The Cosmic-Ray Contribution to LiBeB: Interpretation of LiBeB Abundances from CRIS

Abstract

The bulk of galactic Li, Be, and B (LiBeB) abundances is believed to be created during energetic inelastic collisions of cosmic-ray and interstellar medium (ISM) nuclei. Additional sources such as big bang nucleosynthesis or neutrino-driven spallation within Type II supernovae may also add a small contribution. However, measurements of the elemental ratios Be/H, B/H, and Fe/H in old, low-metallicity halo stars indicate an overabundance of LiBeB that can not be accounted for by fragmentation of cosmic-ray CNO. This interpretation assumes that the ISM in any epoch serves as a source of material both for star formation and for cosmic rays, which contribute fragmentation material in later epochs. We have simulated cosmic-ray transport using a simple model and present an interpretation of the abundance measurements from the Cosmic Ray Isotope Spectrometer (CRIS) during the past three years. We will discuss the implications on cosmic-ray LiBeB production at lower energies.

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