The Upper Luminosity Limit of Massive Stars

Observations suggest that there is a maximum luminosity (Lmax) that massive stars can have during the Red Supergiant (RSG) phase of their evolution. The commonly accepted explanation for this phenomenon is that stellar winds, which scale with mass, strip the star of its H-rich envelope if the star has a mass above some threshold, which in turn prohibits the formation of a RSG. However, neither observations nor theory have been rigorously tested. In this project, the student will firstly provide the most comprehensive measurement of Lmax to date by studying the stellar populations in various nearby galaxies. Secondly, they will perform detailed population synthesis, using both existing and new stellar evolution calculations, to provide a robust comparison of observations to theoretical predictions.