IceCube Constraints on Fast-Spinning Pulsars as High-Energy Neutrino Sources

TL;DR

This paper uses IceCube neutrino observations to constrain the role of fast-spinning pulsars as sources of ultra-high-energy cosmic rays, finding that current data limit their contribution significantly.

Contribution

It provides new constraints on pulsar-based cosmic-ray acceleration models by analyzing neutrino non-detections and considering different supernova ejecta scenarios.

Findings

IceCube limits nearly exclude pulsars as major UHE cosmic-ray sources under certain assumptions.

Current non-observation of 10^18 eV neutrinos constrains pulsar birthrates and acceleration efficiencies.

Jet-like escape scenarios could reconcile pulsar models with neutrino observations.

Abstract

Relativistic winds of fast-spinning pulsars have been proposed as a potential site for cosmic-ray acceleration from very high energies (VHE) to ultrahigh energies (UHE). We re-examine conditions for high-energy neutrino production, considering the interaction of accelerated particles with baryons of the expanding supernova ejecta and the radiation fields in the wind nebula. We make use of the current IceCube sensitivity in diffusive high-energy neutrino background, in order to constrain the parameter space of the most extreme neutron stars as sources of VHE and UHE cosmic rays. We demonstrate that the current non-observation of $10^{18}$ eV neutrinos put stringent constraints on the pulsar scenario. For a given model, birthrates, ejecta mass and acceleration efficiency of the magnetar sources can be constrained. When we assume a proton cosmic ray composition and spherical supernovae ejecta, we find that the IceCube limits almost exclude their significant contribution to the observed UHE cosmic-ray flux. Furthermore, we consider scenarios where a fraction of cosmic rays can escape from jet-like structures piercing the ejecta, without significant interactions. Such scenarios would enable the production of UHE cosmic rays and help remove the tension between their EeV neutrino production and the observational data.