Hot Jupiter diversity and the onset of TiO/VO revealed by a large grid of non-grey global circulation models

Abstract

ABSTRACT The population of hot Jupiters is extremely diverse, with large variations in their irradiation, period, gravity, and chemical composition. To understand the intrinsic planet diversity through the observed population level trends, we explore the a priori scatter in the population created by the different responses of atmospheric circulation to planetary parameters. We use the SPARC/MITgcm three-dimensional global circulation model to simulate 345 planets spanning a wide range of instellation, metallicity, gravity, and rotation periods typical for hot Jupiters, while differentiating between models with and without titanium oxide (TiO)/vanadium oxide (VO) in their atmosphere. We show that the combined effect of the planetary parameters leads to a large diversity in the ability of atmospheres to transport heat from day-side to night-side at a given equilibrium temperature. We further show that the hotspot offset is a non-monotonic function of planetary rotation period and explain our findings by a competition between the rotational and divergent parts of the circulation. As a consequence, hotspot offset and phase curve amplitude are not necessarily correlated. Finally, we compare the observables from our grid to the population of Spitzer and Hubble observations of hot Jupiters. We find that the sudden jump in brightness temperature observed in the Spitzer secondary eclipse measurements can be naturally explained by the cold-trapping of TiO/VO at approximately 1800 K. Spectra, phase curves and thermal structures from the model grid used in this study are available to the community, for more details see the data availability section.