Minimum Orbital Period of Precataclysmic Variables
Bibliographic record
Abstract
Abstract More than 20 precataclysmic variable (pre-CV) systems have now been discovered with very short orbital periods ranging from 250 minutes down to 68 minutes. A pre-CV consists of a white dwarf (WD) or hot subdwarf primary and a low-mass companion star, where the companion star has successfully ejected the common envelope (CE) of the primary progenitor, but mass transfer from the companion star to the primary has not yet commenced. In this short-period range, a substantial fraction of the companion stars are likely to be either brown dwarfs with masses ≲0.07 M ⊙ or stars at the bottom of the main sequence (MS; ≲0.1 M ⊙). The discovery of these short-period pre-CVs raises the question, what is the shortest possible orbital period of such systems? We ran 500 brown dwarf/low-mass MS models with Modules for Experiments in Stellar Astrophysics that cover the mass range from 0.002 to 0.1 M ⊙. We find that the shortest possible orbital period is 40 minutes, with a corresponding brown dwarf mass of 0.07 M ⊙ for an age equal to a Hubble time. We discuss the past evolution of these systems through the CE and suggest that many of the systems with present-day WD primaries may have exited the CE with the primary as a helium-burning hot subdwarf. We also characterize the future evolution of the observed systems, which includes a phase as CVs below the conventional period minimum.
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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 | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".