scholarly journals The Infrared, Optical and Ultraviolet Properties of Active Nuclei

1984 ◽  
Vol 110 ◽  
pp. 73-83
Author(s):  
Marie-Helene Ulrich
Keyword(s):  
Energy Distribution ◽  
Temporal Variations ◽  
Optical Polarization ◽  
Broad Line ◽  
Continuum Spectrum ◽  
Broad Line Region ◽  
Line Region ◽  
The Continuum

We review the important properties of active nuclei, in particular (i) the optical polarization and its relation to the jets found by VLBI (ii) the energy distribution and the temporal variations of the continuum spectrum and (iii) the distribution of the matter in the broad line region.

Ultraviolet variability of NGC 5548 - Dynamics of the continuum production region and geometry of the broad-line region

1991 ◽  
Vol 371 ◽  
pp. 541 ◽  
Author(s):  
J. H. Krolik ◽  
Keith Horne ◽  
T. R. Kallman ◽  
M. A. Malkan ◽  
R. A. Edelson ◽  
...  
Keyword(s):  
Broad Line ◽  
Production Region ◽  
Broad Line Region ◽  
Line Region ◽  
Ngc 5548 ◽  
The Continuum

scholarly journals Broad line region and black hole mass of PKS 1510-089 from spectroscopic reverberation mapping

2020 ◽  
Vol 642 ◽  
pp. A59
Author(s):  
Suvendu Rakshit
Keyword(s):  
Black Hole ◽  
Root Mean Square ◽  
Thermal Emission ◽  
Light Curves ◽  
Broad Line ◽  
Mean Square ◽  
Black Hole Mass ◽  
Broad Line Region ◽  
Line Region ◽  
The Continuum

Reverberation results of the flat spectrum radio quasar PKS 1510-089 from 8.5 years of spectroscopic monitoring carried out at Steward Observatory over nine observing seasons between December 2008 and June 2017 are presented. Optical spectra show strong Hβ, Hγ, and Fe II emission lines overlying on a blue continuum. All the continuum and emission line light curves show significant variability with fractional root-mean-square variations of 37.30 ± 0.06% (f5100), 11.88 ± 0.29% (Hβ), and 9.61 ± 0.71% (Hγ); however, along with thermal radiation from the accretion disk, non-thermal emission from the jet also contributes to f5100. Several methods of time series analysis (ICCF, DCF, von Neumann, Bartels, JAVELIN, χ2) are used to measure the lag between the continuum and line light curves. The observed frame broad line region size is found to be 61.1−3.2+4.0 (64.7−10.6+27.1) light-days for Hβ (Hγ). Using the σline of 1262 ± 247 km s−1 measured from the root-mean-square spectrum, the black hole mass of PKS 1510-089 is estimated to be 5.71−0.58+0.62 × 107 M⊙.

scholarly journals Analyzing temporal variations of AGN emission line profiles in the context of (dusty) cloud structure formation in the broad line region

2019 ◽  
Vol 621 ◽  
pp. A46 ◽  
Author(s):  
J. Esser ◽  
J.-U. Pott ◽  
H. Landt ◽  
W. D. Vacca
Keyword(s):  
Active Galactic Nuclei ◽  
Accretion Disk ◽  
Galactic Nuclei ◽  
Temporal Variations ◽  
Cloud Formation ◽  
Broad Line ◽  
Ngc 4151 ◽  
Broad Line Region ◽  
The Past ◽  
Line Region

The formation processes and the exact appearance of the dust torus and broad line region (BLR) of active galactic nuclei (AGN) are under debate. Theoretical studies show a possible connection between the dust torus and BLR through a common origin in the accretion disk. However observationally the dust torus and BLR are typically studied separately. NGC 4151 is possibly one of the best suited Seyfert 1 galaxies for simultaneous examinations because of its high number of both photometric and spectroscopic observations in the past. Here we compare changes of the dust radius to shape variations of broad emission lines (BEL). While the radius of the dust torus decreased by almost a factor of two from 2004 to 2006 shape variations can be seen in the red wing of BELs of NGC 4151. These simultaneous changes are discussed in a dust and BEL formation scheme. We also use the BEL shape variations to assess possible cloud distributions, especially in azimuthal direction, which could be responsible for the observed variations. Our findings can best be explained in the framework of a dust inflated accretion disk. The changes in the BELs suggest that this dusty cloud formation does not happen continuously, and over the whole accretion disk, but on the contrary in spatially confined areas over rather short amount of times. We derive limits to the azimuthal extension of the observed localized BEL flux enhancement event.

