EDP Sciences
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Volume 427, Number 3, December I 2004
Page(s) 933 - 936
Section Stellar structure and evolution
DOI http://dx.doi.org/10.1051/0004-6361:20041449

A&A 427, 933-936 (2004)
DOI: 10.1051/0004-6361:20041449

A new Böhm-Vitense gap in the temperature range 5560 to 5610 K in the main sequence

V. V. Kovtyukh1, C. Soubiran2 and S. I. Belik1

1  Astronomical Observatory of Odessa National University and Isaac Newton Institute of Chile, Shevchenko Park, 65014, Odessa, Ukraine
    e-mail: val@deneb.odessa.ua
2  Observatoire Aquitain des Sciences de l'Univers, CNRS UMR 5804, BP 89, 33270 Floirac, France

(Received 10 June 2004 / Accepted 20 July 2004)

Highly precise temperatures ( $\sigma = 10{-}15$ K) have been determined from line depth ratios for a set of 248 F-K field dwarfs of about solar metallicity ( $-0.5 < {\rm [Fe/H]} < +0.4$), based on high resolution ( $R=42\,000$), high S/N echelle spectra. A new gap has been discovered in the distribution of stars on the Main Sequence in the temperature range 5560 to 5610 K. This gap coincides with a jump in the microturbulent velocity Vt and the well-known Li depression near 5600 K in field dwarfs and open clusters. As the principal cause of the observed discontinuities in stellar properties we propose the penetration of the convective zone into the inner layers of stars slightly less massive than the Sun and related to it, a change in the temperature gradient.

Key words: stars: fundamental parameters -- convection -- stars: Hertzsprung-Russell (HR) and C-M diagrams -- stars: abundances

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