The nature of X-ray spectral variability in MCG–6-30-15

Kammoun, E. S.; Papadakis, I. E.

doi:10.1093/mnras/stx2181

Cited by 7 publications

(4 citation statements)

References 42 publications

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“…reflection). Reinforcing this analysis, disk reflection is reported in the literature for eight out of these nine Sy1s(Lohfink et al 2012;Porquet et al 2017;Patrick et al 2012;Brenneman et al 2011;Walton et al 2013aWalton et al , 2018Kammoun & Papadakis 2017;Done et al 2000;Reynolds 2014;Ebrero et al 2011). The exception is NGC 5548.…”

supporting

confidence: 58%

The dust-gas AGN torus as constrained from X-ray and mid-infrared observations

Esparza-Arredondo¹,

González‐Martín²,

Dultzin³

et al. 2021

A&A

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Context. In recent decades, several multiwavelength studies have been dedicated to exploring the properties of the obscuring material in active galactic nuclei (AGN). Various models have been developed to describe the structure and distribution of this material and constrain its physical and geometrical parameters through spectral fitting techniques. However, questions around the way in which torus mid-infrared (mid-IR) and X-ray emission are related remain unanswered. Aims. In this work, we aim to study whether the dust continuum at mid-IR and gas reflection at X-rays have the same distribution in a sample of AGN. Methods. We carefully selected a sample of 36 nearby AGN with NuSTAR and Spitzer spectra available that satisfy the following criteria: (1) the AGN component dominates the mid-IR spectra (i.e., the stellar and interstellar medium components contribute less than 50% to the spectrum), and (2) the reflection component contributes significantly to the X-ray spectrum. Furthermore, we discarded the sources whose reflection component could be produced by ionized material in the disk. We derived the properties of the nuclear dust and gas through a spectral fitting, using models developed for mid-IR and X-ray wavelengths assuming smooth and clumpy distributions for this structure. Results. We find that a combination of smooth and clumpy distributions of gas and dust, respectively, is preferred for ∼80% of sources with good spectral fits according to the Akaike criterion. However, considering extra information about each individual source, such as the absorption variability, we find that ∼50% of our sources are best described by a clumpy distribution of both dust and gas. The remaining ∼50% of our sources can still be explained with a smooth distribution of gas and a clumpy distribution of dust. Furthermore, we explored the torus dust-to-gas ratio, finding that it is [0.01–1] times that of the interstellar medium. Conclusions. The results presented in this paper suggest that the distribution of the gas and dust in AGN is complex. We find at least six scenarios to explain the observed properties of our sample. In these scenarios, three gas–dust distribution combinations are possible: clumpy–clumpy, smooth–smooth, and smooth–clumpy. Most of them are in agreement with the notion that gas could also be located in the dust-free region, which is consistent with the dust-to-gas ratio found.

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supporting

confidence: 58%

The dust-gas AGN torus as constrained from X-ray and mid-infrared observations

Esparza-Arredondo¹,

González‐Martín²,

Dultzin³

et al. 2021

A&A

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“…The eight NLS1s that required warm absorbers were Mrk 335 (Gallo et al 2013), NGC 4051 (Mizumoto & Ebisawa 2017;Nucita et al 2010), Mrk 766 (Buisson 2018;Emmanoulopoulos et al 2011), Was 61 (Dou et al 2016), MCG-6-30-15 (Chiang & Fabian 2011;Emmanoulopoulos et al 2011;Kammoun & Papadakis 2017), NGC 5506 (Sun et al 2018), PG 1448+273, and IRAS 17020+4544 (Longinotti 2015;Leighly et al 1997;Komossa & Bade 1998).…”

Section: Appendix A: Additional Spectral Resultsmentioning

confidence: 99%

The soft X-ray excess: NLS1s versus BLS1s

Gliozzi

Williams

2019

Monthly Notices of the Royal Astronomical Society

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The soft X-ray excess -the excess of X-rays below 2 keV with respect to the extrapolation of the hard X-ray spectral continuum model -is a very common feature among type 1 active galactic nuclei (AGN); yet the nature of the soft X-ray excess is still poorly understood and hotly debated. To shed some light on this issue, we have measured in a model-independent way the soft excess strength in a flux-limited sample of broad-line and narrow-line Seyfert 1 galaxies (BLS1s and NLS1s) that are matched in X-ray luminosity but different in terms of the black hole mass and the accretion rate values, with NLS1s being characterized by smaller M BH and larger m values. Our analysis, in agreement with previous studies carried out with different AGN samples, indicates that: 1) a soft excess is ubiquitously detected in both BLS1s and NLS1s; 2) the strength of the soft excess is significantly larger in the NLS1 sample, compared to the BLS1 sample; 3) combining the two samples, the strength of the soft excess appears to positively correlate with the photon index as well as with the accretion rate, whereas there is no correlation with the black hole mass. Importantly, our work also reveals the lack of an anticorrelation between the soft excess strength and the luminosity of the primary X-ray component, predicted by the absorption and reflection scenarios. Our findings suggest that the soft excess is consistent with being produced by a warm Comptonization component. Larger, more complete samples of NLS1s and BLS1s are needed to confirm these conclusions.

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“…For single-epoch, low-resolution spectra, indirect or complementary arguments, such as energy conservation, fractional variability, or model-independent techniques (e.g. Kammoun & Papadakis 2017), are still recommended to support the conclusions of the spectral analysis. Spectral variability, however, could greatly help in constraining the constant parameters in the reflection models, such as the spin, inclination, and iron abundance, as already proved by the NGC 1365 campaign, while high resolution can remove the ambiguities associated with the introduction of ad hoc absorption components.…”

Section: Discussionmentioning

confidence: 99%

Testing the accuracy of reflection-based supermassive black hole spin measurements in AGN

Kammoun

Nardini

Risaliti

2018

A&A

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Context. X-ray reflection is a very powerful method to assess the spin of supermassive black holes (SMBHs) in active galactic nuclei (AGN), yet this technique is not universally accepted. Indeed, complex reprocessing (absorption, scattering) of the intrinsic spectra along the line of sight can mimic the relativistic effects on which the spin measure is based. Aims. In this work, we test the reliability of SMBH spin measurements that can currently be achieved through the simulations of high-quality XMM-Newton and NuSTAR spectra. Methods. Each member of our group simulated ten spectra with multiple components that are typically seen in AGN, such as warm and (partial-covering) neutral absorbers, relativistic and distant reflection, and thermal emission. The resulting spectra were blindly analysed by the other two members.Results. Out of the 60 fits, 42 turn out to be physically accurate when compared to the input model. The SMBH spin is retrieved with success in 31 cases, some of which (9) are even found among formally inaccurate fits (although with looser constraints). We show that, at the high signal-to-noise ratio assumed in our simulations, neither the complexity of the multi-layer, partial-covering absorber nor the input value of the spin are the major drivers of our results. The height of the X-ray source (in a lamp-post geometry) instead plays a crucial role in recovering the spin. In particular, a success rate of 16 out of 16 is found among the accurate fits for a dimensionless spin parameter larger than 0.8 and a lamp-post height lower than five gravitational radii.

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The nature of X-ray spectral variability in MCG–6-30-15

Cited by 7 publications

References 42 publications

The dust-gas AGN torus as constrained from X-ray and mid-infrared observations

The dust-gas AGN torus as constrained from X-ray and mid-infrared observations

The soft X-ray excess: NLS1s versus BLS1s

Testing the accuracy of reflection-based supermassive black hole spin measurements in AGN

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