Neutrino Fluence from Gamma-Ray Bursts: Off-Axis View of Structured Jets

We investigate the expected high-energy neutrino fluence from internal shocks produced in the relativistic outflow of gamma-ray bursts. Previous model predictions have primarily focussed on on-axis observations of uniform jets. Here we present a generalization to account for arbitrary viewing angles and jet structures. Based on this formalism, we provide an improved scaling relation that expresses off-axis neutrino fluences in terms of on-axis model predictions. We also find that the neutrino fluence from structured jets can exhibit a strong angular dependence relative to that of gamma-rays and can be far more extended. We examine this behavior in detail for the recent short gamma-ray burst GRB 170817A observed in coincidence with the gravitational wave event GW170817.