The Isotopic Composition of Galactic Cosmic-ray Iron Nuclei
نویسندگان
چکیده
We report high-resolution observations made in interplanetary space of 83-284 MeV per nucleon galactic cosmic-ray iron isotopes and directly establish that 56Fe is the dominant cosmic-ray Fe isotope. We find the following percentage abundances for Fe at the cosmic-ray source: 54Fe = 9(+8, -5)%, 55Fe:::; 7%, 56Fe = 91(+5, -11)%, 57Fe:::; 8%, and 58Fe:::; 6%. When compared to calculated nucleosynthesis yields and other observations, these results place significant constraints on the neutron excess of the environment where cosmic-ray Fe originates. Subject headings: cosmic rays: abundances-nucleosynthesis
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