Internal hydrodynamical shocks as a mechanism for GRB prompt emission

Relativistic outflows, common in astrophysical objects featuring accretion and/or explosions, are observed as sources of bright non-thermal emission, indicating conversion of their kinetic energy into radiation. Internal shocks, collisions between parts of the outflow with different velocities, are one of the proposed dissipation mechanism in many astrophysical contexts. This internal shock scenario has been successfully used to model the prompt emission of gamma-ray bursts (GRBs), but the observed spectral signature of many bursts could not be explained without including other physical components.
In this talk, I investigate the internal shocks scenario again from the ground up, based on a full hydrodynamical analytic derivation and spherically-symmetric hydro simulations. The new analytical model naturally obtains key features of prompt GRB emission, and the simulations highlight spherical effects that were not predicted by simple propagation models. These spherical effects bring the predicted hardness - intensity diagram closer to GRB observations over a wider range of physical parameters of the central engine. Finally, I'll introduce effects brought by considering proper synchrotron cooling of the electron population.