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.
Highlights
The X-ray emission of active galactic nuclei (AGNs) is believed to originate from thermal Comptonization of optical–UV photons, emitted by the accretion disc, in a hot corona
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 jet-emitting disc (JED) playing the role of a hard X-ray emitting hot corona
In this paper we investigate the properties of the hot corona and the physical origin of the soft excess in the Seyfert 1 galaxy HE 1143-1810 (z = 0.0328, Jones et al 2009) through a joint XMM–Newton and NuSTAR monitoring programme carried out in 2017
Summary
The X-ray emission of active galactic nuclei (AGNs) is believed to originate from thermal Comptonization of optical–UV photons, emitted by the accretion disc, in a hot corona (see e.g. Haardt & Maraschi 1991; Haardt et al 1994, 1997). Crummy et al 2006; Ponti et al 2006; Walton et al 2013; Jiang et al 2018; García et al 2019) and “warm” Comptonization (see e.g. Magdziarz et al 1998; Mehdipour et al 2011; Done et al 2012; Petrucci et al 2013, 2018; Boissay et al 2014; Matt et al 2014; Middei et al 2018, 2019; Porquet et al 2018; Ursini et al 2018) In the latter hypothesis the optical–UV emission and soft X-ray excess could originate from the upper layer of the accretion disc, consisting of a warm (kTe ∼ 1 keV) optically thick (τ ∼ 10−20) slab-like corona (Rózanska et al 2015; Petrucci et al 2018).
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