Light element variations in globular clusters via nucleosynthesis in black hole accretion discs

TL;DR

This paper proposes a novel scenario where light element variations in globular clusters originate from nucleosynthesis in black hole accretion disks, explaining observed chemical anti-correlations.

Contribution

It introduces a new model linking black hole accretion processes to multiple stellar populations in globular clusters, addressing previous observational challenges.

Findings

Black hole accretion can produce observed light element anti-correlations.

Each black hole processes about 300 solar masses of material within a few million years.

The accretion rates are comparable to known X-ray binary systems.

Abstract

Ancient globular clusters contain multiple stellar populations identified by variations in light elements (e.g., C, N, O, Na). Although many scenarios have been suggested to explain this phenomenon, all are faced with challenges when compared with all the observational evidence. In this Letter, we propose a new scenario in which light element variations originate from nucleosynthesis in accretion discs around black holes. Since the black holes form after a few $Myrs$, the cluster is expected to still be embedded in a gas rich environment. Through a simplified accretion model, we show that the correct light element anti-correlations can be produced. Assuming a Kroupa stellar initial mass function (IMF), each black hole would only have to process ${\approx}300M_{\odot}$ of material in order to explain multiple populations; over a period of $3Myr$ this corresponds to $ \sim10^{-4} M_{\odot}yr^{-1}$ (similar to the estimated accretion rate for the X-ray binary SS 433).