The nature of flux variations in the continua and broad-line regions of selected active galactic nuclei

2020 ◽  
Vol 496 (1) ◽  
pp. 784-800
Author(s):  
A Bewketu Belete ◽  
L J Goicoechea ◽  
B L Canto Martins ◽  
I C Leão ◽  
J R De Medeiros
Keyword(s):  
Active Galactic Nuclei ◽  
Moving Average ◽  
Sampling Rate ◽  
Galactic Nuclei ◽  
Small Sample ◽  
Light Curves ◽  
Ngc 4151 ◽  
The Given ◽  
Ngc 7469 ◽  
The Continuum

ABSTRACT We present a multifractal analysis of the long-term light curves of a small sample of type 1 active galactic nuclei: NGC 4151, Arp 102B, 3C 390.3, E1821+643 and NGC 7469. We aim to investigate how the degrees of multifractality of the continuum and Hβ line vary among the five different objects and to check whether the multifractal behaviours of the continuum and the Hβ line correlate with standard accretion parameters. The backward (θ  = 0) one-dimensional multifractal detrended moving average procedure was applied to light curves covering the full observation period and partial observation periods containing an equal number of epochs for each object. We detected multifractal signatures for the continua of NGC 4151, Arp 102B and 3C 390.3 and for the Hβ lines of NGC 4151 and 3C 390.3. However, we found nearly monofractal signatures for the continua of E1821+643 and NGC 7469, as well as for the Hβ lines of Arp 102B, E1821+643 and NGC 7469. In addition, we did not find any correlations between the degree of multifractality of the Hβ line and accretion parameters, while the degree of multifractality of the continuum seems to correlate with the Eddington ratio (i.e. the smaller the ratio is, the stronger the degree of multifractality). The given method is not robust, and these results should be taken with caution. Future analysis of the sampling rate and other properties of the light curves should help with better constraining and understanding these results.

scholarly journals Results from Five Years of Spectrophotometric Monitoring of 28 Palomar-Green Quasars

1997 ◽  
Vol 159 ◽  
pp. 159-162
Author(s):  
Shai Kaspi
Keyword(s):  
Active Galactic Nuclei ◽  
Time Lag ◽  
Monitoring Program ◽  
Galactic Nuclei ◽  
Light Curves ◽  
Reliable Measurement ◽  
Line Region ◽  
Order Of Magnitude ◽  
Sampling Intervals ◽  
The Continuum

AbstractWe present 5 years of results from a spectrophotometric monitoring program of 28 quasars. The typical sampling intervals are several months. We show the light curves obtained for two quasars, PG 0804+762 and PG 0953+414. Both sources show Balmer emissionline variations which follow those of the continuum with a time lag of order 100 days. This is the first reliable measurement of such a lag in active galactic nuclei with luminosity L > 1045 erg s−1. The broad-line region (BLR) size that is implied is almost an order of magnitude larger than that measured in several Seyfert 1 galaxies and is consistent with the hypothesis that the BLR size grows as L0.5.

scholarly journals New Constraints on the Continuum Emission Mechanism of Active Galactic Nuclei: Intensive Monitoring of NGC 7469 in the X‐Ray and Ultraviolet

1998 ◽  
Vol 505 (2) ◽  
pp. 594-606 ◽  
Author(s):  
K. Nandra ◽  
J. Clavel ◽  
R. A. Edelson ◽  
I. M. George ◽  
M. A. Malkan ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Continuum Emission ◽  
Emission Mechanism ◽  
X Ray ◽  
Intensive Monitoring ◽  
Ngc 7469 ◽  
The Continuum

scholarly journals A geometric method of analysis for the light curves of active galactic nuclei

2020 ◽  
Author(s):  
Isao Shoji ◽  
Tadafumi Takata ◽  
Yoshihiko Mizumoto
Keyword(s):  
Time Series ◽  
Vector Field ◽  
Active Galactic Nuclei ◽  
Dynamic Properties ◽  
Flux Ratio ◽  
Galactic Nuclei ◽  
Light Curves ◽  
Geometric Method ◽  
Function Form ◽  
Filtering Method

