scholarly journals Light Curves of Tidal Disruption Events in Active Galactic Nuclei

2020 ◽  
Vol 903 (1) ◽  
pp. 17 ◽  
Author(s):  
Chi-Ho Chan ◽  
Tsvi Piran ◽  
Julian H. Krolik
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Light Curves ◽  
Tidal Disruption

scholarly journals Epicyclic oscillations in spinning particle motion around Kerr black hole applied in models fitting the quasi-periodic oscillations observed in microquasars and AGNs

2021 ◽  
Vol 81 (12) ◽  
Author(s):  
Misbah Shahzadi ◽  
Martin Kološ ◽  
Zdeněk Stuchlík ◽  
Yousaf Habib
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
High Frequency ◽  
Kerr Black Hole ◽  
Galactic Nuclei ◽  
Tidal Disruption ◽  
Periodic Oscillations ◽  
Spinning Particle ◽  
X Ray ◽  
Test Particles

AbstractThe study of the quasi-periodic oscillations (QPOs) of X-ray flux observed in the stellar-mass black hole (BH) binaries or quasars can provide a powerful tool for testing the phenomena occurring in strong gravity regime. We thus fit the data of QPOs observed in the well known microquasars as well as active galactic nuclei (AGNs) in the framework of the model of geodesic oscillations of Keplerian disks modified for the epicyclic oscillations of spinning test particles orbiting Kerr BHs. We show that the modified geodesic models of QPOs can explain the observational fixed data from the microquasars and AGNs but not for all sources. We perform a successful fitting of the high frequency QPOs models of epicyclic resonance and its variants, relativistic precession and its variants, tidal disruption, as well as warped disc models, and discuss the corresponding constraints of parameters of the model, which are the spin of the test particle, mass and rotation of the BH.

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.

scholarly journals Tidal Disruption Events in Active Galactic Nuclei

2019 ◽  
Vol 881 (2) ◽  
pp. 113 ◽  
Author(s):  
Chi-Ho Chan ◽  
Tsvi Piran ◽  
Julian H. Krolik ◽  
Dekel Saban
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Tidal Disruption

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 To TDE or not to TDE: the luminous transient ASASSN-18jd with TDE-like and AGN-like qualities

2020 ◽  
Vol 494 (2) ◽  
pp. 2538-2560 ◽  
Author(s):  
J M M Neustadt ◽  
T W-S Holoien ◽  
C S Kochanek ◽  
K Auchettl ◽  
J S Brown ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Spectral Energy Distribution ◽  
Galactic Nuclei ◽  
Spectral Energy ◽  
Tidal Disruption ◽  
Optical Telescope ◽  
X Ray ◽  
Radiated Energy ◽  
The Galaxy ◽  
Order Of Magnitude

ABSTRACT We present the discovery of ASASSN-18jd (AT 2018bcb), a luminous optical/ultraviolet(UV)/X-ray transient located in the nucleus of the galaxy 2MASX J22434289–1659083 at z = 0.1192. Over the year after discovery, Swift UltraViolet and Optical Telescope (UVOT) photometry shows the UV spectral energy distribution of the transient to be well modelled by a slowly shrinking blackbody with temperature $T \sim 2.5 \times 10^{4} \, {\rm K}$, a maximum observed luminosity of $L_{\rm max} = 4.5^{+0.6}_{-0.3}\times 10^{44} \, {\rm erg \,s}^{-1}$, and a radiated energy of $E = 9.6^{+1.1}_{-0.6} \times 10^{51} \, {\rm erg}$. X-ray data from Swift X-Ray Telescope (XRT) and XMM–Newton show a transient, variable X-ray flux with blackbody and power-law components that fade by nearly an order of magnitude over the following year. Optical spectra show strong, roughly constant broad Balmer emission and transient features attributable to He ii, N iii–v, O iii, and coronal Fe. While ASASSN-18jd shares similarities with tidal disruption events (TDEs), it is also similar to the newly discovered nuclear transients seen in quiescent galaxies and faint active galactic nuclei (AGNs).

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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