Fourier spectrum of KIC 8975515 (pink). Panel a: frequency spectrum associated with LC observations (pink) and the significant frequencies with S/N ≥ 4.0 in a box size of 2 d⁻¹ (black). Panel b: same as (a) but for the SC observations (referring to the quarters Q2.3 as well as Q5.1, 5.2, and 5.3). There is no significant frequency between 25 and 50 d⁻¹ and we clipped it off from the illustration.