Exploring membership and variability in NGC 7419: an open cluster rich in supergiants and Be type stars
Bibliographic record
Abstract
ABSTRACT NGC 7419 is a young open cluster notable for hosting five red supergiants and a high abundance of Classical Be (CBe) stars. CBe stars are main-sequence non-supergiant B-type stars that exhibit or have exhibited Balmer-line emissions in their spectra. We perform a membership analysis using Gaia DR3 data and machine learning techniques like Gaussian mixture models and Random Forest and determine the cluster’s mean distance to be ${3.6^{+1.0}_{-0.6}}$ kpc. We identify 499 Gaia-based members with a mass above $\sim$1.2 M$_\odot$, and estimate the cluster’s age to be $21.1 ^{+1.6}_{-0.6}$ Myr. Using our revised H α excess-based analysis, we find 42 CBe stars containing many known CBe stars, bringing the total number of CBe stars in NGC 7419 to 49 and the fraction of CBe to (B + CBe) members to 12.7 per cent. We investigate the variability of the candidate members from Zwicky Transient Facility and NEOWISE data using standard deviation, median absolute deviation, and Stetson index (J), and their periodicity using the Generalized Lomb–Scargle periodogram variability. We find that 66 per cent of CBe stars are variable: 23 per cent show periodic signals, typical of pulsation/rotation, 41 per cent display variability characteristic of disc dynamics or binarity, and 14 per cent exhibit long-term changes, consistent with disc dissipation/formation. We also find that all pulsating CBe stars are early-type, while 50 per cent of stars with long-term variations are early-type, and the other 50 per cent are mid-type. Our results agree with previous findings in the literature and confirm that CBe stars display variability through multiple mechanisms across different time-scales.
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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 | 0.002 | 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) | 0.001 | 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".