Cosmic Extremes: Time-Domain Astrophysics in a Multi-Messenger World

The Department of Physics welcomes Kate Alexander (Northwestern University) to present during their virtual colloquium.

Dr. Kate D. Alexander is currently a NASA Einstein Postdoctoral Fellow at Northwestern University. She completed her undergraduate degree in physics at Brown University in 2012 and received her PhD in Astronomy & Astrophysics from Harvard University in 2018, where she was an NSF Graduate Research Fellow. Her research focuses on extreme events in the cosmos, including stellar explosions, neutron star mergers, and tidal disruptions of stars by supermassive black holes.

Abstract: Time-domain astrophysics provides a unique opportunity to study the most extreme physical processes in the Universe, including the deaths of massive stars, the creation and merger of compact objects like neutron stars and black holes, and the tidal disruption of stars by supermassive black holes. Dr. Alexander will discuss her recent and ongoing work to reveal the formation and structure of relativistic jets and outflows in the most extreme classes of astrophysical transients, including gamma-ray bursts (GRBs) and tidal disruption events (TDEs). In particular, she will show that radio observations of these transients can reveal the total energy contained in outflowing material, the magnetic field strength and geometry, and the density of the surrounding environment, which can provide clues to the progenitors of stellar explosions (GRBs) and probe models of black hole growth and accretion (TDEs). With the pioneering detections of gravitational waves, astronomers and physicists have gained a new, complementary tool to study compact object mergers and their associated GRBs, with implications for fields as wide-ranging as general relativity, nuclear physics, cosmology, and shock physics.