Stellar Evolution in the Disks of Active Galactic Nuclei Produces Rapidly Rotating Massive Stars

Stars can either be formed in or captured by the accretion disks in active galactic nuclei (AGNs). These AGN stars are irradiated and subject to extreme levels of accretion, which can turn even low-mass stars into very massive ones (M > 100M (circle dot)) whose evolution may result in the formation of massive compact objects (M > 10M (circle dot)). Here we explore the spins of these AGN stars and the remnants they leave behind. We find that AGN stars rapidly spin up via accretion, eventually reaching near-critical rotation rates. They further maintain near-critical rotation even as they shed their envelopes, become compact, and undergo late stages of burning. This makes them good candidates to produce high-spin massive black holes, such as the ones seen by LIGO-Virgo in GW 190521g, as well as long gamma-ray bursts and the associated chemical pollution of the AGN disk.

Automated summary

Stars in active galactic nuclei (AGN) can be formed or captured by accretion disks, experiencing extreme levels of accretion that can lead to their transformation into very massive stars. These AGN stars rapidly spin up due to accretion, maintaining near-critical rotation rates even as they evolve and shed their envelopes. They are considered potential sources of high-spin massive black holes and contribute to phenomena like long gamma-ray bursts and chemical pollution in AGN disks.