NuSTAR/XMM–Newton monitoring of the Seyfert 1 galaxy HE 1143-1810

Testing the two-corona scenario

¹ INAF-Osservatorio di astrofisica e scienza dello spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy
e-mail: [email protected]
² Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
³ Dipartimento di Matematica e Fisica, Università degli Studi Roma Tre, via della Vasca Navale 84, 00146 Roma, Italy
⁴ Villanova University, Department of Physics, Villanova, PA 19085, USA
⁵ Nicolaus Copernicus Astronomical Center, 00-716 Warsaw, Poland
⁶ INAF-Istituto di Astrofisica e Planetologia Spaziali, via Fosso del Cavaliere, 00133 Roma, Italy
⁷ IRAP, Université de Toulouse, CNRS, UPS, CNES, Toulouse, France
⁸ ASI-Unitá di Ricerca Scientifica, Via del Politecnico snc, 00133 Roma, Italy
⁹ Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse, 85748 Garching, Germany
¹⁰ Núcleo de Astronomía de la Facultad de Ingeniería, Universidad Diego Portales, Av. Ejército Libertador 441, Santiago, Chile

Received: 9 August 2019
Accepted: 5 December 2019

Abstract

Aims. We test the two-corona accretion scenario for active galactic nuclei in the case of the “bare” Seyfert 1 galaxy HE 1143-1810.

Methods. We perform a detailed study of the broad-band UV–X-ray spectral properties and of the short-term variability of HE 1143-1810. We present results of a joint XMM–Newton and NuSTAR monitoring of the source, consisting of 5 × 20 ks observations, each separated by 2 days, performed in December 2017.

Results. The source is variable in flux among the different observations, and a correlation is observed between the UV and X-ray emission. Moderate spectral variability is observed in the soft band. The time-averaged X-ray spectrum exhibits a cut-off at ∼100 keV consistent with thermal Comptonization. We detect an iron Kα line consistent with being constant during the campaign and originating from a mildly ionized medium. The line is accompanied by a moderate, ionized reflection component. A soft excess is clearly present below 2 keV and is well described by thermal Comptonization in a “warm” corona with a temperature of ∼0.5 keV and a Thomson optical depth of ∼17 − 18. For the hot hard X-ray emitting corona, we obtain a temperature of ∼20 keV and an optical depth of ∼4 assuming a spherical geometry. A fit assuming a jet-emitting disc (JED) for the hot corona also provides a nice description of the broad-band spectrum. In this case, the data are consistent with an accretion rate varying between ∼0.7 and ∼0.9 in Eddington units and a transition between the outer standard disc and the inner JED at ∼20 gravitational radii.

Conclusions. The broad-band high-energy data agree with an accretion flow model consisting of two phases: an outer standard accretion disc with a warm upper layer, responsible for the optical–UV emission and the soft X-ray excess, and an inner slim JED playing the role of a hard X-ray emitting hot corona.