The Core Collapse of a 16.5 M☉ Star

We investigate the 1D stellar evolution of a 16.5M zero-age main-sequence star having di erent initial rotations. Starting from the pre-main-sequence, the models evolve up to the onset of the core collapse stage. The collapse of such a massive star can result in several kinds of energetic transients, such as Gamma-Ray Bursts (GRBs), Supernovae, etc. Using the simulation parameters, we calculate their free-fall timescales when the models reach the stage of the onset of core collapse. Estimating the free-fall timescale is crucial for understanding the duration for which the central engine can be fueled, allowing us to compare the free-fall timescale with the T90 duration of GRBs. Our results indicate that, given the constraints of the parameters and initial conditions in our models, rapidly rotating massive stars might serve as potential progenitors of Ultra-Long GRBs (T90 >> 500 s). In contrast, the non-rotating or slowly rotating models are more prone to explode as hydrogen-rich Type IIP-like core-collapse supernovae.