What question did this study set out to answer?

This research investigates whether very massive star core-collapse events are the source of LFBOTs.

January 18, 2026

Luminous fast blue optical transients as very massive star core-collapse events

Key Points

This research investigates whether very massive star core-collapse events are the source of LFBOTs.
Examined binary population synthesis models for massive black hole formation rates.
Compared progenitor metallicities with observed values from LFBOT host galaxies.
Analyzed mass-loss rates and fallback masses of progenitor stars within LFBOT contexts.
Formation rate of black holes above ~30–40 solar masses parallels the observed LFBOT rate.
Identified progenitors exhibit low metallicity and H- and He-poors with dense environments.
Some host galaxies have higher metallicities than predicted, linked to later mass loss.

Abstract

Luminous fast blue optical transients (LFBOTs) are rare extragalactic events of unknown origin. Tidal disruption events (TDEs) involving white dwarfs by intermediate mass black holes (BHs), mergers of BHs and Wolf-Rayet (WR) stars, and failed supernovae (SNe) are among the proposed explanations. In this paper, we explore the viability of very massive star core-collapse (CC) events as the origin of LFBOTs. The appeal of such a model is that the formation of massive BHs via CC events could yield observational signatures that can match the disparate lines of evidence that point towards both CC and TDE origins for LFBOTs. We explored the formation rate of massive BHs in binary population synthesis models and compared the metallicities of their progenitors with the observed metallicities of LFBOT host galaxies. We further examined the composition, mass-loss rates, and fallback masses of these stars, placing them in the context of LFBOT observations. We determined the formation rate of BHs with masses greater than ∼30--40, M_⊙ to be similar to the observed LFBOT rate. The stars producing these BHs are biased towards a low metallicity (Z<0. 3, Z_⊙) and they are H- and He-poor, with dense circumstellar media. However, some LFBOTs have host galaxies with higher metallicities than predicted and they typically have denser local environments (plausibly due to late stage mass loss not captured in the models). We find that long-lived emission from an accretion disc (as implicated in the prototypical LFBOT AT, 2018cow) can only be produced in these events under maximal disc mass and angular momentum conditions. We conclude that a (very) massive star CC scenario is a plausible explanation for at least some LFBOTs, but it still faces challenges. The preferred progenitors for LFBOTs in the failed SN interpretation overlap with those predicted to produce super-kilonovae (super-KNe). We therefore suggest that LFBOTs are promising targets in the search for super-KNe and that they could offer a non-negligible contribution to the r-process enrichment of galaxies.

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