Roaring Storms in the Planetary-mass Companion VHS 1256-1257 b: Hubble Space Telescope Multiepoch Monitoring Reveals Vigorous Evolution in an Ultracool Atmosphere
Bibliographic record
Abstract
Abstract The photometric and spectral variability of brown dwarfs probes heterogeneous temperature and cloud distributions and traces the atmospheric circulation patterns. We present a new 42 hr Hubble Space Telescope (HST) Wide Field Camera 3 G141 spectral time series of VHS 1256-1257 b, a late L-type planetary-mass companion that has been shown to have one of the highest variability amplitudes among substellar objects. The light curve is rapidly evolving and best fit by a combination of three sine waves with different periods and a linear trend. The amplitudes of the sine waves and the linear slope vary with the wavelength, and the corresponding spectral variability patterns match the predictions by models invoking either heterogeneous clouds or thermal profile anomalies. Combining these observations with previous HST monitoring data, we find that the peak-to-valley flux difference is 33% ± 2% with an even higher amplitude reaching 38% in the J band, the highest amplitude ever observed in a substellar object. The observed light curve can be explained by maps that are composed of zonal waves, spots, or a mixture of the two. Distinguishing the origin of rapid light curve evolution requires additional long-term monitoring. Our findings underscore the essential role of atmospheric dynamics in shaping brown-dwarf atmospheres and highlight VHS 1256-1257 b as one of the most favorable targets for studying the atmospheres, clouds, and atmospheric circulation of planets and brown dwarfs.
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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 | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| 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".