Banca de DEFESA: RAFAEL RAMON FERREIRA
Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.STUDENT : RAFAEL RAMON FERREIRA
DATE: 11/06/2021
TIME: 14:00
LOCAL: Plataforma Google Meet
TITLE:
SPECTROSCOPIC STUDY OF CHROMOSPHERIC ACTIVITY IN SOLAR TYPE STARS: The search for characterizing analogs stars in Maunder minimum
KEY WORDS:
chromospheric activity, activity cycle, Maunder minimum
PAGES: 186
BIG AREA: Ciências Exatas e da Terra
AREA: Física
SUMMARY:
Since the first observations of sunspots made by Thomas Harriot and subsequently by Galileo and several other scientists, astronomers looking for methods to better understand the magnetic phenomena in the Sun and in solar-type stars. It is well established that the first indicators used to characterize magnetic activity were sunspots. It is also worth highlighting one of the most intriguing phenomena of the evolution of solar magnetism known as Maunder's minimum, which occurred specifically between 1645 and 1715. What makes this minimum of activity is enigmatic is the registration of very few sunspots and practically no variability in the area. over 70 years, remaining to this day without a consolidated explanation. In the twentieth century, with the advancement of observational techniques related to spectroscopy, astronomers began to make observations of solar/stellar activity also through the spectra. The solar/stellar chromospheric activity, has been the subject of exhaustive treatment over the last six decades in the literature. The main spectroscopic indicators come from the Ca II H\&K resonant lines, particularly the indicators SMW and the index with photosphere correction RHK are the main ones. Spectroscopic measurements of the activity of solar-type stars have been carried out since 1960, in an attempt to answer the question of how unique the magnetic evolution of the Sun is in relation to other solar-type stars. All this background has allowed to determine that stars of the solar type have activity cycles, in the case of the Sun a primary cycle of 11 years is well established and a possible secondary cycle of 88 years. In our work we obtained as main results: 1) The characterization and determination of the activity cycle of the solar analog HD43587, as well as estimates of its rotational period and characterization of the magnetic field; 2) Development of theoretical tools to estimate the observations of stellar spots globally in other stars of the solar type; 3) Analysis and determination of the activity cycle of 30 stars of the solar type indicated in the literature as in the state of Maunder Minimum; 4) Calibration of activity indexes based on the Ca II H&K lines using the Coudé spectrograph located at the Pico dos Dias Observatory.
BANKING MEMBERS:
Externa à Instituição - ADRIANA BENETTI MARQUES VALIO - UPM
Externo à Instituição - GUSTAVO FREDERICO PORTO DE MELLO - UFRJ
Interno - 2496004 - JOSE DIAS DO NASCIMENTO JUNIOR
Presidente - 2887830 - MATTHIEU SEBASTIEN CASTRO
Externa à Instituição - SILVIA HELENA PAIXAO ALENCAR - UFMG