Gamma-Ray Bursts: Physical Mechanisms

A burst typically includes a prompt gamma-ray phase followed by afterglows at X-ray, optical, radio, and other wavelengths. Relativistic jets collimate much of the energy, so observed brightness depends strongly on viewing angle.

A newly formed compact object and accretion flow can launch an ultra-relativistic jet. Internal dissipation produces prompt gamma rays, while the jet's collision with surrounding material drives an external shock responsible for much of the afterglow.

Fermi and other satellites localize bursts; redshifts place them at cosmological distances; long bursts coincide with broad-lined Type Ic supernovae; GW170817 linked a short gamma-ray burst with a neutron-star merger.

An ultra-relativistic jet dissipates energy internally or magnetically during the prompt phase, then drives an external shock into surrounding material, producing a fading afterglow. Jet physics adds an important mechanism distinction. Internal magnetic dissipation or shocks can create prompt gamma rays, while the later afterglow usually comes from an external blast wave sweeping up ambient matter. Treating prompt and afterglow emission as one zone fails to reproduce their different timing and spectra.