Abstract
In order to clarify the properties of the secondary clump star HD 226808 (KIC 5307747), we combined four years of data from Kepler space photometry with high-resolution spectroscopy of the ...High Efficiency and Resolution Mercator Échelle Spectrograph mounted on the Mercator telescope. The fundamental atmospheric parameters, radial velocities, rotation velocities, and elemental abundance for Fe and Li were determined by analyzing line strengths and fitting-line profiles, based on a 1D local thermodynamic equilibrium model atmosphere. Second, we analyzed a photometric light curve obtained by Kepler and we extracted asteroseismic data of this target using Lets Analysis, Use and Report of Asteroseismology, a new seismic tool developed for the study of evolved FGK solar-like stars. We determined the evolutionary status and effective temperature, surface gravity, metallicity, microturbulence, and chemical abundances for Li, Ti, Fe, and Ni for HD 226808, by employing spectroscopy, asteroseismic scaling relations, and evolutionary structure models built in order to match observed data. Our results also show that an accurate synergy between good spectroscopic analysis and asteroseismology can provide a jump toward understanding evolved stars.
In order to clarify the properties of the secondary clump star HD 226808 (KIC 5307747), we combined four years of data from Kepler space photometry with high-resolution spectroscopy of the High ...Efficiency and Resolution Mercator Échelle Spectrograph mounted on the Mercator telescope. The fundamental atmospheric parameters, radial velocities, rotation velocities, and elemental abundance for Fe and Li were determined by analyzing line strengths and fitting-line profiles, based on a 1D local thermodynamic equilibrium model atmosphere. Second, we analyzed a photometric light curve obtained by Kepler and we extracted asteroseismic data of this target using Lets Analysis, Use and Report of Asteroseismology, a new seismic tool developed for the study of evolved FGK solar-like stars. We determined the evolutionary status and effective temperature, surface gravity, metallicity, microturbulence, and chemical abundances for Li, Ti, Fe, and Ni for HD 226808, by employing spectroscopy, asteroseismic scaling relations, and evolutionary structure models built in order to match observed data. Our results also show that an accurate synergy between good spectroscopic analysis and asteroseismology can provide a jump toward understanding evolved stars.
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Previous issue date: 2016-05-20
Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico (CNPq)
Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES)
O estudo das estrelas do tipo-solar inclui naturalmente as estrelas an?logas e g?meas, que s?o estrelas id?nticas ao Sol. Estes objetos desempenham um papel fundamental no ?mbito da astrof?sica moderna, principalmente, na investiga??o da nossa estrela como um objeto comum. Dentre os diversos par?metros f?sicos observ?veis, a atividade magn?tica e cromosf?rica - para um conjunto de estrelas muito similares ao Sol (an?logas e g?meas) - s?o essenciais para compreendermos a evolu??o din?mica da atividade estelar em escalas de tempo da ordem de v?rios bilh?es de anos, isto ? tempo de vida de uma estrela do tipo-solar sobre a sequ?ncia principal. Neste trabalho, entre outros aspectos, investigaremos as rela??es existentes entre o per?odo de rota??o, abund?ncia de l?tio, atividade magn?tica e cromosf?rica, massa e idades destes grupos de estrelas. Analisaremos ainda as determina??es das idades de acordo com a t?cnica da girocronologia. O objetivo principal do nosso trabalho ? investigar a lei de decaimento de cada um dos destes par?metros com base em uma ampla amostra de estrelas classificadas como an?logas e g?meas solares. Nossos resultados deram origem a quatro publica??es em revistas indexadas, dos quais dois j? se encontram em modo ?impress?. Estes resultados mostram que as leis de evolu??o (decaimento da abund?ncia de l?tio, da rota??o e do campo magn?tico) s?o fortemente dependentes do tipo-estelar, mostrando-se mais nitidez para as estrelas an?logas e g?meas.
The interest in studying the objects similar to the Sun, stars labeled as solar-type stars,;
analogs and solar twins, brings in its essence an attempt to end out another reference;
star and, furthermore, provides an investigation of evolutionary dynamic of our star as;
a function of various parameters. For this, we used three distinct samples of observable;
data, 170 solar-type stars from BCool catalog and observed with spectropolarimeters;
ESPaDOnS e NARVAL, 88 solar-twin stars of HARPS surveys, and 20 solar-analog stars;
from Kepler. From these data, we have investigated mainly the correlation among the rotation;
period, lithium abundance and stellar age. For the BCool stars and solar-twin from;
HARPS, we have used the rotation period determined through of chromospheric activity,;
in the case of Kepler solar analogs, the rotation period it is derived from photometric;
modulation. The lithium abundance for most of the solar-type and solar-twin stars have;
been collected from literature, while for the solar analogs, the lithium abundance were;
determined in the LTE regime using Kurucz atmospheric models and the MOOG code.;
For stellar age, we have used the gyrochronology method, which was calibrated using the;
Sun and a selection of open clusters, to redetermine them and comparing them with those;
derived from standard isochronal. Our results indicate that exist a decay law for the rotation period as a function of lithium abundance. This correlation becomes more clear for the solar-analog and solartwin;
stars, even the rotation period being determined through distinct mechanisms for each case. For stellar ages, measured from standard isochronal and gyrochronology, we realized that they diverge considerably when the stars are older than the Sun. This result has also been investigated by van Saders et al. (2016) and reect our limitation about thestellar evolution and mixing mechanisms. Our work has resulted in five publications in indexed journals, two already in print format, one recently submitted and other in final stage of conclusion.
In order to clarify the properties of the secondary clump star HD 226808 (KIC 5307747), we combined four years of data from Kepler space photometry with high-resolution spectroscopy of the High ...Efficiency and Resolution Mercator Échelle Spectrograph mounted on the Mercator telescope. The fundamental atmospheric parameters, radial velocities, rotation velocities, and elemental abundance for Fe and Li were determined by analyzing line strengths and fitting-line profiles, based on a 1D local thermodynamic equilibrium model atmosphere. Second, we analyzed a photometric light curve obtained by Kepler and we extracted asteroseismic data of this target using Lets Analysis, Use and Report of Asteroseismology, a new seismic tool developed for the study of evolved FGK solar-like stars. We determined the evolutionary status and effective temperature, surface gravity, metallicity, microturbulence, and chemical abundances for Li, Ti, Fe, and Ni for HD~226808, by employing spectroscopy, asteroseismic scaling relations, and evolutionary structure models built in order to match observed data. Our results also show that an accurate synergy between good spectroscopic analysis and asteroseismology can provide a jump toward understanding evolved stars.}
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