Explaining cosmic ray antimatter with secondaries from old supernova remnants

Abstract

Despite significant efforts over the past decade, the origin of the cosmic ray positron excess has still not been unambiguously established. A popular class of candidate sources are pulsars or pulsar wind nebulae but these cannot also account for the observed hard spectrum of cosmic ray antiprotons. We revisit the alternative possibility that the observed high-energy positrons are secondaries created by spallation in supernova remnants during the diffusive shock acceleration of the primary cosmic rays, which are further accelerated by the same shocks. The resulting source spectrum of positrons at high energies is then naturally harder than that of the primaries, as is the spectrum of other secondaries such as antiprotons. We present the first comprehensive investigation of the full parameter space of this model -- both the source parameters as well as those governing galactic transport. Various parameterisations of the cross sections for the production of positrons and antiprotons are considered, and the uncertainty in the model parameters discussed. We obtain an excellent fit to recent precision measurements by AMS-02 of cosmic ray protons, helium, positrons and antiprotons, as well as of various primary and secondary nuclei. This model thus provides an economical explanation of the spectra of all secondary species -- from a single well-motivated population of sources.

10 pages, 5 figures

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Cited by in corpus (10)

• Diffuse Emission of Galactic High-Energy Neutrinos from a Global Fit of Cosmic Rays
• Grammage of cosmic rays in the proximity of supernova remnants embedded in a partially ionized medium
• Interpretations of the cosmic ray secondary-to-primary ratios measured by DAMPE
• Stochasticity of Cosmic Rays from Supernova Remnants and the Ionization Rates in Molecular Clouds
• Constraining dark matter annihilation with cosmic ray antiprotons using neural networks
• The importance of Fe fragmentation for LiBeB analyses: Is a Li primary source needed to explain AMS-02 data?
• Observing Signals of Spectral Features in the Cosmic-Ray Positrons and Electrons from Milky Way Pulsars
• Transport parameters from AMS-02 F/Si data and fluorine source abundance
• Erosion of Icy Interstellar Objects by Cosmic Rays and Implications for `Oumuamua
• New estimate for the contribution of the Geminga pulsar to the positron excess