Excesso infravermelho e atividade magnética em estrelas da sequência principal

Abstract

There are several studies related to chromospheric and coronal magnetic activity, as a determinant of age, as well as the relations with metallicity and rotation of stars. However, the relationship between magnetic activity and the excess of stellar infrared (IR) radiation, which indicates the presence of circumstellar discs or planets, is not yet well known. For the accomplishment of this unprecedented study, we selected 128 stars, from the catalog Eiroa et al. (2013), with spectral type F, G and K, class of luminosity V and that have values for the fluxes Ca II (−5.4 < log R0 HK < −4.0) and X-ray, indicators the magnetic activity in the chromosphere and in the corona of the star, respectively. These parameters were related to infrared fluxes in the WISE (3.4 µm and 22 µm), IRAS (12 µm and 25 µm), AKARI (9 µm and 18 µm) and SPITZER / MIPS (24 µm and 70 µm) photometric bands for a subsample of 33 stars that shows IR excess, in order to study the behavior of magnetic activity in the presence of circumstellar discs. In this context, we noticed that the medium IR fluxes increase as the Ca II flux decreases, this tendency is also shown to be increased for the higher temperature stars. In addition, we observed a similar anticorrelation between coronal emission and IR flux, but with greater evidence for type G stars. For the far IR, we noticed a weak correlation with the chromospheric and coronal activity. In a last analysis, we observed the correlation between R0 HK and RX of the sample which, as expected, agrees with several works present in the literature, we also noticed that such behavior does not differentiate in the presence, or not, of circumstellar discs.