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 Quiroz; Roque 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

arXiv · 2310.17024

SPLUS J142445.34-254247.1: An R-Process Enhanced, Actinide-Boost, Extremely Metal-Poor star observed with GHOST

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Abstract

We report on the chemo-dynamical analysis of SPLUS J142445.34-254247.1, an extremely metal-poor halo star enhanced in elements formed by the rapid neutron-capture process. This star was first selected as a metal-poor candidate from its narrow-band 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 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 logeps(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 was 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 Msun, and the heavy-element (Z>=38) abundance pattern can be reproduced by the yields from a neutron star merger (1.66Msun and 1.27Msun) 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.

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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 Quiroz, Roque 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. 2023-10-25. SPLUS J142445.34-254247.1: An R-Process Enhanced, Actinide-Boost, Extremely Metal-Poor star observed with GHOST. https://arxiv.org/abs/2310.17024

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