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Abundâncias Qu´Imicas De Estrelas An˜As G E K E Modelos

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Abundâncias Qu´Imicas De Estrelas An˜As G E K E Modelos Universidade de S~aoPaulo Instituto de Astronomia, Geof´ısicae Ci^enciasAtmosf´ericas Departamento de Astronomia Mar´ılia Gabriela Cardoso Corr^eaCarlos Abund^anciasqu´ımicasde estrelas an~asG e K e modelos de evolu¸c~aoestelar para [Fe/H] = −1:8 e [Fe/H] = −1:0 com enriquecimento-α S~aoPaulo 2020 Mar´ılia Gabriela Cardoso Corr^eaCarlos Abund^anciasqu´ımicasde estrelas an~asG e K e modelos de evolu¸c~aoestelar para [Fe/H] = −1:8 e [Fe/H] = −1:0 com enriquecimento-α Tese apresentada ao Departamento de Astro- nomia do Instituto de Astronomia, Geof´ısicae Ci^enciasAtmosf´ericasda Universidade de S~ao Paulo como requisito parcial para a obten¸c~ao do t´ıtulode Doutor em Ci^encias. Area´ de Concentra¸c~ao:Astronomia Orientador: Prof. Dr. Jorge Mel´endezMo- reno Vers~aoCorrigida. O original encontra-se dis- pon´ıvel na Unidade. S~aoPaulo 2020 Aos meus pais Silvia e Edmar Agradecimentos A` minha fam´ıliaque, com paci^encia,me ajudou muito durante o doutorado. Aos meus pais, Edmar e Silvia, pelo suporte emocional e financeiro em ´epoca t~aodif´ıcilde investimen- tos em ci^enciasno Brasil. Aos meus irm~aos,Amanda, Fernanda e Pedro, pelos momentos de descontra¸c~ao.Aos meus sobrinhos, Rafaela e Arthur, pelo carinho e brincadeiras. Ao meu orientador, Jorge Mel´endez,pelos ensinamentos, ajuda e paci^encia;sem o qual n~aoteria chegado at´eaqui. A` Professora Amanda Karakas, da Monash University, pela hospitalidade e todo o ensinamento adquirido durante meu aprendizado na Austr´alia. Aos meus amigos e colegas que tornaram essa jornada mais leve e descontra´ıda. A todos os pesquisadores da institui¸c~aopor todo o conhecimento adquirido ao longo do curso. A todos os funcion´ariosdo IAG que me ajudaram com quest~oest´ecnicasao longo dos ´ultimosanos. A` CAPES pela concess~aoda bolsa de doutorado e aos demais aux´ılios financeiros atrav´esdo Programa de Excel^encia Acad^emica(Proex) e Programa de Doutorado-sandu´ıche no Exterior (PDSE), c´odigode financiamento 001. Esta tese/disserta¸c~aofoi escrita em LATEX com a classe IAGTESE, para teses e disserta¸c~oesdo IAG. Resumo O estudo de composi¸c~aoqu´ımicadas estrelas ´ecrucial para o entendimento tanto sobre estrutura estelar quanto sobre a hist´oriade forma¸c~aoda nossa gal´axia. Levando em considera¸c~aoque o elemento Li ´eum dos mais importantes tra¸cadores astrof´ısicossobre mecanismos de transporte e mistura dentro e abaixo da zona convectiva de estrelas do tipo tardio, conclu´ımosum estudo abrangente sobre deple¸c~aode Li em 85 g^emeassolares do campo na vizinhan¸casolar, e mais tr^esg^emeassolares do aglomerado aberto M67. Encontramos uma forte correla¸c~aoentre deple¸c~aode Li e idade estelar, em acordo com modelos n~ao-padr~aode evolu¸c~aoestelar. Observamos, tamb´em,que o Sol pode ser considerado pobre em Li em compara¸c~aoa outras g^emeassolares de idades similares (por um fator de ∼ 2σ). Nossos resultados tamb´emsugerem que estrelas com os mais baixos conte´udosde Li, para uma dada idade, s~aoacompanhadas de baixos n´ıveis de elementos refrat´arios. Analisamos 8 estrelas an~asK do halo da Gal´axiapara mais informa¸c~oessobre a forma¸c~aodessa componente gal´actica,concluindo uma an´alisequ´ımicadetalhada dos ele- mentos C, Li, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Y, Ba, La, Ce, Nd, Sm e Eu, e tamb´emdos is´otopos 24Mg, 25Mg e 26Mg. Para sete estrelas encontramos um bom acordo em compara¸c~aoa resultados da literatura. Entretanto, a an~aK LHS 173 apre- senta composi¸c~aoan^omalade [α/Fe] e das seguintes outras esp´ecies:baixas quantidades de Mg, Ca e K, e altos valores de Al, Sc, Co, Ni e Zn, em compara¸c~aoa outras estrelas do halo gal´actico.Esse resultado sugere que a an~aLHS 173 pode n~aoter nascido na nossa gal´axia, mas na verdade foi incorporada de uma gal´axiasat´elite. A raz~ao 26Mg/Mg indica que o enriquecimento qu´ımico gal´actico devido a estrelas AGB ocorreu para [Fe/H] ≈ −1:4. Um novo modelo para reproduzir nossos dados sugere que a escala de tempo para a forma¸c~ao do halo deve ser menor do que 1.5 Gano. Finalmente, apresentamos novos modelos de evolu¸c~aoestelar com os respectivos yields para tr^escasos distintos: [Fe/H] = −1:8 escalonado para o padr~aosolar, [Fe/H] = −1:8 com [α/Fe] ≈ 0:30, e [Fe/H] = −1:0 com [α/Fe] ≈ 0:30. Comparamos os resultados de estrutura dos modelos de