2018A&A...618A.167M

We present the multi-epoch spectral analysis of HE 0436-4717, a bright Seyfert 1 galaxy serendipitously observed by the high energy satellite NuSTAR four times between December 2014 and December 2015. The source flux shows modest variability within each pointing and among the four observations. Spectra are well modelled in terms of a weakly variable primary power law with constant photon index (Γ=2.01±0.08). A constant narrow Fe Kα emission line suggests that this feature has an origin far from the central black hole, while a broad relativistic component is not required by the data. The Compton reflection component is also constant in flux with a corresponding reflection fraction R=0.7^+0.2_–0.3. The iron abundance is compatible with solar (A_Fe=1.2^+1.4_–0.4), and a lower limit for the high energy cut-off E_c>280keV is obtained. Adopting a self-consistent model accounting for a primary Comptonized continuum, we obtain a lower limit for the hot corona electron temperature kT_e>65keV and a corresponding upper limit for the coronal optical depth of τ_e<1.3. The results of the present analysis are consistent with the locus of local Seyfert galaxies in the kT_e-τ_e and temperature-compactness diagrams.