scholarly journals Reverberation Mapping Analysis of the Broad-Line Region in Seyfert Galaxy NGC 4151

1998 ◽  
Vol 188 ◽  
pp. 424-425
Author(s):  
S.J. Xue ◽  
F.Z. Cheng
Keyword(s):  
Emission Line ◽  
Time Lag ◽  
Seyfert Galaxy ◽  
Broad Line ◽  
Reverberation Mapping ◽  
Ngc 4151 ◽  
Broad Line Region ◽  
Spectroscopic Monitoring ◽  
Line Region ◽  
The Continuum

One of the primary goals of AGN variability studies has been to determine the size of broad-line region (BLR) through the reverberation mapping technique. In a recent international multiwavelength spectroscopic monitoring campaign, NGC 4151 has been observed intensively by ground-based telescopes for a period of over 2 months, with a typical temporal resolution of 1 day. The main result from this optical campaign is that finding the variation in the emission line flux (Hβ or Hα) lagging the continuum by 0-3 days (1993 campaign: Kaspi et al. 1996). This is in contrast to the past results in which a time lag of 9±2 days was found for the same emission line (1988 campaign: Maoz et al. 1991). Such a BLR “size problem” may be caused by a different variability timescale of the ionizing continuum or a real change in BLR gas distribution in the 5.5 yr interval between the two watch campaigns. In order to clarify which of the two possibilities is most likely the real case, we performed further reverberation analysis on both optical datasets.

scholarly journals Broad-Line Profile Variability

1997 ◽  
Vol 159 ◽  
pp. 183-190
Author(s):  
Ignaz Wanders
Keyword(s):  
Standard Model ◽  
Strong Evidence ◽  
Sampling Rate ◽  
Broad Line ◽  
Line Profiles ◽  
Continuum Source ◽  
Broad Line Region ◽  
Line Region ◽  
The Standard Model ◽  
The Continuum

AbstractMany years of monitoring a sample of 10 AGNs with a median sampling rate of about one spectrum per week yields strong evidence that broad-line profile variations are not induced by reverberation effects, but rather signify real changes in the structure of the continuum-source and broad-line region complex, contrary to line flux variations, which do respond to continuum variations. If the profile variations indeed trace internal changes in the BLR, then the BLR cannot consist of the billions of small clouds as the standard model of the BLR prescribes. Rather, small-number statistics are necessary. The sample of AGNs also indicates there are three preferred ‘components’ in the line profiles. These can be explained as geometrical projection effects due to an anisotropic continuum irradiating an otherwise spherical BLR.

scholarly journals What do Quasars Look Like?

2001 ◽  
Vol 18 (2) ◽  
pp. 176-178
Author(s):  
Paul J. Francis
Keyword(s):  
Continuum Emission ◽  
Broad Line ◽  
Broad Line Region ◽  
Line Region ◽  
Region I ◽  
The Continuum

AbstractMicrolensing observations may give us the first nano-arcsecond scale information about the structure of quasars. I review what is currently known about quasars on these scales, highlighting the principal uncertainties. I cover both the continuum emission and the broad line region. I conclude that little is firmly known about the structure of quasars.

scholarly journals Optical Spectrum Variability of Seyfert Galaxy Nuclei

1980 ◽  
Vol 5 ◽  
pp. 631-639 ◽  
Author(s):  
A. G. de Bruyn
Keyword(s):  
Optical Spectrum ◽  
Seyfert Galaxy ◽  
Optical Emission ◽  
Emission Lines ◽  
Optical Variability ◽  
Broad Line ◽  
Broad Line Region ◽  
Line Region ◽  
Photo Ionization ◽  
The Continuum

