A Chemical Signature from Fast-rotating Low-metallicity Massive Stars: ROA 276 in ω Centauri*

Yong, David; Norris, John E.; Costa, G. S. Da; Stanford, Laura M.; Karakas, Amanda I.; Shingles, Luke J.; Hirschi, Raphaël; Pignatari, M.

doi:10.3847/1538-4357/aa6250

Cited by 17 publications

(10 citation statements)

References 105 publications

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“…Finally, the CEMP-no star ET0097 at [Fe/H] = −2, which has unusually high [Sr, Y, Zr/Ba] > +0.7 (Skúladóttir et al 2015a), was best fit by a rapidly rotating massive star, which was able to explain both the high [C/Fe] and the high lighter n-capture elements. Similar conclusions were reached by Yong et al (2017) for the star ROA 276, in ω Centauri, which has extremely high [X/Fe] > +1 of the lighter n-capture elements (29 < Z < 43). However the massive star models were not able to reproduce the low [C/Fe] < 0 in ROA 276.…”

Section: Discussionsupporting

confidence: 78%

“…These three stars all show enhancements of [Sr, Y, Zr/Ba] > +0.7, which is not typical for CEMP-no stars in the Milky Way (e.g., Allen et al 2012, and references therein). However, stars with high [Sr,Y,Zr/Ba] but [C/Fe] < 0 have been observed in the Galactic halo (Honda et al 2004(Honda et al , 2006(Honda et al , 2007 and in ω Cen (Yong et al 2017). Thus, it is unclear whether the enhancements of carbon and the lighter n-capture elements is connected to the same source, or specifically to the chemical evolution of dwarf galaxies, or if it is merely a coincidence.…”

Section: Introductionmentioning

confidence: 99%

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Neutron-capture elements in dwarf galaxies

Skúladóttir

Hansen

Choplin

et al. 2020

A&A

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The slow (s) and intermediate (i) neutron (n) capture processes occur both in asymptotic giant branch (AGB) stars, and in massive stars. To study the build-up of the s- and i-products at low metallicity, we investigate the abundances of Y, Ba, La, Nd, and Eu in 98 stars, at −2.4 < [Fe/H] < −0.9, in the Sculptor dwarf spheroidal galaxy. The chemical enrichment from AGB stars becomes apparent at [Fe/H] ≈ −2 in Sculptor, and causes [Y/Ba], [La/Ba], [Nd/Ba] and [Eu/Ba] to decrease with metallicity, reaching subsolar values at the highest [Fe/H] ≈ −1. To investigate individual nucleosynthetic sites, we compared three n-rich Sculptor stars with theoretical yields. One carbon-enhanced metal-poor (CEMP-no) star with high [Sr, Y, Zr] > +0.7 is best fit with a model of a rapidly-rotating massive star, the second (likely CH star) with the i-process, while the third has no satisfactory fit. For a more general understanding of the build-up of the heavy elements, we calculate for the first time the cumulative contribution of the s- and i-processes to the chemical enrichment in Sculptor, and compare with theoretical predictions. By correcting for the r-process, we derive [Y/Ba]s/i = −0.85 ± 0.16, [La/Ba]s/i = −0.49 ± 0.17, and [Nd/Ba]s/i = −0.48 ± 0.12, in the overall s- and/or i-process in Sculptor. These abundance ratios are within the range of those of CEMP stars in the Milky Way, which have either s- or i-process signatures. The low [Y/Ba]s/i and [La/Ba]s/i that we measure in Sculptor are inconsistent with them arising from the s-process only, but are more compatible with models of the i-process. Thus we conclude that both the s- and i-processes were important for the build-up of n-capture elements in the Sculptor dwarf spheroidal galaxy.

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Section: Discussionsupporting

confidence: 78%

Section: Introductionmentioning

confidence: 99%

Neutron-capture elements in dwarf galaxies

Skúladóttir

Hansen

Choplin

et al. 2020

A&A

View full text Add to dashboard Cite

show abstract

“…Finally, the CEMP-no star ET0097 at [Fe/H] = −2, which has unusually high [Sr,Y,Zr/Ba] > +0.7 (Skúladóttir et al 2015b), was best fit by a rapidly rotating massive star, which was able to explain both the high [C/Fe] and the high lighter n-capture elements. Similar conclusions were reached by Yong et al (2017) for the star ROA 276, in ω Centauri, which has extremely high [X/Fe] > +1 of the lighter n-capture elements (29 < Z < 43). However the massive star models were not able to reproduce the low [C/Fe] < 0 in ROA 276.…”

