Contribution of Pulsars to the AMS-02 Positron Excess

Abstract

In this paper we tested the pulsar interpretation of positron excess, measured by the Alpha Magnetic Spectrometer-02 (AMS-02), by using the list of objects from the Australian National Telescope Facility pulsar catalog (ATNF catalog). We take into account in the calculation the energy losses that cosmic rays encounter when propagating through the Galaxy and we included the secondary positrons which are produced through the collision of cosmic rays against the atoms of the interstellar space. We firstly hypothesized the possibility of a single pulsar contributing to the positron flux. We consider for this case Geminga since it is near and very powerful. Geminga alone can fit very well the data with a spectral index of 1.8 and an efficiency of 70%. It is however unrealistic that only one pulsar contributes to the AMS-02 positron data. Therefore, we decide to find among all pulsars in the ATNF catalog the top 20 pulsars that contributed to the flux on Earth. We then calculated the total positron flux of these pulsars and found it to fit the AMS-02 data very well at efficiencies between 30~70%. We came to a conclusion that the pulsars are viable interpretations of the positron excess that the AMS-02 detected.