White Dwarf Pulsars as Possible Cosmic Ray Electron-Positron Factories

TL;DR

This paper proposes that white dwarf pulsars could be significant sources of high-energy cosmic ray electrons and positrons, potentially explaining observed excesses and serving as targets for future astrophysical experiments.

Contribution

It introduces the idea that white dwarf pulsars can produce high-energy electrons/positrons, offering an alternative to neutron star models for cosmic ray origins.

Findings

White dwarf mergers can produce rapidly spinning pulsars with energy comparable to neutron stars.

White dwarf pulsars can accelerate electrons/positrons up to 10 TeV.

They may dominate the electron/positron flux above 1 TeV, affecting dark matter searches.

Abstract

We suggest that white dwarf (WD) pulsars can compete with neutron star (NS) pulsars for producing the excesses of cosmic ray electrons/positrons observed by the PAMELA, ATIC/PPB-BETS, Fermi and HESS experiments. A merger of two WDs leads to a rapidly spinning WD with a rotational energy comparable to the NS case. The birth rate is also similar, providing the right energy budget for the cosmic ray electrons/positrons. Applying the NS theory, we suggest that the WD pulsars can in principle produce electrons/positrons up to 10 TeV. In contrast to the NS model, the adiabatic and radiative energy losses of electrons/positrons are negligible since their injection continues after the expansion of the pulsar wind nebula, and hence it is enough that a fraction 1% of WDs are magnetized as observed. The long activity also increases the number of nearby sources, which reduces the Poisson fluctuation in the flux. The WD pulsars could dominate the quickly cooling electrons/positrons above TeV energy as a second spectral bump or even surpass the NS pulsars in the observing energy range 10 GeV - 1 TeV, providing a background for the dark matter signals and a nice target for the future AMS-02, CALET and CTA experiment.