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J/A+A/554/A96  Spectra of LiI(670.8nm) line in metal-poor stars   (Lind+, 2013)

The lithium isotopic ratio in very metal-poor stars. Lind K., Melendez J., Asplund M., Collet R., Magic Z. <Astron. Astrophys. 554, A96 (2013)> =2013A&A...554A..96L
ADC_Keywords: Spectroscopy ; Stars, metal-deficient ; Abundances Keywords: stars: abundances - stars: Population II - primordial nucleosynthesis - techniques: spectroscopic - line: profiles - line: formation Abstract: Un-evolved, very metal-poor stars are the most important tracers of the cosmic abundance of lithium in the early universe. Combining the standard Big Bang nucleosynthesis model with Galactic production through cosmic ray spallation, these stars at [Fe/H]←2 are expected to show an undetectably small 6Li/7Li isotopic signature. Evidence to the contrary may necessitate an additional pre-galactic production source or a revision of the standard model of Big Bang nucleosynthesis. It would also cast doubts on Li depletion from stellar atmospheres as an explanation for the factor 3-5 discrepancy between the predicted primordial 7Li from the Big Bang and the observed value in metal-poor dwarf/turn-off stars. We revisit the isotopic analysis of four halo stars, two with claimed 6Li-detections in the literature, to investigate the influence of improved model atmospheres and line formation treatment. For the first time, a combined 3D, non-local thermodynamic equilibrium (NLTE) modelling technique for Li, Na, and Ca lines is utilised to constrain the intrinsic line-broadening and to determine the Li isotopic ratio. We discuss the influence of 3D NLTE effects on line profile shapes and assess the realism of our modelling using the Ca excitation and ionisation balance. By accounting for NLTE line formation in realistic 3D hydrodynamical model atmospheres, we can model the Li resonance line and other neutral lines with a consistency that is superior to LTE, with no need for additional line asymmetry caused by the presence of 6Li. Contrary to the results from 1D and 3D LTE modelling, no star in our sample has a significant (2 sigma) detection of the lighter isotope in NLTE. Over a large parameter space, NLTE modelling systematically reduces the best-fit Li isotopic ratios by up to five percentage points. As a bi-product, we also present the first ever 3D NLTE Ca and Na abundances of halo stars, which reveal significant departures from LTE. The observational support for a significant and non-standard 6Li production source in the early universe is substantially weakened by our findings. Description: Reduced spectra in the region around the LiI 670.8nm resonance line. Four stars have been observed: HD19445, HD84937, HD140283 and G64-12. For each star, wavelength and normalised flux are given. For the derivation of the Li isotopic ratio, the normalisation has been further fine-tuned in a spectral interval extending 0.17nm from the line centre. Objects: ---------------------------------------------------------- RA (2000) DE Designation(s) ---------------------------------------------------------- 03 08 25.59 +26 19 51.4 HD 19445 = HIP 14594 09 48 56.10 +13 44 39.3 HD 84937 = HIP 48152 15 43 03.10 -10 56 00.6 HD 140283 = HIP 76976 13 40 02.50 -00 02 18.8 G64-12 = HIP 66673 ---------------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file g64-12.dat 27 923 G64-12 wavelength and normalised flux hd140283.dat 27 853 HD 140283 wavelength and normalised flux hd19445.dat 27 921 HD 19445 wavelength and normalised flux hd84937.dat 27 921 HD 84937 wavelength and normalised flux
Byte-by-byte Description of file: *.dat
Bytes Format Units Label Explanations
1- 16 F16.12 nm lambda [669.9/672.6] Wavelength λ 19- 27 F9.7 --- Flux Normalised flux
Acknowledgements: Jorge Melendez, jorge(at)astro.iag.usp.br
(End) Karin Lind [IoA, Cambridge, UK], Patricia Vannier [CDS] 11-Jun-2013
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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