Samadi-Ghadim, A. ; Lampens, P. ; Gizon, L.

Poster presented at PLATO Mission Conference 2021: Exploring exoplanets in the habitable zone of solar-like stars, online event on 2021-10-11

Abstract: More than four years of HERMES observations have confirmed KIC 6951642 is a very long orbit (P ≈ 1770 d) single-lined spectroscopic binary (F0-type) with a fast-rotating companion (vsin i = 123±3 km/s). The Fourier spectrum of its four-year photometric observations includes plenty of significant frequencies (594) in low- and high-frequency regions. The high-frequency modes appear with various time-delay patterns. We detected several rotationally split 𝛿 Scuti pulsations centered at 13.96 per day (and an average frequency spacing of Δ𝑓= 0.723±0.006 per day) for KIC 6951642. The detailed study of all significant low frequencies, ranging from 0.72 to 3.60 per day, revealed that the two most dominant frequencies (with the same amplitude or larger than that of the p-modes) are a combination of the lowest-frequency modes (𝑓3 = 𝑓< 0.17 per day), i.e. 𝑓orhrm + 𝑚𝑓orhrm (𝑚 = 12,14). We suggest the lowest-frequency modes are very large harmonics (orders of 10) of orbital frequency (≈0.0006 per day). We verified the other most dominant low-frequencies as harmonics of rota3on frequency 0.721 per day and its combinations. Finally, we reject the probability of hybrid pulsations in the fast-rotating companion of KIC 6951642, and propose that it is a 𝛿 Scuti pulsator with a candidate rotation frequency of 0.721 per day.

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