Observations of the He I 10830 A line in main-sequence O9-B6 stars and comparison with non-LTE predictions

Details Observations of the He I 10830 A line in main-sequence O9-B6 stars and comparison with non-LTE predictions Observations of the He I 10830 A line in main-sequence O9-B6 stars and comparison with non-LTE predictions

Nov 1989

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1989a%26a...225..439l&link_type=abstract

Astronomy and Astrophysics (ISSN 0004-6361), vol. 225, no. 2, Nov. 1989, p. 439-444.

Astronomy and Astrophysics

Astrophysics

11

B Stars, Helium, Main Sequence Stars, Nonequilibrium Thermodynamics, O Stars, Stellar Spectra, Astronomical Models, Charge Coupled Devices, Spectral Line Width, Thermodynamic Equilibrium

Scientific paper

New high resolution CCD observations of the He I 10830 A line in O9-B6 main-sequence stars are presented and compared with previous non-LTE model atmosphere calculations. While good qualitative agreement with the results of Auer and Mihalas (1973) is found, the theoretical results tend to overestimate the line strength. This is particularly serious at the earliest spectral types where the observations imply that the line is either very weak in absorption or (for Tau Sco) very weak in emission. This line provides a stringent test of the validity of the model atmosphere calculations due to (1) its high sensitivity to non-LTE effects, (2) the transition between low lying levels leading to compact model atom and (3) reliable atomic data available for most processes involving helium atoms or ions. The difficulties inherent to modeling this line are discussed with particular attention being paid to the likely influence of line-blanketing.

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