Varying Faces of Photospheric Emission in Gamma-Ray Bursts

TL;DR

This paper studies the photospheric emission in gamma-ray bursts, analyzing spectral features to understand the underlying dissipation mechanisms and jet properties, based on observations from the Fermi telescope.

Contribution

It provides a comprehensive analysis of photospheric emission features and interprets them through models of dissipation, geometry, and multi-zone emission in GRB jets.

Findings

Many GRBs show narrow, hard spectra indicating optically thick photospheric emission.

Spectral features vary, with some matching pure Planck functions and others showing multi-component spectra.

Insights into dissipation mechanisms and jet properties are derived from spectral analysis.

Abstract

Among the more than 1000 gamma-ray bursts observed by the Fermi Gamma-ray Space Telescope, a large fraction show narrow and hard spectra inconsistent with non-thermal emission, signifying optically thick emission from the photosphere. However, only a few of these bursts have spectra consistent with a pure Planck function. We will discuss the observational features of photospheric emission in these GRBs as well as in the ones showing multi-component spectra. We interpret the observations in light of models of subphotospheric dissipation, geometrical broadening and multi-zone emission, and show what we can learn about the dissipation mechanism and properties of GRB jets.