6^Li in the atmosphere of GJ 117 Revisited

TL;DR

This study revisits the detection of lithium-6 in the atmosphere of GJ 117, using high-resolution spectra to refine measurements and assess the origin of lithium isotopes in the star.

Contribution

The paper provides an updated measurement of 6Li/7Li ratio in GJ 117 with high-resolution data and improved analysis techniques, confirming previous findings within uncertainties.

Findings

6Li/7Li ratio is approximately 0.05±0.02.

No significant spectral asymmetries affecting lithium line profile.

Results are consistent with lithium production via stellar surface spallation.

Abstract

Detection of 6^Li has been shown for energetic solar events, one chromospherically active binary, and several dwarf halo stars. We had previously found a 6^Li/7^Li = 0.03+/-0.01 for active K dwarf GJ 117 using VLT UVES observations. Here we present high signal-to-noise (>1000) high spectral resolution observations taken with the McDonald Observatory's 2.7m and echelle spectrometer of GJ 117. We have used the solar spectrum and template stars to eliminate possible blends, such as Ti I, in the 6^Li spectral region. Our new analysis, using an updated PHOENIX model atmosphere finds 6^Li/7^Li = 0.05+/-0.02. Additionally, bisector analysis showed no significant red asymmetries that would affect the lithium line profile. No changes above the statistical uncertainties are found between the VLT and McDonald data. The amount of 6^Li derived for GJ 117 is consistent with creation in spallation reactions on the stellar surface, but we caution that uncertainties in the continuum level may cause additional uncertainty in the 6^Li fraction.