DIX Planetary Science Seminar

ExoCubed: A Riemann-Solver based Cubed-Sphere Dynamic Core for Planetary Atmospheres

The computational fluid dynamics on a sphere is relevant to global simulations of geophysical fluid dynamics. Using the conventional spherical-polar (or lat-lon) grid results in a singularity at the poles, with orders of magnitude smaller cell sizes at the poles in comparison to the equator. To address this problem, we developed a general circulation model (dynamic core) with a gnomonic equiangular cubed-sphere configuration. This model is developed based on the Simulating Nonhydrostatic Atmospheres on Planets (SNAP) model, using a finite volume numerical scheme with a Riemann-solver-based dynamic core and the vertical implicit correction (VIC) scheme. This change of the horizontal configuration gives a 20-time acceleration of global simulations compared to the lat-lon grid with a similar number of cells at medium resolution. Standard tests are conducted, ranging from 2D shallow-water models to 3D general circulation tests, including earth-like planets and shallow hot Jupiters, to validate the accuracy of the model. This model is then specifically designed to handle the regime of planetary atmospheres, and the method used is generic to transform any existing finite-volume hydrodynamic model in the Cartesian geometry to the spherical geometry.

Probing the Origins of the Young Triple System ROXs 42 B with Atmospheric Retrievals and Orbital Fits

ROXs 42 B is a young hierarchical triple system located in the Rho-Ophiuchus star forming region, with a planetary-mass companion ROXs 42 B b (~10 MJ) at 180 au orbiting a close M-dwarf binary (~10 au separation). The ROXs 42 B system offers a unique test bed for formation theories of planetary-mass companions at wide separations as one of the youngest of these systems known and one of the few with a binary host. We present atmospheric retrievals on the companion using the retrieval code petitRADTRANS on both medium-resolution JHK-band spectra from Keck/OSIRIS and Gemini/NIFS, as well as a high resolution K-band spectrum from pre-upgrade Keck/NIRSPAO. We also characterize the binary host stars by providing a new orbital fit from ~15 years of monitoring, as well as fitting for both the chemical composition and other physical properties of the two stars using the SPHINX model grid. Our combined constraints on the composition and orbital properties of both the companion and the binary host stars provide new insights into the formation history of this system.