HE0144-4657: A Carbon-Enhanced Ultra Metal-Poor Star ([Fe/H] ~ -4.1) from the Helmi Stream Disrupted Dwarf Galaxy

Abstract

We present the discovery of HE0144-4657, an ultra metal-poor, CNO-enhanced star dynamically associated with the Helmi Stream disrupted dwarf-galaxy remnant. This star was first identified as a carbon-enhanced, metal-poor star candidate from the Hamburg/ESO objective-prism survey, then followed up with medium- and high-resolution spectroscopy. At [Fe/H]=-4.11, HE0144-4657 is the lowest metallicity star found in a stellar stream to date. Its chemistry is consistent with field halo stars in the same metallicity regime, and the light-element (atomic number Z<=30) chemical abundance pattern suggests that HE0144-4657 is a bona-fide second-generation star with a possible Population III progenitor in the 50Msun mass range with low explosion energy. One possible scenario for the origin of HE0144-4657 is that it was formed in an ultra-faint dwarf galaxy accreted by the Helmi Stream progenitor system before merging with the Milky Way. This discovery provides further evidence for the extragalactic origin of carbon-enhanced ultra metal-poor stars in the Milky Way and for the specific environments conducive to their formation.

17 pages, 3 figures, published on ApJL on March 20, 2026

References in corpus (56)

• The Gaia mission
• Gaia Data Release 3: Summary of the content and survey properties
• Estimating distances from parallaxes. V: Geometric and photogeometric distances to 1.47 billion stars in Gaia Early Data Release 3
• The Dartmouth Stellar Evolution Database
• The mass distribution and gravitational potential of the Milky Way
• Gaia Early Data Release 3: Parallax bias versus magnitude, colour, and position
• Nucleosynthetic signatures of the first stars
• New Grids of ATLAS9 Model Atmospheres
• Carbon Enhanced Metal-Poor Stars. I. Chemical Compositions of 26 Stars
• First stars VI - Abundances of C, N, O, Li, and mixing in extremely metal-poor giants. Galactic evolution of the light elements
• Streams, substructures and the early history of the Milky Way
• Evidence from the H3 Survey that the Stellar Halo is Entirely Comprised of Substructure
• Carbon-Enhanced Metal-Poor Star Frequencies in the Galaxy: Corrections for the Effect of Evolutionary Status on Carbon Abundances
• CMasher: Scientific colormaps for making accessible, informative and 'cmashing' plots
• Synthetic Stellar Photometry - I. General considerations and new transformations for broad-band systems
• HE 0557-4840 - Ultra-Metal-Poor and Carbon-Rich
• The Frequency of Carbon-Enhanced Metal-Poor Stars in the Galaxy from the HERES sample
• A non-LTE study of neutral and singly-ionized calcium in late-type stars
• Observational Constraints on First-Star Nucleosynthesis. I. Evidence for Multiple Progenitors of CEMP-no Stars
• The stellar content of the Hamburg/ESO survey. IV. Selection of candidate metal-poor stars
• Bright Metal-Poor Stars from the Hamburg/ESO Survey. I. Selection and Follow-up Observations from 329 Fields
• An Elemental Assay of Very, Extremely, and Ultra Metal-Poor Stars
• Robust Data-driven Metallicities for 175 Million Stars from Gaia XP Spectra
• Non-LTE aluminium abundances in late-type stars
• StarHorse results for spectroscopic surveys + Gaia DR3: Chrono-chemical populations in the solar vicinity, the genuine thick disk, and young-alpha rich stars
• Exploiting the Gaia EDR3 photometry to derive stellar temperatures
• Exploring the Origin of Lithium, Carbon, Strontium and Barium with four new Ultra Metal-Poor Stars
• An Ultra-Faint Galaxy Candidate Discovered in Early Data from the Magellanic Satellites Survey
• linemake: An Atomic and Molecular Line List Generator
• Carbon-Enhanced Metal-Poor Stars: Relics from the Dark Ages
• A Low-Mass Stellar-Debris Stream Associated with a Globular Cluster Pair in the Halo
• Faint Population III supernovae as the origin of the most iron-poor stars
• The Gaia DR3 view of dynamical substructure in the stellar halo near the Sun
• Galactic Archaeology with Gaia
• Detailed Abundances in the Ultra-faint Magellanic Satellites Carina II and III
• Observational Constraints on First-Star Nucleosynthesis. II. Spectroscopy of an Ultra Metal-Poor CEMP-no Star
• Dynamically Tagged Groups of Very Metal-poor Halo Stars from the HK and Hamburg/ESO Surveys
• A New Type of Extremely Metal Poor Star
• Red Supergiant Stars as Cosmic Abundance Probes. III. NLTE effects in J-band Magnesium lines
• Zero-metallicity hypernova uncovered by an ultra metal-poor star in the Sculptor dwarf spheroidal galaxy
• The S2 Stream: the shreds of a primitive dwarf galaxy
• Tracing Pop III supernovae with extreme energies through the Sculptor dwarf spheroidal galaxy
• Abundance Patterns of $\alpha$ and Neutron-capture Elements in the Helmi Stream
• Carbon-Enhanced Metal-Poor star candidates from BP/RP Spectra in $Gaia$ DR3
• Phase-space Properties and Chemistry of the Sagittarius Stellar Stream Down to the Extremely Metal-poor ($[Fe/H]\lesssim -3$) Regime
• A bound on the 12C/13C ratio in near-pristine gas with ESPRESSO
• Machine learning detects multiplicity of the first stars in stellar archaeology data
• Enrichment by Extragalactic First Stars in the Large Magellanic Cloud
• Extremely metal-poor stars in the Fornax and Carina dwarf spheroidal galaxies
• Extending the Chemical Reach of the H3 Survey: Detailed Abundances of the Dwarf-galaxy Stellar Stream Wukong/LMS-1
• Four-hundred Very Metal-poor Stars Studied with LAMOST and Subaru. III. Dynamically Tagged Groups and Chemodynamical Properties
• Discovery of an $[Fe/H]\sim -4.8$ Star in $Gaia$ XP Spectra
• Unravelling the mass spectrum of destroyed dwarf galaxies with the metallicity distribution function
• Spectroscopic Analysis of Pictor II: a very low metallicity ultra-faint dwarf galaxy bound to the Large Magellanic Cloud
• Unveiling the nature of HE 0107-5240
• A second-generation star in a relic dwarf galaxy