| Name: Projjwal Banerjee |
| Affiliation: Indian Institute of Technology Palakkad |
| Conference ID: ASI2026_325 |
| Title: Rapidly Rotating Early Massive Stars as a Source of High Carbon and Heavy Elements in the Early Galaxy |
| Abstract Type: Invited |
| Abstract Category: Plenary |
| Author(s) and Co-Author(s) with Affiliation: Projjwal Banerjee(Indian Institute of Technology Palakkad, Kanjikode - 678623, India) |
| Abstract: I will discuss how rapidly rotating massive first (Pop III) and early (Pop II) stars that undergo quasi-chemically homogeneous (QCH) evolution can help resolve multiple unresolved puzzles related to the chemical evolution of the early Galaxy. One of the important puzzles is the origin of high carbon enrichment in the early Galaxy as deduced from Carbon Enhanced Metal-Poor-no (CEMP-no) stars, which are thought to have formed from gas polluted primarily by Pop III massive stars. Regular supernovae from non-rotating massive stars can account for moderate carbon enrichment and cannot explain the carbon enhancement in the majority of CEMP-no stars. In contrast, carbon-enriched winds and supernovae from Pop III QCH models can account for the entire range of carbon abundance observed in CEMP-no stars. Remarkably, Pop II QCH stars, in addition to producing carbon, also produce copious amounts of heavy elements via the slow neutron capture process (s-process), producing elements up to bismuth. This makes Pop II QCH stars a rare source of the main s-process in the early Galaxy, in contrast to the usual site of the main s-process in low-mass asymptotic giant branch stars, which does not contribute to very early Galactic enrichment. This can naturally explain important unresolved puzzles such as the early onset of s-process and the ubiquity of heavy elements in the early Galaxy as observed in very metal-poor stars. Additionally, the wind from Pop II QCH models can match the abundance of CEMP stars enhanced in s-process (CEMP-s stars) and even some of the CEMP stars with a mixture of rapid (r) and s-process patterns (CEMP-r/s stars). These results suggest that a large fraction of Pop III and Pop II stars were rapidly rotating. |
