Physics Colloquium - Christy Lecture

Neutron Star Mergers, Kilonovae, and Kilonova Impostors

During the collision and aftermath of a neutron star (NS) merger, some neutron-rich matter can be flung out into space and form the heaviest elements. Other material may drain into the merged remnant (often a black hole), powering relativistic jets. The gravitational-wave source GW170817 confirmed this picture: the detection of a coincident gamma-ray burst (GRB) indicated a jet, while a longer-lasting optical/infrared glow revealed non-relativistic outflows composed of radioactive isotopes—a kilonova. These observations provided the first direct evidence of heavy-element production through rapid neutron capture. Since then, no additional NS mergers with both gravitational-wave and electromagnetic counterparts have been identified. But intriguing—if puzzling—results have emerged in GRB follow-up: a handful of bursts show a fading, reddish glow reminiscent of a kilonova. The durations of these GRBs are longer than expected for NS mergers, and the spectral properties of the putative kilonovae are not explained by existing models. I will review the physics involved and discuss whether these events reflect genuine kilonova behavior or instead are kilonova impostors from phenomena such as disrupted white dwarfs, and what modeling may tell us about their contribution to the heavy elements.

Join via Zoom:
https://caltech.zoom.us/j/84497014003
Meeting ID: 844 9701 4003

The colloquium is held in Feynman Lecture Hall, 201 E. Bridge.