MSc Defense: Manuel Goimil García

Title: Tidal Disruption Events as Sources of High-Energy Neutrinos

Abstract:
Tidal Disruption Events (TDEs) are rare transient sources that occur when a star is disintegrated by strong gravitational forces in the vicinity of a supermassive black hole. These cataclysmic events are visible by a luminous electromagnetic flare with a timescale of the order of months. It has been argued that TDEs are also candidate sources of high-energy cosmic rays and neutrinos.
In this thesis we present a time-dependent model of neutrino production in three TDEs associated with events in the IceCube Observatory: AT2019dsg, AT2019fdr and AT2019aalc. Comparisons between typical time scales of diffusive shock acceleration and energy losses are used to place a high-energy cut-off on an initial power-law spectrum of cosmic rays, whose time evolution is determined numerically with a linear Fokker-Planck equation dominated by continuous (photo)hadronic and radiative cooling. Secondary neutrino, gamma-ray and electron fluxes are then calculated by folding the resulting spectrum with analytic estimates of their production cross sections. The electromagnetic spectrum of primary electrons and secondary products of cosmic-ray interactions is compared with Fermi-LAT upper bounds from the non-detection of gamma-rays, and features that could serve as evidence of (photo)hadronic interactions in TDEs are discussed. Likewise, the neutrino flux is integrated over the duration of the events to compare the total fluence with IceCube differential limits.