Speaker
Description
Traditionally, the lower edge of the Pair Instability (PI) mass gap was firmly established to occur at masses of 50 M$\odot$. This assumption has been questioned with recent Gravitational Wave (GW) observations, which has shown that there are black holes (BHs) present above the 50 M$\odot$ limit, prompting questions on how this occurs. We present stellar evolution models for massive single stars which retain a large Hydrogen envelope at low (10-3 - ZSMC) metallicity and can remain dynamically stable without PI. Using these models, we produce fits for the core mass and final mass, and find that the maximum BH mass before PI is ~ 90 M$\odot$. Additionally, we independently calculate critical core mass values using the $\Gamma$1 criterion. Finally, we use the aforementioned fits to produce a small population synthesis and show that we should expect to see many more BHs towards the lower edge of the traditional PI gap due in part to the Initial Mass Function (IMF), but also the same stellar interior physics which sets the maximum.
