Twenty-day two-mode fits predict two known KIC 5520878 combination signals with relative errors below 0.35 in Kepler Q11 to Q16

We test a local two-mode relation for two known combination signals of KIC 5520878. A complex response fitted in Kepler release 25 quarters 2 to 10 predicts quarters 11 to 16 with relative RMS errors of 0.174 to 0.345 in 20-day fits of aperture and corrected flux. Constant child coefficients give errors of 0.887 to 0.945. Ten-day and 30-day fits retain the prediction gain. An exact flux-to-magnitude test with both child terms removed does not reproduce the measured magnitude coefficients. The nearly steady primary limits the interpretation: a gain times the secondary alone predicts nearly as well. The result does not identify a physical coupling mechanism, a new mode, or a planet. Both flux products share exposures. Independent instrument confirmation is absent. Code, selected samples, input hashes, tables, controls, and reproduction instructions are included.

Kepler · RR Lyrae · combination frequencies · nonlinear pulsation · KIC 5520878