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Astron. Astrophys. 364, 674-682 (2000)

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4. Influence of atmospheric parameters on abundances

In order to estimate the errors due to uncertainties on the atmospheric parameters, the variation of the equivalent width of the Li line W(Li) as a function of temperature, gravity and lithium abundance was calculated, by adopting a model with solar abundances. The lithium abundance is hereafter designated by log N(Li). We are interested here in analysing the computed W(Li) sensitivity for variations of the atmospheric parameters in both cases: lower and higher temperatures.

Fig. 2 shows W(Li) as a function of the adopted parameters. It can be noted for temperatures around 3500 K that log N(Li) has an important dependence on shifts in log g. For temperatures around 5000 K, log N(Li) is mainly sensitive to variations in [FORMULA]. An evaluation of these dependencies is shown in Table 4, which gives the variation of log N(Li) corresponding to shifts on [FORMULA] and log g for three different values of temperature. The mean errors derived from the maximal shifts on [FORMULA] and log g are slightly different for lower and higher temperatures. Errors of 0.3 dex for stars with [FORMULA][FORMULA] 4000 K, and of [FORMULA]0.2 dex for 4000 [FORMULA] [FORMULA] [FORMULA] 5000 K are predicted.

[FIGURE] Fig. 2. Variation of the equivalent width (expressed in [FORMULA]) of the Li I 670.78 nm line, as a function of temperature, gravity, and abundance. Curves are plotted to represent 4 different abundance values. For lower temperatures, log N(Li) is most sensitive to variations in log g, and for higher temperatures it is sensitive to [FORMULA] variations


[TABLE]

Table 4. The sensitivity of log N(Li) to shifts in the atmospheric parameters, verified for W(Li) [FORMULA] 300 m[FORMULA]. Three different values of temperature were adopted. The shifts [FORMULA][FORMULA] and [FORMULA]log [FORMULA] correspond to the maximal uncertainties of the adopted parameters.


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© European Southern Observatory (ESO) 2000

Online publication: January 29, 2001
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