High-energy monitoring of NGC 4593 with<i>XMM–Newton</i>and<i>NuSTAR</i>. X-ray spectral analysis

Ursini, F.; Petrucci, Pierre-Olivier; Matt, Giorgio; Bianchi, S.; Cappi, M.; Marco, Barbara De; Rosa, A. De; Malzac, J.; Marinucci, Andrea; Ponti, G.; Tortosa, A.

doi:10.1093/mnras/stw2022

Cited by 44 publications

(57 citation statements)

References 77 publications

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“…The source was observed simultaneously by XMM-Newton and NuSTAR, thus data extend from the optical-UV band up to the hard X-rays. A phenomenological spectral analysis of the campaign is reported in Ursini et al (2016), hereafter P1. In P1 the source was found to be variable, both in flux and spectral shape, and the characteristic softer-whenbrighter behaviour was observed.…”

Section: Introductionmentioning

confidence: 99%

High-energy monitoring of NGC 4593 II. Broad-band spectral analysis: testing the two-corona model

Middei

Bianchi

Petrucci

et al. 2018

Monthly Notices of the Royal Astronomical Society

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It is widely believed that the primary X-ray emission of AGN is due to the Comptonisation of optical-UV photons from a hot electron corona, while the origin of the 'soft-excess' is still uncertain and matter of debate. A second Comptonisation component, called warm corona, was therefore proposed to account for the soft-excess, and found in agreement with the optical-UV to X-ray emission of a sample of Seyfert galaxies. In this context, we exploit the broadband XMM-Newton and NuSTAR simultaneous observations of the Seyfert galaxy NGC 4593 to further test the so called "two corona model". The NGC 4593 spectra are well reproduced by the model, from the optical/UV to the hard X-rays. Moreover, the data reveal a significant correlation between the hot and the warm corona parameters during our monitoring campaign.

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Section: Introductionmentioning

confidence: 99%

High-energy monitoring of NGC 4593 II. Broad-band spectral analysis: testing the two-corona model

Middei

Bianchi

Petrucci

et al. 2018

Monthly Notices of the Royal Astronomical Society

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“…In the X-ray band, spectral variability has mostly been studied for individual sources (e.g. Magdziarz et al 1998;McHardy 2001;Zdziarski et al 2003; Ursini et al 2016), while few ensemble studies have been made on the topic, such as the one by Sobolewska & Papadakis (2009). The trend these studies have found is quite the opposite of the optical one, since a softer when brighter behaviour was found in both individual and ensemble studies, even at higher energies (Soldi et al 2014).…”

Section: Introductionmentioning

confidence: 99%

Quasar spectral variability from theXMM-Newtonserendipitous source catalogue

Serafinelli

Vagnetti

Middei

2017

A&A

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Context. X-ray spectral variability analyses of active galactic nuclei (AGN) with moderate luminosities and redshifts typically show a "softer when brighter" behaviour. Such a trend has rarely been investigated for high-luminosity AGNs (L bol 10 44 erg/s), nor for a wider redshift range (e.g. 0 z 5). Aims. We present an analysis of spectral variability based on a large sample of 2700 quasars, measured at several different epochs, extracted from the fifth release of the XMM-Newton Serendipitous Source Catalogue. Methods. We quantified the spectral variability through the parameter β defined as the ratio between the change in the photon index Γ and the corresponding logarithmic flux variation, β = −∆Γ/∆log F X . Results. Our analysis confirms a softer when brighter behaviour for our sample, extending the previously found general trend to high luminosity and redshift. We estimate an ensemble value of the spectral variability parameter β = −0.69 ± 0.03. We do not find dependence of β on redshift, X-ray luminosity, black hole mass or Eddington ratio. A subsample of radio-loud sources shows a smaller spectral variability parameter. There is also some change with the X-ray flux, with smaller β (in absolute value) for brighter sources. We also find significant correlations for a small number of individual sources, indicating more negative values for some sources.

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“…4. TEST ON AGNS WITH CLAIMED E C VARIATIONS In literature, using NuSTAR observations (often together with simultaneous exposures from other instruments), cut-off energy (corona temperature) variations have been claimed in five individual AGNs, including MCG -5-23-16 (Zoghbi et al 2017); 3C 382 (Ballantyne et al 2014); NGC 4593 (Ursini et al 2016); NGC 5548 (Ursini et al 2015) and Mrk 335 (Keek & Ballantyne 2016).…”

Section: The Usefulness Of Spectra Ratiosmentioning

confidence: 99%

On Measuring the Variation of High-energy Cutoff in Active Galactic Nuclei

Zhang

Wang

Zhu

2018

ApJ

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The variation in the high energy cut-off E c in active galactic nuclei uniquely probes the corona physics. In this work we show that the ratio of two NuSTAR spectra (in analogy to difference imaging technique widely used in astronomy) is uniquely useful in studying E c variations. The spectra ratio could directly illustrate potential E c variation between two spectra. By comparing with the ratio of two spectral fitting models, it also examines the reliability of the spectral-fitting measured E c variation. Assisted with this technique, we revisit the 5 AGNs in literature 3C 382, NGC 4593, NGC 5548 and Mrk 335) for which E c (kT e ) variations have been claimed with NuSTAR observations. We show the claimed E c variations appear inconsistent with the spectra ratios in three of them, thus need to be revised, demonstrating the striking usefulness of spectra ratio. We present thereby improved spectral fitting results and E c variations. We also report a new source with E c variations based on NuSTAR observations (radio galaxy 4C +74.26). We find the corona tends to be hotter when it brightens NGC 5548, Mrk 335 and 4C +74.27, show no evidence of significant E c variations. Meanwhile all 6 sources in this small sample appear softer-when-brighter. Changes in corona geometry are required to explain the observed hotter-when-brighter trends.

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High-energy monitoring of NGC 4593 withXMM–NewtonandNuSTAR. X-ray spectral analysis

Cited by 44 publications

References 77 publications

High-energy monitoring of NGC 4593 II. Broad-band spectral analysis: testing the two-corona model

High-energy monitoring of NGC 4593 II. Broad-band spectral analysis: testing the two-corona model

Quasar spectral variability from theXMM-Newtonserendipitous source catalogue

On Measuring the Variation of High-energy Cutoff in Active Galactic Nuclei

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