Supergiants and their shells in young globular clusters

Dorottya Szécsi
University of Birmingham, UK


The first stellar generation in globular clusters may have contained low-metallicity massive stars. We modelled the evolution of such stars with masses 100-600 Msun and found that they evolve into cool supergiants. These supergiants are particular because they spend not only their helium-burning phase, but even the last 15% of their core-hydrogen-burning phase on the supergiant branch. Their wind therefore contains hot-hydrogen-burning products. Due to the presence of hot massive TWUIN stars in the cluster at the same time, the winds can be trapped in photoionization-confined shells. We simulate the shell formation and show that gravitational instabilities lead to star formation. We propose a scenario in which these shells form the second generation low-mass stars in globular clusters with anomalous surface abundances.
Related publication: http://adsabs.harvard.edu/abs/2017arXiv171104007S