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Title:
Statistical equilibrium and photospheric abundance of nitrogen in the Sun and in Vega.
Authors:
Rentzsch-Holm, I.
Publication:
Astronomy and Astrophysics, v.305, p.275 (A&A Homepage)
Publication Date:
01/1996
Origin:
A&A via CDS
A&A Keywords:
SUN: ABUNDANCES, STARS: ABUNDANCES, {ALPHA} LYR, ATOMIC DATA
Bibliographic Code:
1996A&A...305..275R

Abstract

Non-LTE calculations for nitrogen in the Sun and in the prototype A0 V star Vega are presented. The model atom comprises 96 levels and 82 lines of neutral and singly ionized nitrogen. The influence of atomic data and atmospheric parameters on the resulting non-LTE abundance corrections is investigated in detail. In the Sun non-LTE effects are small; abundance corrections (with respect to standard LTE calculations) are typically -0.05dex. The solar abundance of nitrogen derived by non-LTE analysis becomes log ɛ_N_=8.05+/-0.09. In Vega, non-LTE effects are found to be large and to depend on the adopted abundance of carbon via the UV radiation field. Collision cross-sections, which are still poorly known, play an important role in this analysis. For a standard set of Ni lines in the visible and near infrared, a non-LTE abundance correction of -0.32dex is derived. The corresponding abundance of nitrogen in Vega is logɛ_N_=7.76+/-0.14, implying a deficiency of -0.29dex with respect to the Sun.

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