~26& \xmm/PN& $<$0.0007& [2] \\
2002 Oct.~3 & \xmm/PN& 1& [2] \\
2004 Mar. 28 & \xmm/PN	& $<$0.0007& [2] \\
2004 Aug. 31& \xmm/PN & $<$0.0002& [2] \\
2005 Apr. 10& \integ/ISGRI& 31.9	& [3],[4] \\
2005 Jun. 5& \chandra/HRC	& 10	& [5],[6] \\
2005 Jul. 1& \chandra/ACIS	& 1.7	& [5],[6] \\
2006 Feb. 27& \xmm/PN		& $<$0.0058	& [2] \\
2006 Sep. 8	& \xmm/PN		& $<$0.0057	& [2] \\
2006 Sep. $\sim$20& \swift/XRT		& 1.2		& [7] \\
2007 Feb. 15 & \integ/ISGRI		& 13		& [4],[8] \\
2007 Feb. 16& \swift/XRT		& 15		& [9],[2] \\
2007 Feb. 22& \chandra/ACIS& 3	& [10] \\
2007 Feb. 27& \xmm/PN	& 11.6	& [2] \\
2007 Mar.& \swift/XRT	& 26& [7] \\
2007 Apr. 2 & \xmm/PN	& 13.1	& [11],[2] \\
2007 Apr. 4& \xmm/PN & 5.5 	& [11],[2] \\
2007 Sep. 6& \xmm/PN	& $<$0.0026	& [2] \\
2008 Mar. 23& \xmm/PN	& $<$0.0003	& [2] \\
\hline
\end{tabular}}
\medskip
$^a$ \mbox{X-ray} flux in the ranges 2--8~keV for \xmm~and \chandra, 20--60~keV for \integ/ISGRI, 3--10~keV for \integ/JEM-X, and 2--10~keV for \swift/XRT; $^b$~references: [1] \cite{muno03b}, [2]~This work, [3] \cite{kuulkers07c},  [4]~\cite{kuulkers07b}, [5]~\cite{wijnands05}, 
[6] \cite{wijnands06},  [7]~\cite{degenaar09}, [8]~\cite{kuulkers07a},  [9]~\cite{wijnands07},  [10]~\cite{muno07},  [11]~\cite{porquet07}. 
\end{table}