In this contribution I will present some results of a program aimed at determining the optical variability characteristics of Seyfert galaxy nuclei. It has been known for more than a decade that the continuous, non-stellar light of Seyfert nuclei can vary significantly on a time scale of months to years (see, e.g., Lyutyi, 1973, 1977; Penston et al., 1974; Penfold, 1979). In recent years there also have been various reports of variations in the intensity of the broad optical emission lines (Boksenberg and Netzer, 1977; Tohline and Osterbrock, 1976) following the pioneering work by Souffrin et al. (1973) and Cherepashchuk and Lyutyi (1973). However, very little is known on the details of the continuum variations and how they relate to the line variability. Such information could provide valuable constraints on the fashionable photo-ionization models for the broad line region (BLR) and the structure of the latter.

scholarly journals Long-term optical spectroscopic variations in blazar 3C 454.3

2019 ◽  
Vol 631 ◽  
pp. A4 ◽  
Author(s):  
Krzysztof Nalewajko ◽  
Alok C. Gupta ◽  
Mai Liao ◽  
Krzysztof Hryniewicz ◽  
Maitrayee Gupta ◽  
...  
Keyword(s):  
Spectral Energy Distribution ◽  
Line Emission ◽  
Spectral Energy ◽  
Broad Line ◽  
Line Flux ◽  
Broad Line Region ◽  
Relativistic Jet ◽  
Line Region ◽  
The Continuum

Aims. Characterisation of the long-term variations in the broad line region in a luminous blazar, where Comptonisation of broad-line emission within a relativistic jet is the standard scenario for production of γ-ray emission that dominates the spectral energy distribution. Methods. We analysed ten years of optical spectroscopic data from the Steward Observatory for the blazar 3C 454.3, as well as γ-ray data from the Fermi Large Area Telescope (LAT). The optical spectra are dominated by a highly variable non-thermal synchrotron continuum with a prominent Mg II broad emission line. The line flux was obtained by spectral decomposition including significant contribution from the Fe II pseudo-continuum. Three methods were used to characterise variations in the line flux: (1) stacking of the continuum-subtracted spectra, (2) subtracting the running mean light curves calculated for different timescales, and (3) evaluating potential time delays via the discrete correlation function (DCF). Results. Despite very large variations in the γ-ray and optical continua, the line flux changes only moderately (<0.1 dex). The data suggest that the line flux responds to a dramatic change in the blazar activity from a very high state in 2010 to a deep low state in 2012. Two interpretations are possible: either the line flux is anti-correlated with the continuum or the increase in the line luminosity is delayed by ∼600 days. If this time delay results from the reverberation of poorly constrained accretion disc emission in both the broad-line region (BLR) and the synchrotron emitting blazar zone within a relativistic jet, we would obtain natural estimates for the BLR radius RBLR, MgII ≳ 0.28 pc and for the supermassive black hole mass MSMBH ∼ 8.5 × 108 M⊙. We did not identify additional examples of short-term “flares” of the line flux, in addition to the previously reported case observed in 2010.

LOCATING THE BLAZAR EMISSION SITE WITH FERMI VARIABILITY

2012 ◽  
Vol 08 ◽  
pp. 37-42
Author(s):  
MARKOS GEORGANOPOULOS ◽  
AMANDA DOTSON ◽  
DEMOSTHENES KAZANAS ◽  
ERIC PERLMAN
Keyword(s):  
Energy Dissipation ◽  
Broad Line ◽  
Jet Formation ◽  
Spectral Variability ◽  
Ongoing Debate ◽  
Broad Line Region ◽  
Photon Field ◽  
First Case ◽  
Line Region

This work presents a method for settling the following ongoing debate: is the GeV emission of powerful blazars produced inside the sub-pc size broad line region (BLR) or further out at scales of ~ 10 pc where the IR photon field of the dusty molecular torus dominates over that the UV field of the BLR? In the first case the GeV emission is most probably external Compton (EC) scattering of the ~ 10 eV BLR photons21, while in the second the seed photons for the EC GeV emission are the ~ 0.1 eV photons of the dust9 in the molecular torus8. The issue of the energy dissipation location is connected to the jet formation and collimation process25 and, as we argue here, can be resolved with Fermi spectral variability observations.

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