2023ApJ...955...39C

Stars with masses of 80-130 M_⊙ can encounter pulsational pair-instability at the end of their lives, which triggers consecutive episodes of explosive burning that eject multiple massive shells. Collisions between these shells produce bright transients known as pulsational pair-instability supernovae (PPI SNe) that may explain some extreme supernovae. In this paper, we present the first 2D and 3D radiation hydrodynamics simulations of PPI SNe with the CASTRO code. Radiative cooling causes the collided shells to evolve into thin, dense structures with hot spots that can enhance the peak luminosity of the SN by factors of 2-3. The light curve peaks at 1.9-2.1 × 10⁴³ erg s^–1 for 50 days and then plateaus at 2-3 × 10⁴² erg s^–1 for 200 days, depending on the viewing angle. The presence of ¹²C and ¹⁶O and the absence of ²⁸Si and ⁵⁶Fe in its spectra can uniquely identify this transient as a PPI SN in follow-up observations. Our models suggest that multidimensional radiation hydrodynamics is required to model the evolution and light curves of all shell-collision SNe, such as Type IIne, not just PPI SNe.