The core collapse of a 16.5 M$_{\odot}$ star

TL;DR

This study models the evolution of a 16.5 solar mass star with varying initial rotations to understand its core collapse, linking stellar rotation to potential outcomes like gamma-ray bursts or supernovae.

Contribution

It provides new insights into how initial stellar rotation influences the core collapse process and the resulting transient phenomena, including potential progenitors of ultra-long GRBs.

Findings

Rapidly rotating stars may produce ultra-long GRBs.

Non-rotating stars are more likely to result in hydrogen-rich supernovae.

Free-fall timescales help distinguish between different explosive outcomes.

Abstract

We investigate the 1D stellar evolution of a 16.5 M$_{\odot}$ zero-age main-sequence star having different 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 T$_{\rm 90}$ 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 (T$_{\rm 90}$ $>>$ 500 sec). In contrast, the non-rotating or slowly rotating models are more prone to explode as hydrogen-rich Type IIP-like core-collapse supernovae.