High‐energy monitoring of Seyfert galaxies: The case of NGC 4593

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

doi:10.1002/asna.201612346

Cited by 3 publications

(4 citation statements)

References 33 publications

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“…Above 0.5 counts/s there is a very slight softening of the spectrum with increasing count rate. This spectral softening is similar to that found in NGC 4593 by Ursini et al (2016a) and for AGN in general by Sobolewska & Papadakis (2009). Although they use 0.3-1.5 keV and 1.5-10 keV as their soft and hard band respectively, and define hardness ratio as H/S rather than the (H-S)/(H+S) used here, similar results are shown by Pal & Naik (2017).…”

Section: X-ray Spectral Variability and X-ray Energy Dependence Of Lagssupporting

confidence: 87%

X-ray/UV/optical variability of NGC 4593 with Swift: reprocessing of X-rays by an extended reprocessor

McHardy

Connolly

Horne

et al. 2018

Monthly Notices of the Royal Astronomical Society

106

126

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We report the results of intensive X-ray, UV and optical monitoring of the Seyfert 1 galaxy NGC 4593 with Swift. There is no intrinsic flux-related spectral change in the the variable components in any band with small apparent variations due only to contamination by a second constant component, possibly a (hard) reflection component in the X-rays and the (red) host galaxy in the UV/optical bands. Relative to the shortest wavelength band, UVW2, the lags of the other UV and optical bands are mostly in agreement with the predictions of reprocessing of high energy emission from an accretion disc. The U-band lag is, however, far larger than expected, almost certainly because of reprocessed Balmer continuum emission from the more distant broad line region gas. The UVW2 band is well correlated with the X-rays but lags by ∼ 6× more than expected if the UVW2 results from reprocessing of X-rays on the accretion disc. However, if the lightcurves are filtered to remove variations on timescales > 5d, the lag approaches the expectation from disc reprocessing. MEMEcho analysis shows that direct X-rays can be the driver of most of the variations in the UV/optical bands as long as the response functions for those bands all have long tails (up to 10d) in addition to a strong peak (from disc reprocessing) at short lag (< 1 d). We interpret the tails as due to reprocessing from the surrounding gas. Comparison of X-ray to UVW2 and UVW2 to V-band lags for 4 AGN, including NGC 4593, shows that all have UVW2 to V-band lags which exceed the expectations from disc resprocessing by ∼ < 2. However the X-ray to UVW2 lags are, mostly, in greater excess from the expectations from disc reprocessing and differ between AGN. The largest excess is in NGC 4151. Absorption and scattering may be affecting X-ray to UV lags.

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Section: X-ray Spectral Variability and X-ray Energy Dependence Of Lagssupporting

confidence: 87%

X-ray/UV/optical variability of NGC 4593 with Swift: reprocessing of X-rays by an extended reprocessor

McHardy

Connolly

Horne

et al. 2018

Monthly Notices of the Royal Astronomical Society

106

126

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show abstract

“…From these plots, it can be seen that a higher flux is associated with a lower hardness ratio, i.e. we observe a "softer when brighter" behaviour (see also Ursini et al 2016). During the first observation, both flux and spectral variability are particularly strong.…”

Section: Observations and Data Reductionmentioning

confidence: 61%

“…This is the first monitoring carried out by XMM-Newton and NuSTAR specifically designed to study the high-energy emission of an AGN through the analysis of its variability on time-scales of days. We reported preliminary results from a phenomenological timing analysis in Ursini et al (2016). Here we focus on the broad-band (0.3-80 keV) X-ray spectral analysis.…”

Section: Introductionmentioning

confidence: 99%

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

Ursini¹,

Petrucci²,

Matt³

et al. 2016

Mon. Not. R. Astron. Soc.

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We present results from a joint XMM-Newton/NuSTAR monitoring of the Seyfert 1 NGC 4593, consisting of 5 × 20 ks simultaneous observations spaced by two days, performed in January 2015. The source is variable, both in flux and spectral shape, on time-scales down to a few ks and with a clear softer-when-brighter behaviour. In agreement with past observations, we find the presence of a warm absorber well described by a two-phase ionized outflow. The source exhibits a cold, narrow and constant Fe K α line at 6.4 keV, and a broad component is also detected. The broadband (0.3-79 keV) spectrum is well described by a primary power law with Γ 1.6−1.8 and an exponential cut-off varying from 90 +40 −20 keV to > 700 keV, two distinct reflection components, and a variable soft excess correlated with the primary power law. This campaign shows that probing the variability of Seyfert 1 galaxies on different timescales is of prime importance to investigate the high-energy emission of AGNs.

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“…Measuring the spin of supermassive BH is important but still challenging when using the relativistic X-ray reflection method (e.g., Reynolds 2014; Kammoun et al 2018). Although most of these concerned Seyfert galaxies have been extensively studied in X-ray (e.g., Nandra et al 1997Nandra et al , 2007Shu et al 2010;Walton et al 2013), up to now, only the BH spin of NGC 4151 has been found to be near-maximal (Keck et al 2015;Beuchert et al 2017), while ambiguous spins are still assumed in literature for the other sources (e.g., NGC 4593: Ursini et al 2016b;NGC 5548: Kammoun et al 2019a;NGC 4395: Kammoun et al 2019b). Therefore, we assume zero spin for the later three sources.…”

Section: Modeling Local Seyfert Galaxiesmentioning

confidence: 99%

EUCLIA. II. On the puzzling large UV to X-ray lags in Seyfert galaxies

Cai,

Wang,

Sun

2020

Preprint

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Recent intense X-ray and UV monitoring campaigns with Swift have detected clear UV lags behind X-ray in several local active galactic nuclei (AGNs). The UV to X-ray lags are often larger (by a factor up to ∼20) than expected if the UV variation is simply due to the X-ray reprocessing. We previously developed a model in which the UV/optical variations are attributed to disk turbulences, and the effect of large-scale turbulence is considered. Our model, which overcomes many severe challenges to the reprocessing scheme, can well explain the observed variations in NGC 5548, particularly the correlations and lags among the UV/optical bands. In this work, assuming the corona heating is associated with turbulences in the inner accretion disk, we extend our study to model the correlations and lags between the X-ray and UV/optical bands. We find that our model, without the need of light echoing, can well reproduce the observed UV to X-ray lags and the optical to UV lags simultaneously in four local Seyfert galaxies, including NGC 4151, NGC 4395, NGC 4593, and NGC 5548. In our scenario, relatively larger UV to X-ray lag is expected for AGN with smaller innermost disk radius and thus more compact corona. Interestingly, for these Seyfert galaxies studied in this work, sources with relatively larger UV to X-ray lags do have broader Fe Kα lines, indicative of relativistic broadening due to more compact corona and smaller innermost disk radius. If confirmed with more X-ray and UV monitoring campaigns, this interesting discovery would provide a new probe to the inner disk/corona.

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High‐energy monitoring of Seyfert galaxies: The case of NGC 4593

Cited by 3 publications

References 33 publications

X-ray/UV/optical variability of NGC 4593 with Swift: reprocessing of X-rays by an extended reprocessor

X-ray/UV/optical variability of NGC 4593 with Swift: reprocessing of X-rays by an extended reprocessor

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

EUCLIA. II. On the puzzling large UV to X-ray lags in Seyfert galaxies

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