1207.0010 (Norita Kawanaka)

Escape of Secondary Cosmic-Ray Positrons Produced in a Supernova Remnant    [PDF]

Norita Kawanaka

We discuss the acceleration and escape of secondary particles, especially positrons produced by hadronic interactions in a supernova remnant (SNR) shock. During the shock acceleration, protons would interact with ambient gas and produce charged secondary particles, which would also be accelerated in a SNR and injected into the interstellar medium as cosmic-rays (CRs). Some previous studies proposed that the positron excess observed by PAMELA can be explained with this process. We calculate the energy spectra of CR protons and secondary CR positrons escaping a SNR into the interstellar medium in a time-dependent manner. We show that, on the contrary to the results presented previously, the observed spectra of secondary CR particles generated in SNRs would be softer than those of primary CR particles. This is because protons with higher energy would be trapped around the shock only for a shorter time compared to those with lower energy when the maximum CR energy is escape-limited, which results in a smaller number of secondary CR particles with higher energy.

View original: http://arxiv.org/abs/1207.0010