Young giants of intermediate mass Evidence of rotation and mixing

Abstract

In the search of a sample of metal-poor bright giants using Str{ö}mgren photometry, we serendipitously found a sample of 26 young (ages younger than 1 Gyr) metal-rich giants, some of which have high rotational velocities.We determined the chemical composition and rotational velocities of these stars in order to compare them with predictions from stellar evolution models. These stars where of spectral type A to B when on the main sequence, and we therefore wished to compare their abundance pattern to that of main-sequence A and B stars.Stellar masses were derived by comparison of the position of the stars in the colour-magnitude diagram with theoretical evolutionary tracks. These masses, together with Gaia photometry and parallaxes, were used to derive the stellar parameters. We used spectrum synthesis and model atmospheres to determine chemical abundances for 16 elements (C, N, O, Mg, Al, Ca, Fe, Sr, Y, Ba, La, Ce, Pr, Nd, Sm, and Eu) and rotational velocities.The age-metallicity degeneracy can affect photometric metallicity calibrations. We identify 15 stars as likely binary stars. All stars are in prograde motion around the Galactic centre and belong to the thin-disc population. All but one of the sample stars present low [C/Fe] and high [N/Fe] ratios together with constant [(C+N+O)/Fe], suggesting that they have undergone CNO processing and first dredge-up. The observed rotational velocities are in line with theoretical predictions of the evolution of rotating stars.

Astronomy and Astrophysics - A\&A, EDP Sciences, 2021

References in corpus (16)

• The Gaia mission
• The mass distribution and gravitational potential of the Milky Way
• An Analysis of the Shapes of Interstellar Extinction Curves. VII. Milky Way Spectrophotometric Optical-through-Ultraviolet Extinction and Its R-Dependence
• Three-dimensional mapping of the local interstellar medium with composite data
• On the fine structure of the Cepheid metallicity gradient in the Galactic thin disk
• Rotational mixing in low-mass stars II. Self-consistent models of Pop II RGB stars
• Diagnoses to unravel secular hydrodynamical processes in rotating main sequence stars
• Stroemgren survey for Asteroseismology and Galactic Archaeology: let the SAGA begin
• Populations of rotating stars III. SYCLIST, the new Geneva Population Synthesis code
• Exploiting the Gaia EDR3 photometry to derive stellar temperatures
• Galactic abundance gradients from Cepheids : On the iron abundance gradient around 10-12 kpc
• Analysis of 26 Barium Stars I. Abundances
• The Gaia-ESO Survey: Galactic evolution of lithium from iDR6
• Abundance analysis of barium and mild barium stars
• The Gaia-ESO Survey: A new approach to chemically characterising young open clusters II. Abundances of the neutron-capture elements Cu, Sr, Y, Zr, Ba, La, and Ce
• The Gaia-ESO Survey: Carbon abundance in the Galactic thin and thick disks

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• SDSS J102915.14+172927.9: Revisiting the chemical pattern
• The true nature of HE0057-5959, the most metal-poor Li-rich star
• Neutron-Capture Element Signatures in Globular Clusters: Insights from the Gaia-ESO Survey
• MINCE III. Detailed chemical analysis of the UVES sample
• The Pristine survey. XXVI. Chemical abundances of subgiant stars of the extremelymetal-poor stream C-19
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