Physics & Astronomy ETDs


Robert Mesler

Publication Date



Long-Duration Gamma-Ray Bursts (GRBs) are the most powerful explosions in the universe, yet relatively little is known about the progenitor that produces them despite more than forty years of study by the astronomical community. The current model of the progenitor is the collapse of a massive star and the ejection of a relativistic jet into a pure stellar wind. In this dissertation, a semi-analytic model is produced to describe the evolution of the GRB jet and the resultant afterglow for an alternative class of binary merger stellar progenitors. It is shown that, in the case of GRB 030329, a single-component, relativistic jet propagating into a pure stellar wind does not best explain the burst afterglow. Stellar merger progenitors are invoked as a possible alternative to the collapse of a single star, and are shown to produce circumburst density profiles that are profoundly more complex than the generally accepted stellar wind. Moreover, the interaction of the jet with these complex density profiles is shown to produce discernible features in the afterglow light curve which may, in principle, be used to constrain the nature of the burst progenitor.

Degree Name


Level of Degree


Department Name

Physics & Astronomy

First Committee Member (Chair)

Pihlstrom, Ylva

Second Committee Member

Taylor, Greg

Third Committee Member

Rand, Richard

Fourth Committee Member

Gilmore, Mark




gamma ray burst, MHD, GRB, stellar evolution, hydrodynamics

Document Type