The polar orbit of the warm Neptune GJ 436b seen with VLT/ESPRESSO
Bibliographic record
Abstract
GJ 436b might be the prototype of warm Neptunes that have undergone late migration induced by an outer companion. Precise determination of the orbital architecture of such systems is critical to constraining their dynamical history and evaluating the role of delayed migration in the exoplanet population. To this purpose we analyzed the Rossiter–McLaughlin (RM) signal of GJ 436 b in two transits – recently observed with ESPRESSO – using three different techniques. The high level of precision achieved in radial velocity (RV) measurements allows us to detect the deviation from the Keplerian orbit, despite the slow rotation of the M dwarf host ( v sin i * = 272.0 −34.0 +40.0 m s −1 ), and to measure the sky-projected obliquity ( λ = 102.5 −18.5 +17.2 ° ). The Reloaded RM technique, which allows the stellar RV field along the transit chord to be analyzed, yields λ = 107.5 −19.3 +26.6 ° and v sin i * = 292.9 −49.9 +41.9 m s −1 . The RM Revolutions technique, which allows us to fit the spectral profiles from all planet-occulted regions together, yields λ = 114.1 −17.8 +22.8 ° and v sin i * = 300.5 −57.0 +45.9 m s −1 . The consistent results between these three techniques, and with published results from HARPS/HARPS-N data, confirm the polar orbit of GJ 436b and support the hypothesis that its origin lies in Kozai migration. Results from a joint RM Revolutions analysis of the ESPRESSO, HARPS, and HARPS-N datasets ( λ = 113.5 −17.3 +23.3 ° ; v sin i * = 293.5 −52.2 +43.7 m s −1 ) combined with a revised stellar inclination ( i * = 35.7 −7.6 +5.9 ° or 144.2 −5.9 +7.6 ° ) lead us to constrain the 3D obliquity Ψ to 103.2 −11.5 +12.8 ° .
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".