UC Santa Barbara

Observations of the transient, explosive deaths of massive stars are well-poised to provide insight into stellar physics when combined with theoretical understanding. From spherically symmetric stellar evolution models, we confirm and sharpen early analytic calculations for the Supernova (SN) plateau luminosity and duration as a function of the red supergiant (RSG) progenitor properties. When the RSG radius at the time of the explosion is known, we show how the explosion energy and ejecta mass can be directly inferred; otherwise, we show that a family of explosions could produce the same plateau luminosity, duration, and photospheric velocity. We also explore the impact of large-scale radial stellar pulsations on these predictions. Then, motivated in part as an effort to understand the turbulent outer envelope responsible for early-time SN emission, we complete global 3D radiation-hydrodynamics (RHD) simulations of RSG envelopes with Athena++. These simulations reveal an extended density structure with large-scale convective plumes spanning large fractions of the stellar surface. These computations also provide insights to guide evolutionary modeling efforts, such as a physically-motivated calibration of the convective mixing length which helps determine the envelope density structure. Driving a strong shock through these 3D simulations, we then show novel results on how the inhomogeneous 3D convective structure leads to a longer-duration, fainter shock breakout (SBO) signal compared to predictions from semi-analytic and spherically-symmetric models.