Search for: All records

Context.In recent years, theR-Process Alliance (RPA) has conducted a successful search for stars that are enhanced in elements produced by the rapid neutron-capture (r-)process. In particular, the RPA has uncovered a number of stars that are strongly enriched in lightr-process elements, such as Sr, Y, and Zr. These so-called limited-rstars were investigated to explore the astrophysical production site(s) of these elements. Aims.We investigate the possible formation sites for light neutron-capture elements by deriving detailed abundances for neutron-capture elements from high-resolution spectra with a high signal-to-noise ratio of three limited-rstars. Methods.We conducted a kinematic analysis and a 1D local thermodynamic equilibrium spectroscopic abundance analysis of three stars. Furthermore, we calculated the lanthanide mass fraction (X_La) of our stars and of limited-rstars from the literature. Results.We found that the abundance pattern of neutron-capture elements of limited-rstars behaves differently depending on their [Ba/Eu] ratios, and we suggest that this should be taken into account in future investigations of their abundances. Furthermore, we found that theX_Laof limited-rstars is lower than that of the kilonova AT2017gfo. The latter seems to be in the transition zone between limited-rX_Laand that ofr-I andr-II stars. Finally, we found that unliker-I andr-II stars, the current sample of limited-rstars is largely born in the Galaxy and is not accreted. 

ABSTRACT We report the discovery of SMSS J160540.18−144323.1, a new ultra metal-poor halo star discovered with the SkyMapper telescope. We measure $$\left[\rm {Fe}/\rm {H}\right]= -6.2 \pm 0.2$$ (1D LTE), the lowest ever detected abundance of iron in a star. The star is strongly carbon-enhanced, $$\left[\rm {C}/\rm {Fe}\right] = 3.9 \pm 0.2$$, while other abundances are compatible with an α-enhanced solar-like pattern with $$\left[\rm {Ca}/\rm {Fe}\right] = 0.4 \pm 0.2$$, $$\left[\rm {Mg}/\rm {Fe}\right] = 0.6 \pm 0.2$$, $$\left[\rm {Ti}/\rm {Fe}\right] = 0.8 \pm 0.2$$, and no significant s- or r-process enrichment, $$\left[\rm {Sr}/\rm {Fe}\right] \lt 0.2$$ and $$\left[\rm {Ba}/\rm {Fe}\right] \lt 1.0$$ (3σ limits). Population III stars exploding as fallback supernovae may explain both the strong carbon enhancement and the apparent lack of enhancement of odd-Z and neutron-capture element abundances. Grids of supernova models computed for metal-free progenitor stars yield good matches for stars of about $$10\, \rm M_\odot$$ imparting a low kinetic energy on the supernova ejecta, while models for stars more massive than roughly $$20\, \rm M_\odot$$ are incompatible with the observed abundance pattern. 

Abstract Nuclear astrophysics is a field at the intersection of nuclear physics and astrophysics, which seeks to understand the nuclear engines of astronomical objects and the origin of the chemical elements. This white paper summarizes progress and status of the field, the new open questions that have emerged, and the tremendous scientific opportunities that have opened up with major advances in capabilities across an ever growing number of disciplines and subfields that need to be integrated. We take a holistic view of the field discussing the unique challenges and opportunities in nuclear astrophysics in regards to science, diversity, education, and the interdisciplinarity and breadth of the field. Clearly nuclear astrophysics is a dynamic field with a bright future that is entering a new era of discovery opportunities.