Revisiting the Phase Curves of WASP-43b: Confronting Reanalyzed Spitzer Data with Cloudy Atmospheres

TL;DR

This study reanalyzed Spitzer phase curves of WASP-43b, improving data accuracy, and used advanced GCMs to compare cloudfree and cloudy atmospheric models with observations, revealing insights into the planet's cloud distribution and composition.

Contribution

It presents an improved analysis of Spitzer data and introduces non-hydrostatic GCM simulations to better understand cloud effects on WASP-43b's atmosphere.

Findings

Reanalysis reduces residual noise and increases nightside flux.

Clouds are confined to the nightside with a finite cloud-top pressure.

Enhanced CO2 is needed to explain the 4.5 μm phase curve.

Abstract

Recently acquired Hubble and Spitzer phase curves of the short-period hot Jupiter WASP-43b make it an ideal target for confronting theory with data. On the observational front, we re-analyze the 3.6 and 4.5 $\mu$m Spitzer phase curves and demonstrate that our improved analysis better removes residual red noise due to intra-pixel sensitivity, which leads to greater fluxes emanating from the nightside of WASP-43b, thus reducing the tension between theory and data. On the theoretical front, we construct cloudfree and cloudy atmospheres of WASP-43b using our Global Circulation Model (GCM), THOR, which solves the non-hydrostatic Euler equations (compared to GCMs that typically solve the hydrostatic primitive equations). The cloudfree atmosphere produces a reasonable fit to the dayside emission spectrum. The multi-phase emission spectra constrain the cloud deck to be confined to the nightside and have a finite cloud-top pressure. The multi-wavelength phase curves are naturally consistent with our cloudy atmospheres, except for the 4.5 $\mu$m phase curve, which requires the presence of enhanced carbon dioxide in the atmosphere of WASP-43b. Multi-phase emission spectra at higher spectral resolution, as may be obtained using the James Webb Space Telescope, and a reflected-light phase curve at visible wavelengths would further constrain the properties of clouds in WASP-43b.