TY - JOUR
T1 - The Most Metal-poor Stars. V. the CEMP-no Stars in 3D and Non-LTE
AU - Norris, John E.
AU - Yong, David
N1 - Publisher Copyright:
© 2019. The American Astronomical Society. All rights reserved.
PY - 2019/7/1
Y1 - 2019/7/1
N2 - We explore the nature of carbon-rich ([C/Fe]1D,LTE > +0.7), metal-poor ([Fe/H1D,LTE] <-2.0) stars in the light of post 1D,LTE literature analyses, which provide 3D-1D and NLTE-LTE corrections for iron, and 3D-1D corrections for carbon (from the CH G-band, the only indicator at lowest [Fe/H]). High-excitation C i lines are used to constrain 3D,NLTE corrections of G-band analyses. Corrections to the 1D,LTE compilations of Yoon et al. and Yong et al. yield 3D,LTE and 3D,NLTE Fe and C abundances. The number of CEMP-no stars in the Yoon et al. compilation (plus eight others) decreases from 130 (1D,LTE) to 68 (3D,LTE) and 35 (3D,NLTE). For stars with-4.5 < [Fe/H] <-3.0 in the compilation of Yong et al., the corresponding CEMP-no fractions change from 0.30 to 0.15 and 0.12, respectively. We present a toy model of the coalescence of pre-stellar clouds of the two populations that followed chemical enrichment by the first zero-heavy-element stars: The C-rich, hyper-metal-poor and the C-normal, very-metal-poor populations. The model provides a reasonable first-order explanation of the distribution of the 1D,LTE abundances of CEMP-no stars in the A(C) and [C/Fe] versus [Fe/H] planes, in the range-4.0 < [Fe/H] <-2.0. The Yoon et al. CEMP Group I contains a subset of 19 CEMP-no stars (14% of the group), four out of nine of which are binary, and which have large [Sr/Ba]1D,LTE values. The data support the conjectures of Hansen et al. and Arentsen et al.That these stars may have experienced enrichment from asymptotic giant branch stars and/or "spinstars.".
AB - We explore the nature of carbon-rich ([C/Fe]1D,LTE > +0.7), metal-poor ([Fe/H1D,LTE] <-2.0) stars in the light of post 1D,LTE literature analyses, which provide 3D-1D and NLTE-LTE corrections for iron, and 3D-1D corrections for carbon (from the CH G-band, the only indicator at lowest [Fe/H]). High-excitation C i lines are used to constrain 3D,NLTE corrections of G-band analyses. Corrections to the 1D,LTE compilations of Yoon et al. and Yong et al. yield 3D,LTE and 3D,NLTE Fe and C abundances. The number of CEMP-no stars in the Yoon et al. compilation (plus eight others) decreases from 130 (1D,LTE) to 68 (3D,LTE) and 35 (3D,NLTE). For stars with-4.5 < [Fe/H] <-3.0 in the compilation of Yong et al., the corresponding CEMP-no fractions change from 0.30 to 0.15 and 0.12, respectively. We present a toy model of the coalescence of pre-stellar clouds of the two populations that followed chemical enrichment by the first zero-heavy-element stars: The C-rich, hyper-metal-poor and the C-normal, very-metal-poor populations. The model provides a reasonable first-order explanation of the distribution of the 1D,LTE abundances of CEMP-no stars in the A(C) and [C/Fe] versus [Fe/H] planes, in the range-4.0 < [Fe/H] <-2.0. The Yoon et al. CEMP Group I contains a subset of 19 CEMP-no stars (14% of the group), four out of nine of which are binary, and which have large [Sr/Ba]1D,LTE values. The data support the conjectures of Hansen et al. and Arentsen et al.That these stars may have experienced enrichment from asymptotic giant branch stars and/or "spinstars.".
KW - Galaxy: formation
KW - Galaxy: halo
KW - abundances
KW - early universe
KW - nuclear reactions
KW - nucleosynthesis
KW - stars: abundances
UR - http://www.scopus.com/inward/record.url?scp=85069476886&partnerID=8YFLogxK
U2 - 10.3847/1538-4357/ab1f84
DO - 10.3847/1538-4357/ab1f84
M3 - Article
SN - 0004-637X
VL - 879
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 1
M1 - 37
ER -