Costa, Jefferson Soares daSilva, Marina Tatiane Ribeiro da2018-01-102021-09-292018-01-102021-09-292017-12-08SILVA, Marina Tatiane Ribeiro da. Campos magnéticos de estrelas G-K e Dividing Lines no Diagrama HR. 2017. 54 f. Trabalho de Conclusão de Curso (Graduação em Física Bacharelado) - Departamento de Física Teórica e Experimental, Universidade Federal do Rio Grande do Norte, Natal, 2017.https://repositorio.ufrn.br/handle/123456789/40225We investigate the surface magnetic field of 35 G-K stars. In our sample, 14 stars present moderate to strong signs of magnetic activity, as known from the literature. Other 7 stars seem not to have been through thermohaline mixing, which could be due to hosting a strong magnetic field. Subsequently, we observed 14 additional very bright stars which allowed us to improve our ability with spectropolarimetry. Lastly, we analysed the existence of dividing lines in the Hertzsprung-Russell diagram. Using the data from spectropolarimeters NARVAL and ESPaDOnS, it was possible to detect circular polarisation within the photospheric absorption lines of our targets. Here, we use the Least-Squares Deconvolution (LSD) method to create high signal-to-noise ratio mean Stokes V profiles. Then, we detect the magnetic field and evaluate its relation to the dividing lines in the HR diagram. The presence of the dividing line in the HR diagram causes the late-type stars to divide into two groups. To the left, we find solar-type stars, with an atmospheric structure composed by chromosphere, transition region, crown and solar-type winds. To the right, the stars have extended chromosphere and heavy cold winds. We unquestionably determined the surface magnetic field for 3 stars from our sample and concluded that other 18 of them show no detection of magnetic activity. The magnetic stars lie to the left of the dividing line, as the non-magnetic stars lie to the right of the line, showing evidence of affiliation between the magnetic field behaviour and the dividing line.openAccessCampo Magnético, Diagrama HR, Dividing Line, LSD.bachelorThesis