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

Abstract

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$\hat{I}\pm$ emission line in all the spectra, with weaker contributions from Fe K${\hat{I}}^2$, neutral Ni K$\hat{I}\pm$ 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 ($\hat{I}“$=$1.78\pm 0.02$), together with a high energy cut-off $E_{\mathrm{cut}}=170_{-40}^{+60}$ keV. Adopting a self-consistent Comptonization model, these values correspond to an average coronal electron temperature of kT=$45_{-12}^{+15}$ keV and, assuming a spherical geometry, an optical depth $\ddot{I}„=2.6\pm 0.9$. 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 $kT=0.67\pm 0.03$ keV and a corresponding optical depth $\ddot{I}„=9.2\pm 0.2$.

11 pages, 5 figures, accepted by A&A