Deuterium abundance toward G191-B2B: Results from the Far Ultraviolet Spectroscopic Explorer (FUSE) Mission
Bibliographic record
Abstract
High-resolution spectra of the hot white dwarf G191-B2B, covering the wavelength region 905-1187A, were obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE). This data was used in conjunction with existing high-resolution Hubble Space Telescope STIS observations to evaluate the total HI, DI, OI and NI column densities along the line of sight. Previous determinations of N(DI) based upon GHRS and STIS observations were controversial due to the saturated strength of the DI Lyman-alpha line. In the present analysis the column density of DI has been measured using only the unsaturated Lyman-beta and Lyman-gamma lines observed by FUSE. A careful inspection of possible systematic uncertainties tied to the modeling of the stellar continuum or to the uncertainties in the FUSE instrumental characteristics has been performed. The column densities derived are: log N(DI) = 13.40 +/-0.07, log N(OI) = 14.86 +/-0.07, and log N(NI) = 13.87 +/-0.07 quoted with 2-sigma uncertainties. The measurement of the HI column density by profile fitting of the Lyman-alpha line has been found to be unsecure. If additional weak hot interstellar components are added to the three detected clouds along the line of sight, the HI column density can be reduced quite significantly, even though the signal-to-noise ratio and spectral resolution at Lyman-alpha are excellent. The new estimate of N(HI) toward G191-B2B reads: log N(HI) = 18.18 +/-0.18 (2-sigma uncertainty), so that the average (D/H) ratio on the line of sight is: (D/H) = 1.66 (+0.9/-0.6) *10^-5 (2-sigma uncertainty).
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".