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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, whoser-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 systemr-process residual pattern. The Te abundances in these stars correlate more closely with the lighterr-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 thirdr-process-peak elements. The concept ofr-process universality that is recognized among the lanthanide and third-peak elements inr-process-enhanced stars may also apply to Se, Sr, Y, Zr, Nb, Mo, and Te, provided the overall abundances of the lighterr-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 secondr-process peaks.
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This content will become publicly available on August 22, 2026
Complete Survey of r -process Conditions: The (Un)robustness of the r -process(es)
Abstract Heavy elements are synthesized by ther-process in neutron star mergers and potentially in rare supernovae linked to strong magnetic fields. Expensive hydrodynamic simulations of these extreme environments are usually postprocessed to calculate the nucleosynthesis. In contrast, here we follow a site-independent approach based on three key parameters: electron fraction, entropy, and expansion timescale. Our model reproduces the results based on hydrodynamic simulations. Moreover, the 120,000 astrophysical conditions analyzed allow us to systematically and generally explore the astrophysical conditions of ther-process, also beyond those found in current simulations. Our results show that a wide range of conditions produce very similar abundance patterns explaining the observed robustness of ther-process between the second and third peak. Furthermore, we cannot find a single condition that produces the full solarr-process pattern from first to third peak. Instead, a superposition of at least two or three conditions or components is required to reproduce the typicalr-process pattern as observed in the solar system and very old stars. The different final abundances are grouped into eight nucleosynthesis clusters, which can be used to select representative conditions for comparisons to observations and investigations of the nuclear physics input.
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- Award ID(s):
- 1927130
- PAR ID:
- 10649170
- Publisher / Repository:
- IOP
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 990
- Issue:
- 1
- ISSN:
- 0004-637X
- Page Range / eLocation ID:
- 37
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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