This work benefited from a workshop supported by the National Science Foundation under grant No. OISE-1927130 (IReNA), the Kavli Institute for Cosmological Physics, and the University of Chicago Data Science Institute. A.P.J. acknowledges Ani Chiti and Guilherme Limberg for helpful conversations. We acknowledge support awarded by U.S. National Science Foundation (NSF) grants AST-2206264 (A.P.J., P.T., S.A.U.), OISE-1927130 (IReNA; A.P.J., M.P.), PHY-1430152 (JINA-CEE; A.P.J., M.P.), AST-2303869 (AAPF; S.C.), and AST-2202135 (AAPF; E.J.G.). We acknowledge funding from the European Research Council (ERC) under several of the European Union's Horizon 2020 research and innovation programs: grant agreement Nos. 101008324 (ChETEC-INFRA; M.P.), 949173 (M.B.), 852839 (J.A., C.L.), and 833925 (STAREX; G.M.). A.H. was supported, in part, by the Australian Research Council (ARC) Centre of Excellence (CoE) for All Sky Astrophysics in 3 Dimensions (ASTRO 3D) through project No. CE170100013 and acknowledges software development support from Astronomy Australia Limited's ADACS scheme (Project IDs AHeger_2022B, AHeger_2023A) for the development of the StarFit code used here. M.P. is thankful for the support from the NKFI via K-project 138031 and the ERC Consolidator Grant (Hungary) program (RADIOSTAR, G.A. n. 724560). M.P. acknowledges the support to NuGrid from STFC (through the University of Hull's consolidated grant ST/R000840/1) and ongoing access to viper, the University of Hull High Performance Computing Facility. M.P. acknowledges the support from the "Lendület-2023" LP2023-10 Programme of the Hungarian Academy of Sciences (Hungary). M.B. is supported through the Lise Meitner grant from the Max Planck Society. We acknowledge support by the Collaborative Research center SFB 881 (projects A5, A10), Heidelberg University, of the Deutsche Forschungsgemeinschaft (DFG; German Research Foundation). H.R. acknowledges support from a Carnegie Fellowship. C.F. was supported by the United States Department of Energy, Office of Science, Office of Nuclear Physics (award No. DE-FG02-02ER41216).

Stars that formed with an initial mass of over 50 M⊙ are very rare today, but they are thought to be more common in the early Universe. The fates of those early, metal-poor, massive stars are highly uncertain. Most are expected to directly collapse to black holes, while some may explode as a result of rotationally powered engines or the pair-creation instability. We present the chemical abundances of J0931+0038, a nearby low-mass star identified in early follow-up of the SDSS-V Milky Way Mapper, which preserves the signature of unusual nucleosynthesis from a massive star in the early Universe. J0931+0038 has a relatively high metallicity ([Fe/H] = −1.76 ± 0.13) but an extreme odd–even abundance pattern, with some of the lowest known abundance ratios of [N/Fe], [Na/Fe], [K/Fe], [Sc/Fe], and [Ba/Fe]. The implication is that a majority of its metals originated in a single extremely metal-poor nucleosynthetic source. An extensive search through nucleosynthesis predictions finds a clear preference for progenitors with initial mass >50 M⊙, making J0931+0038 one of the first observational constraints on nucleosynthesis in this mass range. However, the full abundance pattern is not matched by any models in the literature. J0931+0038 thus presents a challenge for the next generation of nucleosynthesis models and motivates the study of high-mass progenitor stars impacted by convection, rotation, jets, and/or binary companions. Though rare, more examples of unusual early nucleosynthesis in metal-poor stars should be found in upcoming large spectroscopic surveys.

Alexander P. Ji et al.

Peer reviewed