Distinguishing super-Nyquist frequencies via their temporal variation in gamma Doradus stars from continuous photometry

Abstract

Given their tendency to mix in with real pulsations, the reflection of super-Nyquist frequencies (SNFs) pose a threat to asteroseismic properties. Although SNFs have been studied in several pulsating stars, a systematic survey remains to be explored. Here, we propose a method for identifying SNFs from Kepler and TESS photometry by characterizing their periodic frequency modulations using a sliding Fourier transform. After analyzing long-cadence photometry in the Kepler legacy, we identified 304 SNFs in 56 stars from 45607 frequencies in $ gamma Doradus stars, corresponding to a fraction of approximately $0.67<!PCT!>$ and $9.2<!PCT!>$, respectively. Most SNFs were detected in the frequency range of pressure mode over 120\,mu Hz and the fraction of SNF detection increases as frequency up to $ We found only two potential SNFs mixed with gravity modes in two gamma Doradus stars. These findings indicate that SNFs have a negligible impact on global seismic properties, such as those derived from period spacing in gamma Doradus stars. However, we stress that SNFs must be carefully and systematically examined by this method in other pulsating stars, particularly delta Scuti and hot B subdwarf stars, to establish a solid foundation for the precise asteroseismolgy of various types of pulsators.