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SUMMARY:Star cluster population of binary black hole mergers in the gravit
 ational wave data
DTSTART;VALUE=DATE-TIME:20260527T123000Z
DTEND;VALUE=DATE-TIME:20260527T140000Z
DTSTAMP;VALUE=DATE-TIME:20260516T230500Z
UID:indico-event-882@indico.gssi.it
DESCRIPTION:Speakers: Fabio Antonini (Cardiff University)\n\nI will show t
 hat gravitational-wave observations reveal a clear transition in the black
 -hole merger population at a primary mass of ~45 solar masses. Below this 
 mass\, the population is broadly consistent with low-spin\, first-generati
 on black holes formed through stellar collapse. Above it\, mergers show br
 oader and isotropic spin distributions\, consistent with hierarchical merg
 ers formed in dense star clusters. This transition is consistent with the 
 existence of a pair-instability mass gap caused by electron–positron pai
 r production in the cores of massive stars\, which suppresses the direct f
 ormation of black holes above this scale. These results point to a connect
 ion between gravitational wave astronomy and nuclear astrophysics and high
 light dense stellar clusters as key environments in the growth of black ho
 les. \n\nhttps://indico.gssi.it/event/882/
URL:https://indico.gssi.it/event/882/
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