THE ATMOSPHERIC CIRCULATION OF THE HOT JUPITER WASP-43b: COMPARING THREE-DIMENSIONAL MODELS TO SPECTROPHOTOMETRIC DATA

Abstract

The hot Jupiter WASP-43b (2 M J , 1 R J , T orb = 19.5 hr) has now joined the ranks of transiting hot Jupiters HD 189733b and HD 209458b as an exoplanet with a large array of observational constraints. Because WASP-43b receives a similar stellar flux as HD 209458b but has a rotation rate four times faster and a higher gravity, studying WASP-43b probes the effect of rotation rate and gravity on the circulation when stellar irradiation is held approximately constant. Here we present three-dimensional (3D) atmospheric circulation models of WASP-43b, exploring the effects of composition, metallicity, and frictional drag. We find that the circulation regime of WASP-43b is not unlike other hot Jupiters, with equatorial superrotation that yields an eastward-shifted hotspot and large day-night temperature variations (∼600 K at photospheric pressures). We then compare our model results to HST/WFC3 spectrophotometric phase curve measurements of WASP-43b from 1.12-1.65 microns. Our results show the 5× solar model lightcurve provides a good match to the data, with a peak flux phase offset and planet/star flux ratio that is similar to observations; however, the model nightside appears to be brighter. Nevertheless, our 5× solar model provides an excellent match to the WFC3 dayside emission spectrum. This is a major success, as the result is a natural outcome of the 3D dynamics with no model tuning. These results demonstrate that 3D circulation models can help interpret exoplanet atmospheric observations, even at high resolution, and highlight the potential for future observations with HST, JWST and other next-generation telescopes.

Variability in the super-Earth 55 Cnc e

“…Local changes in the chemical composition or temperature profiles of the observable atmosphere are unlikely to contribute such large and variable opacity on the time-scales of our observations which, nevertheless, need to be confirmed by hydrodynamical simulations of the super-Earth atmosphere (e.g. Zalucha et al 2013;Carone et al 2014;Kataria et al 2015).…”

A Comparison of Simulated JWST Observations Derived from Equilibrium and Non-equilibrium Chemistry Models of Giant Exoplanets

“…As for oxygen, its elemental abundance is harder to constrain as water is so much out of equilibrium on Jupiter (and the probe fell into a hot presumably dry spot and did not finish it's measurements). For exoplanet analysis, it has been a popular assumption to use solar metallicity Fortney et al 2006;Fortney 2007;Fortney et al 2008;Venot et al 2012;Moses et al 2011;Koskinen et al 2013;Zahnle & Marley 2014;Wakeford & Sing 2015;Heng 2016;Kataria et al 2016;Barstow et al 2017;Gao et al 2017), or a linear scaling of solar metallicity (Freedman et al 2014;Kataria et al 2015;Charnay et al 2015;Wakeford et al 2017), and hence why we chose to model it as one of our metallicity cases. The bulk composition of a planet's atmosphere plays a major role in the chemistry at work in the planet's atmosphere.…”

Transitions in the Cloud Composition of Hot Jupiters

“…As shown in Kataria et al (2015), a metal enrichment of 5 timessolar should increase the temperature on the dayside by ≈100 K compared to a solarcomposition. This should translate to a shift in the offset and albedo versus equilibrium temperature curves of Figure 6 toward cooler equilibrium temperatures by ≈100 K.…”

“…We discretize the equations on the cubed-sphere grid,as described in Adcroft et al (2004),and use a horizontal fourth-order Shapiro filter in order to smooth horizontal noise (Shapiro 1970). This model has been successfully used to model hot Jupiteratmospheres over the past decade(e.g., Showman et al 2009Showman et al , 2013Showman et al , 2015Lewis et al 2010Lewis et al , 2014Kataria et al 2013Kataria et al , 2015Parmentier et al 2013).…”