The first carbon-enhanced metal-poor star found in the Sculptor dwarf spheroidal ocr issue

被引:59
作者
Skuladottir, A. [1 ]
Tolstoy, E. [1 ]
Salvadori, S. [1 ]
Hill, V. [2 ]
Pettini, M. [3 ]
Shetrone, M. D. [4 ]
Starkenburg, E. [5 ]
机构
[1] Univ Groningen, Kapteyn Astron Inst, NL-9700 AV Groningen, Netherlands
[2] Univ Nice Sophia Antipolis, Lab Lagrange, CNRS, Observ Cote Azur, F-06304 Nice 4, France
[3] Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England
[4] Univ Texas Austin, Mcdonald Observ, TX 79734 USA
[5] Univ Victoria, Dept Phys & Astron, STN CSC, Victoria, BC V8W 3P6, Canada
来源
ASTRONOMY & ASTROPHYSICS | 2015年 / 574卷
关键词
stars: abundances; stars: individual: Sculptor dwarf spheroidal; galaxies: abundances; galaxies: dwarf; galaxies: evolution; NEUTRON-CAPTURE ELEMENTS; B-2-SIGMA(+)-X-2-SIGMA(+) VIOLET SYSTEMS; HIGH-DISPERSION-SPECTROGRAPH; EFFECTIVE TEMPERATURE SCALE; R-PROCESS ELEMENTS; CHEMICAL-COMPOSITIONS; EARLY GALAXY; A(2)PI-X-2-SIGMA(+) RED; HOMOGENEOUS SAMPLE; GALACTIC EVOLUTION;
D O I
10.1051/0004-6361/201424782
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
The origin of carbon-enhanced metal-poor (CEMP) stars and their possible connection with the chemical elements produced by the first stellar generation is still highly debated. In contrast to the Galactic halo, not many CFMP stars have been found in the dwarf spheroidal galaxies around the Milky Way. Here we present detailed abundances from ESO VET/IVES high resolution spectroscopy for ET0097, the first CEMP star found in the Sculptor dwarf spheroidal, which is one of the best studied dwarf galaxies in the Local Group, This star has [Fe/H] = 2.03 +/- 0.10, [C/Fe] = 0.51 +/- 0.10 and [N/Fe]) = 1.18 +/- . 0.20, which is the first nitrogen measurement in this galaxy. The traditional definition of CEIVIP Stars is [C/Fe] >= 0.70, but taking into account that this luminous red giant branch star has undergone mixing, it was intrinsically less nitrogen enhanced and more carbon rich when it was formed, and so it falls under the definition of CEMP stars, as proposed by Aoki et al. (2007. ApJ, 655. 492) to account for this effect. By making corrections for this mixing. we conclude that the star had EC/Fel 0.8 during its earlier evolutionary stages. Apart from the enhanced C and N abundances, ET0097 shows no peculiarities in other elements lighter than Zn. and no enhancement of the heavier neutron capture elements (Ba, La, Ce, Ncl, Sm Eu, Dy). making this a CEMP-no star. However, the star does show signs of the weak hprocess. with an overabundance of the lighter neutron-capture elements (Sr, Y, Zr). To explain the abundance pattern observed in ET0097, we explore the possibility that this star was enriched by primordial stars. In addition to the detailed abundances for ET0097. we present estimates and upper limits for C abundances in 85 other stars in Sculptor derived from UN molecular lines. including 11 stars with [Fe/H] <= -2. Combining these limits with observations horn the literature, the fraction of CEMP-no stars in Sculptor seems to be significantly lower than in the Galactic halo.
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页数:14
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