High-amplitude γ Doradus pulsators in the Kepler data

The overall pulsation amplitude of γ Doradus (GDOR) stars is not very actively studied. Paunzen et al. (2020) identified 15 high-amplitude GDOR (HAGDOR) stars, i.e., whose peak-to-peak light variation in the Johnson V band exceeds 0.1 mag. Based on this set and on a similarly small control sample, Paunzen et al. concluded that HAGDOR pulsators are not physically distinct in any way from regular GDOR stars, except that they are situated at the high end of the continuous GDOR amplitude distribution. To extend this search, we investigated the original 4-year-long Kepler data exhaustively, and identified more than 3200 GDOR stars. Among these, about 100 are high-amplitude ones. We found that these HAGDORs all belong to one specific subclass of GDOR stars, which was defined by Balona et al. (2011) as ASYM. Furthermore, about half of these stars exhibit quasi-equidistant frequency groups in their Fourier amplitude spectra (studied in detail by Kurtz et al. 2015). Some HAGDORs are episodic, showing only a couple of high-amplitude episodes during the 4-year-long Kepler observations. We did not identify any fast-rotating GDOR with high amplitude. In our sample, there are no HAGDOR/δ Scuti hybrids, with one single exception.