Utilizing cosmic-ray positron and electron observations to probe the averaged properties of Milky Way pulsars

Abstract

Pulsars have long been studied in the electromagnetic spectrum. Their environments are rich in high-energy cosmic-ray electrons and positrons likely enriching the interstellar medium with such particles. In this work we use recent cosmic-ray observations from the AMS-02, CALET and DAMPE collaborations to study the averaged properties of the local Milky Way pulsar population. We perform simulations of the local Milky Way pulsar population, for interstellar medium assumptions in agreement with a range of cosmic-ray nuclei measurements. Each such simulation contains $\sim 10^4$ pulsars of unique age, location, initial spin-down power and cosmic-ray electron/positron spectra. We produce more than $7\times 10^3$ such Milky Way pulsar simulations. We account for and study i) the pulsars' birth rates and the stochastic nature of their birth, ii) their initial spin-down power distribution, iii) their time evolution in terms of their braking index and characteristic spin-down timescale, iv) the fraction of spin-down power going to cosmic-ray electrons and positrons and v) their propagation through the interstellar medium and the Heliosphere. We find that pulsars of ages $\sim 10^5-10^7$ yr, have a braking index that on average has to be 3 or larger. Given that electromagnetic spectrum observations of young pulsars find braking indices lower than 3, our work provides strong hints that pulsars' braking index increases on average as they age, allowing them to retain some of their rotational energy. Moreover, we find that pulsars have relatively uniform properties as sources of cosmic-ray electrons and positrons in terms of the spectra they produce and likely release O($10\%$) of their rotational energy to cosmic-rays in the ISM. Finally, we find at $\simeq$12 GeV positrons a spectral feature that suggests a new subpopulation of positron sources contributing at these energies.

20 pages, 13 figures and 6 tables. Simulations are available at https://zenodo.org/record/5659004#.YYqnbi-ZN0s

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Cited by in corpus (11)

• The Third Fermi Large Area Telescope Catalog of Gamma-ray Pulsars
• New determination of the production cross section for secondary positrons and electrons in the Galaxy
• A novel prediction for secondary positrons and electrons in the Galaxy
• Pulsars Do Not Produce Sharp Features in the Cosmic-Ray Electron and Positron Spectra
• Revisiting GeV-scale annihilating dark matter with the AMS-02 positron fraction
• Constraining the Charge-, Time- and Rigidity-Dependence of Cosmic-Ray Solar Modulation with AMS-02 Observations during Solar Cycle 24
• Observing Signals of Spectral Features in the Cosmic-Ray Positrons and Electrons from Milky Way Pulsars
• Possible counterpart signal of the Fermi bubbles at the cosmic-ray positrons
• Possible spectral irregularities in the AMS-02 positron spectrum
• New estimate for the contribution of the Geminga pulsar to the positron excess
• SECRET: Stochasticity Emulator for Cosmic Ray Electrons