| Name: MUHAMMED RIYAS A |
| Affiliation: UNIVERSITY OF CALICUT |
| Conference ID: ASI2026_810 |
| Title: Actinide tracing in CEMP-rs stars: Thorium and Uranium detection |
| Abstract Type: Poster |
| Abstract Category: Stars, Interstellar Medium, and Astrochemistry in Milky Way |
| Author(s) and Co-Author(s) with Affiliation: Akkara Muhammed Riyas(Department of Physics, University of Calicut, Kerala-673635, India.), Drisya Karinkuzhi(Department of Physics, University of Calicut, Kerala-673635, India.), Sophie Van Eck(Institut d’Astronomie et d’Astrophysique, Université Libre de Bruxelles, ULB, Bruxelles-1050, Belgium), Arthur Choplin(Institut d’Astronomie et d’Astrophysique, Université Libre de Bruxelles, ULB, Bruxelles-1050, Belgium) |
| Abstract: The detection of heavy radioactive elements like thorium (Th) and uranium (U) in ancient stars offers valuable clues into the astrophysical sites of nucleosynthesis and the early chemical enrichment history of the Galaxy. Among metal-poor stars, the CEMP-r/s subclass shows simultaneous enhancement of both s- and r-process elements, indicating complex formation scenarios. The intermediate neutron-capture process (i-process), operating at neutron densities between those of the s- and r-processes, has been proposed as a possible contributor to these abundance patterns. In this study, we investigate the presence of Th and U in a sample of CEMP-rs stars to test the role of the i-process in the synthesis of actinides. High-resolution, high signal-to-noise UVES spectra of three CEMP-rs stars were used for the analysis. These stars were selected based on the enhancement of neutron-capture elements in their atmosphere and spectral quality in the blue region, where the key Th II and U II lines are located. The stellar parameters and abundances were derived under non-local thermodynamic equilibrium (NLTE) conditions using the latest version of the TURBOSPECTRUM radiative transfer code.
We could detect thorium in all three stars, while uranium, which is much harder to detect due to very weak lines and blending, upper limits are established. These measurements offer new observational evidence that the i-process plays a significant role in actinide synthesis and allow the application of nucleocosmochronometry to estimate stellar ages. In our earlier research, we had shown that i-process nucleosynthesis is also able to produce very heavy r-process elements, such as Tb, Tm, Yb, Ta, Os, Ir, and Ho. In our presentation, we will discuss the observational challenges associated with detecting Th and U and discuss their implications for i-process nucleosynthesis and early Galactic chemical evolution. |
