Probing the Neutron‐Capture Nucleosynthesis History of Galactic Matter

By J. Truran, J. Cowan, C. Pilachowski, C. Sneden. 2002

145 citations recorded by the source corpus.

The heavy elements formed by neutron‐capture processes have an interesting history from which we can extract useful clues to and constraints upon both the characteristics of the processes themselves and the star formation and nucleosynthesis history of Galactic matter. Of particular interest in this regard are the heavy‐element compositions of extremely metal deficient stars. At metallicities [Fe/H] ≤ −2.5, the elements in the mass region past barium (A≳130–140) have been found (in non–carbon‐rich stars) to be pure r‐process products. The identification of an environment provided by massive stars and associated Type II supernovae as an r‐process site seems compelling. Increasing levels of heavy s‐process (e.g., barium) enrichment with increasing metallicity, evident in the abundances of more metal rich halo stars and disk stars, reflect the delayed contributions from the low‐ and intermediate‐mass (M∼1–3 M⊙) stars that provide the site for the main s‐process nucleosynthesis component during the asymptotic giant branch phase of their evolution. New abundance data in the mass region 60≲A≲130 are providing insight into the identity of possible alternative r‐process sites. We review recent observational studies of heavy‐element abundances in both low‐metallicity halo stars and disk stars, discuss the observed trends in light of nucleosynthesis theory, and explore some implications of these results for Galactic chemical evolution, nucleosynthesis, and nucleocosmochronology.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/04a177cf96360cda6d3f939c46e5d662b9cfb332

How researchers see this paper

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In Astronomy and Astrophysics

1. Timothy C. Beers
2. C. Sneden
3. Roberto Gallino
4. A. Frebel
5. J. Cowan
6. J. Norris
7. Wak Aoki
8. Martin Asplund

In Instrumentation

1. Timothy C. Beers
2. A. Frebel
3. C. Sneden
4. Roberto Gallino
5. J. Cowan
6. J. Norris
7. Jason Tumlinson
8. M. Walker

Citations in the corpus

• Neutron-Capture Elements in the Very Metal Poor Star HD 122563 (2006, methodology): “U) is referred to as ‘‘main r-process’’ (e.g., Truran et al. 2002; Wanajo & Ishimaru 2006).”
• DETAILED CHEMICAL ABUNDANCES IN THE r-PROCESS-RICH ULTRA-FAINT DWARF GALAXY RETICULUM 2 (2016, background): “Candidates include the weak component of the r process (e.g., Truran et al. 2002; Arcones & Thielemann 2013) and charged particle reactions (e.g., Woosley & Hoffman 1992) operating in core-collapse supernovae or the weak component of the s process (e.g., Raiteri et al. 1991; Pignatari et al. 2008)…”
• Nucleosynthesis in the Early Galaxy (2007, background): “This is the same conclusion that has been drawn from the abundance pattern of the few very metalpoor, strongly r-process enhanced stars where a large range of elemental abundance have been determined (see for example the reviews by Truran et al. (2002); Cowan et al. (2006)).”
• Neutron-Capture Elements in the Early Galaxy (2008, methodology): “The details of the r-process are quite different from the s-process (see the following r-process reviews: Hillebrandt 1978; Mathews & Cowan 1990; Cowan, Thielemann & Truran 1991a; Meyer 1994; Truran et al. 2002; Sneden & Cowan 2003; Cowan & Thielemann 2004; and Arnould, Goriely & Takahashi 2008).”
• THE HISTORY OF R-PROCESS ENRICHMENT IN THE MILKY WAY (2014, background): “Of particular interest in this regard is the heavy element composition of Galactic halo stars (Truran et al. 2002; Cowan & Sneden 2006).”
• Chemical Evolution in Hierarchical Models of Cosmic Structure. I. Constraints on the Early Stellar Initial Mass Function (2005, background): “The relative abundances (i.e., [Eu/Ba]) are similar enough to the solar ratios to suggest that the details of the r-process are unchanged over more than 3 decades of metallicity (Truran et al. 2002).”
• Abundance Variations within Globular Clusters (2004, background): “First, their bulk amounts vary from star to star by more than two orders of magnitude, roughly –0.5 ≥ [n-capture/Fe] ≥ +2.0 (e.g., McWilliam et al. 1995, Burris et al. 2000, Truran et al. 2002).”
• HE 1327–2326, an Unevolved Star with [Fe/H] < –5.0. I. A Comprehensive Abundance Analysis (2005, background): “Type II supernovae are the most promising sites for this process, although other possibilities have also been proposed ( Truran et al. 2002 and references therein).”
• The s-Process in Massive Stars at Low Metallicity: The Effect of Primary 14N from Fast Rotating Stars (2008, background): “The s process in fast rotating massive stars could provide a new scenario to explain the Sr enrichment coupled with high Sr/Ba observed in many stars (Truran et al. 2002; Aoki et al. 2005) at very low metallicity, including also the spread in the observed Sr/Ba ratio.”
• The Hamburg/ESO R-process enhanced star survey (HERES). II. Spectroscopic analysis of the survey sample (2005, methodology): “Our result seems to be in disagreement with that found at low metallicities by Truran et al. (2002), who compiled data from a number of studies, and found a large scatter in Ba/Eu.”
• Spectroscopic Studies of Extremely Metal-Poor Stars with the Subaru High Dispersion Spectrograph. II. The r-Process Elements, Including Thorium (2004, methodology): “This correlation is much clearer in our figure than in Figure 10 of Truran et al. (2002), presumably because their sample includes several rather metal-rich objects, which could well be affected by the contribution of s-process nucleosynthesis.”
• Spectroscopic Studies of Very Metal-poor Stars with the Subaru High Dispersion Spectrograph. III. Light Neutron-Capture Elements (2005, background): “Truran et al. (2002) pointed out the existence of a group of stars that exhibit high Sr /Ba ratios but low Ba abundances and emphasized the contrast to r-process-enhanced stars that have relatively low Sr /Ba ratios.”
• THE DISCOVERY AND ANALYSIS OF VERY METAL-POOR STARS IN THE GALAXY (2005, background): “4.5. r-Process–Enhanced Stars Recent comprehensive summaries of the nuclear physics and astrophysics of the r-process are provided by Truran et al. (2002), Qian (2003), and Cowan & Thielemann (2004).”
• The s process: Nuclear physics, stellar models, and observations (2010, background): “Apart from the r process and weak s process, recent studies on light neutron-capture elements suggest a LEPP as an additional source of these elements in the very early Galaxy (Aoki et al., 2005; Travaglio et al., 2004; Truran et al., 2002) as discussed in Sec.”
• Distances and ages of NGC 6397, NGC 6752 and 47 Tuc (2003, background): “In spite of these admirable efforts, real uncertainties of such determinations are difficult to assess and are likely large, because they depend on the adopted model for the-process that is still quite uncertain (see e.g. Truran et al. 2002).”
• Near-Ultraviolet Observations of HD 221170: New Insights into the Nature of r-Process-rich Stars (2006, background): “The ideal chronometer pair for these age determinations is Th/U, since both elements are made entirely in the r-process and are nearby in mass number (see discussions in the reviews of Truran et al. 2002, Sneden & Cowan 2003, Cowan & Sneden 2004, and Cowan & Thielemann 2004).”