Abstract

Contributed Talk - Splinter StarClusters

Tuesday, 08 September 2026, 14:15   (MW-2050)

Quantifying collision-driven mass loss in supermassive star formation

Paulo Solar
Univ. of Hamburg

Observations of high-redshift galaxies with JWST have renewed interest in scenarios where supermassive stars form via runaway stellar collisions in dense clusters; however, the impact of collision-driven mass loss on their growth remains uncertain. We explore this effect through a post-processing analysis of 3D hydrodynamical simulations of the formation of a supermassive star, applying an analytic mass-loss prescription to stellar collisions while exploring different assumptions for the internal stellar structure. We consider a polytropic main-sequence model, a semi-analytic accreting protostar model, and structures derived from stellar evolution calculations. We find that the cumulative mass-loss fraction depends sensitively on the adopted stellar structure, ranging from #10-25% for more compact configurations up to # 25-40% for more extended protostellar models. The importance of mass loss further depends on the dynamical state of the system including the ratio of stellar velocity dispersion to the stellar surface escape velocity. We find significant uncertainty depending on the prescription used. As a result, collision-driven mass loss could significantly limit the growth of the central object, at least in some cases. Overall, our results indicate that uncertainties in the internal structure of rapidly accreting protostars represent a major source of systematic uncertainty and must be better constrained to robustly assess the viability of runaway-collision pathways for forming massive black hole seeds.