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Astron. Astrophys. 323, 461-468 (1997)

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3. Stellar parameters of the sample supergiants

The model atmospheres used in the analysis were computed by B. Plez (private communication) - see Plez et al. (1992) for a description of their model calculations. The grid consists of models for 5 [FORMULA] stars in the range of temperatures 3600 [FORMULA] [FORMULA] [FORMULA] 4750, in steps of 200/250 K, gravities -0.5 [FORMULA] log g [FORMULA] 3.5 in steps of 0.5 dex, metallicities -0.6 [FORMULA] [Fe/H] [FORMULA] +0.6 in steps of 0.3 dex, and microturbulent velocity [FORMULA] = 2 km s-1. A code for interpolation in this grid was used to obtain the models corresponding to the stellar parameters of the sample stars.

In Table 1 are reported the instrument used, visual magnitude and given in Prévot et al. (1983), and the stellar parameters effective temperature [FORMULA], gravity log g, metallicity [Fe/H] and microturbulent velocity [FORMULA] obtained in Paper I.


Table 1. Stellar parameters adopted from Paper I

In the derivation of stellar parameters, models with log providing the ionisation equilibrium hypothesis have been adopted, although in these extended atmospheres, departures from LTE cause an overionisation effect. The gravity derived from stellar evolutionary tracks is higher by about 0.3 to 0.5 dex relative to the spectroscopic value where ionisation equilibrium is imposed, and the difference between the two gravity values corresponds to what is expected from the overionisation due to NLTE effects. A more detailed discussion on the stellar parameters derivation, in particular on gravity, is given in Paper I.

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© European Southern Observatory (ESO) 1997

Online publication: June 5, 1998