The 7Li/6Li Isotope Ratio Near the Supernova Remnant IC 443

TL;DR

This study measures 7Li/6Li isotope ratios near supernova remnant IC 443, revealing cosmic-ray-induced lithium production and providing insights into nucleosynthesis processes in the interstellar medium.

Contribution

First detailed analysis of 7Li/6Li ratios near IC 443, linking isotope variations to cosmic-ray interactions and constraining lithium production mechanisms.

Findings

Lower 7Li/6Li ratio in regions affected by cosmic rays

No evidence of neutrino-induced lithium synthesis

Ratios consistent with cosmic-ray spallation models

Abstract

We present an analysis of 7Li/6Li isotope ratios along four sight lines that probe diffuse molecular gas near the supernova remnant IC 443. Recent gamma-ray observations have revealed the presence of shock-accelerated cosmic rays interacting with the molecular cloud surrounding the remnant. Our results indicate that the 7Li/6Li ratio is lower in regions more strongly affected by these interactions, a sign of recent Li production by cosmic rays. We find that 7Li/6Li ~ 7 toward HD 254755, which is located just outside the visible edge of IC 443, while 7Li/6Li ~ 3 along the line of sight to HD 43582, which probes the interior region of the supernova remnant. No evidence of 7Li synthesis by neutrino-induced spallation is found in material presumably contaminated by the ejecta of a core-collapse supernova. The lack of a neutrino signature in the 7Li/6Li ratios near IC 443 is consistent with recent models of Galactic chemical evolution, which suggest that the nu-process plays only a minor role in Li production.