Where’s the Weather? Lack of Variability Between Repeated Spitzer Phase Curves of WASP-43b

Phase curve observations currently offer the best glimpse into the global climate of an exoplanet. Upcoming JWST observations will use infrared phase curves to learn about exoplanet atmospheres and climates in unprecedented detail. However, we have little idea how global weather will affect these phase curves as very few planets have received repeated phase curve observations in the same band. Weather may cause the disk-integrated emission at each rotational phase to vary in time. Single phase curves cannot probe this, and force the community to assume the derived properties of the atmosphere do not change in time. In anticipation of JWST’s first science observations, the veracity of this assumption is more important than ever. In this talk, I will present three Spitzer/IRAC 4.5-micron phase curves of the hot Jupiter WASP-43b. These represent the first set of repeated mid-infrared phase curves of a hot Jupiter, including a reanalysis of a 2014 observation and two new observations from 2019. Our observations place an upper limit on variation in WASP-43b’s phase curve over time. By comparing our observations to general circulation models, we have constrained the degree to which the cloud thickness in WASP-43b’s atmosphere may be changing in time given this lack of observed variability. I will discuss what these results mean for the interpretation of other past, single Spitzer phase curves, and how these results pave the way for how JWST observations are planned and ensure the results of JWST observations are correctly understood.