A uniform analysis of boron in F and G disk dwarfs from Hubble space telescope archival spectra.
CUNHA K., SMITH V.V., BOESGAARD A.M. and LAMBERT D.L.
Abstract (from CDS):
The boron abundance is derived for 14 near-solar metallicity F and G dwarfs from the archived data set of spectra obtained with the Hubble Space Telescope Goddard High Resolution Spectrograph in the region of the B I resonance line near 2497 Å. These abundances are derived in a uniform way with respect to recent work on solar boron. The synthetic spectra of the B I region were calculated by means of an improved linelist to fit the spectra of the stars spanning a range in Teff between 5650 and 6700 K and metallicity between [Fe/H]=-0.75 and +0.15. The synthetic spectra were computed considering all major sources of metal opacities and, in particular, an updated lower value of Mg I b-f opacity at 2500 Å was used in the calculations. Adopting Li and Be abundances from the literature, significant B depletions (∼0.3-0.5 dex) are found only for the two stars with the most extreme Li depletions (≥2.5 dex) and Be depletions (≥1.5 dex), although the trend of B versus Be indicates that mild B depletions may exist in many of the stars. These results are in concordance with the Boesgaard et al. conclusion that a slow mixing in the outer envelope is responsible for depletions of Li, Be, and B. Stars with less severe Li and Be depletions exhibit roughly solar [B/Fe] ratios. A comparison of the boron abundances from the disk stars (with undepleted boron) with metal-poor halo dwarfs reveals that B is linearly related to Fe over the entire range of metallicities from [Fe/H]~-2.5 to 0.1. The B/Be ratio found for stars with near-solar metallicities and no Li depletion is B/Be=27±5, equal to the solar ratio (B/Be=23).