HD 22496 b: The first ESPRESSO stand-alone planet discovery
Bibliographic record
Abstract
Context. The ESPRESSO spectrograph is a new powerful tool developed to detect and characterize extrasolar planets. Its design allows an unprecedented radial velocity precision (down to a few tens of cm s−1) and long-term thermomechanical stability. Aims. We present the first stand-alone detection of an extrasolar planet by blind radial velocity search using ESPRESSO; our aim is to show the power of the instrument in characterizing planetary signals at different periodicities in long observing time spans. Methods. We used 41 ESPRESSO measurements of HD 22496 obtained within a time span of 895 days with a median photon noise of 18 cm s−1. A radial velocity analysis was performed to test the presence of planets in the system and to account for the stellar activity of this K5-K7 main-sequence star. For benchmarking and comparison, we attempted the detection with 43 archive HARPS measurements and in this work we compare the results yielded by the two datasets. We also used four TESS sectors to search for transits. Results. We find radial velocity variations compatible with a close-in planet with an orbital period of P = 5.09071 ± 0.00026 days when simultaneously accounting for the effects of stellar activity on longer timescales (Prot = 34.99−0.53+0.58 days). We characterize the physical and orbital properties of the planet and find a minimum mass of 5.57−0.68+0.73 M⊕, right in the dichotomic regime between rocky and gaseous planets. Although not transiting according to TESS data, if aligned with the stellar spin axis, the absolute mass of the planet must be below 16 M⊕. We find no significant evidence for additional signals in the data with semi-amplitudes above 56 cm s−1 at 95% confidence. Conclusions. With a modest set of radial velocity measurements, ESPRESSO is capable of detecting and characterizing low-mass planets and constraining the presence of planets in the habitable zone of K dwarfs down to the rocky-mass regime.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 0.003 |
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".