Mario Spera

Formation and evolution of merging compact-object binaries: 
the curious case of GW190814 and GW190521

The evolution and mass spectrum of compact objects are both very uncertain. 
The LIGO-Virgo interferometers have already detected the inspiral and merger of 
tens of stellar black holes and of a few neutron stars, but detailed 
theorietical models of the formation and evolution of merging compact-object 
binaries are still missing. State-of-the-art models for the evolution of massive 
stars predict the existence of a gap in the black-hole mass function between ~60 
and ~120 solar masses, as a consequence of pulsational and pair-instability 
supernovae. Furthermore, most population-synthesis studies show that mergers 
with very asymmetric masses are remarkably rare. In this talk, I will present 
the compact-object mass spectrum and the statistics of merging binary black 
holes obtained with the SEVN code, our new population-synthesis tool. I also 
present a new evolutionary channel to populate the black-hole mass gap and I 
show the role of stellar dynamics for the formation of mergers with more 
asymmetric masses. Finally, I discuss the implications of our results in the 
framework of LIGO-Virgo detections with main focus on GW190814 (the event with 
the most asymmetric masses) and GW190521 (the event with the heaviest black 
holes, likely in the mass gap).