Year: 2024
Type: article
Abstract: Context. The third r-process peak (Os, Ir, Pt) is poorly understood due to observational challenges, with spectral lines located in the blue or near-ultraviolet region of stellar spectra. These challenges need to be overcome for a better understanding of the r-process in a broader context. Aims. To understand how the abundances of the third r-process peak are synthesised and evolve in the Universe, it is necessary to carry out a homogeneous chemical analysis of metal-poor stars using high-quality data observed in the blue region of the electromagnetic spectrum (<400 nm). We provide a homogeneous set of abundances for the third r-process peak (Os, Ir, Pt) and Hf, increasing their availability in the literature by up to one order of magnitude. Methods. We performed a classical 1D, local thermodynamic equilibrium (LTE) analysis of four elements (Hf, Os, Ir, Pt) using ATLAS model atmospheres to fit synthetic spectra on high signal-to-noise-ratio spectra of 52 red giants observed with UVES/VLT in high resolution (>40,000). Due to the heavy line blending involved, we carefully determined upper limits and uncertainties. The observational results are compared with state-of-the-art nucleosynthesis models. Results. Our sample displays larger abundances of Ir (Z=77) in comparison to Os (Z=76), both of which have been measured in a few stars in the past. The results also suggest decoupling between the abundances of third r-process peak elements with respect to Eu (a rare earth element) in Eu-poor stars. This seems to contradict a co-production scenario of Eu and the third r-process peak elements Os, Ir, and Pt in the progenitors of these objects. Our results are challenging to explain from a nucleosynthetic point of view: the observationally derived abundances indicate the need for an additional early, primary formation channel (or a non-robust r-process).
Source: Astronomy and Astrophysics
Institutions: Goethe University Frankfurt, Technische Universität Darmstadt, Helmholtz Institute Jena, GSI Helmholtz Centre for Heavy Ion Research, Max Planck Institute for Nuclear Physics, Universitat de València, Centre National de la Recherche Scientifique, Université Paris Sciences et Lettres, Observatoire de Paris, Galaxies, Etoiles, Physique et Instrumentation, Friedrich Schiller University Jena
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,732
Funders: European Space Agency, European Commission, Deutsche Forschungsgemeinschaft, Universität Wien, Generalitat Valenciana, Ministerio de Ciencia e Innovación, Uppsala Universitet, Horizon 2020, Agencia Estatal de Investigación, High Energy Physics, European Social Fund, H2020 European Research Council, NextGenerationEU
Awards: G120905174, G1272927172, G138487567, G1530851820, G2432848478, G2478736931, G280048558, G3480869486, G357246561, G3973965102, G434337789, G4700745511, G4929807042, G4994891542, G531036588, G6401356132, Chemical Elements as Tracers of the Evolution of the Cosmos - Infrastructures for Nuclear Astrophysics, SpectroPhotometric Imaging in Astronomy with Kinetic Inductance Detectors, G7084143925, SFB 1245: Atomkerne: Von fundamentalen Wechselwirkungen zu Struktur und Sternen, G8471505197
OpenAlex ID: W4405360187