High-resolution optical spectroscopy of the sharp-lined B-type star HD83206

Details High-resolution optical spectroscopy of the sharp-lined B-type star HD83206 High-resolution optical spectroscopy of the sharp-lined B-type star HD83206

May 2000

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000mnras.314..199l&link_type=abstract

Monthly Notices of the Royal Astronomical Society, Volume 314, Issue 1, pp. 199-208.

Astronomy and Astrophysics

Astronomy

6

Stars: Abundances, Stars: Atmospheres, Stars: Early-Type, Stars: Individual: Hd83206

Scientific paper

Very-high-resolution (R~160000) spectroscopic observations are presented for the early B-type star, HD83206. Because it has very sharp metal lines, this star affords an opportunity to test theories of model atmospheres and line formation. Non-LTE model atmosphere calculations have been used to estimate the atmospheric parameters and absolute metal abundances (C, N, O, Mg and Si); an LTE analysis was also undertaken to investigate the validity of this simpler approach and to estimate an iron abundance. For the non-LTE calculations, there is excellent agreement with observations of the Balmer lines Hα and Hδ and the lines of Siii and Siiii for atmospheric parameters of Teff~=21700+/-600K and logg~=4.00+/-0.15dex. The agreement is less convincing for the LTE calculations, and a higher gravity is deduced. Careful comparison of the metal line profiles with non-LTE calculations implies that the projected rotational and microturbulent velocities have maximum values of ~=5 and ~=2kms-1, respectively. The latter value is smaller than has often been adopted in LTE model atmosphere analyses of main-sequence stars. Non-LTE absolute metal abundances are estimated, and a comparison with those for normal B-type stars (deduced using similar non-LTE techniques) shows no significant differences. A comparison of the abundances deduced using non-LTE and LTE calculations implies systematic differences of 0.1-0.2dex, showing the importance of using a non-LTE approach when accurate absolute abundances are required. Its location in the Hertzsprung-Russell diagram and normal metal abundance lead us to conclude that HD83206 is probably a main-sequence B-type star. As such, it is among the sharpest-lined young B-type star discovered to date.

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