Date of Award
Doctor of Philosophy (PhD)
Michael S. Briggs
Gamma ray bursts
Gamma-ray bursts (GRBs) are ultra-relativistic jets produced by either the core-collapse of massive, stripped envelope stars (i.e., "collapsars") or the merging of compact binary objects, such as neutron stars. GRBs are among the most energetic transients in the Universe, yet despite over 5 decades of study, a full description of their intrinsic energetics remains incomplete. This is primarily due to a combination of cosmological, relativistic, and observational effects that have impeded obtaining GRB redshift measurements and robustly associating GRBs with their progenitors. In this dissertation, I study source-frame properties of GRBs from collapsars and binary neutron star (BNS) mergers. In particular, I constrain the luminosity functions and rate distributions of GRBs by applying a forward-folding method to fit data taken by the Fermi Gamma-ray Burst Monitor (GBM). The data are found to be best-fit with a GRB population composed of ~45% originating from BNS mergers. The collapsar GRBs are fit to the cosmic star formation rate, normalized to a local rate of 3.9 (+9.9, -3.3; 90% confidence) Gpc-3 yr-1 and a broken power law luminosity function with indices αL = -1.5 (+1.1, -0.2) and βL=-2.0 (+0.5, -1.7) and a break at log10L = 52.8 (+1.9, -3.2) ergs s-1. The merger GRBs are described by a delayed star formation rate (P(td) ∝ td-1) with a local event rate of 3.2 (+27.0, -2.4) Gpc-3 yr-1 and a cut-off power law luminosity function with index αL = -0.5 (+0.4, -0.5) and a break at log10L = 51.6 (+0.7, -0.7) ergs s-1. I also search for short GRB progenitors associated with GWs detected in the LIGO/Virgo first and second observing runs (i.e., O1 and O2, respectively). Although no GW/GRB coincidences are found other than GW170817/GRB 170817A, the GBM detection algorithm is improved for weak short GRBs and the joint search statistic method.
Hamburg, Rachel, "Constraining intrinsic properties of gamma-ray bursts from core-collapse supernovae and neutron star mergers" (2022). Dissertations. 255.