ASD Colloquium Series
|Deciphering the origin of the heavy elements in the light and gravitational waves of a neutron star merger
Daniel Kasen, UC Berkeley and Lawrence Berkeley Laboratory
Abstract: The discovery of the gravitational wave source GW170817 and its associated electromagnetic (EM) counterpart provides a remarkable opportunity to dissect the physics of merging neutron stars and address long standing questions as to the origin of the heaviest elements. Theoretical modeling has suggested that matter ejected in the violent merger of neutron stars may assemble into heavy isotopes in a process of rapid neutron capture ("r-process") nucleosynthesis. The radioactive decay of these isotopes has been theorized to power a distinctive thermal EM glow (a "kilonova"). In addition, relativistic outflows may produce non-thermal emission from gamma-ray to radio wavelengths. I will review our theoretical understanding of mergers and compare the expected signals to the extraordinary data now obtained for GW170817 and its EM counterpart. Observations at optical through infrared wavelengths closely resemble theoretical predictions of a kilonova, and allow us to infer the production of two spatially distinct components of ejecta, one composed of light (atomic mass number A < 140) and one of heavy (A > 140) r-process material. Estimating a merger rate, the inferred mass ejected implies that mergers are a dominant mode of r-process production in the universe. This marks the emergence of a new field of astrophysics, whereby we can constrain the dynamics of neutron star mergers and analyze the signatures of heavy elements at their production site.
ASD Colloquia are Tuesdays at 3:45 pm (Meet the Speaker at 3:30 pm) in Bldg 34, Room W150 unless otherwise noted.
|Date||November 28, 2017|
|Start/End Time||03:30 PM - 05:00 PM|
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