Unveiling the intricate symphony of nonlinear pulsation mode interactions in high-amplitude δ Scuti stars

Abstract

Information on the interiors of stars can be gleaned from 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 determine the interior structures of stars. Here, we report the discovery of peculiar pulsation mode interactions in the high-amplitude δ Scuti star KIC 6382916 (J19480292+4146558) that challenge the reliability of independent pulsation modes as indicators of a star’s internal structure. Through analysis of archival data, we find distinct variations in the amplitudes and frequencies of three independent pulsation modes and their harmonics and 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 reveal additional pulsation mode interaction details and patterns. Notably, our findings regarding the phenomena related to the harmonics of independent pulsation modes challenge the traditional understanding in this area. These discoveries serve as cornerstones for future research and advance nonlinear asteroseismology.