Chemo-dynamical Analysis of a CNO-Enhanced Ultra Metal-poor Star ([Fe/H] < −4): Insights into Early Enrichment by Faint Population III Supernova
Abstract
We report an independent identification of the ultra metal-poor (UMP) star ([Fe/H] =−4.06) Gaia DR3 sourceid 4795913112968206720 (GDR3_479591) in the Gaia mission's Blue and Red Photometer 'XP' spectro-photometric catalog. We combine multi-band photometry, astrometry, and high-resolution spectroscopy to confirm GDR3_479591 as a red giant-branch (RGB) star located at ∼ 6 kpc from the Sun. Abundance analysis under local thermodynamic equilibrium reveals significant enhancements, relative to the solar level, in carbon ([C/Fe] = +1.54, after evolutionary correction for depletion in the RGB), nitrogen ([N/Fe] = +2.64), and oxygen ([O/Fe] = +2.62). The CNO-enhanced GDR3_479591 is thus one of only 5 UMP stars with a detected oxygen abundance. The CNO excess is accompanied by enhancements in several other light elements, such as Na, Mg, Al, and Si. We demonstrate that the chemical pattern of GDR3_479591 can be reproduced by the yields of a single Population~III 'faint' supernova with progenitor mass of ∼21-to-28M⊙ and a low explosion energy of (0.3 ≤ ESN/(1051 erg) ≤ 0.9). Additionally, we use literature metal-poor stars to show that, contrary to recent propositions for high-redshift galaxies, a mild enhancement in [C/O] does not automatically translate to the high [C/Fe] typically observed in UMP stars in the Milky Way and its satellites. GDR3_479591 could not be dynamically associated with any of the most relevant accreted substructures in the Galactic halo, and we speculate that it was formed in an ultra-faint dwarf galaxy environment that later merged with the Milky Way.
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BibTeX
@misc{limberg2026chemodynamical,
title = {{Chemo-dynamical Analysis of a CNO-Enhanced Ultra Metal-poor Star ($\rm[Fe/H] < -4$): Insights into Early Enrichment by Faint Population III Supernova}},
author = {Guilherme Limberg and Vinicius M. Placco and Alexander P. Ji and Yupeng Yao and Friedrich Anders and Wendy Q. Sun and Anna de Graaff and Rohan P. Naidu and Harley Katz and Pierre N. Thibodeaux and Anirudh Chiti and Mohammad K. Mardini and Anna Frebel},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.13373},
eprint = {2609.13373},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.13373},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Chemo-dynamical Analysis of a CNO-Enhanced Ultra Metal-poor Star ([Fe/H] < −4): Insights into Early Enrichment by Faint Population III Supernova
AU - Guilherme Limberg
AU - Vinicius M. Placco
AU - Alexander P. Ji
AU - Yupeng Yao
AU - Friedrich Anders
AU - Wendy Q. Sun
AU - Anna de Graaff
AU - Rohan P. Naidu
AU - Harley Katz
AU - Pierre N. Thibodeaux
AU - Anirudh Chiti
AU - Mohammad K. Mardini
AU - Anna Frebel
PY - 2026
DA - 2026/09/25
PB - arXiv
DO - 10.48550/arxiv.2609.13373
UR - https://arxiv.org/abs/2609.13373
AB - We report an independent identification of the ultra metal-poor (UMP) star ([Fe/H] =−4.06) Gaia DR3 source_id 4795913112968206720 (GDR3_479591) in the Gaia mission's Blue and Red Photometer 'XP' spectro-photometric catalog. We combine multi-band photometry, astrometry, and high-resolution spectroscopy to confirm GDR3_479591 as a red giant-branch (RGB) star located at ∼ 6 kpc from the Sun. Abundance analysis under local thermodynamic equilibrium reveals significant enhancements, relative to the solar level, in carbon ([C/Fe] = +1.54, after evolutionary correction for depletion in the RGB), nitrogen ([N/Fe] = +2.64), and oxygen ([O/Fe] = +2.62). The CNO-enhanced GDR3_479591 is thus one of only 5 UMP stars with a detected oxygen abundance. The CNO excess is accompanied by enhancements in several other light elements, such as Na, Mg, Al, and Si. We demonstrate that the chemical pattern of GDR3_479591 can be reproduced by the yields of a single Population~III 'faint' supernova with progenitor mass of ∼21-to-28M_⊙ and a low explosion energy of (0.3 ≤ E_SN/(10^51 erg) ≤ 0.9). Additionally, we use literature metal-poor stars to show that, contrary to recent propositions for high-redshift galaxies, a mild enhancement in [C/O] does not automatically translate to the high [C/Fe] typically observed in UMP stars in the Milky Way and its satellites. GDR3_479591 could not be dynamically associated with any of the most relevant accreted substructures in the Galactic halo, and we speculate that it was formed in an ultra-faint dwarf galaxy environment that later merged with the Milky Way.
ER -