A 43 d transiting Neptune and two 25 d Saturns from <i>TESS</i> , NGTS, and ASTEP
Bibliographic record
Abstract
ABSTRACT Beyond orbital periods of 10 d, there is a dearth of known transiting gas giants. On longer orbits, planets are less affected by their host star, and become ideal probes of planet formation, migration, and evolution. We report the discovery of a long-period Neptune and two Saturns, each initially identified as single transits in the TESS (Transiting Exoplanet Survey Satellite) photometry, and solved through additional transits from ground-based follow-up photometric observations by NGTS (Next Generation Transit Survey) and ASTEP (Antarctic Search for Transiting ExoPlanets). High-resolution radial velocity mass measurements using CORALIE and HARPS (High Accuracy Radial Velocity Planet Searcher) confirm their planetary nature. From joint modelling of the photometric and spectroscopic data, we determine an orbital period of $43.12655_{-0.00017}^{+0.00012}~$ d, radius of $3.65\pm 0.22~\mathrm{R_{\hbox{$\oplus $}}}$, and mass of $19.1_{-4.5}^{+4.9}~\mathrm{M_{\hbox{$\oplus $}}}$ for NGTS-34 b, making it one of the longest period well-characterized transiting Neptunes. Orbiting a late F-type star, bright in the K band (Kmag$~\simeq 7.9$), it is amenable for cool atmosphere studies using James Webb Space Telescope or Ariel (Atmospheric Remote-sensing Infrared Exoplanet Large). TOI-4940 b is a small Saturn on a $25.867811_{-0.000056}^{+0.000058}~$ d orbit with a radius of $6.61\pm 0.37~\mathrm{R_{\hbox{$\oplus $}}}$ and an upper mass limit $< 89~\mathrm{M_{\hbox{$\oplus $}}}$. NGTS-35 b(=TOI-6669 b) is a larger Saturn on a $25.241192\pm 0.000022~$ d, moderately eccentric orbit ($e = 0.192_{-0.033}^{+0.037}$), with a radius of $10.90\pm 0.65~\mathrm{R_{\hbox{$\oplus $}}}$ and a mass of $152_{-19}^{+22}~\mathrm{M_{\hbox{$\oplus $}}}$. With an assumed albedo $A=0.3$, each of these planets has an equilibrium temperature below 700 K, with NGTS-35 b especially cold at $450~$ K. These three giants add to the small but growing population of long-period planets that can further our understanding of planet formation mechanisms.
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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 | 0.000 | 0.000 |
| 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 | 0.000 |
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".