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July 29, 2015 to August 6, 2015
World Forum
Europe/Amsterdam timezone

The millisecond pulsar contribution to the rising positron fraction

Aug 5, 2015, 3:00 PM
15m
Yangtze 2 (World Forum)

Yangtze 2

World Forum

Churchillplein 10 2517 JW Den Haag The Netherlands
Oral contribution CR-TH Parallel CR22 TH

Speaker

Christo Venter (North-West University, Potchefstroom Campus)

Description

Pair cascades from MSPs may be a primary source of Galactic electrons and positrons that contribute to the increase in positron flux above 10 GeV as observed by PAMELA and AMS-02. The Fermi Large Area Telescope has increased the number of detected gamma-ray millisecond pulsars (MSPs) tremendously. Light curve modelling furthermore favours abundant pair production in MSP magnetospheres, so that models of primary cosmic-ray positrons from pulsars should include the contribution from the larger numbers of MSPs and their potentially higher positron output per source. We model the contribution of Galactic MSPs to the terrestrial cosmic-ray electron / positron flux by using a population synthesis code to predict the source properties of present-day MSPs. We simulate pair spectra assuming an offset-dipole magnetic field which boosts pair creation rates. We also consider positrons and electrons that have additionally been accelerated to very high energies in the strong intrabinary shocks in black widow and redback binary systems. We transport these particles to Earth by calculating their diffusion and the radiative energy losses they suffer in the Galaxy. Our model particle flux increases for non-zero offsets of the magnetic polar caps. We find that pair cascades from MSP magnetospheres contribute only modestly around a few tens of GeV to the measured fluxes. Black widow and redback fluxes may reach a few tens of percent of the observed flux at tens of TeV. Future observations should constrain the source properties in this case.
Collaboration FERMI
Registration number following "ICRC2015-I/" 889

Primary author

Christo Venter (North-West University, Potchefstroom Campus)

Co-authors

Dr Alice Harding (NASA Goddard Space Flight Center) Dr Andreas Kopp (Institut fuer Experimentelle und Angewandte Physik, Christian-Albrechts-Universitaet zu Kiel) Dr Ingo Buesching (North-West University, Potchefstroom Campus) Peter Gonthier (Hope College)

Presentation materials