Hadronic Supercriticality in temporal evolution of compact high energy sources
Ioulia Florou
Relativistic hadronic plasmas have an intriguing property, coined as "hadronic supercriticality", according to which they can abruptly and efficiently release the energy stored in relativistic protons through violent photon outbursts. These photon flares may have a direct analogy to those observed from compact astrophysical objects, such as Gamma Ray Bursts (GRBs). In the present doctoral thesis we perform a comprehensive study of the parameter space by investigating the onset of hadronic supercriticalities in a non expanding source for a wide range of initial parameters. As a second step, we extend our analysis and investigate the manifestation and the properties of hadronic supercriticality in the case of adiabatically expanding sources. We apply this idea to the GRB phenomenology by assuming several expanding blobs released from a central GRB engine. Each blob contains initial parameters that ensure the onset of supercriticality. We then perform a Monte Carlo simulation in order to randomly select the physical parameters of each blob. We let the system evolve and compute numerically the time dependent electromagnetic signals coming from each blob and finally construct the γ ray light curves and broadband photon spectra from the superposition of blobs. The resulting picture represents a typical GRB prompt emission. Finally, for comparison reasons, we investigate an alternative hadronic model for the interpretation of the GRB prompt emission. We therefore consider that the radiating particles are once again relativistic protons and investigate the idea that the prompt emission originates from the synchrotron radiation in the marginally fast cooling regime. We compute the source parameters required for such a scenario to work and investigate analytically and numerically how additional processes, namely photohadronic interactions and γγ pair production, contribute to the overall spectrum. We apply our results to a small fraction of GRBs with available data down to soft X-rays (∼0.5 keV) which have been shown to feature a spectral break in the low energy part of their prompt emission spectrum.
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