Gamma-Ray Bursts

TL;DR

Gamma-ray bursts are intense, short-lived cosmic events originating from relativistic jets caused by massive star collapse or binary mergers, with diverse emissions that help probe the universe's early history.

Contribution

This chapter provides a comprehensive overview of GRB observational facts, theoretical models of jet dynamics, and their applications in cosmology, integrating recent advances in understanding GRB phenomena.

Findings

GRBs originate from relativistic jets driven by stellar collapse or mergers.

The afterglow emission spans radio to gamma-ray wavelengths, revealing jet dynamics.

GRBs can be used to probe the early universe and constrain cosmological parameters.

Abstract

Gamma-ray bursts (GRB) are short and intense bursts of $\sim$100 keV$-$1MeV photons, usually followed by long-lasting decaying afterglow emission in a wide range of electromagnetic wavelengths from radio to X-ray and, sometimes, even to GeV gamma-rays. These emissions are believed to originate from a relativistic jet, which is driven due to the collapse of special massive stars and the mergers of compact binaries (i.e., double neutron stars or a neutron star and a black hole). This chapter first briefly introduces the basic observational facts of the GRB phenomena, including the prompt emission, afterglow emission, and host galaxies. Secondly, a general theoretical understanding of the GRB phenomena is described based on a relativistic jet's overall dynamical evolution, including the acceleration, propagation, internal dissipation, and deceleration phases. Here a long-lasting central engine of the GRBs can substantially influence the dynamical evolution of the jet. In addition, a supernova/kilonova emission can appear in the optical afterglow of some nearby GRBs, which can provide an important probe to the nature of the GRB progenitors. Finally, as luminous cosmological phenomena, it is expected to use GRBs to probe the early universe and to constrain the cosmological parameters.