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 The Amplitude–Time Lag Relation for Emission-Line Flares of AGN

1994 ◽  
Vol 159 ◽  
pp. 173-176
Author(s):  
Ivan I. Shevchenko
Keyword(s):  
Emission Line ◽  
Time Lag ◽  
Light Curves ◽  
Broad Line ◽  
Broad Line Region ◽  
Line Region ◽  
Relative Increment ◽  
Models Comparison ◽  
Emission Line Spectrum ◽  
Phase Functions

The amplitude–time lag (“ΔA-Δt”) relation is considered in order to describe behaviour of the emission-line spectrum of an active galactic nucleus during a separate active event. Here ΔA, called the amplitude, is the maximum relative increment of the flux in a line, and Δt is the time lag between the maximum of the ionizing continuum flare and the maximum of the flare in a line. As suggested by Shevchenko (1988), the construction and analysis of such relations can be used to discriminate between broad-line region models. Comparison of theoretical “ΔA-Δt” relations with the observed one composed by data for flares in various lines during a separate active event, is proved to be a useful tool for investigating the geometry of a broad-line region, for studies of the form of phase functions of a typical line-emitting cloud in various lines, as well as for clearing up the duration and amplitude of the initial flare in the ionizing continuum. The advantage of this method is that it utilizes the most general observed characteristics of the emission-line flares and nevertheless provides basic information on the allowed BLR models before the detailed modelling of emission-line light curves is performed.

scholarly journals Testing broad-line region models with reverberation mapping

2020 ◽  
Vol 494 (2) ◽  
pp. 1611-1621 ◽  
Author(s):  
Hagai Netzer
Keyword(s):  
Time Lag ◽  
Galactic Nuclei ◽  
Balmer Line ◽  
Broad Line ◽  
Escape Probability ◽  
Reverberation Mapping ◽  
Broad Line Region ◽  
Line Region ◽  
High Metallicity ◽  
Good Agreement

ABSTRACT New reverberation mapping (RM) measurements, combined with accurate luminosities and line ratios, provide strong constraints on the location of the line emitting gas in the broad-line region (BLR) of active galactic nuclei (AGNs). In this paper, I present new calculations of radiation pressure and magnetic pressure confined clouds and apply them to a ‘generic AGN’ and to NGC 5548. The new calculations are in good agreement with the observed lags of all broad emission lines, and with the luminosities of Ly α, C iv 1549, O vi 1035, and He ii 1640. They are also in reasonable agreement with the luminosities of Mg ii 2798 and the 1990 Å blend of C iii] and Si iii] lines for high-metallicity gas. They explain the changes in time-lag following an increase in continuum luminosity and their dependencies on the inner and outer boundaries of the BLR. They also predict very strong Balmer and Paschen continua with important implications to continuum RM experiments. However, the calculated Balmer and Paschen line luminosities are too weak, by factors of 2–5. This ‘Balmer line crisis’ was noted in several earlier works and is now confirmed and constrained by RM measurements that were not available in the past. It seems that present photoionization codes that use the escape probability formalism fail to correctly compute the Balmer line luminosities in high-density, large optical depth gas.

The size of the broad-line region in the Seyfert galaxy NGC 4151

1988 ◽  
Vol 330 ◽  
pp. 111 ◽  
Author(s):  
Bradley M. Peterson ◽  
Stephen A. Cota
Keyword(s):  
Seyfert Galaxy ◽  
Broad Line ◽  
Ngc 4151 ◽  
Broad Line Region ◽  
Line Region

scholarly journals Emission-Line Variability in AGN

1989 ◽  
Vol 134 ◽  
pp. 100-102
Author(s):  
Dan Maoz
Keyword(s):  
Emission Line ◽  
Cross Correlation ◽  
Time Lag ◽  
Correlation Method ◽  
Seyfert Galaxy ◽  
Light Curves ◽  
Broad Line ◽  
Line Region ◽  
Order Of Magnitude

It has been apparent for some time that comparison of continuum and emission-line light curves of AGN may enable determination of the dimensions and structure of the Broad Line Region (BLR)(see Peterson 1988, and references therein). Observations to this end (Antonucci and Cohen 1983, Peterson et al. 1985, Clavel et al. 1987) and their analysis using cross-correlation to find the time lag between line and continuum variations (Gaskell and Sparke 1986), indicate BLR sizes an order of magnitude smaller than allowed by standard photoionization models for several AGN. Gaskell and Peterson (1987) analyzed errors in the cross-correlation method as applied to AGN time series in general and specifically to the Seyfert galaxy Akn120. In order to generalize and extend their analysis we investigated the significance of BLR sizes derived by cross-correlation under different model assumptions and observational circumstances (Maoz and Netzer 1988).

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 X-Ray Structure between the Innermost Disk and Optical Broad-line Region in NGC 4151

2018 ◽  
Vol 865 (2) ◽  
pp. 97 ◽  
Author(s):  
J. M. Miller ◽  
E. Cackett ◽  
A. Zoghbi ◽  
D. Barret ◽  
E. Behar ◽  
...  
Keyword(s):  
Broad Line ◽  
X Ray ◽  
Ngc 4151 ◽  
Broad Line Region ◽  
Line Region

scholarly journals Reverberation Mapping and Broad-Line Region Models

1997 ◽  
Vol 159 ◽  
pp. 138-145
Author(s):  
D. Maoz
Keyword(s):  
Broad Line ◽  
Future Directions ◽  
Reverberation Mapping ◽  
Broad Line Region ◽  
Line Region ◽  
Mapping Point

AbstractI review what we have learned about the BLR from reverberation mapping, point to some problems and complications that have emerged, and outline some future directions.

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