State-of-the-art collapsar jet simulations imply undetectable subphotospheric neutrinos
Ersilia Guarini, Irene Tamborra, Ore Gottlieb
Abstract
Mounting evidence suggests that the launching of collapsar jets is magnetically driven. Recent general relativistic magnetohydrodynamic simulations of collapsars reveal that the jet is continuously loaded with baryons, owing to strong mixing with the cocoon. This results in a high photosphere at $\ensuremath{\gtrsim}{10}^{12}\text{ }\text{ }\mathrm{cm}$. Consequently, collisionless internal shocks below the photosphere are disfavored, and neutrino production in the deepest jet regions is prevented, in contrast to what has been assumed in the literature. We find that subphotospheric neutrino production could take place in the presence of collisionless subshocks or magnetic reconnection. Efficient particle acceleration is not possible in the cocoon, at the cocoon-countercocoon shock interface, or at the shock driven by the cocoon in the event of a jet halted in an extended envelope. These subphotospheric neutrinos have energy ${E}_{\ensuremath{\nu}}\ensuremath{\lesssim}{10}^{5}\text{ }\text{ }\mathrm{GeV}$ for initial jet magnetizations ${\ensuremath{\sigma}}_{0}=15--2000$. More than one neutrino event is expected to be observed in Hyper-Kamiokande and IceCube DeepCore for bursts occurring at $z\ensuremath{\lesssim}\mathcal{O}(0.1)$. Because of their energy, these neutrinos cannot contribute to the diffuse flux detected by the IceCube Neutrino Observatory. Our findings have implications on neutrino searches ranging from gamma-ray bursts to luminous fast blue optical transients.