Busca por discos circunstelares em torno de estrelas cromosfericamente ativas

Abstract

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 plataform 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.