\begin{table}%t1
\caption{\label{obslog}Observation log. }
%\centerline
{
\begin{tabular}{ccccrcrr}
  \hline\hline
  \noalign{\smallskip}
   Observation interval & Time after   & Expo.-time & Rev.  & Count rate &
                   {\it HR}1 & {\it HR}2~~ & {\it HR}3  \\
          (UT)      & Max. (days)  &  (ks)~~  &       & (cts/ks)~ & & & \\
 \noalign{\smallskip}
 \hline
 \noalign{\smallskip}
  2000-07-25 22:48--2000-07-26 03:19 & ~17 & 16.26~~ & 115& $ 5.0 \pm 0.6 $&
                                      -- & 	$1.00 \pm 2.00$& $0.00\pm0.11$  \\
  2000-08-28 13:53--2000-08-28 16:40 & ~51 & 10.00~~ & 132& $21.0 \pm 1.6 $&
                                                            $0.70 \pm 0.07$&$ -0.56\pm0.06$ & $-0.66\pm0.16 $ \\
  2001-03-29 19:10--2001-03-29 21:22 & 294 & 10.54~~ & 239 & $<$1.0  &
      -- & --~~~~~~ & --~~~~~~ \\
\hline
\end{tabular}}
\smallskip
(1) The hardness ratios are defined as 
              $HR1 = (B-A)/(B+A)$, $HR2 = (C-B)/(B+C)$ and  $HR3 =(D-C)/(D+C)$,
           where $A (0.2{-}0.5$~keV), $B (0.5{-}2.0$~keV), $C (2.0{-}4.5$~keV),
           $D (4.5{-}7.5$~keV), 
            are the counts in the given energy range.
\end{table}