Thermal emission from WASP-33b, the hottest known planet

TL;DR

This study measures the thermal emission of the ultra-hot exoplanet WASP-33b, revealing extremely high brightness temperatures and inefficient heat redistribution, along with stellar pulsation analysis.

Contribution

First ground-based detection of WASP-33b's thermal emission at 0.91 microns, providing insights into its temperature and heat redistribution.

Findings

Brightness temperature of 3620 K, higher than equilibrium predictions.

Inefficient heat redistribution from day to night side.

Detection of stellar pulsations with periods between 42 and 77 minutes.

Abstract

We report ground-based observations at 0.91 microns of the occultation of the hot Jupiter WASP-33b by its A5 host star. We measure the planet to be 0.109 +/- 0.030 per cent as bright as its host star at 0.91 microns. This corresponds to a brightness temperature, T_B = 3620 +200 -250 K, significantly higher than the zero-albedo equilibrium temperature for both isotropic re-radiation (2750 +/- 37 K) and uniform day-side only re-radiation (3271 +/- 44 K), but consistent with the zero-redistribution temperature (3515 +/- 47 K). This indicates that the heat redistribution from the day-side of WASP-33b to the night side is inefficient, and further suggest that there is immediate re-radiation, and therefore little or no redistribution, of heat within the day-side. We also detected the stellar pulsations of WASP-33, which we model as the sum of four sinusoids, with periods of between 42 and 77 minutes and amplitudes of 0.5 to 1.5 mmag.