Solar noble gas abundances

Elemental abundance values of noble gases in the sun recommended here are listed in Table 2, and isotopic compositions are given in Tables 3-5. In the next two subsections, we comment on these adopted values. Note that in Tables 7, 11, and 13 (found later in this chapter) elemental abundances in various reservoirs are stated relative to solar abundances. These are always the values as reported in the original references, i.e., they have not been renormalized to the solar abundances used here. 

Elemental abundances. (A) Helium. Solar models are able to deduce accurate, although somewhat model-dependent, protosolar He values by fits to the observed present-day luminosity (e.g., Christensen-Dalsgaard 1998, see Helium in the sun section). The value stated in the body of Table 2 in three different notations is from the compilation by Grevesse and Sauval (1998), two other values for the initial He mass fraction are given in the Table caption (see also next section). In summary, the models provide the protosolar He abundance with an uncertainty of only a few percent. 

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