NuSTAR view of the Seyfert galaxy HE 0436-4717

¹ Dipartimento di Matematica e Fisica, Università degli Studi Roma Tre, via della Vasca Navale 84, 00146 Roma, Italy
e-mail: riccardo.middei@uniroma3.it
² Dipartimento di Fisica, Università di Roma “Tor Vergata”, via della Ricerca Scientifica 1, 00133 Roma, Italy
³ INAF Astronomical Observatory of Rome, Via Frascati 33, 00078 Monteporzio Catone, Italy
⁴ Department of Astronomy, University of Maryland, College Park, MD, 20742 USA
⁵ NASA/Goddard Space Flight Center, Code 662, Greenbelt, MD, 20771 USA
⁶ INAF – Osservatorio di astrofisica e scienza dello spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy
⁷ INAF/Istituto di Astrofisica e Planetologie Spaziali, Via Fosso del Cavaliere, 00133 Roma, Italy

Received: 8 June 2018
Accepted: 25 July 2018

Abstract

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 > 280 keV 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 > 65 keV 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.