The 2023 TESS pulse delays of HD 133729 favor low eccentricity with linear or quadratic pulse clocks

Two studies give different orbital eccentricities for the pulsating binary HD 133729: 0.0055 and 0.163. Both use TESS sectors 11 and 38. We test the pulse-delay shape in sector 65, which neither orbit study used. We measure pulse phases in separate half-day windows from 9907 public flux samples. We then fit an exact Kepler light delay and a pulse clock for the visit. With a linear clock, the best free eccentricity is 0.00785 and the residual RMS is 1.39 seconds. With eccentricity fixed at 0.163, the best residual RMS is 4.80 seconds. This comparison permits a free orbit orientation, phase, and amplitude. With a quadratic clock, the RMS values are 1.33 and 3.42 seconds. A circular orbit also fits well. All tested flux products, window lengths, pulse harmonics, and baseline choices favor low eccentricity. Signal recovery with the real sampling recovers an injected eccentricity of 0.163. The result supports a low-eccentricity delay shape under the Kepler model and the tested pulse clocks. It does not establish a small nonzero eccentricity. The visit covers about one orbit, and intrinsic pulse-phase changes remain a limitation. We provide the original light curves, source hashes, phase measurements, code, figures, and resampling results.

HD 133729 · TIC 75934024 · blue large-amplitude pulsator · TESS · binary stars · orbital eccentricity · pulse timing · light travel time · reproducible astronomy