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Abstract Understanding the abundance pattern of metal-poor stars and the production of heavy elements through various nucleosynthesis processes offers crucial insights into the chemical evolution of the Milky Way, revealing primary sites and major sources of rapid neutron-capture process (r-process) material in the Universe. In this fifth data release from theR-Process Alliance (RPA), we present the detailed chemical abundances of 41 faint (down toV= 15.8) and extremely metal-poor (down to [Fe/H] = −3.3) halo stars selected from the RPA. We obtained high-resolution spectra for these objects with the HORuS spectrograph on the Gran Telescopio Canarias. We measure the abundances of light,α, Fe-peak, and neutron-capture elements. We report the discovery of five carbon-enhanced metal-poor, one limited-r, threer-I, and fourr-II stars, and six Mg-poor stars. We also identify one star of a possible globular cluster origin at an extremely low metallicity at [Fe/H] = −3.0. This adds to the growing evidence of a lower-limit metallicity floor for globular cluster abundances. We use the abundances of Fe-peak elements and theα-elements to investigate the contributions from different nucleosynthesis channels in the progenitor supernovae. We find the distribution of [Mg/Eu] as a function of [Fe/H] to have different enrichment levels, indicating different possible pathways and sites of their production. We also reveal differences in the trends of the neutron-capture element abundances of Sr, Ba, and Eu of variousr-I andr-II stars from the RPA data releases, which provide constraints on their nucleosynthesis sites and subsequent evolution.
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This content will become publicly available on May 1, 2026
The R-Process Alliance: Hunting for gold in the near-UV spectrum of 2MASS J05383296–5904280
Context. Over the past few years, theR-Process Alliance (RPA) has successfully carried out a search for stars that are highly enhanced in elements produced via the rapid neutron-capture (r-) process. In particular, the RPA has identified a number of relatively bright, highlyr-process-enhanced (r-II) stars, suitable for observations with the Hubble Space Telescope (HST), facilitating abundance derivation of elements such as gold (Au) and cadmium (Cd). Aims. This paper presents the detailed abundances derived for the metal-poor ([Fe/H] = −2.55) highlyr-process-enhanced ([Eu/Fe] = +1.29)r-II star 2MASS J05383296–5904280. Methods. One-dimensional local thermodynamic equilibrium (LTE) elemental abundances were derived via equivalent width and spectral synthesis using high-resolution high signal-to-noise near-UV HST/STIS and optical Magellan/MIKE spectra. Results. Abundances were determined for 43 elements, including 26 neutron-capture elements. In particular, abundances of the rarely studied elements Nb, Mo, Cd, Lu, Os, Pt, and Au are derived from the HST spectrum. These results, combined with RPA near-UV observations of two additionalr-II stars, increase the number of Cd abundances derived forr-process-enriched stars from seven to ten and Au abundances from four to seven. A large star-to-star scatter is detected for both of these elements, highlighting the need for more detections enabling further investigations, specifically into possible non-LTE effects.
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- Award ID(s):
- 2307436
- PAR ID:
- 10637296
- Publisher / Repository:
- Astronomy & Astrophysics
- Date Published:
- Journal Name:
- Astronomy & Astrophysics
- Volume:
- 697
- ISSN:
- 0004-6361
- Page Range / eLocation ID:
- A127
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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