Analyses of light-ion spectra in stellar atmospheres. II. The calciumII K-line in B-stars.

Abstract

view Abstract Citations (50) References (30) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Analyses of light-ion spectra in stellar atmospheres. II. The calcium II K-line in B stars. Mihalas, D. Abstract A calculation of the Ca ii K-line strength in the middle B stars has been performed by means of a self-consistent solution of the equations of transfer and steady-state statistical equilibrium. The multilevel model ion, with many explicitly computed bound-bound transitions, is treated as part of a multi-ion system (Ca ii, Ca iii, Ca iv). Results are given for two abundances and microturbulent velocities, and are used to assess systematic errors in LTE diagnostics of these parameters. Near the main sequence for the middle B stars the results show that departures from LTE have a negligibly important effect on the K-line equivalent width, but at higher temperature and lower gravities these departures become ever more important, and in the extreme cases can result in errors in the abundance deduced from LTE of a factor of five, or spurious micro turbulent velocities of up to 3 km 5 - . These effects are less spectacular than those found earlier by the author for Mg ii, but insofar as the K-line is at all typical of a line of comparable strength in these stars, the results may have fartherreaching implications of errors in the usual LTE diagnostics. A discussion of the K-line strengths in L Her and y Peg indicates that they are compatible with a Ca abundance in these stars equal to the solar abundance. Subject headings: abundances, stellar - atmospheres, stellar - early-type stars - line formation Publication: The Astrophysical Journal Pub Date: January 1973 DOI: 10.1086/151859 Bibcode: 1973ApJ...179..209M full text sources ADS | data products SIMBAD (9) Related Materials (3) Part 1: 1972ApJ...177..115M Part 3: 1973ApJ...179..827M Part 4: 1973ApJS...25..433A