First Stars XI. Chemical composition of the extremely metal-poor dwarfs in the binary CS 22876--032

Details First Stars XI. Chemical composition of the extremely metal-poor dwarfs in the binary CS 22876--032 First Stars XI. Chemical composition of the extremely metal-poor dwarfs in the binary CS 22876--032

2007-12-18

arxiv.org/abs/0712.2949v1

Astronomy and Astrophysics

Astrophysics

Accepted for publication in Astronomy & Astrophysics

Scientific paper

10.1051/0004-6361:20078847

We have used high-resolution, high-S/N ratio spectra from the UVES spectrograph at the ESO VLT telescope. Long-term radial-velocity measurements and broad-band photometry allow us to determine improved orbital elements and stellar parameters for both components. We use OSMARCS 1D models and the {{\scshape turbospectrum}} spectral synthesis code to determine the abundances of Li, O, Na, Mg, Al, Si, Ca, Sc, Ti, Cr, Mn, Fe, Co and Ni. We also use the CO$^5$BOLD model atmosphere code to compute the 3D abundance corrections, especially for Li and O. We find a metallicity of [Fe/H]$\sim -3.6$ for both stars, using 1D models with 3D corrections of $\sim -0.1$ dex from averaged 3D models. We determine the oxygen abundance from the near-UV OH bands; the 3D corrections are large, -1 and -1.5 dex for the secondary and primary respectively, and yield [O/Fe] $\sim 0.8$, close to the high-quality results obtained from the [OI] 630 nm line in metal-poor giants. Other [$\alpha$/Fe] ratios are consistent with those measured in other dwarfs and giants with similar [Fe/H], although Ca and Si are somewhat low ([X/Fe]$\la 0$). Other element ratios follow those of other halo stars. The Li abundance of the primary star is consistent with the Spite plateau, but the secondary shows a lower abundance; 3D corrections are small. The Li abundance in the primary star supports the extension of the {{\em Spite Plateau}} value at the lowest metallicities, without any decrease. The low abundance in the secondary star could be explained by endogenic Li depletion, due to its cooler temperature. If this is not the case, another, yet unknown mechanism may be causing increased scatter in A(Li) at the lowest metallicities.

Affiliated with

Also associated with

No associations

Rating

First Stars XI. Chemical composition of the extremely metal-poor dwarfs in the binary CS 22876--032 does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with First Stars XI. Chemical composition of the extremely metal-poor dwarfs in the binary CS 22876--032, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and First Stars XI. Chemical composition of the extremely metal-poor dwarfs in the binary CS 22876--032 will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-549474