A survey of eight hot Jupiters in secondary eclipse using WIRCam at CFHT

TL;DR

This study provides high-precision near-infrared photometry of eight hot Jupiters during secondary eclipses, revealing excess thermal emission and potential additional radiation sources, with implications for planetary heat redistribution.

Contribution

It introduces a new observational approach using WIRCam at CFHT for high-precision eclipse measurements and analyzes the thermal emission of multiple hot Jupiters.

Findings

Detected excess brightness temperatures compared to blackbody predictions.

Found a trend of larger excess in cooler hot Jupiters.

Achieved photometric precision as low as 0.11%.

Abstract

We present near infrared high-precision photometry for eight transiting hot Jupiters observed during their predicted secondary eclipses. Our observations were carried out using the staring mode of the WIRCam instrument on the Canada-France-Hawaii Telescope (CFHT). We present the observing strategies and data reduction methods which delivered time series photometry with statistical photometric precisionas low as 0.11%. We performed a Bayesian analysis to model the eclipse parameters and systematics simultaneously. The measured planet-to-star flux ratios allowed us to constrain the thermal emission from the day side of these hot Jupiters, as we derived the planet brightness temperatures. Our results combined with previously observed eclipses reveal an excess in the brightness temperatures relative to the blackbody prediction for the equilibrium temperatures of the planets for a wide range of heat redistribution factors. We find a trend that this excess appears to be larger for planets with lower equilibrium temperatures. This may imply some additional sources of radiation, such as reflected light from the host star and/or thermal emission from residual internal heat from the formation of the planet.