Distinguishing SNFs via their temporal variation

Although SNFs have been studied in several pulsating stars, a systematic survey remains scarcely to be explored. Here we propose a method to identify 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 have identified 304 SNFs in 56 stars from 45607 frequencies in ~600 {gamma} Doradus stars, corresponding to a fraction of approximately 0.67% and 9.2%, respectively. Most SNFs are detected in the frequency range of pressure mode over 120{mu}Hz and the fraction of SNF detection increases as frequency up to ~7%. We barely found two potential SNFs mixed with gravity modes in two {gamma} Doradus stars.