Generating functions for L-harmonics

Gaskell, R.

doi:10.1016/s0010-4655(84)82889-1

Cited by 17 publications

(16 citation statements)

References 9 publications

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“…In fact previous studies (Lawrence 1987;Gaskell 1984;Zhang et al 2008;Gaskell 2009) show emission line differences between type 1 and type 2 AGN similar to the 3CR BLOs and HIGs. Direct evidence for a compact and dense NLR component comes from the detection of variability of the [O III] flux in NGC 5548 over a timescale of a few years (Peterson et al 2013); they derived a size of a few pc and an electronic density of ∼10 5 cm −3 .…”

Section: Discussionmentioning

confidence: 59%

An optical spectroscopic survey of the 3CR sample of radio galaxies withz< 0.3

Baldi¹,

Capetti²,

Buttiglione³

et al. 2013

A&A

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We explore the implications of our optical spectroscopic survey of 3CR radio sources with z < 0.3 for the unified model (UM) for radio-loud AGN, focusing on objects with a "edge-brightened" (FR II) radio morphology. The sample contains 33 high ionization galaxies (HIGs) and 18 broad line objects (BLOs). According to the UM, HIGs, the narrow line sources, are the nuclearly obscured counterparts of BLOs. The fraction of HIGs indicates a covering factor of the circumnuclear matter of 65% that corresponds, adopting a torus geometry, to an opening angle of 50• ± 5. No dependence on redshift and luminosity on the torus opening angle emerges. We also consider the implications for a "clumpy" torus. The distributions of total radio luminosity of HIGs and BLOs are not statistically distinguishable, as expected from the UM. Conversely, BLOs have a radio core dominance, R, more than ten times larger with respect to HIGs, as expected in case of Doppler boosting when the jets in BLOs are preferentially oriented closer to the line of sight than in HIGs. Modeling the R distributions leads to an estimate of the jet bulk Lorentz factor of Γ ∼ 3−5. The test of the UM based on the radio source size is not conclusive due to the limited number of objects and because the size distribution is dominated by the intrinsic scatter rather than by projection effects. In conclusion, the radio and narrow line region (NLR) properties of HIGs and BLOs are consistent with the UM predictions when the partial obscuration of the NLR is taken into account. We also explored the radio properties of 21 3CR low ionization galaxies with a FR II radio morphology at z < 0.3. We find evidence that they cannot be part of the model that unifies HIGs and BLOs, but they are instead intrinsically different source, still reproduced by a randomly oriented population.

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Section: Discussionmentioning

confidence: 59%

An optical spectroscopic survey of the 3CR sample of radio galaxies withz< 0.3

Baldi¹,

Capetti²,

Buttiglione³

et al. 2013

A&A

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“…In Veilleux and Osterbrock (1987), they adopted Hα/Hβ = 3.1 for active galaxies and 2.85 for H II region galaxies (e.g., Ferland & Netzer 1983;Gaskell 1984;Gaskell & Ferland 1984). Recently, the large sample statistics suggests that the intrinsic value of broad-line Hα/Hβ is 3.06 with a standard deviation of 0.03 dex (Dong et al 2008).…”

Section: Balmer and Paschen Emission Linesmentioning

confidence: 99%

Reddening and He i^∗ λ10830 Absorption Lines in Three Narrow-line Seyfert 1 Galaxies

Zhang

Zhou

Shi

et al. 2017

ApJ

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We report the detection of heavy reddening and the He I* λ10830 absorption lines at the AGNs' redshift in three Narrow-line Seyfert 1 galaxies: SDSS J091848.61+211717.0, SDSS J111354.66+124439.0, and SDSS J122749.13+321458.9. They exhibit very red optical to nearinfrared colors, narrow Balmer/Paschen broad emission lines and He I* λ10830 absorption lines. The ultraviolet-optical-infrared nucleus continua are reddened by the SMC extinction law of E(B − V ) ∼ 0.74, 1.17, and 1.24 mag for three objects, which are highly consistent with the values obtained from the broad-line Balmer decrements, but larger than those of narrow emission lines. The reddening analysis suggests the extinction dust simultaneously obscure the accretion disk, the broad emission line region, and the hot dust from the inner edge of the torus. It is possible that the dust obscuring the AGN structures are the dusty torus itself. Furthermore, the Cloudy analysis of the He I* λ10830 absorption lines propose the distance of the absorption materials to be the extend scale of the torus. That greatly increases probabilities of the obscure and absorption materials being the dusty torus.

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“…The most extreme X-ray variability is found in so-called narrow-line Seyfert 1 galaxies (NLS1s). Narrow-line Seyfert 1 galaxies (Gaskell 1984;Osterbrock & Pogge 1985) are so called because the central engine with its surrounding dense gas can be seen directly, as in Seyfert 1 galaxies, but the permitted optical emission lines arising from gas (the broad-line region) are much narrower than in normal Seyfert 1 galaxies. Boller et al (1996) showed that, as a class, NLS1s also have strong soft X-ray excesses and an order-of-magnitude greater X-ray variability than would be expected for their luminosity.…”

Section: U Umentioning

confidence: 99%

Lognormal X-Ray Flux Variations in an Extreme Narrow-Line Seyfert 1 Galaxy

Gaskell

2004

ApJ

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We show that the large variations in the X-ray flux of the extreme narrow-line Seyfert 1 galaxy IRAS 13224Ϫ 3809, measured during a 10 day ASCA observation, have a two-parameter lognormal distribution of multiplicative standard deviation and that the amplitude of variability at any given moment is proportional to the flux j p 2.7 mult level. We find similar behavior in earlier ROSAT soft X-ray monitoring. There is no evidence of a nonvariable component. The flux-dependent behavior of the variability rules out linear shot-noise models. Although at first glance the variations of the ASCA light curve for IRAS 13224Ϫ3809 appear to exhibit nonstationary behavior with quiescent low states and more active flaring high states, our results show that the multiplicative variance is constant. Monte Carlo simulations of constant j mult give excellent matches to the observed X-ray light curve without the need to invoke special low and high states. This supports a picture in which the long-term variability is fundamental both in active galactic nuclei and in X-ray binaries. The lognormal flux distribution and the constancy of j mult are incompatible with the power-law distribution of flaring amplitudes expected from self-organized critical behavior. We discuss mechanisms that can generate lognormal flux distributions.

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Generating functions for L-harmonics

Cited by 17 publications

References 9 publications

An optical spectroscopic survey of the 3CR sample of radio galaxies withz< 0.3

An optical spectroscopic survey of the 3CR sample of radio galaxies withz< 0.3

Reddening and He i^∗ λ10830 Absorption Lines in Three Narrow-line Seyfert 1 Galaxies

Lognormal X-Ray Flux Variations in an Extreme Narrow-Line Seyfert 1 Galaxy

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Generating functions for L-harmonics

Cited by 17 publications

References 9 publications

An optical spectroscopic survey of the 3CR sample of radio galaxies withz< 0.3

An optical spectroscopic survey of the 3CR sample of radio galaxies withz< 0.3

Reddening and He i∗ λ10830 Absorption Lines in Three Narrow-line Seyfert 1 Galaxies

Lognormal X-Ray Flux Variations in an Extreme Narrow-Line Seyfert 1 Galaxy

Contact Info

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Reddening and He i^∗ λ10830 Absorption Lines in Three Narrow-line Seyfert 1 Galaxies