White Dwarf Pulsars as Possible Cosmic Ray Electron-Positron Factories

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.Comment: 20 pages, 7 figures and 1 tabl