High-resolution abundance analysis of very metal-poor r-I stars

Mello, C. Siqueira; Hill, V.; Barbuy, B.; Spite, M.; Spite, F.; Beers, Timothy C.; Caffau, E.; Bonifacio, P.; Cayrel, Roger; François, P.; Schatz, H.; Wanajo, Shinya

doi:10.1051/0004-6361/201423826

Cited by 66 publications

(29 citation statements)

References 84 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It was established that r-II and r-I stars have a very similar heavy-element abundance pattern in the Ba-Hf region that, in turn, is consistent with a scaled solar system (SS) r-process abundance distribution (see for example Sneden et al 2008;Cowan et al 2002;Ivans et al 2006;Sitnova & Mashonkina 2011;Siqueira-Mello et al 2014). This suggests a universal production ratio of the second r-process peak elements during the Galaxy history.…”

Section: Introductionmentioning

confidence: 66%

“…Roederer et al (2009) revised Eu and Th abundances of 15 MP stars that reveal pure r-process neutron-capture elements. Figure 9 displays the Th/Eu abundance ratios of the Roederer et al (2009) sample and also HE 2327−5642 (Paper V), CS 30315-029 (Siqueira-Mello et al 2014), and HE 2252−4225. It appears that 12 of the 18 stars have no obvious enhancement of thorium with respect to the scaled solar r-process pattern, and for each of them, its stellar age agrees within the error bars with the cosmic age 13.772 ± 0.059 Gyr (Bennett et al 2013) derived from the updated results of the Wilkinson Microwave Anisotropy Probe (WMAP).…”

Section: Thorium In R-process Enhanced Starsmentioning

confidence: 99%

See 1 more Smart Citation

The Hamburg/ESO R-process Enhanced Star survey (HERES)

Mashonkina

Christlieb

Eriksson

2014

A&A

View full text Add to dashboard Cite

Context. Studies of the r-process enhanced stars are important for understanding the nature and origin of the r-process better.Aims. We present a detailed abundance analysis of a very metal-poor giant star discovered in the HERES project, HE 2252-4225, which exhibits overabundances of the r-process elements with [r/Fe] = +0.80. Methods. We determined the stellar atmosphere parameters, T eff = 4710 K, log g = 1.65, and [Fe/H] = −2.63, and chemical abundances by analysing the high-quality VLT/UVES spectra. The surface gravity was calculated from the non-local thermodynamic equilibrium (NLTE) ionisation balance between Fe i and Fe ii.Results. Accurate abundances for a total of 38 elements, including 22 neutron-capture elements beyond Sr and up to Th, were determined in HE 2252−4225. For every chemical species, the dispersion in the single line measurements around the mean does not exceed 0.12 dex. This object is deficient in carbon, as expected for a giant star with T eff < 4800 K. The stellar Na-Zn abundances are well fitted by the yields of a single supernova of 14.4 M . For the neutron-capture elements in the Sr-Ru, Ba-Yb, and Os-Ir regions, the abundance pattern of HE 2252−4225 is in excellent agreement with the average abundance pattern of the strongly r-process enhanced stars CS 22892-052, CS 31082-001, HE 1219-0312, and HE 1523-091. This suggests a common origin of the first, second, and third r-process peak elements in HE 2252−4225 in the classical r-process. We tested the solar r-process pattern based on the most recent s-process calculations of Bisterzo, Travaglio, Gallino, Wiescher, and Käppeler and found that elements in the range from Ba to Ir match it very well. No firm conclusion can be drawn about the relationship between the first neutron-capture peak elements, Sr to Ru, in HE 2252−4225 and the solar r-process, owing to the uncertainty in the solar r-process. The investigated star has an anomalously high Th/Eu abundance ratio, so that radioactive dating results in a stellar age of τ = 1.5 ± 1.5 Gyr that is not expected for a very metal-poor halo star.

