Pulsars Do Not Produce Sharp Features in the Cosmic-Ray Electron and Positron Spectra

TL;DR

This paper demonstrates that pulsars do not produce sharp spectral features in cosmic-ray electron and positron spectra, challenging previous assumptions and implications for dark matter detection.

Contribution

The study reveals that the expected sharp spectral cutoff from pulsar cooling processes is an artifact of approximation, not a physical feature.

Findings

Sharp spectral cutoff does not exist in pulsar models

Inverse-Compton scattering is a discrete process, not continuous

Spectral features cannot distinguish dark matter from pulsars

Abstract

Pulsars are considered to be the leading explanation for the excess in cosmic-ray positrons detected by PAMELA and AMS-02. A notable feature of standard pulsar models is the sharp spectral cutoff produced by the increasingly efficient cooling of very-high-energy electrons by synchrotron and inverse-Compton processes. This spectral break has been employed to: (1) constrain the age of pulsars that contribute to the excess, (2) argue that a large number of pulsars must significantly contribute to the positron flux, and (3) argue that spectral cutoffs cannot distinguish between dark matter and pulsar models. We prove that this spectral feature does not exist -- it appears due to approximations that treat inverse-Compton scattering as a continuous, instead of as a discrete and catastrophic, energy-loss process. Astrophysical sources do not produce sharp spectral features via cooling, reopening the possibility that such a feature would provide incontrovertible evidence for dark matter.