Spectral synthesis in G and K dwarf stars

Marília Carlos

Universidade de São Paulo

Abstract:

The study of the chemical composition of stars is crucial to understand the formation history of our galaxy. In particular, main sequence stars provide the chemical composition
at the time and place that the stars were formed. Thus, dwarf stars of different populations, metallicities and ages, can provide clues about the different components of our galaxy and
also how it was formed and how it evolved.
During my PhD I analysed G and K dwarfs through the spectral synthesis technique using the code MOOG.
In the case of G dwarfs, we study lithium abundances in solar twins at different ages to better understand the mixture process in the stellar inner regions and its evolution with age.
We performed a comprehensive study of more than 80 field solar twins (Carlos et al. 2016,2019) plus three solar twins in the M67 open cluster (which is about solar age and solar metallicity)
using data from the HARPS/ESO and GRACES/Gemini spectrographs.
We also determine magnesium isotopic ratios in metal poor K dwarfs stars to constrain the onset of AGB star nucleosynthesis in the Galactic halo, using high resolution and good signal to noise
HIRES spectra. The results were compared to theoretic galactic models, which take in consideration the contribution of supernovae and AGB stars, in order to determine a timescale for formation of
the Galactic halo (Carlos et al. 2018).