Studying atmosphere-dominated hot Jupiter Kepler phase curves: Evidence that inhomogeneous atmospheric reflection is common

TL;DR

This study analyzes Kepler phase curves of three hot Jupiters dominated by atmospheric processes, revealing common inhomogeneous reflection patterns likely due to clouds, with implications for understanding exoplanet atmospheres and detecting non-transiting planets.

Contribution

It demonstrates that inhomogeneous atmospheric reflection is common in hot Jupiters with atmosphere-dominated phase curves, using efficient modeling of reflection and thermal emission.

Findings

Inhomogeneous atmospheric reflection is present in all three studied planets.

Reflective clouds on the west side cause observed phase shifts.

Atmospheric signals can reveal non-transiting planets with small masses.

Abstract

(abridged) We identify 3 Kepler transiting planets, Kepler-7b, Kepler-12b, and Kepler-41b, whose orbital phase-folded light curves are dominated by planetary atmospheric processes including thermal emission and reflected light, while the impact of non-atmospheric (i.e. gravitational) processes, including beaming (Doppler boosting) and tidal ellipsoidal distortion, is negligible. Therefore, those systems allow a direct view of their atmospheres without being hampered by the approximations used in the inclusion of both atmospheric and non-atmospheric processes when modeling the phase curve shape. Here we analyze Kepler-12b and Kepler-41b atmosphere based on their Kepler phase curve, while the analysis of Kepler-7b was presented elsewhere. The model we used efficiently computes reflection and thermal emission contributions to the phase curve, including inhomogeneous atmospheric reflection due to longitudinally varying cloud coverage. We confirm Kepler-12b and Kepler-41b show a westward phase shift between the brightest region on the planetary surface and the substellar point, similar to Kepler-7b. We find that reflective clouds located on the west side of the substellar point can explain the phase shift. The existence of inhomogeneous atmospheric reflection in all 3 of our targets, selected due to their atmosphere-dominated Kepler phase curve, suggests this phenomenon is common. Therefore it is likely to be present also in planetary phase curves that do not allow a direct view of the planetary atmosphere as they contain additional orbital processes. We discuss the implications of a bright-spot shift on the analysis of phase curves where both atmospheric and gravitational processes appear. We also discuss the potential detection of non-transiting but otherwise similar planets, whose mass is too small to show a gravitational photometric signal but their atmospheric signal is detectable.