New hydrogen-deficient (pre-) white dwarfs in the Sloan Digital Sky Survey Data Release 10
Bibliographic record
Abstract
We have detected 21 new, very hot hydrogen-deficient (pre-) white dwarfs (spectral types O(He), hot DO, PG1159) in the Data Release 10 of the Sloan Digital Sky Survey. We present the results of non-local thermodynamic equilibrium (non-LTE) model-atmosphere analyses. The seven PG1159 stars have effective temperatures and surface gravities in the ranges Teff = 100 000–140 000 K and log g = 6–7.5. The hottest one is a new member of the rare hybrid-PG1159 subtype, indicating the presence of residual hydrogen. The ten new hot DOs span Teff = 65 000–120 000 K and log g = 7.5–8. Carbon abundances were derived and it is found that the PG1159 star values (C/He = 0.33–0.03 by number) and the DO values (<0.0004–0.01) cover distinct but adjacent ranges. With the discovery of four new O(He) stars (Teff = 80 000–100 000 K, log g = 5–5.5, C/He = 0.002–0.01), we double the number of known members of this rare spectral class. One of them is particularly interesting because it is unusually rich in C, N, O, and Si. Unexpected problems arose with the DOs because many He ii lines of every other star are so deep that they cannot be matched by any model. This is most conspicuous in the case of one object which exhibits the occurrence of ultrahigh-ionization metal features, a hitherto unexplained phenomenon that is known from a disquieting large fraction of hot DOs.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".