Near infrared and optical emission of WASP-5 b

TL;DR

This study uses new near infrared and optical data, including TESS observations and follow-up in the Ks band, to analyze WASP-5 b's orbital eccentricity and atmospheric properties, revealing a nearly circular orbit and challenging simple black body emission models.

Contribution

It provides the first combined analysis of TESS and near infrared data to constrain the orbital and atmospheric characteristics of WASP-5 b, highlighting discrepancies with current atmospheric models.

Findings

Orbit is nearly circular with e=0.005+/-0.015.

Ks band flux depression excludes simple black body emission.

High geometric albedo suggests efficient atmospheric circulation.

Abstract

CONTEXT: Thermal emission from extrasolar planets makes it possible to study important physical processes in their atmospheres and derive more precise orbital elements. AIMS: By using new near infrared and optical data, we examine how these data constrain the orbital eccentricity and the thermal properties of the planet atmosphere. METHODS: The full light curves acquired by the TESS satellite from two sectors are used to put upper limit on the amplitude of the planet's phase variation and estimate the occultation depth. Two, already published and one, yet unpublished followup observations in the 2MASS K (Ks) band are employed to derive a more precise occultation light curve in this near infrared waveband. RESULTS: The merged occultation light curve in the Ks band comprises 4515 data points. The data confirm the results of the earlier eccentricity estimates, suggesting circular orbit: e=0.005+/-0.015. The high value of the flux depression of (2.70+/-0.14) ppt in the Ks band excludes simple black body emission at the 10 sigma level and disagrees also with current atmospheric models at the (4-7) sigma level. From the analysis of the TESS data, in the visual band we found tentative evidence for a near noise level detection of the secondary eclipse, and placed constraints on the associated amplitude of the planet's phase variation. A formal box fit yields an occultation depth of (0.157+/-0.056) ppt. This implies a relatively high geometric albedo of Ag=0.43+/-0.15 for fully efficient atmospheric circulation and Ag=0.29+/-0.15 for no circulation at all. No preference can be seen either for the oxygen-enhanced, or for the carbon-enhanced atmosphere models.