DETECCÃO DE EXOPLANETAS AO REDOR DE ESTRELAS FRACAS OBSERVADAS PELA MISSÃO KEPLER

Abstract

Abstract The Kepler mission was designed to search for Earth-sized planets orbiting main-sequence stars. To achieve its goal, it used the transit method, analyzing light curves and searching for periodic decreases in flux that could be caused by celestial bodies passing in front of the stellar disks. The Kepler field of view contains ~4.5 million stars, although only ~150,000 stars with magnitudes Kp < 16 were continuously analyzed with the production of light curves. The remaining stars were only observed 53 times in a series of observations known as Full Frame Images (FFIs) of which the first 8 were distributed over a period of 36 hours and the remaining were produced with an approximately monthly-cadence, until the end of the mission. Our study relies on precise photometry to obtain light curves for 137,209 stars with 16.0 ≤ Kp ≤ 16.5 with the goal of detecting exoplanets, brown dwarfs and eclipsing binaries. Larger and more complete samples of these objects are fundamental to many statistical studies, such as the estimation of the occurrence rate of hot Jupiters around stars of different spectral types. To develop this work, we used the f3 algorithm, which allows us to make adaptative aperture photometry, and applied it to stars in our sample selecting light curves that present possible transits with statistical significance higher than 15σ. After manually checking the apertures used for the selected stars, we obtained the final light curves, inferred the minimum radius of the candidates and classified then as planets and brown dwarfs or eclipsing binary stars. Our analysis resulted in 230 stars with 236 possible transits. If we consider that each transit corresponds to a different celestial object, we found 30 planets or brown dwarf candidates, 179 eclipsing binary candidates and 27 celestial objects for which we could not infer the radius and, therefore, a classification. Given the large number of stars only observed in the Kepler mission FFIs, our preliminary study has a great potential to reveal thousands of possible new planets, brown dwarfs and eclipsing binaries, which will have to be confirmed and characterized later by more detailed studies. These data can be very important to estimate the frequency of hot Jupiters, characterization of the brown dwarf desert and improvement of stellar evolution models. Keywords: planets and satellites; detection - planets and satellites; fundamental parameters - (stars:) binaries; eclipsing - (stars:) brown dwarfs - techniques; photometric