Cosmic Ray Ion and Electron Production at Relativistic Shocks in Gamma-Ray Bursts

William Marsh Rice University, Houston TX

Investigators

Abstract

Gamma-Ray Bursts (GRBs) are fascinating and enigmatic objects in the Universe. Ultra-High Energy Cosmic Rays (UHECR) have similarly caught the attention of physicists and astrophysicists, leading to, among other ideas, postulates of exotic origin based on predictions from particle physics. To make clearer a possible connection between UHECRs and GRBs, one needs to refine our understanding of how the cosmic ray spectrum couples to burst gamma-ray emission. Forging a more robust model of this connection is a principal goal of this proposal. The mandate to do so has been enhanced by the recent confirmation of the existence of the Greisen-Zatsepin-Kuzmin (GZK) cutoff in the UHECR spectrum at around 6 °? 1019 eV by the Pierre Auger experiment. This project will address how does the relativistic nature of the shocked outflow in bursts influence the prompt emission spectra that was detected in the gamma-ray band. A second question that will be addressed is what is the relative efficiency of accelerating electrons and ions in relativistic shocks thought to be present in GRBs, and how can photon data from these sources be used to probe this efficiency ratio,. Two other questions that will be investigated are whether GRB shocks efficiently generate ion populations up to the extremely high UHECR energies, and what are the anticipated neutrino fluxes from GRBs as potential signals for the IceCube experiment? The broader impacts are that the results will be adapted for display on publicly maintained Web sites. A graduate student will be engaged as an integral part of the work and this student will be involved in teaching at least two lectures per year on gamma-ray bursts in appropriate ndergraduate Rice courses. A long term goal of the PI is to develop a summer course at Rice offered to senior undergraduates including the topic of gamma-ray bursts. The PI plans to present aspects of this work, and highlights of the exciting field of gamma-ray bursts, to the general public and Houston area schools,continuing an established relationship with the Houston area astronomy societies and K-12 programs