The Relation of Optical/Ultraviolet and X-Ray Emission in Low-Luminosity Active Galactic Nuclei

Xu, Yujie

doi:10.1088/0004-637x/739/2/64

Cited by 27 publications

(46 citation statements)

References 65 publications

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“…1(b), (c), (d) investigate the correlations between αox and λ, RUV and λ, Γ and λ, respectively. Similarly, we don't detect any significant correlations in these figures, in contrast with the negative correlations between αox and λ, and between Γ and λ in LLAGN (e.g., Gu & Cao 2009;Xu 2011).…”

Section: Results For Rlagncontrasting

confidence: 77%

A nearby luminous AGN sample optically selected from Hubble Space Telescope

2019

Monthly Notices of the Royal Astronomical Society

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In this work, a nearby luminous AGN sample is selected from HST, where only sources with both X-ray emission observed by Chandra/XMM-Newton and radio flux detected by VLA/VLBA/VLBI/MERLIN are adopted to keep high precision. We get a sample of 30 luminous AGNs finally, which consist of 11 RLAGN and 19 RQAGN. It is found that the relationship between R UV and α ox , which was firstly reported by Li & Xie (2017) in LLAGN, and other relationships are all absent in RLAGN, probably due to the complex physical process therein. Our results indicate that the X-ray emission from jet should play an important role in RLAGN and further support the transition of accretion mode between LLAGN and RLAGN. On the other hand, the traditional relationships in RQAGN, such as α ox and λ, Γ and λ, are found to be well consistent with previous works.

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Section: Results For Rlagncontrasting

confidence: 77%

A nearby luminous AGN sample optically selected from Hubble Space Telescope

2019

Monthly Notices of the Royal Astronomical Society

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“…It has been suggested in the literature that the accretion mechanism in low-luminosity active galactic nuclei (LLAGN) is different from that in more powerful AGN (e.g., Seyferts), and more similar to that in X-ray binaries (XRB) in their low/hard state (Yamaoka et al 2005;Yuan et al 2007;Gu & Cao 2009;Younes et al 2011;Xu 2011). The X-ray emission is supposed to originate from the Comptonization process in advectiondominated accretion flow (ADAF), where accretion is inneficient for L bol /L Edd < 10 −3 .…”

Section: Accretion Mechanismmentioning

confidence: 99%

X-ray spectral variability of seven LINER nuclei withXMM-NewtonandChandradata

Hernández-García

González‐Martín

Márquez

et al. 2013

A&A

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Context. One of the most distinctive features in active galactic nuclei (AGN) is the variability of their emission. Variability has been discovered at X-ray, UV, and radio frequencies on timescales from hours to years. Among the AGN family and according to theoretical studies, low-ionization nuclear emission line region (LINER) nuclei would be objects variable on long timescales. Aims. Our purpose is to investigate spectral X-ray variability in LINERs and to understand the nature of these types of objects, as well as their accretion mechanism. Methods. Chandra and XMM-Newton public archives were used to compile X-ray spectra of seven LINER nuclei at different epochs with timescales of years. To search for variability we fit all spectra from the same object with a set of models to identify the parameters responsible for the variability pattern. We also analyzed the light curves to search for short timescale (from hours to days) variability. Whenever possible, UV variability was also studied. Results. We found spectral variability in four objects (NGC 1052, NGC 3226, NGC 4278, and NGC 4552), with variations mostly related to hard energies (2-10 keV). These variations are generated by several possible changes that act either alone or in combination: changes in the soft excess or in the absorber. Added to this can be intrinsic variations of the source, which may also be responsible by themselves for the spectral variability. These variations occurred within years, the shortest timescale being found for NGC 4278 (two months). Another two galaxies (NGC 4261 and NGC 5846) apparently do not vary. No short timescale variations during individual observations were found. Our analysis confirms the previously reported anticorrelation between the X-ray spectral index, Γ, and the Eddington ratio, L bol /L Edd , and also the correlation between the X-ray to UV flux ratio, α ox , and the Eddington ratio, L bol /L Edd . These results support an advection dominated accretion flow as the accretion mechanism in LINERs.

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“…When combined with the X-ray luminosity the range of BH masses indicates that NGC 3227 is radiating at 0.4% of the Eddington luminosity limit (Winter et al 2011;Xu 2011;Vasudevan & Fabian 2009). …”

Section: References Therein) the Question Remains What Exactly Does mentioning

confidence: 99%

The Size, Structure, and Ionization of the Broad-Line Region in NGC 3227

Devereux

2013

ApJ

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Hubble Space Telescope spectroscopy of the Seyfert 1.5 galaxy, NGC 3227, confirms previous reports that the broad Hα emission line flux is time variable, decreasing by a modest ∼11% between 1999 and 2000 in response to a corresponding ∼37% decrease in the underlying continuum. Modeling the gas distribution responsible for the broad Hα, Hβ, and Hγ emission lines favors a spherically symmetric inflow as opposed to a thin disk. Adopting a central black hole mass of 7.6 × 10 6 M , determined from prior reverberation mapping, leads to the following dimensions for the size of the region emitting the broad Hα line: an outer radius ∼90 lt-days and an inner radius ∼3 lt-days. Thus, the previously determined reverberation size for the broad-line region (BLR) consistently coincides with the inner radius of a much larger volume of ionized gas. However, the perceived size of the BLR is an illusion, a consequence of the fact that the emitting region is ionization bounded at the outer radius and diminished by Doppler broadening at the inner radius. The actual dimensions of the inflow remain to be determined. Nevertheless, the steady-state mass inflow rate is estimated to be ∼10 −2 M yr −1 which is sufficient to explain the X-ray luminosity of the active galactic nucleus (AGN) in terms of radiatively inefficient accretion. Collectively, the results challenge many preconceived notions concerning the nature of BLRs in AGNs.

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The Relation of Optical/Ultraviolet and X-Ray Emission in Low-Luminosity Active Galactic Nuclei

Cited by 27 publications

References 65 publications

A nearby luminous AGN sample optically selected from Hubble Space Telescope

A nearby luminous AGN sample optically selected from Hubble Space Telescope

X-ray spectral variability of seven LINER nuclei withXMM-NewtonandChandradata

The Size, Structure, and Ionization of the Broad-Line Region in NGC 3227

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