Calculating Time Lags From Unevenly-Sampled Light Curves

Abstract

Timing techniques offer powerful tools to study dynamical astrophysical phenomena. In the X-ray band, they offer the potential of probing accretion physics down to the event horizon. Recent work has used frequency and energy-dependent time lags as a tool for studying relativistic reverberation around the black holes in several Seyfert galaxies. This was achieved thanks to the evenly-sampled light curves obtained using XMM-Newton. Continuous-sampled data is however not always available and standard Fourier techniques are not applicable. Here, building on the work of Miller et al. (2010), we discuss and use a maximum likelihood method to obtain frequency-dependent lags that takes into account light curve gaps. Instead of calculating the lag directly, the method estimates the most likely lag values at a particular frequency given two observed light curves. We use Monte Carlo simulations to assess the method's applicability, and use it to obtain lag-energy spectra from Suzaku data for two objects, NGC 4151 and MCG-5-23-16, that had previously shown signatures of iron K reverberation. The lags obtained are consistent with those calculated using standard methods using XMM-Newton data.

Accepted for publication in ApJ

References in corpus (3)

• X-ray Properties of Black-Hole Binaries
• Discovery of multiple Lorentzian components in the X-ray timing properties of the Narrow Line Seyfert 1 Ark 564
• X-ray Variability of the Seyfert 1 Markarian 335: Power Spectrum and Time Lags

Cited by in corpus (31)

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• Did ASAS-SN Kill the Supermassive Black Hole Binary Candidate PG1302-102?
• Revisiting The Spectral and Timing Properties of NGC 4151
• Observations of MCG-5-23-16 with Suzaku, XMM-Newton and NuSTAR: Disk tomography and Compton hump reverberation
• Frequency-resolved lags in UV/optical continuum reverberation mapping
• Hard X-ray Lags in Active Galactic Nuclei: Testing the Distant Reverberation Hypothesis with NGC 6814
• Low frequency X-ray timing with Gaussian processes and reverberation in the radio-loud AGN 3C 120
• Statistical properties of Fourier-based time-lag estimates
• The Innermost Extremes of Black Hole Accretion
• Modelling the Multiwavelength Variability of Mrk 335 using Gaussian Processes
• X-ray and UV Monitoring of the Seyfert 1.5 Galaxy Markarian 817
• 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
• X-ray Reverberation Mapping of Ark 564 using Gaussian Process Regression
• A Negative Long Lag from the Optical to the UV Continuum in Fairall 9
• X-ray/UVOIR Frequency-resolved Time Lag Analysis of Mrk 335 Reveals Accretion Disk Reprocessing
• A Hard Look At Relativistic Reverberation in MCG-5-23-16 & SWIFT J2127.4+5654: Testing the Lamp-Post Model
• Measuring Light Echos in NGC 4051
• X-ray variability analysis of a large series of XMM-Newton + NuSTAR observations of NGC 3227
• Wavelet spectral timing: X-ray reverberation from a dynamic black hole corona hidden beneath ultrafast outflows
• X-ray Lags in PDS 456 Revealed by Suzaku Observations
• On measuring the Hubble constant with X-ray reverberation mapping of active galactic nuclei
• Observations of X-ray reverberation around black holes
• Modelling variability power spectra of active galaxies from irregular time series
• Detection of Asymmetry in the Narrow Fe K$\alpha$ Emission Line in MCG-5-23-16 with Chandra
• Fourier Domain
• Untangling the Complex Nature of AGN Variability with Fairall 9