Sgr A East as a possible high energy neutron factory in the Galactic Centre

Abstract

Sgr A East is a supernova remnant located within few parsecs from the Galactic Centre (GC). There are good reasons to believe that this object is the source of the γ-ray excess detected by HESS in the direction of the GC meaning that Sgr A East is likely to be an efficient cosmic-ray (CR) accelerator. Some observations suggest that strong magnetic fields may be present in that region which may allow the acceleration of composite nuclei in Sgr A East beyond the EeV. We show that, if this is case, EeV neutrons should be effectively produced by the photo-disintegration of ultra high energy nuclei onto the infrared photon background (with temperature ∼40 K) in which Sgr A East is embedded. Neutrons with such an energy can reach the Earth before decaying and may be detectable under the form of a CR point-like excess in the direction of the GC. We determine the expected energy spectrum and the amplitude of this signal showing that it may be measurable by the AUGER observatory.