On Correlated-noise Analyses Applied To Exoplanet Light Curves

Abstract

Time-correlated noise is a significant source of uncertainty when modeling exoplanet light-curve data. A correct assessment of correlated noise is fundamental to determine the true statistical significance of our findings. Here we review three of the most widely used correlated-noise estimators in the exoplanet field, the time-averaging, residual-permutation, and wavelet-likelihood methods. We argue that the residual-permutation method is unsound in estimating the uncertainty of parameter estimates. We thus recommend to refrain from this method altogether. We characterize the behavior of the time averaging's rms-vs.-bin-size curves at bin sizes similar to the total observation duration, which may lead to underestimated uncertainties. For the wavelet-likelihood method, we note errors in the published equations and provide a list of corrections. We further assess the performance of these techniques by injecting and retrieving eclipse signals into synthetic and real Spitzer light curves, analyzing the results in terms of the relative-accuracy and coverage-fraction statistics. Both the time-averaging and wavelet-likelihood methods significantly improve the estimate of the eclipse depth over a white-noise analysis (a Markov-chain Monte Carlo exploration assuming uncorrelated noise). However, the corrections are not perfect, when retrieving the eclipse depth from Spitzer datasets, these methods covered the true (injected) depth within the 68\% credible region in only $\sim$45--65\% of the trials. Lastly, we present our open-source model-fitting tool, Multi-Core Markov-Chain Monte Carlo ({MC${}^3$}). This package uses Bayesian statistics to estimate the best-fitting values and the credible regions for the parameters for a (user-provided) model. {MC${}^3$} is a Python/C code, available at https://github.com/pcubillos/MCcubed.

Accepted for publication in ApJ

References in corpus (9)

• Detection of Thermal Emission from an Extrasolar Planet
• The effect of red noise on planetary transit detection
• Homogeneous studies of transiting extrasolar planets. I. Light curve analyses
• The Transit Light Curve Project. IX. Evidence for a Smaller Radius of the Exoplanet XO-3b
• Possible thermochemical disequilibrium in the atmosphere of the exoplanet GJ 436b
• Spitzer Secondary Eclipses of the Dense, Modestly-irradiated, Giant Exoplanet HAT-P-20b Using Pixel-Level Decorrelation
• The 4.5 $\mu$m full-orbit phase curve of the hot Jupiter HD 209458b
• Accurate Spitzer infrared radius measurement for the hot Neptune GJ 436b
• The Transit Light Curve Project. VII. The Not-So-Bloated Exoplanet HAT-P-1b

Cited by in corpus (58)