evolu¸c~aoestelar, abund^anciassuperficiais finais e yields, para avaliarmos se h´adiferen¸casentre o caso escalonado para o padr~aosolar e o com enriquecimento-α. Encontramos uma diferen¸cam´ınimaentre os modelos de evolu¸c~aoestelar escalonado para o padr~aosolar e os modelos com enriquecimento-α para as esp´eciesmais pesadas (Ga ao Bi), e uma diferen¸camaior para os elementos leves (C ao Zn) para os modelos de maiores massas. Tamb´em,usamos os yields produzidos pelo nosso trabalho em modelos de evolu¸c~ao qu´ımicada Gal´axia.No geral, o elemento mais sens´ıvel aos yields com enriquecimento-α ´eo N, esp´ecieproduzida principalmente por estrelas AGB. Abstract The study of the chemical composition of stars is crucial to understand both stellar structure and the formation history of our galaxy. Taking in consideration that the element Li is one of the most important astrophysical tracers of transport mechanisms and mixing within and below the convective zone of late- type stars, we performed a comprehensive study of Li depletion in 85 field solar twins, plus three solar twins in the M67 open cluster. We find a strong correlation between Li depletion and stellar age, in agreement with non-standard stellar evolution models. Interestingly, we found that the Sun can be considered a Li-poor star in comparison with other solar twins at similar age (by a factor of ∼ 2σ). Our results also suggest that stars with the lowest Li abundances for their ages are accompanied by a lower level of refractory elements. We analyzed 8 halo K dwarfs to shed light on the formation of this particular galactic component, performing a detailed chemical analyses of the elements C, Li, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Y, Ba, La, Ce, Nd, Sm and Eu, including the isotopic abundances of 24Mg, 25Mg and 26Mg. For seven stars we find a good agree- ment with results in the literature. However, the K dwarf LHS 173 presents anomalous composition of [α/Fe] and the following other species: lower amounts of Mg, Ca and K, and higher quantities of Al, Sc, Co, Ni and Zn, in comparison with other halo stars. This result suggests that LHS 173 was not born in our galaxy, but it was actually accreted from a dwarf galaxy. The 26Mg/Mg ratio indicates that the onset of AGB stars in the galactic halo occurred at [Fe/H] ≈ −1:4. A new model to fit our data suggests that the timescale for the formation of the halo should be below 1.5 Gyr. Finally, we present stellar evolution models with their respective yields for three diffe- rent cases: [Fe/H] = −1:8 scaled solar, [Fe/H] = −1:8 with [α/Fe] ≈ 0:30, and [Fe/H] = −1:0 with [α/Fe] ≈ 0:30. We compare the output structure of the stellar evolution models, final surface abundances and yields, in order to see if there is any difference between the scaled solar case to the α-enhanced one. We find almost no difference between the scaled solar and α-enhanced models for the heaviest species (Ga to Bi), and a slightly higher difference for the light elements (C to Zn) for the more massive models. We also use the yields produced in this work to run galactic chemical evolution models. In general, the more sensitive element to the α-enhanced yields is N, an element that is produced mainly in AGB stars. Lista de Figuras 1.1 Evolu¸c~aoestelar para estrelas de metalicidade solar e diferentes massas. 22 1.2 Tabela de nucl´ıdeose os processos s e r. 23 2.1 Spite plateau . 30 2.2 A(Li) vs. [Fe/H] para estrelas do disco espesso e fino da Gal´axia . 31 2.3 Estrelas RGB ricas em Li. 32 2.4 A(Li) versus idade para an´alogassolares. 34 2.5 A(Li) versus idade para algumas g^emeas solares. 36 2.6 Figura gerada pelo pacote de python q2 mostrando a an´aliseda estrela FBC 1877. 44 2.7 Compara¸c~aoentre os par^ametrosatmosf´ericosTef , log g e massa da amostra 3 obtidos tanto pela an´aliseespectrosc´opicadiferencial como por fotometria. 45 2.8 Espectro sint´etico solar na regi~aoda linha Li i em 6707.75 A.˚ . 47 2.9 Espectro sint´eticoem compara¸c~aoao espectro observado da estrela HIP 1954 na determina¸c~aode vsin i......................... 48 2.10 Espectros observados em compara¸c~ao`aespectros sint´eticospara tr^esg^emeas solares de diferentes idades. 49 2.11 Compara¸c~aoA(Li) entre estrelas comuns nas amostras 1 e 2. 54 2.12 A(Li) versus idade estelar para a amostra 1. 56 2.13 Deple¸c~aode Li em fun¸c~aoda idade, com [Fe/H] codificada por cor para a amostra 1. 59 2.14 Deple¸c~aode Li em fun¸c~aoda idade, com massa codificada por cor para a amostra 1.
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