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TeV cosmic-ray electrons from millisecond pulsars




Recent γ-ray observations by Fermi Gamma-Ray Space Telescope suggest that the γ-ray millisecond pulsar (MSP) population is separated into two subclasses with respect to pair multiplicity. Here, we calculate the cosmic-ray electron/positron spectra from MSPs. Based on the assumption of equipartition in the pulsar-wind region, the typical energy of electrons/positrons ejected by a MSP with pair multiplicity of the order of unity is ∼50 TeV. In this case, we find that a large peak in the 10–50 TeV energy range would be observed in the cosmic-ray electron/positron spectrum. Even if the fraction of pair-starved MSPs is 10 per cent, a large peak would be detectable in future observations. We also calculate the contribution from MSPs with high pair multiplicity to the electron/positron spectrum. We suggest that if the multiplicity of the dominant MSP population is ∼103, electrons/positrons from this population may contribute to the observed excess from the background electron/positron flux and positron fraction.