Section: Discussionsupporting

confidence: 78%

“…Allen et al 2012, and references therein). However, stars with high [Sr,Y,Zr/Ba] but [C/Fe] < 0 have been observed in the Galactic halo (Honda et al 2004(Honda et al , 2006(Honda et al , 2007 and in ω Cen (Yong et al 2017). Thus, it is unclear whether the enhancements of carbon and the lighter n-capture elements is connected to the same source, or specifically to the chemical evolution of dwarf galaxies, or if it is merely a coincidence.…”

Section: Carbon-enhanced Metal-poor Starsmentioning

confidence: 99%

Neutron-capture elements in dwarf galaxies II: Challenges for the s- and i-processes at low metallicity

Skúladóttir,

Hansen,

Choplin

et al. 2019

Preprint

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The slow (s) and intermediate (i) neutron (n) capture processes occur both in asymptotic giant branch (AGB) stars, and in massive stars. To study the build-up of the s-and i-products at low metallicity, we investigate the abundances of Y, Ba, La, Nd, and Eu in 98 stars, at −2.4 < [Fe/H] < −0.9, in the Sculptor dwarf spheroidal galaxy. The chemical enrichment from AGB stars becomes apparent at [Fe/H] ≈ −2 in Sculptor, and causes [Y/Ba], [La/Ba], [Nd/Ba] and [Eu/Ba] to decrease with metallicity, reaching subsolar values at the highest [Fe/H] ≈ −1. To investigate individual nucleosynthetic sites, we compared three n-rich Sculptor stars with theoretical yields. One carbon-enhanced metal-poor (CEMP-no) star with high [Sr, Y, Zr] > +0.7 is best fit with a model of a rapidly-rotating massive star, the second (likely CH star) with the i-process, while the third has no satisfactory fit. For a more general understanding of the build-up of the heavy elements, we calculate for the first time the cumulative contribution of the s-and i-processes to the chemical enrichment in Sculptor, and compare with theoretical predictions. By correcting for the r-process, we derive [Y/Ba] s/i = −0.85 ± 0.16, [La/Ba] s/i = −0.49 ± 0.17, and [Nd/Ba] s/i = −0.48 ± 0.12, in the overall s-and/or i-process in Sculptor. These abundance ratios are within the range of those of CEMP stars in the Milky Way, which have either s-or i-process signatures. The low [Y/Ba] s/i and [La/Ba] s/i that we measure in Sculptor are inconsistent with them arising from the s-process only, but are more compatible with models of the i-process. Thus we conclude that both the s-and i-processes were important for the build-up of n-capture elements in the Sculptor dwarf spheroidal galaxy.

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“…For instance, the s-process elemental distribution in the metal poor star ROA 276 in ω Cen(Yong et al 2017) is well explained by the rotating models byFrischknecht et al (2012Frischknecht et al ( , 2016.…”

mentioning

confidence: 99%

HST observations of the globular cluster NGC 6402 (M14) and its peculiar multiple populations

D'Antona,

Milone,

Johnson

et al. 2022

Preprint

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We present Hubble Space Telescope (HST) photometric results for NGC 6402, a highly reddened very luminous Galactic globular cluster (GC). Recent spectroscopic observations of its red giant stars have shown a quite peculiar behavior in the chemistry of its multiple populations. These results have prompted UV and optical HST observations aimed at obtaining the cluster's "Chromosome map" (ChM), an efficient tool to classify GCs and characterize their multiple populations. We find that the discontinuity in the abundance distributions of O, Mg, Al and Na inferred from spectroscopy is more nuanced in the ChM, which is mostly sensitive to nitrogen. Nevertheless, photometry in optical bands reveals a double main sequence, indicating a discontinuity in the helium content of the populations. The population with the largest chemical anomalies (extreme) peaks at a helium mass fraction Y∼0.31. This helium content is consistent with results from the analysis of the distribution of horizontal-branch stars and the spectrophotometry of the red giants. The ChM and the color magnitude diagrams are compared with those in NGC 2808, a prototype GC with helium abundances up to Y 0.35, and both confirm that NGC 6402 does not host stellar populations with such extreme helium content. Further, the ChM reveals the presence of a group of stars with larger metallicity, thus indicating that NGC 6402 is a Type II cluster. The modalities of formation of the multiple populations in NGC 6402 are briefly surveyed, with main attention on the Asymptotic Giant Branch and Supermassive star models, and on possible clusters' merging.

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A Chemical Signature from Fast-rotating Low-metallicity Massive Stars: ROA 276 in ω Centauri*

Cited by 17 publications

References 105 publications

Neutron-capture elements in dwarf galaxies

Neutron-capture elements in dwarf galaxies

Neutron-capture elements in dwarf galaxies II: Challenges for the s- and i-processes at low metallicity

HST observations of the globular cluster NGC 6402 (M14) and its peculiar multiple populations

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