Core Hydrogen Burning Red Supergiants in the Young Globular Clusters

The first stellar generation in galactic globular clusters contained massive low metallicity stars. We modelled the evolution of this massive stellar population and found that such stars with masses 100-600 M_sun evolve into red supergiants. These red supergiants are particularly interesting because they spend not only the helium burning phase but even the last few hundres tousands of years of the core hydrogen burning phase on the RSG branch. Due to the presence of hot massive stars at the same time, we show that the RSG wind is trapped into photoionization confined shells. We simulate the shell formation around such red supergiants and find them to become gravitationally unstable. We propose a scenario in which these shells are responsible for the formation of the second generation low mass stars in globular clusters with anomalous surface abundances.