Speaker
Description
How different astrophysical events contribute to the synthesis of elements heavier than iron and in particular the role of the rapid (r) neutron capture process, remains an actively debated topic [1]. The r-process was recently observed in the kilonova emission accompanying the unique detection of gravitational waves from the neutron star merger event GW170817 [2]. The EM early emission is dominated by the presence of freshly produced light r-process elements and there is evidence for the observation of Sr [3]. A promising approach to investigating the r-process is to study elemental abundances in the atmosphere of old ultra metal-poor (UMP) stars, which likely collected elements from only one or a few nucleosynthesis events. This can be then compared to calculations based on models of different astrophysical events which together with the nuclear data input are able to predict abundances. A difficulty here is the blurring effect induced by nuclear data uncertainties. In particular in the case of the r-process that runs far away from beta-stability, decay data is obtained from theoretical models with modest predictive power [4].
In this contribution, we present new experimental values of decay half-lives and neutron emission probabilities of 37 very neutron-rich nuclei ranging from 75Ni to 92Br, measured at the RIKEN Nishina Center in Japan, including 11 one-neutron and 13 two-neutron emission probabilities and 6 half-lives determined for the first time [5].
We further investigate the impact of our data on the final abundances produced by a weak r-process, which synthesizes first-peak r-process elements. This process occurs in neutrino-driven winds following a neutron star merger. To do that, we use a comprehensive set of simulated thermodynamical trajectories that describe the evolution of matter properties in the merger outflows [6]. We find a sizable increase in the calculated abundances of Y, Zr, Nb and Mo using our data, significantly larger than the spread on relative abundances observed in UMP stars [7]. This emphasizes the necessity of using reliable experimental decay data for very neutron-rich beta-delayed neutron emitters in r-process models to ensure meaningful comparisons with observational data.
[1] A. Arcones et al., Astron. & Astroph. Review 31, 1 (2023)
[2] D. Kasen et al. Nature 551, 80 (2017)
[3] D. Watson et al., Nature 574, 497 (2019); N. Vieira et al., Astroph. J. 944, 123 (2023)
[4] P. Moeller et al., At. Data and Nucl. Data Tables 125, 1 (2019)
[5] A. Tolosa-Delgado, PhD Thesis, University of Valencia (Spain), 2020
[6] D. Martin et al., Astroph. J. 813, 2 (2015)
[7] I. U. Roederer et al., Astroph. J. 936, 84 (2022)
