Discovery of a ~5 day characteristic timescale in the Kepler power spectrum of Zw 229-15

Abstract

We present time series analyses of the full Kepler dataset of Zw 229-15. This Kepler light curve --- with a baseline greater than three years, composed of virtually continuous, evenly sampled 30-minute measurements --- is unprecedented in its quality and precision. We utilize two methods of power spectral analysis to investigate the optical variability and search for evidence of a bend frequency associated with a characteristic optical variability timescale. Each method yields similar results. The first interpolates across data gaps to use the standard Fourier periodogram. The second, using the CARMA-based time-domain modeling technique of Kelly et al. (2014), does not need evenly-sampled data. Both methods find excess power at high frequencies that may be due to Kepler instrumental effects. More importantly both also show strong bends (Δα ~ 2) at timescales of ~5 days, a feature similar to those seen in the X-ray PSDs of AGN but never before in the optical. This observed ~5 day timescale may be associated with one of several physical processes potentially responsible for the variability. A plausible association could be made with light-crossing, dynamical or thermal timescales, depending on the assumed value of the accretion disk size and on unobserved disk parameters such as α and H/R. This timescale is not consistent with the viscous timescale, which would be years in a ~10^7 Solar mass AGN such as Zw 229-15. However there must be a second bend on long (>~1 year) timescales, and that feature could be associated with the viscous timescale.

10 pages, 5 figures, 1 table. To appear in the Astrophysical Journal, Part 1

References in corpus (2)

• Testing thermal reprocessing in AGN accretion discs
• Timescale of variation and the size of the accretion disc in active galactic nuclei

Cited by in corpus (30)

• Astrochemistry During the Formation of Stars
• Optical variability of AGN in the PTF/iPTF survey
• Detection of Possible Quasi-periodic Oscillations in the Long-term Optical Light Curve of the BL Lac Object OJ 287
• Improving Damped Random Walk parameters for SDSS Stripe 82 Quasars with Pan-STARRS1
• Radio and $\gamma$-ray variability in the BL Lac PKS 0219 -164: Detection of quasi-periodic oscillations in the radio light curve
• Discovery of a Candidate Binary Supermassive Black Hole in a Periodic Quasar from Circumbinary Accretion Variability
• Constraints on the temperature inhomogeneity in quasar accretion discs from the ultraviolet-optical spectral variability
• The rms-flux relation in accreting white dwarfs: another nova-like variable and the first dwarf nova
• A physical model for the UV/optical power spectra of AGN
• A Method to Measure the Unbiased Decorrelation Timescale of the AGN Variable Signal from Structure Functions
• AGN STORM 2. VII. A Frequency-resolved Map of the Accretion Disk in Mrk 817: Simultaneous X-ray Reverberation and UVOIR Disk Reprocessing Time Lags
• LSST Cadence Strategy Evaluations for AGN Time-series Data in Wide-Fast-Deep Field
• Analyses on the Variability Asymmetry of Kepler AGNs
• Ensemble power spectral density of SDSS quasars in UV/optical bands
• Measuring time delays: II. Using observations of the unresolved flux and astrometry
• Spectral and Time Series Analyses of the Seyfert 1 AGN: Zw 229.015
• The detection of possible transient Quasi-Periodic Oscillations in the $\gamma$-ray light curve of PKS 0244-470 and 4C+38.41
• Measuring time delays: I. Using a flux time series that is a linear combination of time-shifted light curves
• Complex Variability of Kepler AGN Revealed by Recurrence Analysis
• Observational nonstationarity of AGN variability: The only way to go is down!
• Modelling variability power spectra of active galaxies from irregular time series
• A QPO in Mkn 421 from Archival RXTE Data
• Properties of a Previously Unidentified Instrumental Signature in $\text{Kepler/K2}$ that was Confused for AGN Variability
• Dust Reverberation Mapping and Light-Curve Modelling of Zw229-015
• The Vast Potential of Exoplanet Satellites for High-Energy Astrophysics
• A QPO in NGC 4945 from Archival RXTE Data
• The UV/optical Continuum Reverberation Mapping of Eight Active Galactic Nuclei with Swift: Further Evidence for the Outer Component
• Searching for similarities in the accretion flow of Seyfert 1 galaxies and cataclysmic variables based on flare profiles of IRAS 13224-3809, 1H 0707-495, Mrk 766 and MV Lyr
• Chemistry of Dark Molecular Clouds
• Optical Variability Structure Function of Low-Luminosity AGN using ATLAS Lightcurves