Abstract We propose a geometric method of analysis for the light curves of active galactic nuclei (AGN). The time series of flux ratio is modeled by possibly nonlinear random oscillation without specifying the function form. Based on the model, we map the dynamic behavior of flux ratio to a vector field on a manifold, and then analyze the vector field to retrieve information on the dynamic properties closely linked with the activity of AGN. While the function form of the model is unspecified, the vector fields and those associated quantities can be estimated by applying a nonparametric filtering method. We illustrate the proposed analysis with an application to light curves of two AGNs supplied by the Kepler satellite. The application shows that the vector field, its derivative and their combination will be used as the tools of picking up various signals that help understanding of the activity of AGN. In addition, from a technical viewpoint, the nonparametric filtering method allows the estimation to be robust against outliers. The proposed analysis could be used as alternative time series analysis of the optical variability other than the analysis by spectral densities or structure functions.

Correlation Analysis of Optical and Radio Light Curves for a Large Sample of Active Galactic Nuclei

1995 ◽  
Vol 110 ◽  
pp. 529 ◽  
Author(s):  
S. D. Clements ◽  
A. G. Smith ◽  
H. D. Aller ◽  
M. F. Aller
Keyword(s):  
Correlation Analysis ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Light Curves ◽  
Large Sample

scholarly journals Multifrequency Variability of AGN's: Continuum Variations from the Near IR to the X-rays

1994 ◽  
Vol 159 ◽  
pp. 131-143
Author(s):  
J. Clavel
Keyword(s):  
Active Galactic Nuclei ◽  
Temporal Evolution ◽  
Line Emission ◽  
Galactic Nuclei ◽  
The Other ◽  
X Rays ◽  
Optical Telescope ◽  
Emission Process ◽  
Near Ir ◽  
The Continuum

Because they emit copiously over more than 10 decades in frequency, Active Galactic Nuclei (AGN) cannot be understood without the help of multiwavelength observations. On the other hand, variability monitoring has also proven to be invaluable in understanding the continuum and line emission process as well as the geometry of the innermost regions in these objects. Indeed, at the heart of AGN's lies an object which is so compact that the only way to probe its structure is the study of the temporal evolution of its spectrum. The equivalent resolution which can be achieved in this way is of the order of 10 microarcsecs, far beyond the capability of any UV or optical telescope.

scholarly journals Infrared Line Shapes in Active Galactic Nuclei

1994 ◽  
Vol 159 ◽  
pp. 462-462
Author(s):  
Rodger I. Thompson
Keyword(s):  
Active Galactic Nuclei ◽  
Electron Density ◽  
Galactic Nuclei ◽  
Complete Spectrum ◽  
Line Shapes ◽  
Ngc 4151

This paper presents the complete spectrum of NGC 4151 from 0.87 to 2.5 μm as well as detail of the Paschen α profile in 3C273 at a resolution of about 5000. Analysis of the several observed Fe II lines yields a most probable electron density of 104 and a most likely temperature of 104. The Fe II to H ratio is 2+/− 1 × 10−6 which is 5–7% of the available iron if the Fe/H ratio is solar.

scholarly journals Fluorescence in the Active Galactic Nuclei NGC 4151

2012 ◽  
Vol 8 (S295) ◽  
pp. 266-266
Author(s):  
Mattias Eriksson ◽  
Hans Veenhuizen
Keyword(s):  
Active Galactic Nuclei ◽  
Wavelength Region ◽  
Galactic Nuclei ◽  
Collisional Excitation ◽  
Ngc 4151 ◽  
Uv Emission

AbstractThe possibility of UV lines from Fe II formed in the BLR of NGC 4151 has been examined. As a result Fe II emission has been shown to play an important role for the topology of the 2000 to 3000 Å wavelength region of the NGC 4151 spectra. The Fe II UV emission originates from two processes, collisional excitation and PAR (photoexcitation by accidental resonance).

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