A Backscattering-dominated Prompt Emission Model for the Prompt Phase of Gamma-Ray Bursts

Abstract As a gamma-ray burst (GRB) jet drills its way through the collapsing star, it traps baryonic “cork” ahead of it. Here we explore prompt emission model for GRBs in which does not cross cork, but rather photons that are emitted deep flow largely by pair annihilation scattered inside expanding cork and escape from back end as they push behind. Due to relativistic motion these easily seen an observer close axis peaking at ? peak ? few ×100 keV. We show this naturally explains several key observational features: (1) high-energy power-law index ? 1 ? 2 5 with intermediate thermal spectral region; (2) decay light curve t ?2 ; (3) delay soft photons; (4) energy–isotropic energy (the so-called “Amati”) correlation, ? peak ? iso m , m 0.45, resulting different viewing angles (at low luminosities, our predicts observable turnoff Amati relation); (5) anticorrelation between FWHM time ?1 (6) temporal evolution (7) distribution energies observed GRB population. The is applicable single-pulse curves their respective spectra. discuss consequences view current future observations.