Banca de DEFESA: SUZIERLY ROQUE DE LIRA ARAUJO

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : SUZIERLY ROQUE DE LIRA ARAUJO
DATE: 17/12/2019
TIME: 09:00
LOCAL: Auditório do CCET
TITLE:

On the photometric variability of white dwarf stars

KEY WORDS:

white dwarfs, variability, photometry, wavelet, Lomb-Scargle

PAGES: 113
BIG AREA: Ciências Exatas e da Terra
AREA: Física
SUMMARY:

Photometric variability can provide important information about white dwarfs, whether related to rotation or the presence of companions - planetary, substellar or stellar-remnant. The rotation can provide clues to the physics of white dwarf formation, once it is a remnant of their angular momentum, which went through several stages of stellar evolution. The presence of substellar companions or stellar-remnant provides clues about the final stages of stellar evolution and plays an important role in that evolution. The high photometric precision and the large amount of data provided by space missions, such as Kepler and K2, combined with the correct tools, make it possible to analyze the photometric variability of white dwarf stars. In order to detect the relative periodicities, present in the light curve obtained by these space missions, several mathematical transformations have been applied, such as the Fourier transform, one of the most used in astrophysics, and the Wavelet, which has been applied in a wide range of areas, including Statistics, Geophysics, Image Coding and Compression, Turbulence and Astrophysics. The Wavelet transform is a powerful tool, since it has functions located in both frequency and time, allowing the detection of the temporal evolution of various phenomena, which makes it ideal for analyzing non-stationary signals. In this context, we use these tools in order to study the photometric variability of 25 white dwarf stars observed by the Kepler mission. From the light curves of these stars, we analyze the Lomb-Scargle periodograms, determine the possible physical mechanisms responsible for the detected modulations and perform local and global wavelet spectra. The first one is interpreted as the signal energy distribution, while the second one is the temporal integration of the local map. Finally, we discuss the physical meaning of the results by establishing a comparative study between the periodicities determined in this work and those found in literature.

BANKING MEMBERS:
Interno - 1675216 - BRUNO LEONARDO CANTO MARTINS
Interno - 3060853 - IZAN DE CASTRO LEÃO
Presidente - 346785 - JOSE RENAN DE MEDEIROS
Externo à Instituição - LEONARDO ANDRADE DE ALMEIDA - UERN
Externa à Instituição - MARIA LIDUINA DAS CHAGAS - UNIFESSPA