CCA Colloquium: Anastasios Fragkos

CCA Colloquium: Anastasios Fragkos

Title: Unravelling the astrophysical origin of gravitational-wave sources.

Abstract: The first detection of gravitational waves from coalescing binary black holes by LIGO allowed for the first time the direct observation of stellar-mass black holes, while the simultaneous gravitational wave and electromagnetic signal from the merger of two neutron stars provided the first direct evidence for the origin of short gamma-ray bursts.  Seven years later, we have now entered the era of gravitational-wave source population studies. These gravitational wave source populations, complemented by a half-a-century-long history of indirect observations of accreting compact objects in X-ray binaries, can give us now a more complete picture of the formation and evolution of binary stellar systems containing compact objects. At the same time, they also revealed weaknesses in the theories of stellar and binary evolution and compact object formation. In this talk, I will briefly review the current observed sample of gravitational-wave detections and their astrophysical implications and discuss the different formation pathways that have been proposed in the literature to explain the properties of the observed populations. I will then highlight results from recent studies that aim at exploring how different physical processes taking place during the evolution of binary stars, leave their signatures in the properties of gravitational-wave sources and compare these predictions with the currently observed sample of GW sources, as well as other potential electromagnetic counterparts or precursors. Finally, I will close with a discussion of the “next-generation” models of double compact object formation that we are currently working on and what we expect to learn from them.