A Planetary Companion to γ Cephei A
Bibliographic record
Abstract
We report on the detection of a planetary companion in orbit around the primary star of the binary system γ Cephei. High-precision radial velocity measurements using four independent data sets spanning the time interval 1981-2002 reveal long-lived residual radial velocity variations superposed on the binary orbit that are coherent in phase and amplitude with a period or 2.48 yr (906 days) and a semiamplitude of 27.5 m s -1 . We performed a careful analysis of our Ca II H and K S -index measurements, spectral line bisectors, and Hipparcos photometry. We found no significant variations in these quantities with the 906 day period. We also reanalyzed the Ca II λ8662 measurements of Walker et al., which showed possible periodic variations with the "planet" period when first published. This analysis shows that periodic Ca II equivalent width variations were only present during 1986.5-1992 and absent during 1981-1986.5. Furthermore, a refined period for the Ca II λ8662 variations is 2.14 yr, significantly less than the residual radial velocity period. The most likely explanation of the residual radial velocity variations is a planetary-mass companion with M sin i = 1.7 M J and an orbital semimajor axis of a 2 = 2.13 AU. This supports the planet hypothesis for the residual radial velocity variations for γ Cep first suggested by Walker et al. With an estimated binary orbital period of 57 yr, γ Cep is the shortest period binary system in which an extrasolar planet has been found. This system may provide insights into the relationship between planetary and binary star formation.
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 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".