Stellar Evolution in AGN Disks
  Active Galactic Nuclei are powered by geometrically-thin accretion disks
surrounding a central supermassive black hole. Here we explore the evolution of
stars embedded in these extreme astrophysical environments (AGN stars). Because
AGN disks are much hotter and denser than the interstellar medium, AGN stars
are subject to very different boundary conditions than normal stars. They are
also strongly affected by both mass accretion, which can runaway given the vast
mass of the disk, and mass loss due to super-Eddington winds. Moreover,
chemical mixing plays a critical role in the evolution of these stars by
allowing fresh hydrogen accreted from the disk to mix into their cores. We find
that, depending on the local AGN density and sound speed and the duration of
the AGN phase, AGN stars can rapidly become very massive (M > 100 M$_\odot$).
These stars undergo core-collapse, leave behind compact remnants and contribute
to polluting the disk with heavy elements. We show that the evolution of AGN
stars can have a profound impact on the evolution of AGN metallicities, as well
as the production of gravitational waves sources observed by LIGO-Virgo. We
point to our galactic center as a region well-suited to test some of our
predictions of this exotic stellar evolutionary channel.
