The R-Process Alliance: Abundance Universality among Some Elements at and between the First and Second R-Process Peaks
Abstract
We present new observational benchmarks of rapid neutron-capture process (r-process) nucleosynthesis for elements at and between the first (A ~ 80) and second (A ~ 130) peaks. Our analysis is based on archival ultraviolet and optical spectroscopy of eight metal-poor stars with Se (Z = 34) or Te (Z = 52) detections, whose r-process enhancement varies by more than a factor of 30 (-0.22 ≤ [Eu/Fe] ≤ +1.32). We calculate ratios among the abundances of Se, Sr through Mo (38 ≤ Z ≤ 42), and Te. These benchmarks may offer a new empirical alternative to the predicted solar system r-process residual pattern. The Te abundances in these stars correlate more closely with the lighter r-process elements than the heavier ones, contradicting and superseding previous findings. The small star-to-star dispersion among the abundances of Se, Sr, Y, Zr, Nb, Mo, and Te (≤0.13 dex, or 26%) matches that observed among the abundances of the lanthanides and third r-process-peak elements. The concept of r-process universality that is recognized among the lanthanide and third-peak elements in r-process-enhanced stars may also apply to Se, Sr, Y, Zr, Nb, Mo, and Te, provided the overall abundances of the lighter r-process elements are scaled independently of the heavier ones. The abundance behavior of the elements Ru through Sn (44 ≤ Z ≤ 50) requires further study. Our results suggest that at least one relatively common source in the early Universe produced a consistent abundance pattern among some elements spanning the first and second r-process peaks. * Based on archival observations made with the NASA/ESA Hubble Space Telescope (program GO-7348, program GO-8342, program GO-9455, program GO-14161, and program GO-14672) and observations collected from the Keck Observatory Archive (program U25H).
- Publication:
-
The Astrophysical Journal
- Pub Date:
- September 2022
- DOI:
- 10.3847/1538-4357/ac85bc
- arXiv:
- arXiv:2210.15105
- Bibcode:
- 2022ApJ...936...84R
- Keywords:
-
- Nucleosynthesis;
- R-process;
- Stellar abundances;
- Ultraviolet astronomy;
- 1131;
- 1324;
- 1577;
- 1736;
- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - Earth and Planetary Astrophysics;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 16 pages, 3 figures, including 4 appendices. Published in the Astrophysical Journal