scholarly journals Oscillatory patterns in the light curves of five long-term monitored type 1 active galactic nuclei

2018 ◽  
Vol 475 (2) ◽  
pp. 2051-2066 ◽  
Author(s):  
Andjelka B Kovačević ◽  
Ernesto Pérez-Hernández ◽  
Luka Č Popović ◽  
Alla I Shapovalova ◽  
Wolfram Kollatschny ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Light Curves

scholarly journals Liverpool-Maidanak monitoring of the Einstein Cross in 2006–2019

2020 ◽  
Vol 637 ◽  
pp. A89 ◽  
Author(s):  
L. J. Goicoechea ◽  
B. P. Artamonov ◽  
V. N. Shalyapin ◽  
A. V. Sergeyev ◽  
O. A. Burkhonov ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Emission Scenario ◽  
Galactic Nuclei ◽  
Compact Object ◽  
Light Curves ◽  
Continuum Emission ◽  
Emission Sources ◽  
Uv Emission ◽  
Source Radius

Quasar microlensing offers a unique opportunity to resolve tiny sources in distant active galactic nuclei and study compact object populations in lensing galaxies. We therefore searched for microlensing-induced variability of the gravitationally lensed quasar QSO 2237+0305 (Einstein Cross) using 4374 optical frames taken with the 2.0 m Liverpool Telescope and the 1.5 m Maidanak Telescope. These gVrRI frames over the 2006–2019 period were homogeneously processed to generate accurate long-term multi-band light curves of the four quasar images A–D. Through difference light curves, we found strong microlensing signatures. We then focused on the analytical modelling of two putative caustic-crossing events in image C, finding compelling evidence that this image experienced a double caustic crossing. Additionally, our overall results indicate that a standard accretion disc accounts reasonably well for the brightness profile of UV continuum emission sources and for the growth in source radius when the emission wavelength increases: Rλ ∝ λα, α = 1.33 ± 0.09. However, we caution that numerical microlensing simulations are required before firm conclusions can be reached on the UV emission scenario because the VRI-band monitoring during the first caustic crossing and one of our two α indicators lead to a few good solutions with α ≈ 1.

SDSS J154751.94+025550 with double-peaked broad H β but single-peaked broad H α: a candidate for central binary black hole system?

2021 ◽  
Vol 507 (4) ◽  
pp. 5205-5213
Author(s):  
XueGuang Zhang
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Emission Lines ◽  
Broad Line ◽  
Line Profiles ◽  
Physical Conditions ◽  
Binary Black Hole ◽  
Sinusoidal Function

ABSTRACT In this manuscript, an interesting blue active galactic nuclei (AGNs) SDSS J154751.94+025550 (=SDSS J1547) is reported with very different line profiles of broad Balmer emission lines: double-peaked broad H β but single-peaked broad H α. SDSS J1547 is the first AGN with detailed discussions on very different line profiles of the broad Balmer emission lines, besides the simply mentioned different broad lines in the candidate for a binary black hole (BBH) system in SDSS J0159+0105. The very different line profiles of the broad Balmer emission lines can be well explained by different physical conditions to two central BLRs in a central BBH system in SDSS J1547. Furthermore, the long-term light curve from CSS can be well described by a sinusoidal function with a periodicity about 2159 d, providing further evidence to support the expected central BBH system in SDSS J1547. Therefore, it is interesting to treat different line profiles of broad Balmer emission lines as intrinsic indicators of central BBH systems in broad line AGN. Under assumptions of BBH systems, 0.125 per cent of broad-line AGN can be expected to have very different line profiles of broad Balmer emission lines. Future study on more broad line AGN with very different line profiles of broad Balmer emission lines could provide further clues on the different line profiles of broad Balmer emission lines as indicator of BBH systems.

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.

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.

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 Examining supernova events in Type 1 active galactic nuclei

2020 ◽  
Vol 495 (4) ◽  
pp. 4419-4429
Author(s):  
Beatriz Villarroel ◽  
Iñigo Imaz ◽  
Elisabeta Lusso ◽  
Sébastien Comerón ◽  
M Almudena Prieto ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Detection Rate ◽  
Statistical Study ◽  
Galactic Nuclei ◽  
Core Collapse ◽  
Late Type ◽  
Host Galaxies ◽  
Specific Kind

ABSTRACT A statistical study of intermediate Palomar Transient Factory supernovae (SNe) in Type 1 active galactic nuclei (AGNs) has shown a major deficit of supernovae around Type 1 AGN host galaxies, with respect to Type 2 AGN hosts. The aim of this work is to test whether there is any preference for Type 1 AGNs to host SN of a specific kind. Through the analysis of SN occurrence and their type (thermonuclear versus core-collapse), we can directly link the type of stars producing the SN events, thus this is an indirect way to study host galaxies in Type 1 AGNs. We examine the detection fractions of SNe, the host galaxies and compare the sample properties to typical host galaxies in the Open Supernova Catalog (OSC). The majority of the host galaxies in the AGN sample are late type, similar to typical galaxies hosting SN within the OSC. The findings are supportive of a deficiency of SNe near Type 1 AGNs, although we cannot with certainty assess the overall detection fractions of SNe in Type 1 AGNs relative to other SN host galaxies. We can state that Type 1 AGN has equal detection fractions of thermonuclear versus core-collapse SNe. However, we note the possibility of a higher detection rate of core-collapse supernovae in Type 1 AGN with insecure AGN classifications.

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.

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