We propose that neutron emission from Cen A dominates the cosmic ray sky at the high end of the spectrum. Neutrons that decay generate proton diffusion fronts, whereas those that survive decay produce an angular spike in the direction of the source. We use recent data reported by the Pierre Auger Collaboration to normalize the injection spectrum and estimate the required luminosity in cosmic rays. We find that such a luminosity, $L_{\mathrm{CR}}\sim 5\times {10}^{40}\mathrm{erg}/\mathrm{s}$, is comfortably smaller than the bolometric luminosity of Cen A, $L_{\mathrm{bol}}\sim {10}^{43}\mathrm{erg}/\mathrm{s}$. We compute the incoming current flux density as viewed by an observer on Earth, and we show that the anisotropy amplitude is in agreement with data at the $1\sigma$ level. Regardless of the underlying source model, our results indicate that after a decade of data taking the Pierre Auger Observatory will be able to test our proposal.

• Received 24 April 2011

DOI:https://doi.org/10.1103/PhysRevD.84.067301