A global look at X-ray time lags in Seyfert galaxies

Kara, Erin; Alston, W. N.; Fabian, A. C.; Cackett, E. M.; Uttley, P.; Reynolds, C. S.; Zoghbi, A.

doi:10.1093/mnras/stw1695

Cited by 232 publications

(287 citation statements)

References 65 publications

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“…This trend is consistent with observation (e.g. Fig.7 of Kara et al 2016), though the range of our Eddington ratio is small.…”

Section: Size Of the Dominant Emission Regionsupporting

confidence: 94%

“…Along this line of investigation, significant efforts have been directed toward observationally constraining the corona geometry. It is found that the coronal illumination may originate from a height less than 10R g (Detailed data analyses on the reverberation lag and deduced height of the corona can be found in Fabian et al 2009Fabian et al , 2015De Marco et al 2013;Kara et al 2013Kara et al , 2015Kara et al , 2016Reis & Miller 2013).…”

Section: Radiation Compactness Of the Coronamentioning

confidence: 99%

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Centrally Concentrated X-Ray Radiation from an Extended Accreting Corona in Active Galactic Nuclei

Liu¹,

Taam²,

Qiao³

et al. 2017

ApJ

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The X-ray emission from bright active galactic nuclei (AGNs) is believed to originate in a hot corona lying above a cold, geometrically thin accretion disk. A highly concentrated corona located within ∼ 10 gravitational radii above the black hole is inferred from observations. Based on the accretion of interstellar medium/wind, a disk corona model has been proposed in which the corona is well coupled to the disk by radiation, thermal conduction, as well as by mass exchange (Liu et al. 2015;Qiao & Liu 2017). Such a model avoids artificial energy input to the corona and has been used to interpret the spectral features observed in AGN. In this work, it is shown that the bulk emission size of the corona is very small for the extended accretion flow in our model. More than 80% of the hard X-ray power is emitted from a small region confined within 10 Schwarzschild radii around a non-spinning black hole, which is expected to be even smaller accordingly for a spinning black hole. Here, the corona emission is more extended at higher Eddington ratios. The compactness parameter of the corona, l = L R σT mec 3 , is shown to be in the range of 1-33 for Eddington ratios of 0.02 -0.1. Combined with the electron temperature in the corona, this indicates that electron-positron pair production is not dominant in this regime. A positive relation between the compactness parameter and photon index is also predicted. By comparing the above model predictions with observational features, we find that the model is in agreement with observations.

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“…This trend is consistent with observation (e.g. Fig.7 of Kara et al 2016), though the range of our Eddington ratio is small.…”

Section: Size Of the Dominant Emission Regionsupporting

confidence: 94%

Section: Radiation Compactness Of the Coronamentioning

confidence: 99%

Centrally Concentrated X-Ray Radiation from an Extended Accreting Corona in Active Galactic Nuclei

Liu¹,

Taam²,

Qiao³

et al. 2017

ApJ

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“…Microlensing observations of a number of gravitationally lensed quasars constrain the X-ray emitting region to lie within approximately 10 gravitational radii ( = r GM c g BH 2 ) of the SMBH (Morgan et al 2012;Mosquera et al 2013;Blackburne et al 2014). This has also been inferred from the X-ray variability timescales for many Type 1 AGNs (Uttley et al 2014;Kara et al 2016).…”

Section: Introductionmentioning

confidence: 55%

Space Telescope and Optical Reverberation Mapping PROJECT.VI. Reverberating Disk Models for NGC 5548

Starkey¹,

Horne²,

Fausnaugh³

et al. 2017

ApJ

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We conduct a multiwavelength continuum variability study of the Seyfert 1 galaxy NGC 5548 to investigate the temperature structure of its accretion disk. The 19 overlapping continuum light curves (1158 Å to 9157 Å) combine simultaneous Hubble Space Telescope, Swift, and ground-based observations over a 180 day period from 2014 January to July. Light-curve variability is interpreted as the reverberation response of the accretion disk to irradiation by a central time-varying point source. Our model yields the disk inclination =    i 36 10 , temperature = T 44 6 10 1 3 ( ) K at 1 light day from the black hole, and a temperature-radius slope ( µ a -T r ) of a =  0.99 0.03. We also infer the driving light curve and find that it correlates poorly with both the hard and soft X-ray light curves, suggesting that the X-rays alone may not drive the ultraviolet and optical variability over the observing period. We also decompose the light curves into bright, faint, and mean accretion-disk spectra. These spectra lie below that expected for a standard blackbody accretion disk accreting at = L L 0.1 Edd .

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“…Also in this case, larger values of the source size could extend the upper limit of the allowed mass interval, but sizes significantly greater than 0.6 lt-day are not expected according to RM results (see Kara et al 2016, Uttley et al 2014 and references therein). The low sensitivity of X-ray observations to the microlens mass for M ≥ 1M reflects the fact that the X-ray source becomes point-like (and hence insensitive to the mass function 4 ) with respect to the natural scale of microlensing (the Einstein radius, η ∝ √ M ) in the upper region of the mass range of interest.…”

Section: Dependence Of the Abundance Of Compact Objects On Their Massmentioning

confidence: 68%

Limits on the Mass and Abundance of Primordial Black Holes from Quasar Gravitational Microlensing

Mediavilla

Jiménez-Vicente

Muñoz

et al. 2017

ApJL

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The idea that dark matter can be made of intermediate-mass primordial black holes in the 10M M 200M range has recently been reconsidered, particularly in the light of the detection of gravitational waves by the LIGO experiment. The existence of even a small fraction of dark matter in black holes should nevertheless result in noticeable quasar gravitational microlensing. Quasar microlensing is sensitive to any type of compact objects in the lens galaxy, to their abundance, and to their mass. We have analyzed optical and X-ray microlensing data from 24 gravitationally lensed quasars to estimate the abundance of compact objects in a very wide range of masses. We conclude that the fraction of mass in black holes or any type of compact objects is negligible outside of the 0.05M M 0.45M mass range and that it amounts to 20 ± 5% of the total matter, in agreement with the expected masses and abundances of the stellar component. Consequently, the existence of a significant population of intermediate-mass primordial black holes appears to be inconsistent with current microlensing observations. Therefore, primordial massive black holes are a very unlikely source of the gravitational radiation detected by LIGO.

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A global look at X-ray time lags in Seyfert galaxies

Cited by 232 publications

References 65 publications

Centrally Concentrated X-Ray Radiation from an Extended Accreting Corona in Active Galactic Nuclei

Centrally Concentrated X-Ray Radiation from an Extended Accreting Corona in Active Galactic Nuclei

Space Telescope and Optical Reverberation Mapping PROJECT.VI. Reverberating Disk Models for NGC 5548

Limits on the Mass and Abundance of Primordial Black Holes from Quasar Gravitational Microlensing

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