Um estudo da abundância de lítio, rotação, atividade cromosférica e magnetismo das estrelas análogas e gêmeas solares
The study physical process that control the stellar evolution is strength influenced by several stellar parameters, like as rotational velocity, convective envelope mass deepening, and magnetic field intensity. In this study we analyzed the interconnection of some stellar parameters, as Lithium abun...
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| Formato: | doctoralThesis |
| Idioma: | por |
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Universidade Federal do Rio Grande do Norte
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| Endereço do item: | https://repositorio.ufrn.br/jspui/handle/123456789/16622 |
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| Resumo: | The study physical process that control the stellar evolution is strength
influenced by several stellar parameters, like as rotational velocity, convective
envelope mass deepening, and magnetic field intensity.
In this study we analyzed the interconnection of some stellar parameters,
as Lithium abundance A(Li), chromospheric activity and magnetic field
intensity as well as the variation of these parameters as a function of age,
rotational velocity, and the convective envelope mass deepening for a selected
sample of solar analogs and twins stars. In particular, we analyzed the
convective envelope mass deepening and the dispersion of lithium abundance
for these stars. We also studied the evolution of rotation in subgiants stars,
because its belong to the following evolutionary stage of solar analogs, and
twins stars.
For this analyze, we compute evolutionary models with the TGEC
code to derive the evolutionary stage, as well as the convective envelope
mass deepening, and derive more precisely the stellar mass, and age for this
118 stars.
Our Investigation shows a considerable dispersion of lithium abundance
for the solar analogs stars. We also realize that this dispersion is not by the convective zone deep, in this way we observed which the scattering
of A(Li) can not be explained by classical theories of mixing in the convective
zone. In conclusion we have that are necessary extra-mixing process to
explain this decrease of Lithium abundance in solar analogs and twins stars.
We analyzed the subgiant stars because this are the subsequent evolutionary
stage after the solar analogs and twins stars. For this analysis,
we compute the rotational period for 30 subgiants stars observed by Co-
RoT satellite. For this task we apply two different methods: Lomb-Scargle
algorithm, and the Plavchan Periodogram.
We apply the TGEC code we compute models with internal distribution
of angular momentum to confront the predict results with the models,
and the observational results. With this analyze, we showed which solid
body rotation models are incompatible with the physical interpretation of
observational results.
As a result of our study we still concluded that the magnetic field,
convective envelope mass deepening, and internal redistribution of angular
momentum are essential to explain the evolution of low-mass stars, and its
observational characteristics.
Based on population synthesis simulation, we concluded that the solar
neighborhood presents a considerable quantity of solar twins when compared
with the discovered set nowadays. Altogether we foresee the existence around
400 solar analogs in the solar neighborhood (distance of 100 pc).
We also study the angular momentum of solar analogs and twins, in
this study we concluded that added angular momentum from a Jupiter type
planet, putted in the Jupiter position, is not enough to explain the angular
momentum predicted by Kraft law (Kraft 1970) |
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