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astro-ph.EP · Earth and Planetary Astrophysicsastro-ph.IM · Instrumentation and Methods for Astrophysics

Thirty-eight WASP-4 b transits in 2026 agree with circular and cubic companion models under fixed shape and noise assumptions

We measure 38 transit times of WASP-4 b from public TESS sectors 103, 105, and 106 in 2026. We test forecasts from earlier data under a fixed transit shape and adopted timing errors. Training uses 77 earlier TESS transits, 54 ground timing epochs, and 37 radial velocities. One joint model uses a cubic companion velocity and its integrated light delay. The other uses an exact circular companion orbit and its light delay. Both models have nine fitted parameters. The weighted mean observed time minus forecast is +6.56 ± 11.64 seconds for the cubic model and +5.56 ± 10.65 seconds for the circular model. These errors retain the shared training uncertainty. The two mean forecasts differ by only 1.00 second. The 2026 times do not separate the models at the measured precision. In the circular model, the approximate 95% period profile range changes from 19.6–28.3 years with earlier data to 19.7–25.6 years with all data. All tested baseline, ground-source, and assumed shared-sector error controls give mean residuals within one standard error of zero. We supply raw inputs, measured times, source hashes, code, figures, and a fresh-run comparison. These conditional results do not confirm a new planet or settle the cause of the long-term timing changes.

WASP-4 b · TESS · transit timing · light travel time · radial velocity · forecast covariance · public astronomical data

Admitted 2 citing publications

References

9
  1. usesdoi:10.3847/PSJ/ae21db

    We use the final 22 December 2025 HIRES table, fixed RV jitter values, sector 96 times for a same-exposure check, and the integrated cubic velocity model.

  2. usesdoi:10.3847/1538-3881/ac686f

    We select CORALIE and HARPS velocities from the machine-readable source table and retain its reference labels.

  3. usesdoi:10.3847/1538-4365/ac545b

    We select and combine pre-TESS ground times from table 4 at a frozen Git commit.

  4. usesdoi:10.17909/t9-nmc8-f686

    The eight public TESS SPOC light curves provide the 115 transit measurements, including 38 in 2026.

  5. usesdoi:10.1086/683602

    We use batman to calculate exposure-integrated transit models.

  6. doi:10.1117/12.2233418

    We credit the SPOC pipeline that produced the archived light curves.

  7. doi:10.1093/mnras/stz2620

    Ba19 in the reused Turner table identifies these underlying CORALIE and HARPS reductions.

  8. doi:10.1093/mnras/staf1009

    This prior work gives a different physical interpretation of the WASP-4 timing trend. We do not resolve that question.

  9. usesShared training uncertainty limits the constant-period mean offset to 1.8 standard errors for 35 WASP-12 b TESS transits assuming fixed shapes and independent timing errors sci:sha256:9b822345ee019e5d88bd8be80f46ea9ede25948289d0c33e13191cc943a7cc04

    We use its general principle that a mean forecast test must retain shared training uncertainty. We reuse no code or measurements from this WASP-12 b study.

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