Pulsations change the structures of massive stars before they explode: interpreting the nearby supernova SN 2023ixf

Massive red supergiants (RSGs) are known to become hydrodynamically unstable before they explode. Still, the vast majority of supernova (SN) models assume RSG progenitors in hydrostatic equilibrium. Here, we self-consistently follow the hydrodynamic evolution of RSGs with different masses and the development of radial envelope pulsations. Pulsations significantly alter the observable pre- and post-SN properties, and their importance increases substantially as a function of initial mass. We demonstrate that inferring core masses, let alone initial masses, from a single pre-SN luminosity and effective temperature of high-mass RSGs is inadvisable, as these can vary by an order of magnitude during the pulsation. We find that pulsations can naturally lead to ``early-excess" emission in SN light curves and to variations in early photospheric velocities, which can help break degeneracies in type-II SNe. We compare to SN~2023ixf, for which a pulsating RSG progenitor was discovered. We demonstrate that its pre- and post-SN characteristics agree very well with our exploding pulsating RSG model, whereas hydrostatic stellar models are not well-suited. The data coverage at early times is insufficient to break all degeneracies, but we find constraints on the explosion phase. We find no evidence for the claimed pulsation period of the SN~2024ggi progenitor, as it matches Spitzer's orbital period. This study underscores the importance of hydrodynamical pre-SN stellar models. It implies an important shift in our understanding of the last stages of massive star evolution, the interpretation of pre-SN properties, the connection between SNe and their progenitors, and the missing RSG problem.