Unusual neutron-capture nucleosynthesis in a carbon-rich Galactic bulge star
| Autor: | Richard J. Stancliffe, Melanie Hampel, Andreas Koch, Almudena Arcones, Camilla Juul Hansen, Moritz Reichert, Amanda I. Karakas |
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| Rok vydání: | 2018 |
| Předmět: |
Population II [stars]
bulge [Galaxy] FOS: Physical sciences Astrophysics Astrophysics::Cosmology and Extragalactic Astrophysics Chemical element 01 natural sciences Galactic halo nuclear reactions nucleosynthesis abundances Nucleosynthesis Bulge 0103 physical sciences Asymptotic giant branch Astrophysics::Solar and Stellar Astrophysics Neutron 010303 astronomy & astrophysics Astrophysics::Galaxy Astrophysics Physics carbon [stars] 010308 nuclear & particles physics abundances [Galaxy] Astronomy and Astrophysics Astrophysics - Astrophysics of Galaxies abundances [stars] Stars 13. Climate action Space and Planetary Science Astrophysics of Galaxies (astro-ph.GA) ddc:520 Halo |
| Zdroj: | Astronomy and Astrophysics Koch, A, Reichert, M, Hansen, C J, Hampel, M, Stancliffe, R J, Karakas, A & Arcones, A 2019, ' Unusual neutron-capture nucleosynthesis in a carbon-rich Galactic bulge star ', Astronomy & Astrophysics, vol. 622, A159 . https://doi.org/10.1051/0004-6361/201834241 Astronomy and astrophysics 622, A159-(2019). doi:10.1051/0004-6361/201834241 Astronomy & Astrophysics |
| DOI: | 10.48550/arxiv.1812.07574 |
| Popis: | Metal-poor stars in the Galactic halo often show strong enhancements in carbon and/or neutron-capture elements. However, the Galactic bulge is notable for its paucity of carbon-enhanced metal-poor (CEMP) and/or CH-stars, with only two such objects known to date. This begs the question whether the processes that produced their abundance distribution were governed by a comparable nucleosynthesis in similar stellar sites as for their more numerous counterparts in the halo. Recently, two contenders of such stars were discovered in the bulge, at [Fe/H] = $-1.5$ and $-$2.5 dex, both of which show enhancements in [C/Fe] of 0.4 and 1.4 dex, [Ba/Fe] in excess of 1.3 dex, and also elevated nitrogen. The more metal-poor of the stars is matched by standard $s$-process nucleosynthesis in low-mass Asymptotic Giant Branch (AGB) polluters. The other star shows an abnormally high [Rb/Fe] ratio. Here, we investigate the origin of the abundance peculiarities in the Rb-rich star by new, detailed measurements of heavy element abundances and by comparing the chemical element ratios of 36 species to models of neutron-capture nucleosynthesis. The $i$-process with intermediate neutron densities between those of the $s$- and $r$-processes has been previously found to provide good matches of CEMP stars with enhancements in both $r$- and $s$-process elements, rather than invoking a superposition of yields from the respective individual processes. However, the peculiar bulge star is incompatible with a pure $i$-process from a single ingestion event. Instead, it can, statistically, be better reproduced by models accounting for two proton ingestion events, or by an $i$-process component in combination with $s$-process nucleosynthesis in low-to-intermediate mass AGB stars, indicating multiple polluters. [abridged] Comment: 11 pages, 6 figures, accepted for publication in Astronomy & Astrophysics |
| Databáze: | OpenAIRE |
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