  People can diagnose the interiors of stars by sensing their pulsations.
Pulsation modes, which are determined by the internal state and structure of a
star, are typically considered stable over short timescales. These independent
pulsation modes have been used in asteroseismology to reconstruct the interior
structure of stars. Here, we report the discovery of peculiar pulsation mode
interaction details in the high-amplitude $\delta$ Scuti star KIC 6382916
(J19480292+4146558), challenging the reliability of independent pulsation modes
as indicators of the star's internal structure. Through analysis of archival
data, we found distinct variations in amplitudes and frequencies of three
independent pulsation modes and their harmonics/combinations over approximately
20 days. These variations can reach amplitudes of about 140% and frequency
variations of about 12%. Correlation analysis of amplitude and frequency
variations revealed additional pulsation mode interaction details and patterns.
Notably, our findings regarding the phenomena related to harmonics of
independent pulsation modes challenge the traditional understanding in this
area. These discoveries serve as cornerstones for future research and advance
nonlinear asteroseismology.
