A fixed shape fit to CU Virginis TESS sector 50 flux gives a period 1.34 seconds longer than the printed 2019 clock predicts
We test the printed 2019 fifth-degree phase clock for CU Virginis with public TESS sector 50 observations from 2022. A fixed shape fit with eight Fourier harmonics and slow flux trends connects phase across observation gaps. It uses 11,142 samples with QUALITY=0. It gives a local brightness period of 0.520687602 day at BJD TDB 2459679.619926. The exact reciprocal derivative of the printed clock gives 0.520672053 day. The measured period is 1.3434 seconds longer. A conditional 95 percent range from four-rotation noise blocks is -0.179 to +0.178 second about the fit. Tested trend and harmonic choices span 0.104 second. Fits to the two long intervals differ by 0.45 second. If each interval has a free phase offset, the excess over the polynomial is 1.080 seconds, with a cluster standard error of 0.324 second. The older 66-year cosine clock differs from the full-visit fit by only 0.060 second, but one visit cannot test that cycle. A 2025 study already measured periods from this TESS run. Our contribution is the full-shape local benchmark, the test of printed coefficients, and the error and numerical checks. The result assumes a stable phase pattern. It does not prove a change in the rotation of the whole star. Historical prediction errors are not calibrated. The package preserves the source file, archive queries, code, derived data, figures, and repeat instructions.
CU Virginis · HD 124224 · TESS · stellar rotation · stellar variability · magnetic stars · phase clocks · time series · reproducible research
References
4- usesdoi:10.48550/arXiv.1912.12072
We use the printed fifth-degree phase coefficients and the older cosine phase formula from version 1 to calculate clock values at the 2022 observation time. We preserve the authors' stated limits for changes on time scales of several years.
- doi:10.3390/galaxies13040097
This prior study already measured seasonal periods from the same 2022 TESS run. It establishes the prior use of these observations and the earlier period-decrease result. Our contribution tests the printed fifth-degree coefficients with a full-shape fit and explicit error checks.
- usesdoi:10.17909/fqw7-pc41
We analyze the public SPOC sector 50 light-curve file for TIC 420777918. The package preserves the unmodified file, its hash, pipeline version, source URI, and archive queries.
- A fixed shape fit to HD 142990 TESS sector 91 data gives a longer period than the constant spin-up forecast sci:sha256:f0af84624d3e2ad8310677ae905e2fbec6228711fe0dd61935ad3e481dbf948b
This fixed shape clock test for another magnetic star gives method context. We use no code or data from it.
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