Estudo Fotométrico, Espectroscópico e Polarimétrico de Estrelas Variáveis Azuis Luminosas

Abstract

Abstract: This PhD thesis is related to Luminous Blue Variable stars (LBV), which are some of the most luminous stars and are characterized by eruptive processes that cause intense photometric and spectroscopic variability. Due to their rarity, the small number of studies and the high peculiarity of these stars, their evolutive context and physical properties are still under debate. However, they have attracted the attention of the scientific community due to the possibility, recently discovered, that some of these objects may be supernova progenitors. In this work, we explore observationally all objects classified as LBV or candidates in the Magellanic Clouds, in order to compose a more coherent scenario for these objects at low metallicity. All the 9 confirmed LBVs and 14 candidates were the targets of the main study of this work. As result, a paper with a detailed analysis for the LBVs R 40 and R 110 was published. We obtained the identification of new eruptions for most of the LBVs in our sample, in particular for the lower luminosity stars R 40 and R 71, which are showing their strongest activities ever registered. For R 40, our analysis showed, for the first time, indications of enrichment of s-process elements in LBVs. For other better studied LBVs, we updated the information about their eruptive state and detected new physical parameters, based on data from observations and literature. For R 116, R 85 and S 22, our light curve analysis showed, for the first time in a more systematic way, the presence of eruptive activities for these objects, classifying them as LBVs. Based on qualitative and quantitative analysis, we plot these stars in the HR diagram, comparing their positions to the stellar evolution models of different metallicities and mass ranges, as well as compared the mapped observational features in the sample with suggested models to explain the eruptions of these stars. Additionally, a polarimetric survey of a large sample of LBVs from the Galaxy and the Magellanic Clouds is showed, presenting preliminary results about the incidence of assymetries in the winds of LBVs. For the data reduction of our polarimetric and photometric observations, a new pipeline was developed, astropop, which is available as open source for whole community and also resulted in a published paper.