Neon Abundances of B Stars in the Solar Neighborhood

摘要

We constructed a comprehensive model atom for Ne i–Ne ii using the most-up-to-date atomic data available and evaluated the nonlocal thermodynamic equilibrium (NLTE) line formation for Ne i and Ne ii in classical 1D models representing the atmospheres of B-type stars. We find that the large NLTE strengthening of the Ne i lines corresponding to the 2p~(5)3p–2p~(5)3s transition array occurs due to extremely small photoionization cross sections of the 2p~(5)3s levels that lead to strong overpopulation of these levels relative to their LTE populations. The deviations from LTE for most Ne ii lines are small and do not exceed 0.11?dex in absolute value. We analyzed 20 lines of Ne i and 13 lines of Ne ii for 24 B-type stars in the temperature range of 10,400?≤? ?≤?33,400 K. For five stars, the NLTE leads to consistent abundances of Ne i and Ne ii, while the difference in LTE abundance can reach up to 0.50?dex. Using the experimental oscillator strengths recently measured by Piracha et al. leads to smaller line-by-line scatter for most of the investigated stars. The average neon abundance in 24 B-type stars in the solar neighborhood is 8.02?±?0.05. This value may provide indirect constraints on the solar photospheric neon abundance.