Analysis of the<i>FUSE</i>Spectrum of the Hot, Evolved Star GD 6051
Bibliographic record
Abstract
We present an analysis of the atmospheric properties of the evolved, hydrogen-rich object GD 605 using FUSE , IUE , and optical spectra in conjunction with non-LTE (NLTE) model atmospheres and synthetic spectra. We also present an analysis of the interstellar medium along the line of sight toward this star. Our effective temperature determination relies on the constraints on the ionization balance O IV/O V imposed by the FUSE data, while the surface gravity relies on a match to the Balmer lines in the optical spectrum. Our analysis yields T eff ∼ 85,000 K, log g ∼ 5.25, and a helium abundance close to the solar value. These parameters suggest that GD 605 is in a post-AGB evolutionary phase and belongs to the class of hydrogen-rich central star of planetary nebulae, subclass O(H). Apart from lines of hydrogen and helium, about two dozen photospheric lines are observed in the FUSE data, which are dominated by the O VI λλ1031.9 and 1037.6 transitions. In addition, we detect lines associated with the following ions: N IV, O IV, O V, Si IV, S VI, Ar VII, as well as Fe VII. Synthetic spectra based on NLTE line-blanketed model atmospheres reproduce most of the line profiles observed in what appears to be an atmosphere deficient in heavy elements. Our calculations do not fully reproduce the strength of the strongest ultraviolet lines seen, the O VI doublet, perhaps a sign that some contribution to this structure may arise in the interstellar medium or in a circumstellar environment. We discuss various scenarios to account for the absence of a visible nebula and the dearth of heavy elements in the atmosphere of GD 605.
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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) | 0.000 | 0.000 |
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".