Improved Large-Scale 3D Smoothed Particle Hydrodynamics Simulations of Eta Carinae's Colliding Stellar Winds

We present results from a series of new full-3D Smoothed Particle Hydrodynamics (SPH) simulations of the colliding stellar winds in the massive binary Eta Carinae. The radius of the computational domain of these simulations is 3,875 AU, making them the largest hydrodynamic simulations to date of Eta Carinae's colliding stellar winds. Such large simulations are crucial for generating synthetic observables for direct comparison to detailed spectral mapping data obtained at multiple epochs with the Hubble Space Telescope/Space Telescope Imaging Spectrograph (HST/STIS). Famous for the largest non-terminal stellar explosion ever recorded, Eta Carinae is the most massive (~120 M_Sun) active binary within 10,000 light-years of Earth, containing a Luminous Blue Variable and either a Wolf-Rayet or an extreme O star in a highly eccentric (e ~ 0.9), 5.54-year orbit. Eta Carinae also drives the strongest colliding stellar wind shock in the solar neighborhood. Dramatic changes across multiple wavelengths are routinely observed as the stars move about in their highly elliptical orbits, however, several important stellar, wind, and orbital parameters remain uncertain despite decades of close observation. These new SPH simulations are being coupled to 3D time-dependent radiative-transfer simulations with the goal of producing synthetic data cubes for comparison to available and upcoming HST/STIS observations. Comparison of the models and observations will reveal key details about the binary's orbital motion, photoionization properties, and recent mass loss history, which are essential for understanding the late-stage evolution of this nearby supernova progenitor. Our methods can also be adapted to other colliding wind binaries (e.g. WR 140) that will be the subject of future observations with e.g. the James Webb Space Telescope.