The Value of Progenitor Radius Measurements for Explosion Modeling of Type II-Plateau Supernovae

Using Modules for Experiments in Stellar Astrophysics (MESA)+STELLA, we show that very different physical models can adequately reproduce a specific observed Type II-Plateau supernova (SN). We consider SN2004A, SN2004et, SN2009ib, SN2017eaw, and SN2017gmr, nickel-rich (M-Ni > 0.03 M-circle dot) events with bolometric lightcurves and a well-sampled decline from the plateau. These events also have constraints on the progenitor radius, via a progenitor image, or, in the case of SN2017gmr, a radius from fitting shock-cooling models. In general, many explosions spanning the parameter space of progenitors can yield excellent lightcurve and Fe-line velocity agreement, demonstrating the success of scaling laws in motivating models that match plateau properties for a given radius and highlighting the degeneracy between plateau luminosity and velocity in models and observed events, which can span over 50% in ejecta mass, radius, and explosion energy. This can help explain disagreements in explosion properties reported for the same event using different model calculations. Our calculations yield explosion properties when combined with pre-explosion progenitor radius measurements or a robust understanding of the outermost < 0.1 M-circle dot of material that quantifies the progenitor radius from SN observations a few days after explosion.