NuSTAR Survey of Obscured Swift/BAT-selected Active Galactic Nuclei. II. Median High-energy Cutoff in Seyfert II Hard X-Ray Spectra

Baloković, Mislav; Harrison, Fiona A.; Madejski, G.; Comastri, A.; Ricci, Cláudio; Annuar, A.; Ballantyne, D. R.; Boorman, Peter; Brandt, W. N.; Brightman, Murray; Gandhi, P.; Kamraj, Nikita; Koss, Michael; Marchesi, S.; Marinucci, Andrea; Masini, Alberto; Matt, Giorgio; Stern, Daniel; Urry, C. Megan

doi:10.3847/1538-4357/abc342

Cited by 62 publications

(70 citation statements)

References 102 publications

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“…Moreover, compared with previous fits of a single power-law plus a xillver component, Model A describes the iron complex region with a neutral distant reflection model, although we still can see some systematic residuals in the upper left panel of Figure 5 around the Fe K energies. However, the most peculiar aspect of the warm corona model is the relatively low temperature of the hot corona, which is uncommon for AGN (e.g., Nandra & Pounds 1994;Ricci et al 2017;Baloković et al 2020). This is further discussed in Section 4.1.…”

Section: Model A: Warm Coronamentioning

confidence: 98%

“…Another 18 keV). Though it is uncommon for most of studied AGNs (e.g., Fabian et al 2015Fabian et al , 2017Marinucci et al 2016;Baloković et al 2020), NuSTAR has reported several lowtemperature coronae in recent years, e.g., ∼25 keV (MCG-05-23-016, Baloković et al 2015), ∼50 keV (Ursini et al 2015), ∼15 keV (Ark 564, Kara et al 2017), ∼12 keV (GRS 1734-292, Tortosa et al 2017), and ∼40 keV (IRAS 00521-7054, Walton et al 2019). Ricci et al (2018) also reported a large number of sources with temperatures below 50 keV and found a statistical dependence of the cutoff energy on the Eddington ratio.…”

Section: Physical Properties Of the Warm Corona Modelmentioning

confidence: 99%

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The Nature of Soft Excess in ESO 362-G18 Revealed by XMM-Newton and NuSTAR Spectroscopy

García

Walton

et al. 2021

ApJ

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We present a detailed spectral analysis of the joint XMM-Newton and NuSTAR observations of the active galactic nuclei (AGNs) in the Seyfert 1.5 Galaxy ESO 362-G18. The broadband (0.3-79 keV) spectrum shows the presence of a power-law continuum with a soft excess below 2 keV, iron Kα emission (∼6.4 keV), and a Compton hump (peaking at ∼20 keV). We find that the soft excess can be modeled by two different possible scenarios: a warm (kT e ∼ 0.2 keV) and optically thick (τ ∼ 34) Comptonizing corona, or with a relativistically blurred reflection off a high-density ( [ ]>n log cm 18.3 e 3) inner disk. These two models cannot be easily distinguished solely from their fit statistics. However, the low temperature (kT e ∼ 20 keV) and the thick optical depth (τ ∼ 5) of the hot corona required by the warm corona scenario are uncommon for AGNs. We also fit a "hybrid" model, which includes both disk reflection and a warm corona. Unsurprisingly, as this is the most complex of the models considered, this provides the best fit, and more reasonable coronal parameters. In this case, the majority of the soft excess flux arises in the warm corona component. However, based on recent simulations of warm coronae, it is not clear whether such a structure can really exist at the low accretion rates relevant for ESO 362-G18 ( m 0.015). This may therefore argue in favor of a scenario in which the soft excess is instead dominated by the relativistic reflection. Based on this model, we find that the data would require a compact hot corona (h ∼ 3 R Horizon ) around a rapidly spinning (a å > 0.927) black hole.Unified Astronomy Thesaurus concepts: Supermassive black holes (1663); X-ray astronomy (1810); Seyfert galaxies (1447); High energy astrophysics (739); Active galactic nuclei (16); Astrophysical black holes (98); Spectroscopy (1558); X-ray active galactic nuclei (2035)

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Section: Model A: Warm Coronamentioning

confidence: 98%

Section: Physical Properties Of the Warm Corona Modelmentioning

confidence: 99%

The Nature of Soft Excess in ESO 362-G18 Revealed by XMM-Newton and NuSTAR Spectroscopy

García

Walton

et al. 2021

ApJ

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“…The value of the cut-off energy has been chosen to be consistent with previous similar works (see e.g., Marchesi et al 2017b;Zhao et al 2019b,a). Moreover, recent works (e.g., Baloković et al 2020) show that it is a reasonable value for the extension of the continuum.…”

