Lithium in Turn-off Stars in the Globular Cluster M5: A Quest for Primordial Lithium
Ann Merchant Boesgaard, Constantine P. Deliyannis

TL;DR
This study measures lithium abundances in turn-off stars of the globular cluster M5 and other clusters, revealing a consistent maximum Li level below primordial predictions, with implications for understanding early universe nucleosynthesis.
Contribution
It provides high-resolution Li abundance measurements in old globular cluster stars, highlighting a uniform maximum Li level across clusters and challenging primordial Li predictions.
Findings
Li abundance varies by a factor of two among stars
Maximum Li levels are consistent across six globular clusters
Li levels are below primordial predictions in all observed stars
Abstract
The light element lithium is formed by nucleosynthesis during the Big Bang. Its abundance can help to define the parameters of the early universe. To find this primordial value, it is necessary to determine Li abundances in the oldest stars because it is readily destroyed by nuclear reactions in stellar interiors. We have made high-resolution (~45,000) spectroscopic observations of five identical unevolved turn-off stars in the 13 Gyr old globular cluster M5. In our analysis we find a range in Li abundance of a factor of two; the spread is five times the individual error. The comparison of these results with those for turn-off stars from five other globular clusters reveals similarly large range in Li. Lithium in M5 and the other clusters all have stars above the field star Li plateau, but none are as high as the predictions for primordial Li. The maximum values for Li are the same in…
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Taxonomy
TopicsStellar, planetary, and galactic studies · Astronomy and Astrophysical Research · Scientific Research and Discoveries
