Análises de Fourier e Wavelet para o estudo de variabilidade estelar e trânsito planetário em curvas de luz da missão TESS

Abstract

Computational methods are essential tools for the treatment of various problems in astrophysics. In the present work, we analyzed four light curves from the TESS space mission and studied the stellar variability and planetary transits present in these light curves. Our analysis is based on methods related to integral transforms, specifically the FFT and Lomb-Scargle periodograms, as well as the wavelet transform. The time-frequency analysis of stellar light curves, using the wavelet transform, was an essential practice for an in-depth study in the identification of rotation, planetary transits and pulsation signatures of the stars. We apply the wavelet Morlet of 6th order, which provides a high resolution of time and frequency. When using the wavelet transform in the signal, we obtain the local and global power wavelet spectra. In particular, the wavelet transform is a very useful tool for the study of non-stationary signals. In general, this technique allows a more robust analysis of the variability signatures associated with stellar phenomena if compared with other techniques. We detected stellar rotation periods of certain analyzed light curves and we also identified beat patterns in the local wavelet map of stars that present pulsation. We also analyzed the transits in two light curves that indicate the presence of exoplanets, obtaining basic parameters, such as the planet's orbital periods and the depth and duration of the transits. The results presented in our work were compared with results from the literature, showing to be essentially in agreement with the latter ones. In comparison with most of these works, our results introduce the wavelet technique as an additional contribution that enriches our interpretation.