Chris Belczynski (Copernicus Center,Poland)
"Formation of BH-BH mergers as informed by LIGO/Virgo/KAGRA detections of high-frequency gravitational waves"

LIGO/Virgo Collaboration has published ~100 detections from the first three observational campaigns (O1/O2/O3). The most interesting detections are putting a new perspective on black hole and neutron star formation.
I will discuss the landscape of O1/O2/O3 detections and their implications for stellar evolutionary modeling. Broadly speaking the basic observational properties of detected double black hole mergers are consistent with predictions of the classical isolated binary evolution of massive stars.
However, these detections severely constrain stellar physics that is unaccessible by electromagnetic observations. 
On the other hand, the results from O3 campaign seem to challenge classical binary evolution with black holes found in the lower and upper mass gaps. These are regions in which black holes are not expected to form from stars, but rather form via dynamic interactions of stars in dense clusters. I will discuss these curious events in context of their most likely formation sites.