The Rise of the s-Process in the Galaxy

By J. Simmerer, C. Sneden, J. Cowan, Jason Collier, V. Woolf, J. E. Lawler. 2004

302 citations recorded by the source corpus.

From newly obtained high-resolution, high signal-to-noise ratio spectra the abundances of the elements La and Eu have been determined over the stellar metallicity range -3 < [Fe/H] < +0.3 in 159 giant and dwarf stars. Lanthanum is predominantly made by the s-process in the solar system, while Eu owes most of its solar system abundance to the r-process. The changing ratio of these elements in stars over a wide metallicity range traces the changing contributions of these two processes to the Galactic abundance mix. Large s-process abundances can be the result of mass transfer from very evolved stars, so to identify these cases we also report carbon abundances in our metal-poor stars. Results indicate that the s-process may be active as early as [Fe/H] = -2.6, although we also find that some stars as metal-rich as [Fe/H] = -1 show no strong indication of s-process enrichment. There is a significant spread in the level of s-process enrichment even at solar metallicity.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/5af0dfcae99b48993d86c8989288d75b96e3a946

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

1. C. Sneden
2. Roberto Gallino
3. Timothy C. Beers
4. J. Cowan
5. A. Karakas
6. Wak Aoki
7. A. Frebel
8. N. Christlieb

Citations in the corpus

• THE ABUNDANCES OF NEUTRON-CAPTURE SPECIES IN THE VERY METAL-POOR GLOBULAR CLUSTER M15: A UNIFORM ANALYSIS OF RED GIANT BRANCH AND RED HORIZONTAL BRANCH STARS (2011, background): “…disk star data have been taken from these surveys: Fulbright (2000)(34), Reddy et al. (2003)(76), Cayrel et al. (2004)(20), Cohen et al. (2004)(22), Simmerer et al. (2004)(80), Barklem et al. (2005)(8), Reddy, Lambert & Allende Prieto (2006)(75), François et al. (2007)(31), and Lai et al.…”
• The Dawes Review 2: Nucleosynthesis and Stellar Yields of Low- and Intermediate-Mass Single Stars (2014, methodology): “Simmerer et al. (2004) suggested this epoch occurred around [Fe/H] & −1, but that AGB stars can contribute inhomogeneously (locally) from [Fe/H] & −3.”
• The s-Process in Low Metallicity Stars. II. Interpretation of High-Resolution Spectroscopic Observations with AGB models (2011, background): “…Hill et al. (2000); Johnson & Bolte (2001); Mishenina et al. (2001); Mashonkina et al. (2003); Sneden et al. (2003a); Christlieb et al. (2004); Simmerer et al. (2004); Honda et al. (2004); Barklem et al. (2005); François et al. (2007); Frebel et al. (2007); Aoki & Honda (2008); Hayek et al.…”
• A SEARCH FOR STARS OF VERY LOW METAL ABUNDANCE. VI. DETAILED ABUNDANCES OF 313 METAL-POOR STARS (2014, unknown): “…−0.41 (0.24) +0.00 (0.22) −0.10 (0.15) Cayrel et al. (2004) a 18 −236 (104) −0.68 (0.41) −0.22 (0.14) −0.20 (0.13) Honda et al. (2004b) a 10 −192 (130) −0.76 (0.29) −0.20 (0.31) −0.31 (0.23) Simmerer et al. (2004) a 19 −82 (155) −0.47 (0.35) −0.29 (0.43) −0.22 (0.17) Preston et al. (2006a) b 19…”
• Neutron-Capture Elements in the Early Galaxy (2008, methodology): “We list in column 4 the elemental Solar-system r-only value, Nr [in meteoritic units of N(Si) = 106], and in column 5 we list this same value in spectroscopic log ε units from Simmerer et al. (2004).”
• HIGH-RESOLUTION SPECTROSCOPY OF EXTREMELY METAL-POOR STARS IN THE LEAST EVOLVED GALAXIES: URSA MAJOR II and COMA BERENICES (2009, background): “Three of our stars have Fe abundances above the threshold value of [Fe/H] ∼ −2.6 at which the s-process sets in for halo stars (Simmerer et al. 2004), while the other three have lower metallicities.”
• Origin of the heaviest elements: The rapid neutron-capture process (2019, unknown): “, 2013), mostly adopted from (Simmerer et al., 2004).”
• Spectroscopic Studies of Very Metal-poor Stars with the Subaru High Dispersion Spectrograph. III. Light Neutron-Capture Elements (2005, background): “From the abundance ratios of Ba/Eu or La/Eu,Burris et al. (2000) and Simmerer et al. (2004) concluded that significant contributions from the (main) s-process appear at ½Fe/H 2:3, although a small effect from the s-process is also suggested at slightly lower [Fe/H] ( 2.7).”
• THE DISCOVERY AND ANALYSIS OF VERY METAL-POOR STARS IN THE GALAXY (2005, background): “However, large recent studies of metal-deficient stars have identified stars that exhibit clear s-process signatures with [Fe/H] as low as −2.6 (Simmerer et al. 2004).”
• THE CHEMICAL EVOLUTION OF THE DRACO DWARF SPHEROIDAL GALAXY (2009, methodology): “The r-process ratio shown in the top panel is taken from Simmerer et al (2004); the solar ratio is a mixture of r and s-process material, while the pure s-process ratio for [Ba/Eu] lies higher than the top of the figure.”
• Elemental abundance survey of the Galactic thick disc (2005, result): “Our results generally confirm earlier results for disc and halo stars (Sneden, Gratton & Crocker 1991; Mishenina et al. 2002; Bihain et al. 2004; Simmerer et al. 2004).”
• RADIATIVE TRANSFER SIMULATIONS OF NEUTRON STAR MERGER EJECTA (2013, unknown): “For relative mass fractions, we assume the solar abundance ratios of r-process elements by Simmerer et al. (2004).”
• The two metallicity groups of the globular cluster M 22: a chemical perspective (2011, background): “The solar-system abundances of these three elements are due overwhelmingly to the s-process: Y 72%; Zr 81%, and Ba 85% (e.g., Table 10 of Simmerer et al. 2004).”
• STELLAR ABUNDANCES IN THE SOLAR NEIGHBORHOOD: THE HYPATIA CATALOG (2014, methodology): “%) made by made by the s-process as either 140Ce or 142Ce Arlandini et al. (1999); Simmerer et al. (2004); Käppeler et al. (2011).”
• The Hamburg/ESO R-process enhanced star survey (HERES) - III. HE 0338-3945 and the formation of the r + s stars (2006, background): “…in the very early Galaxy may in general be tiny, as one would expect due to the small fraction of iron to start the nucleosynthesis from, some stars with [Fe/H] as low as about−3 have been found to have clears-element signatures (Johnson & Bolte 2002, Simmerer et al. 2004, Sivarani et al. 2004).”