2023ApJ...955...80S

In this paper, we present an analysis of the pulsating behavior of Kepler target KIC 9845907. Using the data from Kepler, we detected 85 significant frequencies, including the first overtone f₁ = 17.597 day^–1 as the dominant frequency, the non-radial independent frequency f₃ = 31.428 day^–1 (ℓ = 1), as well as two modulation terms f_m1 = 0.065 day^–1 and f_m2 = 1.693 day^–1. We found fourteen pairs of triplet structures with f_m1 or f_m2, four pairs of which can further form quintuplet structures. We note these are the most intriguing features discovered in this study and they were recognized for the first time in δ Scuti stars. We discussed several possible explanations, i.e., beating, the Blazhko effect, combination mode hypothesis, nonlinear mode coupling, large separation, and stellar rotational splitting for these equidistant structures. Our asteroseismic models indicate this modulation with f_m1 might be related to the rotational splitting. The study of more δ Scuti stars with triplet and/or quintuplet structures using high-precision space photometry would be helpful to further explore its origin.