HD 74423's second harmonic does not match a scaled square of its main pulse envelope in 12 TESS sectors
We tested a quadratic model for HD 74423 with 200,515 public TESS exposures from 2019 to 2025. The model requires B(phi) = k A(phi)^2. A is the complex envelope of the observed main pulse. B is the envelope of its second harmonic. The scale k is constant within each sector. It may be complex and may differ between sectors. Independent Fourier fits in 12 sectors do not match this relation. The best scale leaves 98.48% to 99.75% of the fitted harmonic coefficient norm as a residual. A selected two-sideband contrast must be zero under the model. Its magnitude is 219.6 ppm in sector 89 and 223.0 ppm in sector 90. Conditional 95% intervals are 208.9 to 230.6 ppm and 214.3 to 231.9 ppm. The contrast also differs from zero in all earlier sectors. Changes to flux processing, baseline, sideband range, orbit frequency, and orbit harmonics preserve the result in endpoint checks. The 2020 table already suggested a mismatch. This work adds a specified test, later-data replication, and a reusable analysis package. The result concerns a quadratic response after integration across the visible stellar surface. It does not reject a local quadratic surface response. Residual-block intervals depend on the fitted signal and noise model. The package includes original inputs, source hashes, code, fitted coefficients, covariance matrices, and figures.
HD 74423 · TESS · stellar pulsations · tidally tilted pulsator · harmonic envelope · quadratic response · public data · reproducible research
References
5- usesTESS fits show increased central pulse amplitude relative to the second orbit harmonic of HD 74423 from 2019 to 2025 sci:sha256:445f70eb9cf40e44d7ca21ac25cd3d7772a4b80096e20b3fc24542153f3b8edf
We reuse its 12 preserved public TESS files, provenance records, and parts of its sector fit code. We extend the second harmonic range and test a different relation.
- A TESS model gives a conditional 95% upper bound of 3.1% on HD 74423's mean pulse pattern change from 2019 to 2025 sci:sha256:26e9bace1f25a696dcba5562325e8306b1dadcee208761301a2e86926a8be558
This study tests the stability of the main pulse envelope. Our test compares the second harmonic with the square of that envelope.
- usesdoi:10.1038/s41550-020-1035-1
The discovery paper supplies the reference frequencies, orbital phase origin, and original harmonic table. That table guided the selected contrast.
- doi:10.1093/mnras/staa2376
This work models tides, surface pulses, and their integration into observed light. It gives context for the limited physical scope of our test.
- usesdoi:10.17909/T9-NMC8-F686
This public TESS collection is the source of the 12 SPOC light curves. The package records exact MAST product addresses and hashes.
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