Banca de DEFESA: NIZOMAR DE SOUSA GONCALVES

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : NIZOMAR DE SOUSA GONCALVES
DATE: 22/11/2021
TIME: 15:00
LOCAL: Plataforma Zoom
TITLE:

Sobre a relação entre excesso no infravermelho médio e a atividade cromosférica de estrelas do campo.

KEY WORDS:

infrared excess; debris disk; chromospheric activity.

PAGES: 106
BIG AREA: Ciências Exatas e da Terra
AREA: Física
SUMMARY:

Circumstellar disks are components of the formation of planetary systems and, at the same time, a product of these processes.
On the other hand, debris disks are vestiges of the planetary formation process, indicating the formation of planetary systems.
Note that the most important stages of circumstellar disks are: the protoplanetary disk and the secondary disk (or debris disk),
which can be associated with stellar ages. The chromospheric activity index, logR’HK, is used as a star age tracer. Thus, it is
reasonable to seek a relationship between chromospheric activity index and the presence of a circumstellar disc, however,
studies of this nature are still rare. In this scenario, we look for circumstellar disks in a sample of 2845 field stars with known
chromospheric activities. We searched for infrared excess, using WISE data in the bands 3.4 μm, 4.6 μm, 12 μm and 22 μm.
These data, in turn, were combined with data from the 2MASS and GAIA missions to generate a Spectral Energy Distribution
(SED) on the VOSA virtual platform and the SED curves were synthesized by the BT-Settl model. The infrared excess was
characterized by the excess significance and the stars that were candidates to host circumstellar disks underwent visual
inspection of the images, as well as their galactic latitudes were verified. At the end of this process, four stars were confirmed
with circumstellar disks, classified as debris disks. The parameters that characterize the debris disks (temperature, luminosity
fraction, radius and mass) were calculated and compared with the results in the literature. We observe that the luminosity
fraction and mass of debris disks decrease with the age of the star systems. Finally, we found that the debris disks in our
sample were found around more chromospherically active stars. In comparison with the results in the literature, there seems to
be an anti-correlation between the luminosity fraction of the debris disks and the chromospheric activity index.

BANKING MEMBERS:
Presidente - 1675216 - BRUNO LEONARDO CANTO MARTINS
Externo à Instituição - EDUARDO JANOT PACHECO - USP
Interno - 3060853 - IZAN DE CASTRO LEÃO
Interno - 346785 - JOSE RENAN DE MEDEIROS
Externo à Instituição - MARCELO BORGES FERNANDES - ON/MCT