OBSERVATIONAL CONSTRAINTS ON FIRST-STAR NUCLEOSYNTHESIS. I. EVIDENCE FOR MULTIPLE PROGENITORS OF CEMP-NO STARS

Journal Article · Sat Dec 10 04:00:00 EST 2016 · Astrophysical Journal

DOI:https://doi.org/10.3847/0004-637X/833/1/20· OSTI ID:22660957

Yoon, Jinmi; Beers, Timothy C.; Placco, Vinicius M.; Rasmussen, Kaitlin C.; Carollo, Daniela ^[1]; He, Siyu ^[2]; Hansen, Terese T. ^[3]; Roederer, Ian U. ^[4]; Zeanah, Jeff ^[5]

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1. Department of Physics, University of Notre Dame, Notre Dame, IN 46556 (United States)
2. Department of Physics, Xi’an Jiaotong University, Shaanxi, 710049 (China)
3. Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)
4. Joint Institute for Nuclear Astrophysics-Center for the Evolution of the Elements (JINA-CEE) (United States)
5. Z Solutions, Inc., 9430 Huntcliff Trace, Atlanta, GA 30350 (United States)

We investigate anew the distribution of absolute carbon abundance, A (C) = log ϵ (C), for carbon-enhanced metal-poor (CEMP) stars in the halo of the Milky Way, based on high-resolution spectroscopic data for a total sample of 305 CEMP stars. The sample includes 147 CEMP- s (and CEMP- r / s ) stars, 127 CEMP-no stars, and 31 CEMP stars that are unclassified, based on the currently employed [Ba/Fe] criterion. We confirm previous claims that the distribution of A (C) for CEMP stars is (at least) bimodal, with newly determined peaks centered on A (C) = 7.96 (the high-C region) and A (C) = 6.28 (the low-C region). A very high fraction of CEMP- s (and CEMP- r / s ) stars belongs to the high-C region, while the great majority of CEMP-no stars resides in the low-C region. However, there exists complexity in the morphology of the A (C)-[Fe/H] space for the CEMP-no stars, a first indication that more than one class of first-generation stellar progenitors may be required to account for their observed abundances. The two groups of CEMP-no stars we identify exhibit clearly different locations in the A (Na)- A (C) and A (Mg)- A (C) spaces, also suggesting multiple progenitors. The clear distinction in A (C) between the CEMP- s (and CEMP- r / s ) stars and the CEMP-no stars appears to be as successful, and likely more astrophysically fundamental, for the separation of these sub-classes as the previously recommended criterion based on [Ba/Fe] (and [Ba/Eu]) abundance ratios. This result opens the window for its application to present and future large-scale low- and medium-resolution spectroscopic surveys.

• OSTI ID: 22660957
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 833; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ASTROPHYSICS
C REGION
CARBON
ELEMENT ABUNDANCE
LIMITING VALUES
MILKY WAY
MORPHOLOGY
NUCLEOSYNTHESIS
RESOLUTION
SPACE
STAR EVOLUTION
STARS