Motion terms reduce fitted image moment responses at two known weak signals of KIC 5520878 in Kepler Q2 to Q16

We test image moment responses at the two known weak signals near 1.13 cycles per day in KIC 5520878. In Kepler release 25 quarters 2 to 16, adding image motion terms reduces the median fitted moment amplitude from 0.0314 to 0.00883 millipixel with 20-day local fits. The reduction also occurs with 10-day and 40-day fits. A design check gives at most 2.04 percent loss of target information in the main fit. Six of 60 conditional intervals still exclude zero. A selected quarter-7 response does not repeat in three quarters of the same detector season. These tests show strong model dependence. They do not locate the variable source, exclude all blends, or establish a new mode or planet. Errors are conditional, and independent telescope confirmation is absent. The package includes source hashes, code, projected fit matrices, selected data, results and offline checks.

Kepler · KIC 5520878 · image centroid · stellar pulsation · instrument effects