Relationship between low and high frequencies in the δ Scuti star KIC 9764965

Two years of Kepler spacecraft data of the δ Sct/γ Dor star KIC 9764965 revealed 67 statistically significant frequencies from 0.45 to 59.17 c d–1 (0.005 to 0.685 mHz). The 19 low frequencies do not show equidistant period spacing predicted for gravity modes of successive radial order. We note a favored frequency spacing of 2.053 c d–1 that appears in both the low-frequency (gravity mode) region and high-frequency (pressure mode) regions. The value of this frequency spacing also occurs as a dominant low frequency and in a high-frequency triplet. A peak at exactly twice the value of the 2.053 cd–1 mode is shown not to be a Fourier harmonic of the low-frequency peak due to a different amplitude variability. This behavior is also seen in other δ Sct stars. The test for resonant mode coupling between low and high frequencies could not be carried out due to the small amplitudes of the peaks, making it difficult to separate the parent and child modes. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)