2008A&A...480..233G


C.D.S. - SIMBAD4 rel 1.7 - 2019.12.12CET04:06:10

2008A&A...480..233G - Astronomy and Astrophysics, volume 480, 233-246 (2008/3-2)

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

GONZALEZ HERNANDEZ J.I., BONIFACIO P., LUDWIG H.-G., CAFFAU E., SPITE M., SPITE F., CAYREL R., MOLARO P., HILL V., FRANCOIS P., PLEZ B., BEERS T.C., SIVARANI T., ANDERSEN J., BARBUY B., DEPAGNE E., NORDSTROEM B. and PRIMAS F.

Abstract (from CDS):

Unevolved metal-poor stars constitute a fossil record of the early Galaxy, and can provide invaluable information on the properties of the first generations of stars. Binary systems also provide direct information on the stellar masses of their member stars. The purpose of this investigation is a detailed abundance study of the double-lined spectroscopic binary CS 22876-032, which comprises the two most metal-poor dwarfs known. We 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 allowed us to determine improved orbital elements and stellar parameters for both components. We used OSMARCS 1D models and the 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 used the CO5BOLD model atmosphere code to compute the 3D abundance corrections, notably for Li and O. We find a metallicity of [Fe/H]~-3.6 for both stars, using 1D models with 3D corrections of ~-0.1dex from averaged 3D models. We determine the oxygen abundance from the near-UV OH bands; the 3D corrections are large, -1 and -1.5dex for the secondary and primary respectively, and yield [O/Fe]∼0.8, close to the high-quality results obtained from the [OI] 630nm line in metal-poor giants. Other [α/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]≲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 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.

Abstract Copyright:

Journal keyword(s): nuclear reactions, nucleosynthesis, abundances - Galaxy: halo - Galaxy: abundances - cosmology: observations - stars: Population II

Simbad objects: 7

goto Full paper

goto View the reference in ADS

Number of rows : 7

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 SB 44 SB* 00 07 37.5160975025 -35 31 17.710203728   13.23 12.76 12.76   sdF 74 0
2 CD-38 245 Pe* 00 46 36.1954714218 -37 39 33.555736375   12.733 11.929 13.39 10.996 KIIvw 199 0
3 HE 0311-1046 Pe* 03 14 20.8495240680 -10 35 11.279671787   13.54 12.73 12.204 11.693 KIIvw 62 0
4 HD 74000 PM* 08 40 50.8038415228 -16 20 42.513275817 9.84 10.09 9.66     F2 242 0
5 HE 1327-2326 Pe* 13 30 05.9395582011 -23 41 49.699027289 13.761 14.01 13.55 13.50 12.803 CEMP-no 209 0
6 HD 140283 Pe* 15 43 03.0967798658 -10 56 00.595803430 7.508 7.711 7.212 6.63 8.21 F9VkA5mA1 846 0
7 NGC 6397 GlC 17 40 42.09 -53 40 27.6   7.39 5.17     ~ 1761 1

    Equat.    Gal    SGal    Ecl

To bookmark this query, right click on this link: simbad:objects in 2008A&A...480..233G and select 'bookmark this link' or equivalent in the popup menu


2019.12.12-04:06:10

© Université de Strasbourg/CNRS

    • Contact