Multi-wavelength campaign on NGC 7469 IV. The broad-band X-ray spectrum


Abstract in English

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 ($Gamma$=$1.78pm0.02$), 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 $tau=2.6pm0.9$. 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 $kT=0.67pm0.03$ keV and a corresponding optical depth $tau=9.2pm0.2$.

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