Benchmark Tests for Markov Chain Monte Carlo Fitting of Exoplanet Eclipse Observations

Abstract

Ground-based observations of exoplanet eclipses provide important clues to the planets' atmospheric physics, yet systematics in light curve analyses are not fully understood. It is unknown if measurements suggesting near-infrared flux densities brighter than models predict are real, or artifacts of the analysis processes. We created a large suite of model light curves, using both synthetic and real noise, and tested the common process of light curve modeling and parameter optimization with a Markov Chain Monte Carlo (MCMC) algorithm. With synthetic white-noise models, we find that input eclipse signals are generally recovered within 10% accuracy for eclipse depths greater than the noise amplitude, and to smaller depths for higher sampling rates and longer baselines. Red-noise models see greater discrepancies between input and measured eclipse signals, often biased in one direction. Finally, we find that in real data, systematic biases result even with a complex model to account for trends, and significant false eclipse signals may appear in a non-Gaussian distribution. To quantify the bias and validate an eclipse measurement, we compare both the planet-hosting star and several of its neighbors to a separately-chosen control sample of field stars. Re-examining the Rogers et al. (2009) Ks-band measurement of CoRoT-1b finds an eclipse $3190_{-440}^{+370}$ ppm deep centered at ${\varphi }_{me}$=$0.50418_{-0.00203}^{+0.00197}$. Finally, we provide and recommend the use of selected datasets we generated as a benchmark test for eclipse modeling and analysis routines, and propose criteria to verify eclipse detections.

33 pages, 11 tables, 9 figures, accepted to ApJ

References in corpus (14)

• Detection of Thermal Emission from an Extrasolar Planet
• The effect of red noise on planetary transit detection
• The Broadband Infrared Emission Spectrum of the Exoplanet HD 189733b
• Strong Water Absorption in the Dayside Emission Spectrum of the Planet HD 189733b
• Theoretical Spectra and Light Curves of Close-in Extrasolar Giant Planets and Comparison with Data
• Multi-Wavelength Constraints on the Day-Night Circulation Patterns of HD 189733b
• Strong Infrared Emission from the Extrasolar Planet HD189733b
• Transiting exoplanets from the CoRoT space mission I - CoRoT-Exo-1b: a low-density short-period planet around a G0V star
• Re-Evaluating WASP-12b: Strong Emission at 2.315 micron, Deeper Occultations, and an Isothermal Atmosphere
• Thermal Emission of Exoplanet XO-1b
• Thermal Emission from Transiting Very-Hot Jupiters: Prospects for Ground-based Detection at Optical Wavelengths
• Ground-based secondary eclipse detection of the very-hot Jupiter OGLE-TR-56b
• Ground-based K-band detection of thermal emission from the exoplanet TrES-3b
• Secondary eclipses in the CoRoT light curves: A homogeneous search based on Bayesian model selection

Cited by in corpus (7)

• Spitzer Phase Curve Constraints for WASP-43b at 3.6 and 4.5 microns
• Balancing the Energy Budget of Short-Period Giant Planets: Evidence for Reflective Clouds and Optical Absorbers
• A comprehensive study of Kepler phase curves and secondary eclipses -- temperatures and albedos of confirmed Kepler giant planets
• Deciphering the Atmospheric Composition of WASP-12b: A Comprehensive Analysis of its Dayside Emission
• Ground-based near-UV observations of 15 transiting exoplanets: Constraints on their atmospheres and no evidence for asymmetrical transits
• Colour-magnitude diagrams of transiting Exoplanets - II. A larger sample from photometric distances
• Detection of the secondary eclipse of WASP-10b in the Ks-band