Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: 6Li/7Li estimates for metal-poor stars   The presence of the lithium-6 isotope in some metal-poor stars is a matter of
surprise because of the high values observed. Non-standard models of Big Bang
nucleosynthesis and pre-Galactic cosmic ray fusion and spallation have been
proposed to explain these values. However, the observations of this light
isotope are challenging which may make some detections disputable. The goal was
to determine 6Li/7Li for a sample of metal-poor stars; three of them have been
previously studied and the remaining two are new for this type of study. The
purpose was to increase, if possible, the number of lithium-6 detections and to
confirm previously published results. Spectra of the resonance doublet line of
neutral lithium Li I 670.78nm were taken with the High Dispersion Spectrograph
at the Subaru 8.2m-telescope for a sample of five metal-poor stars (-3.12 <
[Fe/H] < -2.19). The contribution of lithium-6 to the total observed line
profile was estimated from the 1D-LTE analysis of the line asymmetry. Observed
asymmetries could be reproduced assuming isotopic abundance ratios 6Li/7Li of
the order of: 0.004 for BD+26 3578, ~ 0.010 for BD+02 3375 and G 64-37, 0.025
for BD+20 3603 and 0.047 for BD-04 3208. We found that these results were very
sensitive to several of the assumptions made in the analysis, in particular,
the treatment of the residual structure in the analysed spectra. Our final
estimates for the errors are respectively delta_6Li/7Li=+- 0.028, 0.029, 0.039,
0.025 and 0.039. The 6Li/7Li ratios for the sample are comparable to or even
lower than these error values, so that detections of lithium-6 can not safely
be claimed despite of the high resolving power (R ~ 95 000) and S/N (400-600).

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The categories of this paper are: comp-gas
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The categories of this paper are: q-fin
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The categories of this paper are: funct-an
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The categories of this paper are: dg-ga
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The categories of this paper are: q-alg
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The categories of this paper are: alg-geom
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The categories of this paper are: adap-org
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The categories of this paper are: bayes-an
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The categories of this paper are: math
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The categories of this paper are: mtrl-th
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The categories of this paper are: supr-con
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The categories of this paper are: atom-ph
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The categories of this paper are: chem-ph
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The categories of this paper are: patt-sol
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The categories of this paper are: nlin
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The categories of this paper are: q-bio