Ultra-short-period giant · stellar activity · TESS

WASP-19 b

A hot Jupiter completing an orbit in under a day, analyzed with timing freedom and explicit noise inflation in a regime where irradiation and stellar variability matter.

REAL TESS DATATIMING-AWARE FITPRIMARY-SOURCE CONTEXTTESTED PIPELINE

AI-generated artist’s interpretation · not a direct image

What the corrected fit shows

Transit supportSUPPORTED (ΔBIC ≥ 10)
Fitted midpoint shift+0.036 h
Model depth22844.2 ± 140.2 ppm
ΔBIC (null − transit)44465.2

The timing-adjusted transit is strongly preferred by ΔBIC = 44465.2. Its fitted midpoint is +0.036 hours from the historical prediction; the model's mid-transit depth is 22844.2 ± 140.2 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-19 b
The dotted vertical line is the historical archive prediction; the dashed colored line marks the fitted midpoint (+0.036 h). The smooth curve fits timing, radius ratio, impact parameter, and a local linear baseline.

Explicit model comparison

Linear nullχ² 56047.03 / 8210 dof

BIC = 56065.05

Limb-darkened transitχ² 11554.80 / 8207 dof

BIC = 11599.87

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 depth22782.8 +/- 265.1 ppm
Supported / fitted sectors3 / 3
Residual beta range3.21-3.42

The archive prediction was timing-adjusted independently in 3 fitted sector(s) (S9, S62, S63), 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 3.21-3.42). The robust inverse-variance model depth across supported sectors is 22782.8 +/- 265.1 ppm; Cochran Q = 0.12 for 2 dof (p = 0.9433). 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-19 b
Independent sector transit fits. Reproduced from the committed public TESS SPOC files.
Sector depth consistency for WASP-19 b
Sector depth consistency. Reproduced from the committed public TESS SPOC files.
Residual RMS time-averaging diagnostic for WASP-19 b
Residual RMS time-averaging diagnostic. Reproduced from the committed public TESS SPOC files.

TESS-only orbital-evolution sensitivity

Independently timed transits89
Timing baseline1,496 days
ΔBIC (linear − quadratic)−3.5
Conditional Ṗ−199 ± 203 ms yr−1

The linear ephemeris is preferred. The three-sector TESS sampling cannot probe the few-ms-per-year regime because Sectors 62 and 63 are adjacent and separated from Sector 9 by a long gap. The conditional 95% negative bound is only Ṗ > −597 ms yr−1, corresponding to Q′★ > 4.7 × 103 under the stated tidal convention. This is a documented sensitivity limit, not a decay detection.

Linear and quadratic timing models fitted to 89 WASP-19 b TESS transits
Top: individual TESS transit times with beta and sector-jitter inflated errors. Bottom: residuals from the preferred linear ephemeris. The unconstrained curvature in the long observing gap explains the weak decay bound.

Petrucci et al. (2020) preferred a constant period using a ten-year baseline. A newer 15-year analysis by Rajkumar et al. (2026) instead reports slow non-linear structure consistent with possible apsidal precession. These TESS sectors alone cannot distinguish those long-baseline interpretations.

Machine-readable outputs: event timings and model statistics.

The system

Radius15.86 Earth radii
Mass366.77 Earth masses
Orbital period0.788839 days
Transit duration1.607 hours
Semi-major axis0.0165 AU
Equilibrium temperature2113 K
Host and distanceWASP-19 · 268.32 pc
Discovery2009 · 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 tess2019058134432-s0009-0000000035516889-0139-s_lc.fits, TESS Sector 9, 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, python scripts/analyze_multisector.py, and python scripts/analyze_timing_limits.py to regenerate the figures and CSVs, then pytest tests/ -v to check the documented values against the real files.

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.
  • Individual timings share sector-level detrending and stellar-activity systematics; a fitted jitter does not make them fully independent.
  • The one-early/two-adjacent-late sector geometry gives a weak quadratic constraint and cannot reject apsidal precession.
  • Published global fits with physical priors, instrument-specific detrending, and simultaneous sectors remain authoritative.

References

  1. Hebb et al. 2010 — discovery reference listed by the NASA Exoplanet Archive.
  2. Ricker et al. (2015), Transiting Exoplanet Survey Satellite (TESS), doi:10.1117/1.JATIS.1.1.014003.
  3. TESS Team, TESS Light Curves — All Sectors, MAST, doi:10.17909/t9-nmc8-f686; Sector 9 used here.
  4. NASA Exoplanet Archive, saved TAP row retrieved 2026-08-15.
  5. Petrucci et al. (2020), Discarding orbital decay in WASP-19b after one decade.
  6. Rajkumar et al. (2026), Long-term monitoring of WASP-19 b, doi:10.1051/0004-6361/202556822.