JWST/MIRI observations of the young TWA 27 system: Hydrocarbon disk chemistry, silicate clouds, and evidence of a circumplanetary disk
Bibliographic record
Abstract
Context . The Mid-Infrared Instrument (MIRI) on board the James Webb Space Telescope (JWST) enables the characterisation of young self-luminous gas giants in a previously inaccessible wavelength range, revealing insights into physical processes of the gas, dust, and clouds. Aims . We aim to characterise the young planetary system TWA 27 (2M1207) in the mid-infrared, revealing the atmosphere and disk spectra of the M9 brown dwarf TWA 27A and its L6 planetary-mass companion TWA 27b. Methods . We obtained data from the MIRI Medium Resolution Spectrometer (MRS) from 4.9 to 20 μm, and MIRI Imaging in the F1000W and F1500W filters. We applied high-contrast imaging data processing methods in order to extract the companion spectral energy distribution up to 15 μm at a separation of 0.″78 and contrast of 60. Using published spectra from JWST/NIRSpec, we analysed the 1-20 μm spectra with self-consistent atmosphere grids, and the molecular disk emission from TWA 27A with 0D slab models. Results . We find that the atmosphere of TWA 27A is well fitted with the BT-SETTL model of effective temperature T eff ~ 2780 K, log g ~ 4.3, and a blackbody component of ∼740 K for the circumstellar disk inner rim. The disk consists of at least 11 organic molecules, and neither water nor silicate dust emission are detected. The atmosphere of the planet TWA 27b matches with a T eff ~ 1400 K low-gravity model when adding extinction, with the ExoREM grid fitting the best. MIRI spectra and photometry for TWA 27b reveal a silicate cloud absorption feature between 8-10 μm, and evidence (>5σ) of infrared excess at 15 μm that is consistent with predictions from circumplanetary disk emission. Conclusions . The MIRI observations present novel insights into the young planetary system TWA 27, showing a diversity of features that can be studied to understand the formation and evolution of circumplanetary disks and young dusty atmospheres.
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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 | 0.001 | 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".