Circular orbital fits give different 2022 to 2024 eclipse changes for two KELT-1 b TESS flux products

We tested the reported eclipse changes of KELT-1 b with all three public 120 s SPOC visits in a fixed archive search. Each circular fit has an eclipse coefficient, independent first and second orbital harmonics, and a cubic spline baseline. PDCSAP corrected flux gives a 2024 minus 2022 depth change of 61 parts per million (ppm), with an approximate 95% block interval from -59 to 182 ppm. Crowding-corrected SAP aperture flux gives 148 ppm, with an interval from 20 to 276 ppm. The products use the same observations. A paired fit with identical exposures and weights accounts for their difference: the product correction contributes -86 ppm to the later contrast, with an interval from -164 to -9 ppm. More orbital harmonics reduce this paired contrast and make its interval include zero. The main products retain the known earlier decrease, but its interval also includes zero in the four-harmonic control. These tests do not give a common answer across flux products about a return to the 2019 brightness. The intervals assume that short orbital blocks describe the errors. They cannot measure errors shared by a full sector. The new contribution is a dataset of full-orbit fits and a paired projection of the flux-product difference. Original data, source records, code, figures, all fixed controls, and an offline repeat check are supplied. This study does not establish a physical cause for the variability.

KELT-1 b · TESS · brown dwarf · secondary eclipse · orbital light curve · PDCSAP · SAP · photometry · data processing · reproducible research