• Markov Chain Monte Carlo Methods for Bayesian Data Analysis in Astronomy
• Hot Exoplanet Atmospheres Resolved with Transit Spectroscopy (HEARTS) - II. A broadened sodium feature on the ultra-hot giant WASP-76b
• Early 2017 observations of TRAPPIST-1 with $\text{Spitzer}$
• Towards Space-like Photometric Precision from the Ground with Beam-Shaping Diffusers
• Atmospheric Regimes and Trends on Exoplanets and Brown Dwarfs
• Sulphur dioxide in the mid-infrared transmission spectrum of WASP-39b
• Transit detection of the long-period volatile-rich super-Earth ${\nu }^2$ Lupi d with $CHEOPS$
• CHEOPS observations of the HD 108236 planetary system: A fifth planet, improved ephemerides, and planetary radii
• A sub-Neptune sized planet transiting the M2.5-dwarf G 9-40: Validation with the Habitable-zone Planet Finder
• A pair of Sub-Neptunes transiting the bright K-dwarf TOI-1064 characterised with CHEOPS
• High atmospheric metal enrichment for a Saturn-mass planet
• Precise photometric transit follow-up observations of five close-in exoplanets : update on their physical properties
• The TESS-Keck Survey IV: A Retrograde, Polar Orbit for the Ultra-Low-Density, Hot Super-Neptune WASP-107b
• Signs of strong Na and K absorption in the transmission spectrum of WASP-103b
• The EBLM Project V. Physical properties of ten fully convective, very-low-mass stars
• Near-ultraviolet Transmission Spectroscopy of HD 209458b: Evidence of Ionized Iron Beyond the Planetary Roche Lobe
• The Transiting Multi-planet System HD15337: Two Nearly Equal-mass Planets Straddling the Radius Gap
• TOI-222: a single-transit TESS candidate revealed to be a 34-day eclipsing binary with CORALIE, EulerCam and NGTS
• The Kepler-11 system: evolution of the stellar high-energy emission and {initial planetary} atmospheric mass fractions
• Close-in sub-Neptunes reveal the past rotation history of their host stars: atmospheric evolution of planets in the HD3167 and K2-32 planetary systems
• Investigating the architecture and internal structure of the TOI-561 system planets with CHEOPS, HARPS-N and TESS
• Homogeneous search for helium in the atmosphere of 11 gas giant exoplanets with SPIRou
• Retrieval of the fluid Love number $k_2$ in exoplanetary transit curves
• Proxima Centauri b is not a transiting exoplanet
• Revisiting the Iconic Spitzer Phase Curve of 55 Cancri e: Hotter Dayside, Cooler Nightside and Smaller Phase Offset
• Mitigating flicker noise in high-precision photometry. I -- Characterization of the noise structure, impact on the inferred transit parameters, and predictions for CHEOPS observations
• Multiple Clues for Dayside Aerosols and Temperature Gradients in WASP-69 b from a Panchromatic JWST Emission Spectrum
• AutoRegressive Planet Search: Methodology
• Multi-season optical modulation phased with the orbit of the super-Earth 55 Cnc e
• DREAM: III.A helium survey in exoplanets on the edge of the hot Neptune desert with GIANO-B@TNG
• A retrieval challenge exercise for the Ariel mission
• Multi-band transit follow up observations of five hot-Jupiters with critical noise treatments: Improved physical properties
• Constraints on Cosmological Parameters with a Sample of Type Ia Supernovae from JWST
• Ground-based follow-up observations of TRAPPIST-1 transits in the near-infrared
• Aerosol Constraints on the Atmosphere of the Hot Saturn-mass planet WASP-49b
• HST/STIS capability for Love number measurement of WASP-121b
• JWST-TST DREAMS: Non-Uniform Dayside Emission for WASP-17b from MIRI/LRS
• A 16 Hour Transit of Kepler-167 e Observed by the Ground-based Unistellar Telescope Network
• Seasonal Changes in the Atmosphere of HD 80606b Observed with JWST's NIRSpec/G395H
• The Hubble/STIS Near-ultraviolet Transmission Spectrum of HD 189733b
• fBLS -- a fast-folding BLS algorithm
• Establishing the accuracy of asteroseismic mass and radius estimates of giant stars. II. Revised stellar masses and radii for KIC 8430105
• Bayesian Methods for Joint Exoplanet Transit Detection and Systematic Noise Characterization
• On the Dayside Atmosphere of WASP-12b
• Discovery of TOI-1260d and the characterisation of the multi-planet system
• Dark skies of the slightly eccentric WASP-18 b from its optical-to-infrared dayside emission
• Searching for orbital decay in a heartbeat star system KIC 3766353
• NGTS-13b: A hot 4.8 Jupiter-mass planet transiting a subgiant star
• Searching for Possible Exoplanet Transits from BRITE Data through a Machine Learning Technique
• Horizontal and vertical exoplanet thermal structure from a JWST spectroscopic eclipse map
• The SPACE Program. I. The featureless spectrum of HD 86226 c challenges sub-Neptune atmosphere trends
• Simultaneous multicolour optical and near-IR transit photometry of GJ 1214b with SOFIA
• Validation of a Temperate Fourth Planet in the K2-133 Multi-planet System
• The CHEOPS view on the climate of WASP-3 b
• Global Chemistry and Thermal Structure Models for the Hot Jupiter WASP-43b and Predictions for JWST
• Modern Earth-like Chemical Disequilibrium Biosignatures Are Challenging To Constrain Through Spectroscopic Retrievals
• Gas-depleted planet formation occurred in the four-planet system around the red dwarf LHS 1903
• Improved characterization of the TOI-2141 system: a dense sub-Neptune with non-transiting inner and outer companions