What is the effect of stellar rotation on the resulting black hole mass and spin?*

The gravitational wave signature of a binary black hole (BBH) merger is dependent on its component mass and spin. If such black holes originate from rapidly rotating progenitors, the large angular momentum reserve in the star could drive a collapsar-like supernova explosion, hence substantially impacting these characteristics of the black holes in the binary. To examine the effect of stellar rotation on the resulting black hole mass and spin, we conduct a 1D general relativistic study of the end phase of the collapse. In this talk, I will show that the resulting black hole mass and spin at times can differ significantly from the previously assumed values. Depending on the hydrodynamics of the accretion flow, I will provide analytical relations for calculating the mass and spin of the black hole based on the progenitor's pre-collapse properties. These findings have implications for the black hole upper mass gap resulting from pair-instability supernovae, the maximum mass of a maximally rotating stellar black hole, and the maximum effective spin of a BBH formed in tidally locked helium star - black hole binary.