Binary neutron star merger remnants as sources of cosmic rays below the “Ankle”

Abstract

We investigate non-thermal electron and nuclei energy losses within the binary neutron star merger remnant produced by the event GW170817. The lack of a cooling feature within the detected synchrotron emission from the source is used to constrain the magnetic field at the mG level, assuming that this emission is electron synchrotron in origin, and that the accelerated spectrum in the electrons follows the form dN/dEe∝Ee−2. The level of subsequent gamma-ray emission from the source is demonstrated to provide a further constraint on the source magnetic field strength. We also put forward alternative strong ( ∼ G) magnetic field scenarios able to support this emission. For such stronger fields, the photo-disintegration of non-thermal nuclei within the source is considered, and a bottleneck period of ∼ 5–30 days is found when this process peaks. We find that this class of source is in principle able to support the population of cosmic rays detected at Earth below the “ankle”.