Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Line shift, line asymmetry, and the 6Li/7Li isotopic ratio determination   Context: Line asymmetries are generated by convective Doppler shifts in
stellar atmospheres, especially in metal-poor stars, where convective motions
penetrate to higher atmospheric levels. Such asymmetries are usually neglected
in abundance analyses. The determination of the 6Li/7Li isotopic ratio is prone
to suffering from such asymmetries, as the contribution of 6Li is a slight
blending reinforcement of the red wing of each component of the corresponding
7Li line, with respect to its blue wing. Aims: The present paper studies the
halo star HD 74000 and estimates the impact of convection-related asymmetries
on the Li isotopic ratio determination. Method: Two methods are used to meet
this aim. The first, which is purely empirical, consists in deriving a template
profile from another element that can be assumed to originate in the same
stellar atmospheric layers as Li I, producing absorption lines of approximately
the same equivalent width as individual components of the 7Li I resonance line.
The second method consists in conducting the abundance analysis based on NLTE
line formation in a 3D hydrodynamical model atmosphere, taking into account the
effects of photospheric convection. Results: The results of the first method
show that the convective asymmetry generates an excess absorption in the red
wing of the 7Li absorption feature that mimics the presence of 6Li at a level
comparable to the hitherto published values. This opens the possibility that
only an upper limit on 6Li/7Li has thus far been derived. The second method
confirms these findings. Conclusions: From this work, it appears that a
systematic reappraisal of former determinations of 6Li abundances in halo stars
is warranted.

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The categories of this paper are: adap-org
1
The categories of this paper are: cs
30
The categories of this paper are: q-alg
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The categories of this paper are: econ
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The categories of this paper are: acc-phys
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The categories of this paper are: patt-sol
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The categories of this paper are: eess
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The categories of this paper are: alg-geom
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The categories of this paper are: atom-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: q-bio
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The categories of this paper are: bayes-an
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The categories of this paper are: hep-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: hep-ex
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The categories of this paper are: math