Theoretical Examination of the Lithium Depletion Boundary
Bibliographic record
Abstract
We explore the sensitivity in open cluster ages obtained by the lithium depletion boundary (LDB) technique to the stellar model input physics. The LDB age technique is limited to open clusters with ages ranging from 20 to 200 Myr. Effective 1 σ errors in the LDB technique due to uncertain input physics are roughly 3% at the oldest age, increasing to 8% at the youngest age. Bolometric correction uncertainties add an additional 10% and 6% error to the LDB age technique for old and young clusters, respectively. Rotation rates matching the observed fastest rotators in the Pleiades affect LDB ages by less than 2%. The range of rotation rates in an open cluster is expected to "smear" the LDB location by only 0.02 mag for a Pleiades-age cluster, increasing to 0.06 mag for a 20 Myr old cluster. Thus, the observational error of locating the LDB (~7%-10%) and the bolometric correction uncertainty currently dominate the error in LDB ages. For our base case, we formally derive an LDB age of 148 ± 19 Myr for the Pleiades, where the error includes 8%, 3%, and 9% contributions from observational, theoretical, and bolometric correction sources, respectively. A maximally plausible 0.3 mag shift in the I -band bolometric correction to reconcile main-sequence isochrone fits with the observed V - I color for the low-mass Pleiades members results in an age of 126 ± 11 Myr, where the error includes observational and theoretical errors only. Upper main sequence-fitting ages that do not include convective core overshoot for the Pleiades (~75 Myr) are ruled out by the LDB age technique.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.006 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.001 | 0.002 |
| Scholarly communication | 0.002 | 0.003 |
| Open science | 0.002 | 0.002 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.007 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".