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

Middei, R. and Bianchi, S. and Cappi, M. and Petrucci, P.-O. and Ursini, F. and Arav, N. and Behar, E. and Branduardi-Raymont, G. and Costantini, E. and De Marco, B. and Di Gesu, L. and Ebrero, J. and Kaastra, J. and Kaspi, S. and Kriss, G. A. and Mao, J. and Mehdipour, M. and Paltani, S. and Peretz, U. and Ponti, G. (2018) Multi-wavelength campaign on NCG 7469 IV. The broad-band X-ray spectrum. Astronomy and Astrophysics, 615. A163. ISSN 0004-6361 (https://doi.org/10.1051/0004-6361/201832726)

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Abstract

We conducted a multi-wavelength 6-month campaign to observe the Seyfert Galaxy NGC 7469, using the space-based observatories HST, Swift, XMM-Newton and NuSTAR. We report the results of the spectral analysis of the seven simultaneous XMM-Newton and NuSTAR observations. The source 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 Fe Kα emission line in all the spectra and weaker contributions from Fe Kβ, neutral Ni Kα, and ionized iron. We find no evidence for variability or relativistic effects acting on the emission lines, which indicates that they originate from distant material. In the joint analysis of XMM-Newton and NuSTAR data, a constant photon index is found (Γ = 1.78 ± 0.02) together with a high energy cut-off Ecut = 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 τ = 2.6 ± 0.9. The reflection component is consistent with being constant and the reflection fraction is 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 warm corona with an average kT = 0.67 ± 0.03 keV and a corresponding optical depth τ = 9.2 ± 0.2.

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