What the corrected fit shows

Transit supportSUPPORTED (ΔBIC ≥ 10)

Fitted midpoint shift+1.444 h

Model depth16785.5 ± 100.3 ppm

ΔBIC (null − transit)30092.5

The timing-adjusted transit is strongly preferred by ΔBIC = 30092.5. Its fitted midpoint is +1.444 hours from the historical prediction; the model's mid-transit depth is 16785.5 ± 100.3 ppm. The support decision uses ΔBIC ≥ 10; timing-search p-values are not presented as blind-detection probabilities.

Timing-adjusted limb-darkened transit fit for WASP-17 b — The dotted vertical line is the historical archive prediction; the dashed colored line marks the fitted midpoint (+1.444 h). The smooth curve fits timing, radius ratio, impact parameter, and a local linear baseline.

Explicit model comparison

Linear nullχ² 34111.14 / 4042 dof

BIC = 34127.75

Limb-darkened transitχ² 3993.76 / 4039 dof

BIC = 4035.28

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

Supported combined depth16828.0 +/- 89.3 ppm

Supported / fitted sectors2 / 2

Residual beta range1.28-1.46

The archive prediction was timing-adjusted independently in 2 fitted sector(s) (S12, S38), of which 2 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 1.28-1.46). The robust inverse-variance model depth across supported sectors is 16828.0 +/- 89.3 ppm; Cochran Q = 0.14 for 1 dof (p = 0.7131). These scaled errors address underestimated scatter and short-timescale correlation, but they are not a full Gaussian-process or physical limb-darkened transit fit.

Independent sector transit fits for WASP-17 b — Independent sector transit fits. Reproduced from the committed public TESS SPOC files.

Sector depth consistency for WASP-17 b — Sector depth consistency. Reproduced from the committed public TESS SPOC files.

Residual RMS time-averaging diagnostic for WASP-17 b — Residual RMS time-averaging diagnostic. Reproduced from the committed public TESS SPOC files.

Published dayside spectrum

Flat testsχ²ν = 8.68–12.45

Pairwise median |Δ|41.7–61.5 ppm

Negative-depth bins21 · 0 · 25

These are three reductions of the same NIRISS/SOSS eclipse, not three independent observations. Every reduction rejects its own weighted-flat model under the supplied marginal errors, establishing wavelength structure but not a molecular identity. Pairwise quadrature-normalized differences are descriptive independence references because the pipelines share photons and systematics.

Three published reductions of the WASP-17 b emission spectrum — Negative optical eclipse depths are retained rather than censored. Data: 10.5281/zenodo.14003330.

Pairwise wavelength-dependent differences between the three reductions — Cross-pipeline differences. The shaded quadrature-error reference is not a formal confidence band because the reductions are correlated.

See methods and claim boundary, validation, and machine-readable agreement diagnostics.

Atmospheric evidence: detection, limit, or unknown?

All three reductions reject a wavelength-independent dayside spectrum. The 6.4σ H2O attribution, supersolar water abundance, and non-inverted temperature-pressure profile come from the paper’s atmospheric retrieval—not from this repository’s flat-spectrum test. The source also shows that the retrieval is sensitive to pressure-temperature parameterization and to whether negative optical eclipse depths are permitted.

Source-graded atmospheric evidence — Literature retrieval evidence is kept separate from calculations reproduced here.

Species	Status	Evidence	Basis
H2O	reported detection	6.4σ	peer-reviewed retrieval
CO / CO2	not established here	no repository retrieval	structure is non-specific
O2	no evidence	not reported	no molecular-oxygen inference

Primary source: Gressier et al. 2025, JWST-TST DREAMS. Water is not molecular oxygen and is not, by itself, a biosignature.

The system

Radius	20.96 Earth radii
Mass	247.91 Earth masses
Orbital period	3.735430 days
Transit duration	4.423 hours
Semi-major axis	0.0515 AU
Equilibrium temperature	1755 K
Host and distance	WASP-17 · 405.91 pc
Discovery	2009 · Transit · SuperWASP

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 tess2019140104343-s0012-0000000066818296-0144-s_lc.fits, TESS Sector 12, 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 plus python scripts/analyze_spectrum.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

Anderson et al. 2010 — 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 12 used here.
NASA Exoplanet Archive, saved TAP row retrieved 2026-08-15.