Fast Optical Transients from Stellar-mass Black Hole Tidal Disruption Events in Young Star Clusters

Abstract

Observational evidence suggests that the majority of stars may have been born in stellar clusters or associations. Within these dense environments, dynamical interactions lead to high rates of close stellar encounters. A variety of recent observational and theoretical indications suggest stellar-mass black holes may be present and play an active dynamical role in stellar clusters of all masses. In this study, we explore the tidal disruption of main-sequence stars by stellar-mass black holes in young star clusters. We compute a suite of over 3000 independent N-body simulations that cover a range of cluster mass, metallicity, and half-mass radii. We find stellar-mass black hole tidal disruption events (TDEs) occur at an overall rate of up to roughly 200 Gpc⁻³ yr⁻¹ in young stellar clusters in the local universe. These TDEs are expected to have several characteristic features, namely, fast rise times of order a day, peak X-ray luminosities of at least 10⁴⁴ erg s⁻¹, and bright optical luminosities (roughly 10⁴¹–10⁴⁴ erg s⁻¹) associated with reprocessing by a disk wind. In particular, we show these events share many features in common with the emerging class of Fast Blue Optical Transients.