Astronomy & Astrophysics

**Table 2:** Radial spectral fitting - best fit values and associated error bars (90% confidence level).
$\begin{displaymath}\begin{tabular}{ccccl} \hline \hline ~$R_{\rm out}$~$^{{a}... ...~1.29 & 0.26$^{{b}}$ & 0.90 (443)\\ \hline \par\end{tabular} \end{displaymath}$ $\:\:\:\:\:\:^{{a}}$ External radius of the annuli, ^b fixed parameter.