High‐Energy Neutrinos Produced by Interactions of Relativistic Protons in Shocked Pulsar Winds

Abstract

We have estimated fluxes of neutrinos and gamma rays that are generated from the decay of charged and neutral pions from a pulsar surrounded by supernova ejecta in our Galaxy, including an effect that has not been taken into consideration before, that is, the interactions between high-energy cosmic rays themselves in the nebula flow, assuming that hadronic components are the energetically dominant species in the pulsar wind. The bulk flow is assumed to be randomized by passing through the termination shock, and the energy distribution functions of protons and electrons behind the termination shock are assumed to obey relativistic Maxwellians. We have found that fluxes of neutrinos and gamma rays depend very sensitively on the wind luminosity, which is assumed to be comparable to the spin-down luminosity. In the case where B = 1012 G and P = 1 ms, neutrinos should be detected by km3 high-energy neutrino detectors such as AMANDA and IceCube. Also, gamma rays should be detected by Cerenkov telescopes such as CANGAROO and HESS, as well as by gamma-ray satellites such as GLAST. On the other hand, in the case where B = 1012 G and P = 5 ms, fluxes of neutrinos and gamma rays will be too low to be detected even by the next-generation detectors. However, even in the case where B = 1012 G and P = 5 ms, there is a possibility that very high fluxes of neutrinos may be realized at early stages of a supernova explosion (t ≤ 1 yr), where the location of the termination shock is very near to the pulsar. We have also found that there is a possibility that protons with energies of ~105 GeV in the nebula flow may interact with the photon field from the surface of the pulsar and produce many pions, which would enhance the intensity of the resulting neutrinos and gamma rays.