# Constraining $\nu$-Process Production of Fluorine through Cosmic Ray Nucleosynthesis

## TL;DR

This paper investigates the origins of fluorine in the galaxy by combining models of cosmic ray nucleosynthesis, stellar evolution, and the neutrino process, concluding that AGB stars are the main source today.

## Contribution

It introduces a combined model of Galactic chemical evolution and cosmic ray nucleosynthesis that constrains the $
u$-process contribution to fluorine using observed isotope ratios.

## Key findings

- The $
u$-process dominates fluorine production at low metallicity.
- Present-day fluorine mainly originates from AGB stars.
- The model constrains neutrino energies using B11/B10 ratios.

## Abstract

Fluorine is massive enough that it is not considered to be a light ($Z\le5$) element, yet compared to its near neighbors, C, N, O, and Ne, it is far underproduced in the course of stellar evolution, making its origin more complex. In fact, the abundance of fluorine is the lowest among all elements between Z = 5 and 21 and is roughly 3-4 orders of magnitude below that of C, N, O, and Ne. There are several plausible sources for F beyond standard stellar evolution. These include the production in the asymptotic giant branch phase (AGB) in intermediate mass stars, production in Wolf-Rayet stars, and the production through neutrino spallation in supernovae. The latter, known as the $\nu$-process, is an important source for B11, and may contribute to the abundance of Li7 as well. We combine a simple model of Galactic chemical evolution with a standard Galactic cosmic ray nucleosynthesis model to treat self-consistently the evolution of the Li, Be, and B isotopes. We include massive star production of F, as well as contributions from AGB stars, and the $\nu$-process. Given the uncertainties in neutrino energies in supernovae, we normalize the $\nu$-process using the observed B11/B10 ratio as a constraint. As a consequence, we are able to determine the relative importance of each contribution to the F abundance. We find that although the $\nu$-process dominates at early times (low metallicity), the present-day F abundance is found to originate primarily from AGB stars.