Journal Article

Accurate fundamental parameters for A-, F- and G-type Supergiants in the solar neighbourhood

Leonid S. Lyubimkov, David L. Lambert, Sergey I. Rostopchin, Tamara M. Rachkovskaya and Dmitry B. Poklad

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 402, issue 2, pages 1369-1379
Published in print February 2010 | ISSN: 0035-8711
Published online February 2010 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2009.15979.x
Accurate fundamental parameters for A-, F- and G-type Supergiants in the solar neighbourhood

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The following parameters are determined for 63 Galactic supergiants in the solar neighbourhood: effective temperature Teff; surface gravity log g; iron abundance log ε(Fe); microturbulent parameter Vt; mass M/M; age t and distance d. A significant improvement in the accuracy of the determination of log g, and all parameters dependent on it, is obtained through application of van Leeuwen rereduction of the Hipparcos parallaxes. The typical error in the log g values is now ±0.06 dex for supergiants with distances d < 300 pc and ±0.12 dex for supergiants with d between 300 and 700 pc; the mean error in Teff for these stars is ±120 K. For supergiants with d > 700 pc, parallaxes are uncertain or unmeasurable, so typical errors in their log g values are 0.2–0.3 dex.

A new Teff scale for A5–G5 stars of luminosity classes Ib–II is presented. Spectral subtypes and luminosity classes of several stars are corrected. Combining the Teff and log g with evolutionary tracks, stellar masses and ages are determined; a majority of the sample has masses between 4 and 15 M and, hence, their progenitors were early to middle B-type main-sequence stars.

Using Fe ii lines, which are insensitive to departures from local thermodynamic equilibrium, the microturbulent parameter Vt and the iron abundance log ε(Fe) are determined from high-resolution spectra. The parameter Vt is correlated with gravity: Vt increases with decreasing log g. The mean iron abundance for the 48 supergiants with distances d < 700 pc is log ε(Fe) = 7.48 ± 0.09, a value close to the solar value of 7.45 ± 0.05, and thus the local supergiants and the Sun have the same metallicity.

Keywords: stars: abundances; stars: fundamental parameters; supergiants

Journal Article.  8206 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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