Observed spectral energy distribution of the thermal emission from the dayside of WASP-46b

TL;DR

This study measures the thermal emission spectrum of WASP-46b's dayside, revealing high brightness temperatures and poor heat redistribution, with tentative evidence of reflective clouds affecting the observed spectrum.

Contribution

First detection of thermal emission from WASP-46b in multiple bands, providing insights into its atmospheric temperature profile and potential cloud presence.

Findings

Detected thermal emission in K band at 4.2-sigma

Brightness temperature consistent with isothermal profile (~2386K)

Indicates poor heat redistribution and possible reflective clouds

Abstract

We aim to construct a spectral energy distribution (SED) for the emission from the dayside atmosphere of the hot Jupiter WASP-46b and to investigate its energy budget. We observed a secondary eclipse of WASP-46b simultaneously in the g'r'i'z'JHK bands using the GROND instrument on the MPG/ESO 2.2m telescope. Eclipse depths of the acquired light curves were derived to infer the brightness temperatures at multibands that cover the SED peak. We report the first detection of the thermal emission from the dayside of WASP-46b in the K band at 4.2-sigma level and tentative detections in the H (2.5-sigma) and J (2.3-sigma) bands, with flux ratios of 0.253 +0.063/-0.060%, 0.194 +/- 0.078%, and 0.129 +/- 0.055%, respectively. The derived brightness temperatures (2306 +177/-187K, 2462 +245/-302K, and 2453 +198/-258K, respectively) are consistent with an isothermal temperature profile of 2386K, which is significantly higher than the dayside-averaged equilibrium temperature, indicative of very poor heat redistribution efficiency. We also investigate the tentative detections in the g'r'i' bands and the 3-sigma upper limit in the z' band, which might indicate the existence of reflective clouds if these tentative detections do not arise from systematics.