X-ray to UV variability correlation in MCG–6-30-15

Arévalo, P.; Papadakis, I. E.; Kuhlbrodt, B.; Brinkmann, W.

doi:10.1051/0004-6361:20041801

Cited by 25 publications

(37 citation statements)

References 30 publications

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“…A similar UV flux/X-ray hardness ratio anti-correlation has been observed in a few other Seyfert galaxies (e.g. MCG-6-30-15: Arévalo et al 2005 andNGC 5548: McHardy et al 2014).…”

Section: Uv/x-ray Connectionmentioning

confidence: 57%

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Energy-dependent variability of the bare Seyfert 1 galaxy Ark 120

Mallick

Dewangan

McHardy

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We present results from a detailed spectral-timing analysis of a long ∼ 486 ks XMM-Newton observation of the bare Seyfert 1 galaxy Ark 120 which showed alternating diminution and increment in the 0.3−10 keV X-ray flux over four consecutive orbits in 2014. We study the energy-dependent variability of Ark 120 through broad-band X-ray spectroscopy, fractional root-mean-squared (rms) spectral modelling, hardness−intensity diagram and flux−flux analysis. The X-ray (0.3−10 keV) spectra are well fitted by a thermally Comptonized primary continuum with two (blurred and distant) reflection components and an optically thick, warm Comptonization component for the soft X-ray excess emission below ∼ 2 keV. During the first and third observations, the fractional X-ray variability amplitude decreases with energy while for second and fourth observations, X-ray variability spectra are found to be inverted-crescent and crescent shaped respectively. The rms variability spectra are well modelled by two constant reflection components, a soft excess component with variable luminosity and a variable intrinsic continuum with the normalization and spectral slope being correlated. The spectral softening of the source with both the soft excess and UV luminosities favour Comptonization models where the soft excess and primary X-ray emission are produced through Compton up-scattering of the UV and UV/soft X-ray seed photons in the putative warm and hot coronae, respectively. Our analyses imply that the observed energy-dependent variability of Ark 120 is most likely due to variations in the spectral shape and luminosity of the hot corona and to variations in the luminosity of the warm corona, both of which are driven by variations in the seed photon flux.

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“…A similar UV flux/X-ray hardness ratio anti-correlation has been observed in a few other Seyfert galaxies (e.g. MCG-6-30-15: Arévalo et al 2005 andNGC 5548: McHardy et al 2014).…”

Section: Uv/x-ray Connectionmentioning

confidence: 57%

“…The X-ray variability may arise due to variations in the accretion rate (e.g. Arévalo et al 2005) and/or intrinsic luminosity of the X-ray emitting hot corona (e.g. Marinucci et al 2014;Mallick et al 2016).…”

Section: Introductionmentioning

confidence: 99%

Energy-dependent variability of the bare Seyfert 1 galaxy Ark 120

Mallick

Dewangan

McHardy

et al. 2017

Monthly Notices of the Royal Astronomical Society

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“…(1) If the majority of the X-rays are produced in a corona that is powered by Compton up-scattering of near-UV seed photons from the thermal inner disk (Reynolds & Nowak 2003), then the X-ray variations would lag the near-UV fluctuations by a fraction of a day to a few days depending on the size of the corona and the inner disk (which are determined by the black hole mass (Arévalo et al 2005) and accretion rate). we compare the variability features in the X-ray and the UVW1 light curves.…”

Section: Discussionmentioning

confidence: 99%

Optical/UV-to-X-Ray Echoes from the Tidal Disruption Flare ASASSN-14li

Pasham

Cenko

Sądowski

et al. 2017

ApJL

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We carried out the first multi-wavelength (optical/UV and X-ray) photometric reverberation mapping of a tidal disruption flare (TDF) ASASSN-14li. We find that its X-ray variations are correlated with and lag the optical/UV fluctuations by 32±4 days. Based on the direction and the magnitude of the X-ray time lag, we rule out X-ray reprocessing and direct emission from a standard circular thin disk as the dominant source of its optical/UV emission. The lag magnitude also rules out an AGN disk-driven instability as the origin of ASASSN-14li and thus strongly supports the tidal disruption picture for this event and similar objects. We suggest that the majority of the optical/UV emission likely originates from debris stream self-interactions. Perturbations at the self-interaction sites produce optical/UV variability and travel down to the black hole where they modulate the X-rays. The time lag between the optical/UV and the X-rays variations thus correspond to the time taken by these fluctuations to travel from the self-interaction site to close to the black hole. We further discuss these time lags within the context of the three variants of the self-interaction model. High-cadence monitoring observations of future TDFs will be sensitive enough to detect these echoes and would allow us to establish the origin of optical/UV emission in TDFs in general.

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“…Several cases with time lags of the order of ∼days with the optical/UV leading the X-rays have also been observed (Shemmer et al (2003), Arévalo et al (2005), Marshall et al (2008)). The direction of the time lag and the order of magnitude are thus compatible with our predicted lags.…”

Section: Correlations Between Optical/uv and X-ray Emissionsmentioning

confidence: 99%

X-ray variability time scales in active galactic nuclei

Ishibashi

Courvoisier

2009

A&A

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X-ray variability in Active Galactic Nuclei (AGN) is commonly analysed in terms of the Power Spectral Density (PSD). The break observed in the power spectrum can be interpreted as a characteristic X-ray variability time scale. Here we study variability properties within the framework of clumpy accretion flows, in which shocks between accreting elements account for the UV and X-ray emissions. We derive a characteristic X-ray time scale, τ X , and compare it with the measured PSD break time scale, T B . A quite good agreement is found in both magnitude and trend. In particular, the model dependence on black hole mass and accretion rate precisely reproduces the empirical relation obtained by McHardy et al. (2006). We suggest a possible physical interpretation of the break time scale and briefly discuss the related aspects of optical/UV variability and correlations between different wavelengths.

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X-ray to UV variability correlation in MCG–6-30-15

Cited by 25 publications

References 30 publications

Energy-dependent variability of the bare Seyfert 1 galaxy Ark 120

Energy-dependent variability of the bare Seyfert 1 galaxy Ark 120

Optical/UV-to-X-Ray Echoes from the Tidal Disruption Flare ASASSN-14li

X-ray variability time scales in active galactic nuclei

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