Multi-wavelength campaign on NGC 7469 IV. The broad-band X-ray spectrum
  We conducted a multi-wavelength six-month campaign to observe the Seyfert
galaxy NGC~7469, using the space-based observatories \textit{HST},
\textit{Swift}, \textit{XMM-Newton} and \textit{NuSTAR}. Here we report the
results of the spectral analysis of the 7 simultaneous \textit{XMM-Newton} and
\textit{NuSTAR} observations. The sources shows significant flux variability
within each observation, but the average flux is less variable among the
different pointings of our campaign. Our spectral analysis reveals a prominent
narrow neutral \ion{Fe} K$\alpha$ emission line in all the spectra, with weaker
contributions from Fe K$\beta$, neutral Ni K$\alpha$ and ionised iron. We find
no evidence for variability or relativistic effects acting on the emission
lines, which indicates that they originate from distant material. Analysing
jointly \textit{XMM-Newton} and \textit{NuSTAR} data a constant photon index is
found ($\Gamma$=$1.78\pm0.02$), together with a high energy cut-off
$E_{\rm{cut}}=170^{+60}_{-40}$ keV. Adopting a self-consistent Comptonization
model, these values correspond to an average coronal electron temperature of
kT=$45^{+15}_{-12}$ keV and, assuming a spherical geometry, an optical depth
$\tau=2.6\pm0.9$. The reflection component is consistent with being constant,
with a reflection fraction in the range $R=0.3-0.6$. A prominent soft excess
dominates the spectra below 4 keV. This is best fit with a second
Comptonization component, arising from a \virg{warm corona} with an average
$kT=0.67\pm0.03$ keV and a corresponding optical depth $\tau=9.2\pm0.2$.
