Volume 652, August 2021
|Number of page(s)||5|
|Published online||16 August 2021|
12C/13C ratio and CNO abundances in the classical very old metal-poor dwarf HD 140283★
GEPI, Observatoire de Paris, PSL Research University, CNRS, Place Jules Janssen,
2 Universidade de São Paulo, IAG, Rua do Matão 1226, Cidade Universitária, 05508-900 São Paulo, Brazil
Accepted: 18 July 2021
Context. The isotope abundances provide powerful diagnostics of the chemical enrichment in our Galaxy. The star HD 140283 is one of the best-studied very metal-poor dwarf stars. It is very old, and the chemical abundance in this star is a good witness of the chemical composition of the matter in the early Galaxy.
Aims. The aim of this work is to measure the precise abundances of carbon, nitrogen, oxygen, and mainly the 12C/13C isotopic ratio in this very old metal-poor star in order to have a good reference for the computations of the chemical evolution of the Galaxy.
Methods. We used very high spectral resolution data, with extremely high signal-to-noise ratios obtained with the spectrographs ESPaDOnS at the CFHT, ESPRESSO at the VLT, and HARPS at the ESO 3.6 m telescope.
Results. For the first time, we were able to measure the 12C/13C ratio in a very old metal-poor dwarf that was born at the very beginning of the Galaxy: 12C/13C = 33−6+12. We also obtained a precise determination of the abundance of the CNO elements in this star. These abundances give information about the early composition of the cloud from which HD 140283 was formed. They suggest that the effect of super-asymptotic giant branch stars or fast-rotating massive stars was significant in the early Galaxy.
Key words: stars: abundances / stars: Population II
Based on observations collected at the CFHT under program 11AB01 (PI: B. Barbuy). We have also used a new ESPRESSO spectrum and HARPS and UVES spectra from observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere: Programme 0101.A-0229(A), PI: M.Spite, and archives of programmes 0103.D-0118(A), PI: V.Adibekian, and 080.D-0347(A), PI: U.Heiter).
© M. Spite et al. 2021
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