Coarse Grain Spectral Analysis for the Low-Amplitude Signature ofMultiperiodic Stellar Pulsators †

Abstract

Coarse Grain Spectral Analysis (CGSA) can explain the possible multiscaling nature of the thousands of low-amplitude peaks observed in the power spectra of some pulsating stars. Spacebased observations allowed for the scientific community to find this kind of structure thanks to their long-duration, high-photometric precision and duty cycle compared to observations from the ground. Although these time series are far from perfect (outliers, trends, gaps, etc.), we used our own data preprocessing method, known as the 2K+1 stage interpolation method, to improve the background noise up to a factor 14, avoiding spurious effects. We applied both techniques, the 2K+1 stage method and the CGSA analysis, to shed some light on a real problem regarding stellar seismology: finding the physical nature of the low-amplitude signature for multiperiodic stellar pulsators.