Stable accretion in young stars: the cases of EX Lupi and TW Hya
Bibliographic record
Abstract
ABSTRACT We examine the long-term spectroscopic and photometric variability of EX Lupi and TW Hya, studying the presence of stable accretion and the role it plays in the observed variability. Analysing the velocity modulations of the emission lines with star-melt, we obtain information on the structure of the accretion columns and the disc–star connection. The emission-line radial velocities reveal that TW Hya, like EX Lupi, has a remarkably stable or slow-varying accretion column footprint, locked to the star for several years. The line-emitting regions are non-polar for both EX Lupi and TW Hya, and species with different energies differ in position. In contrast, the continuum emission as observed in the photometry is very variable and can be modelled by hotspot(s) that change over time in phase, shape, temperature, size, and location with respect to the emission-line region. The continuum emission region may not be limited to the stellar surface, especially during episodes of high accretion. The broad-line emission observed in EX Lupi during episodes of increased accretion reveals a further structure, which can be fitted by non-axisymmetric disc in Keplerian rotation inwards of the corotation radius. Since the radial velocity modulation due to accretion footprints is so stable, we used it to search for further velocity modulations. While no residual modulation (other than caused by stellar rotation) is found in these objects, a similar analysis could help to identify young planets/companions. Therefore, determining whether stable accretion footprints are common among young stars is a key to detect young planets.
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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 | 0.002 |
| 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 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 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".