A rare phosphorus-rich star in an eclipsing binary from TESS
Bibliographic record
Abstract
Context. Few exoplanets around hot stars with radiative envelopes have been discovered, although new observations from the TESS mission are improving this. Stars with radiative envelopes have little mixing at their surface, and thus their surface abundances provide a sensitive test case for a variety of processes, including potentially star–planet interactions. Atomic diffusion is particularly important in these envelopes, producing chemically peculiar objects such as Am and HgMn stars. Aims. An exoplanet candidate around the B6 star HD 235349 was identified by TESS. Here we determine the nature of this transiting object and identify possible chemical peculiarities in the star. Methods. HD 235349 was observed using the long-slit spectrograph at Tartu Observatory, as well as photometrically by the TESS mission. The spectra were modeled to determine stellar parameters and chemical abundances. The photometric light curve was then analyzed in the context of the stellar parameters to determine properties of the transiting object. Results. We find the transiting object is a low-mass stellar companion, not a planet. However, the primary of this eclipsing binary is a rare type of chemically peculiar star. A strong overabundance of P is found with overabundances of Ne and Nd and mild overabundances of Ti and Mn, while He is mildly underabundant. There is also clear evidence for vertical stratification of P in the atmosphere of the star. The lack of Hg and the weak Mn overabundance suggests that this is not a typical HgMn star. It may be in the class of helium-weak phosphorus-gallium (He-weak PGa) stars or an intermediate between these two classes. Conclusions. We show that HD 235349 is a rare type of chemically peculiar star (He-weak PGa) in an eclipsing binary system with a low-mass stellar companion. This appears to be the first He-weak PGa star discovered in an eclipsing binary.
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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 | 0.001 |
| Science and technology studies | 0.001 | 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) | 0.002 | 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".