2018/05/30 by Erika M. Holmbeck, Timothy C. Beers, Ian U. Roederer +8 · 86 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics and Star Formation Studies #Binary star #Giant star #LAMOST #Star (game theory) #Stars #Stellar, planetary, and galactic studies #Symbiotic star #astro-ph.SR
paper · pdf · doi:10.3847/2041-8213/aac722
published in The Astrophysical Journal Letters 859(2), L24 (IOP Publishing) · 8 pages, 3 figures, 2 tables
arxiv created 2018/05/30 · openalex publication_date 2018/06/01 · arxiv updated 2018/06/13 · openalex created_date 2018/06/13 · openalex updated_date 2026/08/05
Abstract We report the discovery of a new actinide-boost star, 2MASS J09544277+5246414, originally identified as a very bright ( V = 10.1), extremely metal-poor ([Fe/H] = −2.99) K giant in the LAMOST survey, and found to be highly r -process-enhanced ( r -II; [Eu/Fe] = +1.28]), during the snapshot phase of the R -Process Alliance (RPA). Based on a high signal-to-noise ratio (S/N), high-resolution spectrum obtained with the Harlan J. Smith 2.7 m telescope, this star is the first confirmed actinide-boost star found by RPA efforts. With an enhancement of [Th/Eu] = +0.37, 2MASS J09544277+5246414 is also the most actinide-enhanced r -II star yet discovered, and only the sixth metal-poor star with a measured uranium abundance ([U/Fe] = +1.40). Using the Th/U chronometer, we estimate an age of 13.0 ± 4.7 Gyr for this star. The unambiguous actinide-boost signature of this extremely metal-poor star, combined with additional r -process-enhanced and actinide-boost stars identified by the RPA, will provide strong constraints on the nature and origin of the r -process at early times.