Dept Colloquium: Drs. Jillian Rastinejad & Tyler Trent, UMD Astronomy

Exploring the Origins of r-Process Elements with GRBs

Speaker: Dr. Jillian Rastinejad, UMD Astronomy

Abstract: The landmark discovery of the first binary neutron star merger and its accompanying kilonova confirmed that these events are responsible for creating at least some of the Universe's r-process elements. Despite the treasure trove of data provided by this discovery, numerous unknowns remain about the origin of the Universe's heavy elements, including the median and span of kilonova yields and the existence of additional r-process production sites. In this talk, I will discuss our work expanding our view of the diversity of kilonovae and their heavy element yields using observations following gamma-ray bursts (GRBs). I will also highlight our efforts to probe a favored secondary r-process production: the supernovae associated with GRBs. 

Drift-Kinetic Particle Dynamics in Black Hole Accretion Flows

Speaker: Dr. Tyler Trent, UMD Astronomy

Abstract: Astrophysical plasmas in relativistic spacetimes, such as black hole accretion flows, are often weakly collisional and require kinetic modeling to capture non-local transport and particle acceleration. However, the extreme scale separation between microscopic and macroscopic processes limits the feasibility of fully kinetic simulations. I present a covariant guiding center formalism which I recently derived to address this challenge in curved spacetimes. I then present a new hybrid numerical algorithm based on this formalism, which evolves the trajectories of charged particles over macroscopic timescales in GRMHD backgrounds. To address numerical instabilities in the equations of motion, I develop a semi-implicit integrator that ensures stable evolution in strong-field environments. I apply my method to GRMHD simulations of black hole accretion flows, demonstrating its accuracy and efficiency across a range of physical conditions.

Host: Dr. Andy Harris