A Comprehensive Analysis Spitzer 4.5 $\mu$m Phase Curve of Hot Jupiters

TL;DR

This paper presents a detailed analysis of 29 hot Jupiter phase curves from Spitzer, evaluating data reduction methods, identifying trends related to planetary and stellar properties, and highlighting the need for larger samples for conclusive atmospheric dynamics insights.

Contribution

It provides a comprehensive reduction and analysis of Spitzer 4.5 micron phase curves using the SPCA pipeline, comparing detrending methods, and exploring correlations with planetary and stellar parameters.

Findings

BLISS mapping is generally the best detrending scheme.

Visual inspection is essential for data consistency.

No definitive correlation between heat transport and planetary parameters.

Abstract

Although exoplanetary science was not initially projected to be a substantial part of the Spitzer mission, its exoplanet observations set the stage for current and future surveys with JWST and Ariel. We present a comprehensive reduction and analysis of Spitzer's 4.5 micron phase curves of 29 hot Jupiters on low-eccentricity orbits. The analysis, performed with the Spitzer Phase Curve Analysis (SPCA) pipeline, confirms that BLISS mapping is the best detrending scheme for most, but not all, observations. Visual inspection remains necessary to ensure consistency across detrending methods due to the diversity of phase curve data and systematics. Regardless of the model selection scheme - whether using the lowest-BIC or a uniform detrending approach - we observe the same trends, or lack thereof. We explore phase curve trends as a function of irradiation temperature, orbital period, planetary radius, mass, and stellar effective temperature. We discuss the trends that are robustly detected and provide potential explanations for those that are not observed. While it is almost tautological that planets receiving greater instellation are hotter, we are still far from confirming dynamical theories of heat transport in hot Jupiter atmospheres due to the sample's diversity. Even among planets with similar temperatures, other factors like rotation and metallicity vary significantly. Larger, curated sample sizes and higher-fidelity phase curve measurements from JWST and Ariel are needed to firmly establish the parameters governing day-night heat transport on synchronously rotating planets.