Ultra–High-Energy Cosmic-Ray Acceleration by Magnetic Reconnection in Newborn Accretion-induced Collapse Pulsars

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Abstract
We here investigate the possibility that the ultra-high-energy cosmic-ray (UHECR) events observed above the Greisen-Zatsepin-Kuzmin (GZK) limit are mostly protons accelerated in reconnection sites just above the magnetosphere of newborn millisecond pulsars that are originated by accretion-induced collapse (AIC). We formulate the requirements for the acceleration mechanism and show that AIC pulsars with surface magnetic fields 1012 G < B 1015 G and spin periods 1 ms P < 60 ms are able to accelerate particles to energies ≥1020 eV. Because the expected rate of AIC sources in our Galaxy is very small (~10-5 yr-1), the corresponding contribution to the flux of UHECRs is negligible and the total flux is given by the integrated contribution from AIC sources produced by the distribution of galaxies located within the distance that is unaffected by the GZK cutoff (~50 Mpc). We find that reconnection should convert a fraction ξ 0.1 of magnetic energy into UHECRs in order to reproduce the observed flux.