SPLUS J142445.34-254247.1: an r-process-enhanced, actinide-boost, extremely metal-poor star observed with GHOST

Vinicius M. Placco*, Felipe Almeida-Fernandes, Erika M. Holmbeck, Ian U. Roederer, Mohammad K. Mardini, Christian R. Hayes, Kim Venn, Kristin Chiboucas, Emily Deibert, Roberto Gamen, Jeong-Eun Heo, Miji Jeong, Venu Kalari, Eder Martioli, Siyi Xu, Ruben Diaz, Manuel Gomez-Jimenez, David Henderson, Pablo Prado, Carlos QuirozRoque Ruiz-Carmona, Chris Simpson, Cristian Urrutia, Alan W. McConnachie, John Pazder, Gregory Burley, Michael Ireland, Fletcher Waller, Trystyn A. M. Berg, J. Gordon Robertson, Zachary Hartman, David O. Jones, Kathleen Labrie, Gabriel Perez, Susan Ridgway, Joanna Thomas-Osip

*Corresponding author for this work

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Abstract

We report on a chemo-dynamical analysis of SPLUS J142445.34−254247.1 (SPLUS J1424−2542), an extremely metal-poor halo star enhanced in elements formed by the rapid neutron-capture process (r-process). This star was first selected as a metal-poor candidate from its narrowband S-PLUS photometry and followed up spectroscopically in medium resolution with Gemini-South/GMOS, which confirmed its low-metallicity status. High-resolution spectroscopy was gathered with GHOST at Gemini-South, allowing for the determination of the chemical abundances for 36 elements, from carbon to thorium. At [Fe/H] = −3.39, SPLUS J1424−2542 is one of the lowest-metallicity stars with measured Th and has the highest log ϵ ( Th / Eu ) observed to date, making it part of the “actinide-boost” category of r-process-enhanced stars. The analysis presented here suggests that the gas cloud from which SPLUS J1424−2542 formed must have been enriched by at least two progenitor populations. The light-element (Z ≤ 30) abundance pattern is consistent with the yields from a supernova explosion of metal-free stars with 11.3-13.4 M , and the heavy-element (Z ≥ 38) abundance pattern can be reproduced by the yields from a neutron star merger (1.66 M and 1.27 M ) event. A kinematical analysis also reveals that SPLUS J1424−2542 is a low-mass, old halo star with a likely in situ origin, not associated with any known early merger events in the Milky Way.

Original languageEnglish
Article number60
Pages (from-to)1-17
Number of pages17
JournalAstrophysical Journal
Volume959
Issue number1
DOIs
Publication statusPublished - 10 Dec 2023

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Copyright the Author(s) 2023. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.

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