Massive black holes from single and binary stars

The first direct detection of gravitational waves in 2015 ushered in a new era for studying compact objects. Upcoming detectors like the Einstein Telescope are expected to contribute thousands of binary coalescence events to the existing data pool. However, uncertainties in the nature of stellar remnants from core-collapse supernovae and binary stellar evolution hinder our theoretical understanding of compact objects binaries. In the first part of my work, we examined the properties of stellar remnants using a grid of rotating and non-rotating massive stars at various metallicities from Limongi and Chieffi, 2018. We simulated supernova explosions of evolved progenitors with the HYdrodynamic Ppm Explosion with Radiation diffusION code (Limongi and Chieffi, 2020), calibrated to match SN1987A’s properties. We found that the heaviest black holes are influenced by initial stellar rotation, metallicity, and the onset of pulsational pair-instability supernovae (PPISNe). Non-rotating progenitors athFe/H] = −3 can form black holes up to 87 M⊙, within the theorized pair-instability mass gap, while rotating progenitors are limited to 41.6 M⊙ due to increased wind mass loss. We provided fitting formulas for compact remnant masses based on progenitor properties, suitable for rapid population synthesis codes. In the second part of my work, I studied binary black hole mass distributions using the rapid population synthesis code Stellar Evolution for N-body (SEVN) (Spera and Mapelli, 2017; Spera et al., 2019; Iorio et al., 2023). We focused on reproducing the observed primary black hole mass distribution from gravitational wave data, particularly the peak at 35 M⊙. Initially attributed to PPISNe (Abbott et al., 2021; Abbott et al., 2023), this peak arises from stable mass transfer in specific binary systems. (Hendriks et al., 2023; Briel, Stevance, and Eldridge, 2023). Additionally, we explored the roles of common envelope ejection efficiency and PPISNe in accumulating black holes in this mass range while examining the influence of varying the initial mass function on the primary black hole mass distribution.