Mass and Spin Growth of Very Massive Stars in Star Clusters Potentially Associated with Little Red Dots
Abstract
Using gravitational N-body simulations, we investigate the evolution of mass and spin for very massive stars (VMSs) in dense star clusters, which could subsequently evolve into Little Red Dots (LRDs). Our results show that VMS masses can reach 103--104 M⊙, depending on the initial conditions of the host clusters. Notably, the VMS mass increases by up to a factor of three when accounting for the bloated state at the Hayashi track induced by stellar collisions, provided that this state is maintained at accretion rates exceeding 3 × 10−2 M⊙ yr−1. In all cases, the spin of the VMS, when normalized to the dimensionless black hole (BH) spin parameter, exceeds $10$, although the mass and spin of VMSs after the post-main sequence phase could be decreased by the stellar evolution process. We nonetheless demonstrate that VMSs formed in dense star clusters can be highly spinning. Such a rapidly spinning VMS is expected to collapse into an intermediate-mass BH surrounded by a massive accretion disk. This BH-disk system could trigger powerful explosions and emit burst gravitational waves, similar to those observed in GW190521 and GW231123, for which the remnant BH masses are estimated to be ≳ 100 M⊙.
Versions
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BibTeX
@misc{tanikawa2026mass,
title = {{Mass and Spin Growth of Very Massive Stars in Star Clusters Potentially Associated with Little Red Dots}},
author = {Ataru Tanikawa and Masaru Shibata and Kunihito Ioka},
howpublished = {arXiv},
year = {2026},
month = aug,
doi = {10.48550/arxiv.2606.01870},
eprint = {2606.01870},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2606.01870},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Mass and Spin Growth of Very Massive Stars in Star Clusters Potentially Associated with Little Red Dots
AU - Ataru Tanikawa
AU - Masaru Shibata
AU - Kunihito Ioka
PY - 2026
DA - 2026/08/08
PB - arXiv
DO - 10.48550/arxiv.2606.01870
UR - https://arxiv.org/abs/2606.01870
AB - Using gravitational N-body simulations, we investigate the evolution of mass and spin for very massive stars (VMSs) in dense star clusters, which could subsequently evolve into Little Red Dots (LRDs). Our results show that VMS masses can reach 10^3--10^4 M_⊙, depending on the initial conditions of the host clusters. Notably, the VMS mass increases by up to a factor of three when accounting for the bloated state at the Hayashi track induced by stellar collisions, provided that this state is maintained at accretion rates exceeding 3 × 10^−2 M_⊙ yr^−1. In all cases, the spin of the VMS, when normalized to the dimensionless black hole (BH) spin parameter, exceeds $10$, although the mass and spin of VMSs after the post-main sequence phase could be decreased by the stellar evolution process. We nonetheless demonstrate that VMSs formed in dense star clusters can be highly spinning. Such a rapidly spinning VMS is expected to collapse into an intermediate-mass BH surrounded by a massive accretion disk. This BH-disk system could trigger powerful explosions and emit burst gravitational waves, similar to those observed in GW190521 and GW231123, for which the remnant BH masses are estimated to be ≳ 100 M_⊙.
ER -