The Hamburg/ESO R-process enhanced star survey (HERES) - III. HE 0338-3945 and the formation of the r + s stars

By K. Jonsell, Paul Barklem, B. Gustafsson, N. Christlieb, V. Hill, Timothy C. Beers, J. H. Uppsala, Hamburg, Paris Meudon, Michigan State and 1 more. 2006

143 citations recorded by the source corpus.

We have derived abundances of 33 elements and upper limits for 6 additional elements for the metal-poor (${\rm [Fe/H]} = -2.42$) turn-off star HE 0338-3945 from high-quality VLT-UVES spectra. The star is heavily enriched, by about a factor of 100 relative to iron and the Sun, in the heavy s -elements (Ba, La, ...). It is also heavily enriched in Eu, which is generally considered an r -element, and in other similar elements. It is less enriched, by about a factor of 10, in the lighter s -elements (Sr, Y and Zr). C is also strongly enhanced and, to a somewhat lesser degree, N and O. These abundance estimates are subject to severe uncertainties due to NLTE and thermal inhomogeneities which are not taken into detailed consideration. However, an interesting result, which is most probably robust in spite of these uncertainties, emerges: the abundances derived for this star are very similar to those of other stars with an overall enhancement of all elements beyond the iron peak. 
We have defined criteria for this class of stars, $r+s$ stars, and discuss nine different scenarios to explain their origin. None of these explanations is found to be entirely convincing. The most plausible hypotheses involve a binary system in which the primary component goes through its giant branch and asymptotic giant branch phases and produces CNO and s -elements which are dumped onto the observed star. Whether the r -element Eu is produced by supernovae before the star was formed (perhaps triggering the formation of a low-mass binary), by a companion as it explodes as a supernova (possibly triggered by mass transfer), or whether it is possibly produced in a high-neutron-density version of the s -process is still unclear. Several suggestions are made on how to clarify this situation.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/41e398c79d5e90011a6b3674d4a12e434cc0439f

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. A. Karakas
2. Roberto Gallino
3. Timothy C. Beers
4. C. Sneden
5. S. Bisterzo
6. M. Lugaro
7. J. Cowan
8. Wak Aoki

In Instrumentation

1. Roberto Gallino
2. Timothy C. Beers
3. C. Sneden
4. J. Norris
5. M. Lugaro
6. A. Karakas
7. J. Cowan
8. N. Christlieb

Citations in the corpus

• Neutron-Capture Elements in the Early Galaxy (2008, background): “The major difference appears to be one of abundance slope, [X/Fe] as a function of atomic number Z. Similar patterns are seen in nearly all low-metallicity s-rich stars (e.g., Aoki et al. 2002c, Lucatello et al. 2003, Jonsell et al. 2006, Preston et al. 2006).”
• A holistic approach to carbon-enhanced metal-poor stars (2009, methodology): “Jonsell et al. (2006) have a statistical argument against this most popular scenario.”
• CARBON-ENHANCED METAL-POOR STAR FREQUENCIES IN THE GALAXY: CORRECTIONS FOR THE EFFECT OF EVOLUTIONARY STATUS ON CARBON ABUNDANCES (2014, unknown): “…Goswami et al. (2006), Gratton et al. (2000), Hansen et al. (2011, 2014), Hollek et al. (2011, 2014), Ito et al. (2013), Johnson et al. (2007), Jonsell et al. (2006), Lai et al. (2007, 2008), Masseron et al. (2010), Mashonkina et al. (2012), McWilliam et al. (1995), Meléndez & Barbuy (2002),…”
• THE s-PROCESS IN ASYMPTOTIC GIANT BRANCH STARS OF LOW METALLICITY AND THE COMPOSITION OF CARBON-ENHANCED METAL-POOR STARS (2011, background): “Many scenarios have been proposed (as summarised by Jonsell et al. 2006; Lugaro et al. 2009) and most of them seem unlikely.”
• Carbon-enhanced Metal-poor Stars. I. Chemical Compositions of 26 Stars (2006, background): “…of recent abundance studies for CEMP stars (Preston&Sneden 2001; Aoki et al. 2002a, 2002b, 2002c, 2002d, 2004; Depagne et al. 2002; Cohen et al. 2003, 2004, 2006; Lucatello et al. 2003; Barklem et al. 2005; Ivans et al. 2005; Tsangarides 2005; Jonsell et al. 2006) with those of the present work.”
• Where, oh where has the r-process gone? (2007, background): “A more recent compilation of such stars, all of which appear to be greatly enhanced in C, can be found in Jonsell et al. (2006).”
• GALACTIC CHEMICAL EVOLUTION AND SOLAR s-PROCESS ABUNDANCES: DEPENDENCE ON THE 13C-POCKET STRUCTURE (2014, background): “…(planetary nebulae, post-AGB, MS, S, C(N), Ba, CH, and CEMP s stars; see, e.g., Smith & Lambert 1990; Péquignot & Baluteau 1994; Aoki et al. 2002; Abia et al. 2002; Allen & Barbuy 2006; Jonsell et al. 2006; Sharpee et al. 2007; Sterling & Dinerstein 2008; Reyniers et al. 2007; Zamora et al. 2009).”
• The s process: Nuclear physics, stellar models, and observations (2010, background): “…reported in the literature with Eu measurements, six stars show an r-process enrichment of ∼2 dex, among which are HE 2148-1247, the first CEMP-s/r star discovered (Cohen et al., 2003), CS 29497-030 (Ivans et al., 2005), HE 0338-3945 (Jonsell et al., 2006), and CS 22898-027 (Aoki et al., 2007).”
• The s-Process in Low Metallicity Stars. II. Interpretation of High-Resolution Spectroscopic Observations with AGB models (2011, background): “…2006, 2007, 2008; Barbuy et al. 2005; Cohen et al. 2003, 2006; Goswami et al. 2006; Goswami & Aoki 2010; Ivans et al. 2005 Ishigaki et al. 2010; Jonsell et al. 2006 Johnson & Bolte 2002, 2004; Lucatello et al. 2003; Lucatello 2004; Masseron et al. 2006, 2010; Pereira & Drake 2009; Preston &…”