Journal article
Extracting information from AGN variability
Monthly notices of the Royal Astronomical Society, v 470(3), pp 3027-3048
01 Sep 2017
Abstract
Active galactic nuclei (AGNs) exhibit rapid, high-amplitude stochastic flux variations across the entire electromagnetic spectrum on time-scales ranging from hours to years. The cause of this variability is poorly understood. We present a Green's function-based method for using variability to (1) measure the time-scales on which flux perturbations evolve and (2) characterize the driving flux perturbations. We model the observed light curve of an AGN as a linear differential equation driven by stochastic impulses. We analyse the light curve of the Kepler AGN Zw 229-15 and find that the observed variability behaviour can be modelled as a damped harmonic oscillator perturbed by a coloured noise process. The model power spectrum turns over on time-scale 385 d. On shorter time-scales, the log-power-spectrum slope varies between 2 and 4, explaining the behaviour noted by previous studies. We recover and identify both the 5.6 and 67 d time-scales reported by previous work using the Green's function of the Continuous-time AutoRegressive Moving Average equation rather than by directly fitting the power spectrum of the light curve. These are the time-scales on which flux perturbations grow, and on which flux perturbations decay back to the steady-state flux level, respectively. We make the software package KALI used to study light curves using our method available to the community.
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Details
- Title
- Extracting information from AGN variability
- Creators
- Vishal P. Kasliwal - Princeton UniversityMichael S. Vogeley - Drexel UniversityGordon T. Richards - Drexel University
- Publication Details
- Monthly notices of the Royal Astronomical Society, v 470(3), pp 3027-3048
- Publisher
- Oxford Univ Press
- Number of pages
- 22
- Grant note
- NASA Science Mission directorate; National Aeronautics & Space Administration (NASA) NNX09AF08G / NASA Office of Space Science; National Aeronautics & Space Administration (NASA) NNX14AL56G; NAS5-26555 / NASA; National Aeronautics & Space Administration (NASA)
- Resource Type
- Journal article
- Language
- English
- Academic Unit
- Physics
- Web of Science ID
- WOS:000406844800038
- Scopus ID
- 2-s2.0-85034610151
- Other Identifier
- 991019168449804721
InCites Highlights
Data related to this publication, from InCites Benchmarking & Analytics tool:
- Collaboration types
- Domestic collaboration
- Web of Science research areas
- Astronomy & Astrophysics