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Atomic diffusion and mixing in old stars II. Observations of stars in the globular cluster NGC 6397 with VLT/FLAMES-GIRAFFE
K. Lind, A. J. Korn, P. S. Barklem +1
Evolutionary trends in the surface abundances of heavier elements have recently been identified in the globular cluster NGC 6397 ([Fe/H]=-2), indicating the operation of atomic dif…
Atomic Diffusion and Mixing in Old Stars I. VLT/FLAMES-UVES Observations of Stars in NGC 6397
A. J. Korn, F. Grundahl, O. Richard +5
We present a homogeneous photometric and spectroscopic analysis of 18 stars along the evolutionary sequence of the metal-poor globular cluster NGC 6397 ([Fe/H] = -2), from the main…
Non-LTE Balmer line formation in late-type spectra: Effects of atomic processes involving hydrogen atoms
P. S. Barklem
(*** abridged ***) Context: The wings of Balmer lines are often used as effective temperature diagnostics for late-type stars under the assumption they form in local thermodynamic…
New Abundances for Old Stars - Atomic Diffusion at Work in NGC 6397
A. J. Korn, F. Grundahl, O. Richard +5
A homogeneous spectroscopic analysis of unevolved and evolved stars in the metal-poor globular cluster NGC 6397 with FLAMES-UVES reveals systematic trends of stellar surface abunda…
The Frequency of Carbon-Enhanced Metal-Poor Stars in the Galaxy from the HERES sample
Sara Lucatello, Timothy Beers, Norbert Christlieb +5
We estimate the frequency of Carbon-Enhanced Metal-Poor (CEMP) stars among very metal-poor stars, based on an analysis of 349 stars with available high-resolution spectra observed…
Electron-impact excitation of neutral oxygen
P. S. Barklem
Aims: To calculate transition rates from ground and excited states in neutral oxygen atoms due to electron collisions for non-LTE modelling of oxygen in late-type stellar atmospher…