Signatures of a two million year old supernova in the spectra of cosmic ray protons, antiprotons and positrons

Understand

The locally observed cosmic ray spectrum has several puzzling features, such as the excess of positrons and antiprotons above $\sim 20$ GeV and the discrepancy in the slopes of the spectra of cosmic ray protons and heavier nuclei in the TeV-PeV energy range.

• We show that these features are consistently explained by a nearby source which was active $\sim 2$ Myr ago and has injected $(1-2)\times 10^{50}$ erg in cosmic rays.
• The transient nature of the source and its overall energy budget point to the supernova origin of this local cosmic ray source.
• The age of the supernova suggests that the local cosmic ray injection was produced by the same supernova that has deposited $^{60}$Fe isotopes in the deep ocean crust.