Signatures of high energy protons in pulsar winds

INAF/Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy

Corresponding author: E. Amato, amato@arcetri.astro.it

Received: 4 July 2002
Accepted: 4 February 2003

Abstract

The resonant cyclotron absorption model (Hoshino et al. 1992; Gallant & Arons 1994) is very successful in describing particle acceleration in plerions. A prediction of this model is the presence of a substantial amount of relativistic protons in pulsar winds. Although difficult to detect, these protons may show up through their interactions either with the photons in the plerion environment or with the thermal gas in the supernova ejecta. Inelastic proton-proton (p-p) collisions are expected to be very effective in young objects, resulting in a copious production of neutral and charged pions. Charged pions produced during the first few hundred years after the supernova explosion may have time to decay into muons, whose subsequent decay may provide an additional source of electrons and positrons in these nebulae, that adds up to the pulsar input. These secondary leptons evolve just as the pairs in the pulsar wind, and signatures of their presence could be found, in principle, even in the synchrotron spectrum of older objects. p-p collisions may remain fairly efficient even in moderately old objects resulting in the production of TeV γ-rays and neutrinos. We apply our calculations to the case of the Crab Nebula, the best studied plerion thus far, and find that existing data already allow us to infer interesting constraints on the physical properties of the Crab pulsar wind.