Section: Tablementioning

confidence: 91%

Compton-Thick AGN in the NuSTAR ERA VII. A joint NuSTAR, Chandra, and XMM-Newton Analysis of Two Nearby, Heavily Obscured Sources

Traina

Marchesi

Vignali

et al. 2021

ApJ

Self Cite

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We present the joint Chandra, XMM-Newton, and NuSTAR analysis of two nearby Seyfert galaxies, NGC 3081 and ESO 565-G019. These are the only two having Chandra data in a larger sample of 10 low-redshift (z ≤ 0.05), candidates Compton-thick (CT) Active Galactic Nuclei selected in the 15–150 keV band with Swift-BAT that were still lacking NuSTAR data. Our spectral analysis, performed using physically motivated models, provides an estimate of both the line-of-sight (l.o.s.) and average (N H,S ) column densities of the two torii. NGC 3081 has a Compton-thin l.o.s. column density N H,z = [0.58–0.62] × 1024 cm−2, but the N H,S , beyond the CT threshold (N H,S = [1.41–1.78] × 1024 cm−2), suggests a “patchy” scenario for the distribution of the circumnuclear matter. ESO 565-G019 has both CT l.o.s. and N H,S column densities (N H,z > 2.31 × 1024 cm−2 and N H,S > 2.57 × 1024 cm−2, respectively). The use of physically motivated models, coupled with the broad energy range covered by the data (0.6–70 keV and 0.6–40 keV, for NGC 3081 and ESO 565-G019, respectively) allows us to constrain the covering factor of the obscuring material, which is C TOR = [0.63–0.82] for NGC 3081, and C TOR = [0.39–0.65] for ESO 565-G019.

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“…We fit this component using a redshifted power law component with a high-energy cut-off zcutoffpl (xspec model). Here the cut-off energy is fixed arbitrarily to 300 keV (Baloković et al 2020); however, since we only consider here X-ray emission below ∼10 keV, the chosen energy is irrelevant as soon as it is above a few tens of keV. The free parameters of this component are the photon index (Γ) and the normalization (F), which is defined as the intrinsic flux of the cut-off power law in the 2 to 10 keV band.…”

Section: Primary Emissionmentioning

confidence: 99%

Reconstructing AGN X-ray spectral parameter distributions with Bayesian methods I: Spectral analysis

Ge,

Paltani,

Eckert

2021

Preprint

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X-ray spectra of active galactic nuclei (AGN) consist of several different emission and absorption components. To determine the spectral parameters, these components are often fitted manually with models chosen on a case-by-case basis. However, this approach has two problems. First, it becomes very hard for a survey with a large number of sources. Second, in the case of low signal-to-noise ratio (S/N), there is a tendency to adopt an overly simplistic model, biasing the parameters and making their uncertainties unrealistic. We develop here a Bayesian method to automatically fit AGN X-ray spectra obtained by XMM-Newton with a consistent and physically motivated model. Our model includes all spectral components, even in case the data quality is low. We use a physical model for the X-ray background, and an empirical one for the non X-ray background. Non-informative priors are applied on the parameters of interest, the photon index (Γ) and the hydrogen column density (N H ), while informative priors obtained from deep surveys are used to marginalize over the parameter space of the nuisance parameters. To improve speed, we develop a specific spectral extraction and fitting procedure. We test this method using a realistic sample of 5000 spectra, which is simulated based on our source model, reproducing typical population properties. Spectral parameters are randomly drawn from the priors taking into account the luminosity function. Well-constrained or meaningful posterior probability density distributions (PDFs) are obtained for the most relevant spectral parameters, e.g., N H , Γ and L X even at low S/N, though in this case we cannot constrain parameters of secondary components like the reflection and soft excess. As a comparison, a maximum-likelihood approach with model selection among six models of different complexities is also applied to this sample. We find clear failures in the measurement of Γ in most cases, and of N H when the source is unabsorbed (N H < 10 22 cm −2 ). The results can hardly be used to reconstruct the parent distributions of the spectral parameters, while our Bayesian method provides meaningful multi-dimensional posteriors that will be used in a subsequent paper for the population inference.

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NuSTAR Survey of Obscured Swift/BAT-selected Active Galactic Nuclei. II. Median High-energy Cutoff in Seyfert II Hard X-Ray Spectra

Cited by 62 publications

References 102 publications

The Nature of Soft Excess in ESO 362-G18 Revealed by XMM-Newton and NuSTAR Spectroscopy

The Nature of Soft Excess in ESO 362-G18 Revealed by XMM-Newton and NuSTAR Spectroscopy

Compton-Thick AGN in the NuSTAR ERA VII. A joint NuSTAR, Chandra, and XMM-Newton Analysis of Two Nearby, Heavily Obscured Sources

Reconstructing AGN X-ray spectral parameter distributions with Bayesian methods I: Spectral analysis

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