ASTROSAT/UVIT Survey of M31, First Results: UV-bright Stars in the Bulge
Bibliographic record
Abstract
Abstract A survey of M31 is being carried out with the ASTROSAT Observatory in ultraviolet (UV), soft X-rays, and hard X-rays using the UltraViolet Imaging Telescope (UVIT), soft X-ray telescope, LAXPC, and CZT instruments. Here we analyze UVIT observations of the first field covering the central (7′) part of the bulge of M31. The UV bands observed cover the range 120–280 nm with four filters with a spatial resolution of 1″. They are sensitive to the UV emission from hot stars (T eff > 10000 K), so can be used to detect the hottest stars in the bulge of M31. We cross-match the UVIT sources with sources from Panchromatic Hubble Andromeda Treasury to obtain multi-band spectral energy distributions (SEDs) for 26 sources. Fits of the SEDs with stellar models show that these are likely main-sequence stars with masses in the range 5–20 M ⊙. This provides evidence for a low, but significant (∼10−5 M ⊙ yr−1), rate of star formation in the bulge of M31, which has occurred in the very recent past (∼10–100 million years).
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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 | 0.002 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".