show abstract

Section: Introductionmentioning

confidence: 66%

Section: Thorium In R-process Enhanced Starsmentioning

confidence: 99%

The Hamburg/ESO R-process Enhanced Star survey (HERES)

Mashonkina

Christlieb

Eriksson

2014

A&A

View full text Add to dashboard Cite

show abstract

“…It has long been recognized that the abundance pattern for the heavy neutroncapture elements in r-II stars follows the solar system r-process pattern (e.g., McWilliam et al 1995;Hill et al 2002;Sneden et al 2003). The same was recently found to be true for the moderately enhanced and more numerous r-I stars (Siqueira Mello et al 2014).…”

mentioning

confidence: 75%

An r-process Enhanced Star in the Dwarf Galaxy Tucana III*

Hansen¹,

Simon²,

Marshall³

et al. 2017

ApJ

121

View full text Add to dashboard Cite

Chemically peculiar stars in dwarf galaxies provide a window for exploring the birth environment of stars with varying chemical enrichment. We present a chemical abundance analysis of the brightest star in the newly discovered ultra-faint dwarf galaxy candidate Tucana III. Because it is particularly bright for a star in an ultra-faint Milky Way satellite, we are able to measure the abundance of 28 elements, including 13 neutron-capture species. This star, DES J235532.66−593114.9 (DES J235532), shows a mild enhancement in neutron-capture elements associated with the r-process and can be classified as an r-I star. DES J235532 is the first r-I star to be discovered in an ultra-faint satellite, and Tuc III is the second extremely low-luminosity system found to contain r-process enriched material, after Reticulum II. Comparison of the abundance pattern of DES J235532 with r-I and r-II stars found in other dwarf galaxies and in the Milky Way halo suggests a common astrophysical origin for the neutron-capture elements seen in all r-process enhanced stars. We explore both internal and external scenarios for the r-process enrichment of Tuc III and show that with abundance patterns for additional stars it should be possible to distinguish between them.

show abstract

“…Abundance ratios of first-and second-peak elements and s-dominant elements such as Ba over r-dominant elements such as Eu can contribute to distinguishing different nucleosynthesis process contributions (e.g. Siqueira-Mello et al 2014;Siqueira-Mello & Barbuy 2014).…”

Section: Introductionmentioning

confidence: 99%

Heavy elements in old very metal-rich stars

Trevisan

Barbuy

2014

A&A

Self Cite

View full text Add to dashboard Cite

Context. We studied a sample of high proper motion, old and metal-rich dwarf stars, selected from the NLTT catalogue. The low pericentric distances and eccentric orbits of these solar neighbourhood stars indicate that they might have originated in the inner parts of the Galaxy. Aims. Chemical tagging can probe the formation history of stellar populations. To identify the origin of a sample of 71 very metal-rich dwarf stars, we derive the abundances of the neutron-capture elements Y, Ba, La, and Eu. Methods. The spectroscopic analysis is based on optical high-resolution échelle spectra obtained with the FEROS spectrograph at the ESO 1.52 m Telescope at La Silla, Chile. The abundances of Y, Ba, La, and Eu were derived through LTE analysis, employing the MARCS model atmospheres.Results. The abundances of Y, Ba, La, and Eu vs. Fe and Mg as the reference elements indicate similarities between our sample of old metal-rich dwarf stars and the thin disk. On the other hand, the abundance ratios using O as the reference element, as well as their kinematics, suggest that our sample is clearly distinct from the thin-disk stars. They could be old inner thin-disk stars, as suggested previously, or bulge stars. In either cases, they would have migrated from the inner parts of the Galaxy to the solar neighbourhood.

show abstract

High-resolution abundance analysis of very metal-poor r-I stars

Cited by 66 publications

References 84 publications

The Hamburg/ESO R-process Enhanced Star survey (HERES)

The Hamburg/ESO R-process Enhanced Star survey (HERES)

An r-process Enhanced Star in the Dwarf Galaxy Tucana III*

Heavy elements in old very metal-rich stars

Contact Info

Product

Resources

About