energy and photon index are shown in Fig. \[fig:cont\_cutoffpl\]. To check for the presence of a reflection component, we replaced the cut-off power law with [[pexrav]{}]{}, leaving the reflection fraction ${\mathcal{R}}$ free and tied among the observations. The fit is not improved and we obtain a stringent upper limit ${\mathcal{R}}< 0.02$.

Then, we replaced the cut-off power law with [[compps]{}]{}, assuming a spherical geometry and a seed photon temperature of 100 eV. We obtained a good fit (${\chi^{2}/\textrm{dof}}=971/1007$), with ${kT_{\textrm{e}}}= {75^{+ 20}_{- 15}}$ keV and $y = {1.20^{+ 0.01}_{- 0.02}}$, corresponding to an optical depth $\tau={2.1 \pm 0.5}$. The best-fitting parameters are reported in Table \[tab:fits\_2110\], while the ${kT_{\textrm{e}}}- y$ contour plots are shown in Fig. \[fig:cont\_compps\].

[ l c c c c]{} & all obs. & XMM & NUS1 & NUS2\
\
$\Gamma$ & [$1.65 \pm 0.02$]{}&(t)&(t)&(t)\
${E_{\textrm{c}}}$ (keV)& [$320^{+ 100}_{- 60}$]{}&(t)&(t)&(t)\
$N_{\textsc{pow}}$ ([$10^{-2}$]{}) & [$2.27 \pm 0.09$]{}&(t)&(t)&(t)\
$K_{\textrm{IBIS--pn}}$ && [$0.34 \pm 0.01$]{} &-&-\
$K_{\textrm{IBIS--NusA}}$ &&- &[$2.63 \pm 0.06$]{}& [$1.79 \pm 0.05$]{}\
$K_{\textrm{IBIS--NusB}}$ && - &[$2.71 \pm 0.06$]{}& [$1.81 \pm 0.05$]{}\
${N_{\textrm{H}}}$ ([$10^{22}$]{} [cm$^{-2}$]{}) & & [$4.4 \pm 0.2$]{}&[$3.5 \pm 0.3$]{}&[$3.6 \pm 0.3$]{}\
$E_{\textsc{ga}}$ (keV) & [$6.42 \pm 0.01$]{}&(t)&(t)&(t)\
$\sigma_{\textsc{ga}}$ (eV) & [$40 \pm 20$]{}&(t)&(t)&(t)\
$N_{\textsc{ga}}$ ([$10^{-4}$]{}) && [$1.5 