The Connection Between Thermal and Non-Thermal Emission in Gamma-ray Bursts: General Considerations and GRB090902B as a Case Study

Understand

Photospheric (thermal) emission is inherent to the gamma-ray burst (GRB) "fireball" model.

• We show here, that inclusion of this component in the analysis of the GRB prompt emission phase naturally explains some of the prompt GRB spectra seen by the Fermi satellite over its entire energy band.
• The sub-MeV peak is explained as multi-color black body emission, and the high energy tail, extending up to the GeV band, results from roughly similar contributions of synchrotron emission, synchrotron self Compton(SSC) and Comptonization of the thermal photons by energetic electrons originating after dissipation of the kinetic energy above the photosphere.
• We show how this analysis method results in a complete, self consistent picture of the physical conditions at both emission sites of the thermal and non-thermal radiation.