J/A+A/628/A111 Li in BPS CS22876-032 spectrum (Gonzalez Hernandez+, 2019)
The 6Li/7Li isotopic ratio in the metal-poor binary CS22876-032.
Gonzalez Hernandez J.I., Bonifacio P., Caffau E., Ludwig H.-G.,
Steffen M., Monaco L., Cayrel R.
<Astron. Astrophys. 628, A111 (2019)>
=2019A&A...628A.111G 2019A&A...628A.111G (SIMBAD/NED BibCode)
ADC_Keywords: Binaries, spectroscopic ; Spectra, ultraviolet
Keywords: stars: population II - stars: individual: CS22876-032 -
Galaxy: abundances - Galaxy: halo - cosmology: observations -
primordial nucleosynthesis
Abstract:
We present high-resolution and high-quality UVES spectroscopic data of
the metal-poor double-lined spectroscopic binary CS 22876-032 ([Fe/H]
approximately -3.7dex). Our goal is to derive the 6Li/7Li isotopic
ratio by analysing the LiI 670.8nm doublet. Methods. We co-added all
28 useful spectra normalised and corrected for radial velocity to the
rest frame of the primary star. We fitted the Li profile with a grid
of the 3D non-local thermodynamic equilibrium (NLTE) synthetic spectra
to take into account the line profile asymmetries induced by stellar
convection, and performed Monte Carlo simulations to evaluate the
uncertainty of the fit of the Li line profile.
We checked that the veiling factor does not affect the derived
isotopic ratio, 6Li/7Li, and only modifies the Li abundance, A(Li),
by about 0.15dex. The best fit of the Li profile of the primary star
provides A(Li)=2.17±0.01dex and 6Li/7Li=8+2-5% at 68%
confidence level. In addition, we improved the Li abundance of the
secondary star at A(Li)=1.55±0.04dex, which is about 0.6 dex
lower than that of the primary star.
The analysis of the Li profile of the primary star is consistent with
no detection of 6Li and provides an upper limit to the isotopic
ratio of 6Li/7Li<10% at this very low metallicity, about 0.5dex
lower in metallicity than previous attempts for detection of 6Li in
extremely metal poor stars. These results do not solve or worsen the
cosmological 7Li problem, nor do they support the need for
non-standard 6Li production in the early Universe.
Description:
Average co-added, rebinned spectra in the region around the LiI
670.8nm resonance line of the two stellar components of the metal-poor
binary CS 22876-032 A and CS 22876-032 B. For each star, wavelength,
normalised flux and flux error are given.
Objects:
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RA (2000) DE Designation(s)
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00 07 37.51 -35 31 17.7 BPS CS 22876-032 = SB 44
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
cs22876a.dat 34 214 CS 22876_032A wavelength, flux and flux error
cs22876b.dat 34 214 CS 22876_032B wavelength, flux and flux error
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Byte-by-byte Description of file: cs22876a.dat cs22876b.dat
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Bytes Format Units Label Explanations
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1- 10 F10.6 nm Lambda [670.65/670.95] Wavelength {wLambda}
13- 22 F10.5 --- NFlux Normalised flux
25- 34 F10.5 --- e_NFlux Flux error
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History:
From Jonay I. Gonzalez Hernandez, jonay(at)iac.es
Acknowledgements:
Based on observations made with the Very Large Telescope (VLT) at ESO
Paranal Observatory, Chile, Programme 080.D-0333.
(End) Jonay Gonzalez Hernandez [IAC, Spain], Patricia Vannier [CDS] 01-Aug-2019