\begin{table} 
\caption{\label{tab_intercal}Summary of the spectral parameters obtained when fitting {\it
Swift}-XRT, {\it XMM-Newton}, {\it Chandra} and {\it RXTE} data for several continuum sources.}
\small%\centerline
 
\begin{tabular}{ccccccc|c c c|c}
\hline \hline
Mode & Grade & Source  & Model  & $N_{\rm H}$ & $\Gamma$ or/and &
$F_{{\rm Obs}}$ [0.3$-$10 keV] &  & {\it XMM-Newton} results & & {\it RXTE} results\\
    & & & & ($\times 10^{22}$ cm$^{-2}$) & $kT$ (keV) & ($\times 10^{-11}$
erg cm$^{-2}$ s$^{-1}$) & PN & MOS1 & MOS2 & \\
\hline
PC & 0--12 & PKS 2155-304 & {\scriptsize WABS*POW} & 0.0124 fixed & $2.538 \pm
0.025$ &  &  $2.676 \pm 0.007$ & $2.590 \pm 0.010$ & $2.560 \pm 0.010$ & \\
& & & & & & $(14.72{-}15.16)$ & $(15.82{-}15.95)$ & $(14.17{-}14.36)$ &
$(15.11{-}15.31)$ &  \\
PC & 0 & & & & $2.523 \pm 0.028$ & $(14.86{-}15.39)$ & & & &\\
\hline
PC & 0--12 & PKS 0745-19 & {\scriptsize TBABS*MEKAL}$^*$ & $0.54\pm 0.01$ &
$6.60\pm 0.22$ &  & & $6.55 \pm 0.19$ & &\\
& & & &  & $0.64\pm 0.07$ & & & $0.74 \pm 0.06$ & &\\
& & & &  &  &  $(4.76{-}4.86)$ & & $(4.44{-}4.53)$ & &\\
PC & 0 & & &  & $6.54\pm0.25$  &  & &  & &\\
&  & & &  & $0.72 \pm 0.08$ &  & &  & &\\
&  & & &  &  &  $(5.05{-}5.18)$ & &  & &\\
\hline
PC & 0--12 & SNR G21.5 & {\scriptsize TBABS*POW}$^{**}$ & $3.21\pm 0.17$ & &  &
$3.06\pm 0.05$ & $3.25 \pm 0.08$ & $3.23 \pm 0.08$ &\\
&  &  & &  & $1.782 \pm 0.072$ &  &
$1.763 \pm 0.021$ & $1.792 \pm 0.036$ & $1.839\pm 0.037$ &\\
&  &  & &  & & $4.53 \pm 0.12$$^\dagger$  &
$4.08 \pm 0.03$$^\dagger$ & $4.45\pm 0.05$$^\dagger$ & $4.59\pm 0.06$$^\dagger$ &\\
PC & 0 &  &  & $3.35\pm 0.19$ & &  & & & &\\
&  &  &  & & $1.834 \pm 0.086$ &  & & & &\\
&  &  &  & &  & $4.72\pm 0.15$$^\dagger$  & & & &\\
\hline
PC & 0--12 & RX J1856.4-3754 & Chandra$^{c}$ & & & $1.020 \pm
0.031$$^\ddagger$ & $0.944\pm0.005$  & $0.950\pm 0.010$ & $1.009\pm 0.010$ & \\
PC & 0 & & & & & $0.994 \pm 0.018$$^\ddagger$ & & & & \\
\hline
\end{tabular}
\end{table}