What the corrected fit shows
The timing-adjusted transit is strongly preferred by ΔBIC = 36870.8. Its fitted midpoint is -0.023 hours from the historical prediction; the model's mid-transit depth is 2925.3 ± 18.8 ppm. The support decision uses ΔBIC ≥ 10; timing-search p-values are not presented as blind-detection probabilities.
Explicit model comparison
BIC = 42153.35
BIC = 5282.55
The null fits a local intercept and slope. The transit adds bounded midpoint, radius-ratio, and impact-parameter freedom while retaining the same baseline terms. Fixed limb darkening and circular geometry make this a diagnostic fit rather than a full system retrieval.
Multi-sector robustness and noise
The archive prediction was timing-adjusted independently in 3 fitted sector(s) (S24, S25, S52), of which 3 meet Delta BIC >= 10. Formal depth errors were inflated by sqrt(max(reduced chi-square, 1)) times the residual time-averaging beta factor (observed range 1.75-3.12). The robust inverse-variance model depth across supported sectors is 2915.2 +/- 23.4 ppm; Cochran Q = 0.20 for 2 dof (p = 0.9069). These scaled errors address underestimated scatter and short-timescale correlation, but they are not a full Gaussian-process or physical limb-darkened transit fit.
Atmospheric evidence: detection, limit, or unknown?
JWST/NIRCam measured CO2 and H2O absorption in this planet's dayside emission. Published retrieval and self-consistent-model studies disagree substantially on the inferred metallicity, so the report presents the molecules as supported while keeping the abundance interpretation model-dependent.
| Species | Status | Evidence | Basis |
|---|---|---|---|
| CO2 | reported detection | strong 4.3-micron feature | JWST emission-spectrum modeling |
| H2O | reported detection | absorption features | JWST emission-spectrum modeling |
| VO | model-dependent hint | circumstantial | later self-consistent atmosphere models |
| O2 | no evidence | not reported | no molecular-oxygen inference |
Primary source: Bean et al. 2023, Nature; Gagnebin et al. 2024. Oxygen-bearing molecules are not detections of molecular oxygen (O2) and are not, by themselves, biosignatures.
The system
| Radius | 8.29 Earth radii |
|---|---|
| Mass | 120.78 Earth masses |
| Orbital period | 2.875890 days |
| Transit duration | 3.140 hours |
| Semi-major axis | 0.0436 AU |
| Equilibrium temperature | 1626 K |
| Host and distance | HD 149026 · 75.86 pc |
| Discovery | 2005 · Radial Velocity · Subaru Telescope |
Values are from the exact saved NASA Exoplanet Archive pscomppars row in data/system_parameters.csv.
Data and reproducibility
The observed photometry is the public MAST file tess2020106103520-s0024-0000000255930614-0180-s_lc.fits, TESS Sector 24, collection DOI 10.17909/t9-nmc8-f686. It is stored unmodified. Exact archive URI, URL, retrieval date, and checksum are in data/SOURCE.md.
Run python scripts/analyze_transit.py and python scripts/analyze_multisector.py and python scripts/analyze_atmospheric_evidence.py to regenerate the figures and CSVs, then pytest tests/ -v to check the documented values against the real file.
Limitations
- The orbit is circular and the quadratic limb-darkening coefficients are fixed representative values.
- The scaled semi-major axis comes from saved composite values whose uncertainties are not propagated.
- The midpoint is searched within a bounded window; ΔBIC is used as the support gate.
- PDCSAP processing, dilution, stellar variability, timing variations, and covariance can bias the geometry.
- Published global fits with physical priors, instrument-specific detrending, and simultaneous sectors remain authoritative.
References
- Sato et al. 2005 — discovery reference listed by the NASA Exoplanet Archive.
- Ricker et al. (2015), Transiting Exoplanet Survey Satellite (TESS), doi:10.1117/1.JATIS.1.1.014003.
- TESS Team, TESS Light Curves — All Sectors, MAST, doi:10.17909/t9-nmc8-f686; Sector 24 used here.
- NASA Exoplanet Archive, saved TAP row retrieved 2026-08-15.