Non-LTE Effects in Mg I Lines for Various Types of Stars

Details Non-LTE Effects in Mg I Lines for Various Types of Stars Non-LTE Effects in Mg I Lines for Various Types of Stars

Aug 2000

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000arep...44..530s&link_type=abstract

Astronomy Reports, Volume 44, Issue 8, August 2000, pp.530-547

Astronomy and Astrophysics

Astronomy

12

Scientific paper

We have performed a detailed statistical-equilibrium analysis based on a 49-level model of the magnesium atom for the atmospheres of stars of various spectral types: T eff=4500 12000 K, logg=0.0 4.5, and [M/H]=0 to -3. In the atmospheres of stars with T eff>5500 K, deviations from LTE for Mg I are due to photoionization by ultraviolet radiation from the 3p level; i.e., neutral magnesium is in a state of “superionization.” When T eff<5500 K, the populations of the Mg I levels differ from their LTE values due to radiative processes in bound-bound transitions. We analyzed Mg I lines in the solar spectrum in order to empirically refine certain atomic parameters (the van der Waals broadening constant C 6 and cross sections for photoionization and collisional interactions with hydrogen atoms) and the magnesium abundance in the solar atmosphere. We studied non-LTE effects for five Mg I lines for a wide range of stellar parameters. In the case of dwarfs and subdwarfs, the magnitude of non-LTE corrections to magnesium abundances does not exceed 0.1 dex for the λλ 4571, 4703, 5528, and 5711 Å lines but can be as large as ±0.2 dex for the λλ 3829 3838, 5172, and 5183 Å lines. The non-LTE corrections for giants and supergiants do not exceed 0.15 dex for the λλ 4571 and 5711 Å lines but can reach ±0.20 dex and even more for the λλ 4703, 5528, 3829 3838, 5172, and 5183 Å lines.

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