Oscar Wistemar: Investigating GRB prompt emission with a photospheric model based on radiation-mediated shocks

Thursday 30 Apr 2026, 13:15 → 14:00 Europe/Stockholm

A5:1003 (AlbaNova Main Building)

We use a photospheric framework to interpret the gamma-ray burst prompt emission from the relativistic jet. The framework is based on radiation-mediated shocks dissipating energy below the photosphere. We use the Kompaneets RMS approximation (KRA) model, which is an RMS analog, to fit the main emission episode of GRB 211211A. The KRA model fits well for the entire main emission and captures the low-energy break (or curvature) in the spectra. The properties of the shock show that there is a strong shock occurring in a hot upstream at low to moderate optical depths. We also introduce a method to estimate properties of the jet outflow and find that the bulk outflow Lorentz factor of the jet is ~250 during the main emission and that the jet is most likely pair loaded, potentially from sideways diffusion of a neutron wind. In conclusion, photospheric emission altered by an RMS can explain the observations of GRB211211A and the KRA model can fit its spectra well, including the additional curvature at energies below the peak (i.e. a low-energy break).