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.

arXiv comment17 pages, 3 figures, published on ApJL on March 20, 2026

References in corpus (110)

• Astropy: A Community Python Package for Astronomy
• The chemical composition of the Sun
• Gaia Data Release 2. Summary of the contents and survey properties
• The Astropy Project: Building an inclusive, open-science project and status of the v2.0 core package
• Measuring Reddening with SDSS Stellar Spectra and Recalibrating SFD
• 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
• Local Kinematics and the Local Standard of Rest
• The Dartmouth Stellar Evolution Database
• The Nucleosynthetic Signature of Population III
• The Galaxy in Context: Structural, Kinematic and Integrated Properties
• The merger that led to the formation of the Milky Way's inner stellar halo and thick disk
• SEGUE: A Spectroscopic Survey of 240,000 stars with g=14-20
• The mass distribution and gravitational potential of the Milky Way
• A 2MASS All-Sky View of the Sagittarius Dwarf Galaxy: I. Morphology of the Sagittarius Core and Tidal Arms
• Co-formation of the Galactic disc and the stellar halo
• Gaia Early Data Release 3: Parallax bias versus magnitude, colour, and position
• The First Stars
• The Universal Stellar Mass-Stellar Metallicity Relation for Dwarf Galaxies
• Nucleosynthesis and Evolution of Massive Metal-Free Stars
• Optimal Techniques in Two-dimensional Spectroscopy: Background Subtraction for the 21st Century
• Debris streams in the solar neighbourhood as relicts from the formation of the Milky Way
• Nucleosynthetic signatures of the first stars
• AGAMA: Action-based galaxy modelling architecture
• Near-Field Cosmology with Metal-Poor Stars
• A stellar relic from the early Milky Way
• New Grids of ATLAS9 Model Atmospheres
• Carbon Enhanced Metal-Poor Stars. I. Chemical Compositions of 26 Stars
• The Hamburg/ESO R-process Enhanced Star survey (HERES) II. Spectroscopic analysis of the survey sample
• The Origin and Evolution of the Galaxy Mass-Metallicity Relation
• The Stellar Abundances for Galactic Archeology (SAGA) Database - Compilation of the Characteristics of Known Extremely Metal-Poor 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
• Non-LTE calculations for neutral Na in late-type stars using improved atomic data
• Evidence from the H3 Survey that the Stellar Halo is Entirely Comprised of Substructure
• In disguise or out of reach: first clues about in-situ and accreted stars in the stellar halo of the Milky Way from Gaia DR2
• NLTE line formation of Fe for late-type stars. I. Standard stars with 1D and <3D> model atmospheres
• 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
• The Abundances of Neutron Capture Species in the Very Metal-Poor Globular Cluster M15: An Uniform Analysis of RGB and RHB Stars
• 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
• Normal and Outlying Populations of the Milky Way Stellar Halo at [Fe/H] < -2
• 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
• Chromium: NLTE abundances in metal-poor stars and nucleosynthesis in the Galaxy
• Carbon-enhanced Metal-poor Stars in SDSS/SEGUE. I. Carbon Abundance Estimation and Frequency of CEMP Stars
• An Elemental Assay of Very, Extremely, and Ultra Metal-Poor Stars
• Carbon-enhanced metal-poor stars: the most pristine objects?
• Abundance Profiling of Extremely Metal-Poor Stars and Supernova Properties in the Early Universe
• JINAbase: A database for chemical abundances of metal-poor stars
• Observational constraints on the origin of the elements. I. 3D NLTE formation of Mn lines in late-type stars
• Robust Data-driven Metallicities for 175 Million Stars from Gaia XP Spectra
• Non-LTE aluminium abundances in late-type stars
• The stellar content of the Hamburg/ESO survey. V. The metallicity distribution function of the Galactic halo
• Ionization balance of Ti in the photospheres of the Sun and four late-type stars
• Draco 119: A Remarkable Heavy Element-deficient Giant
• Characterization and history of the Helmi streams with Gaia DR2
• Red Supergiant Stars as Cosmic Abundance Probes: II. NLTE Effects in J-band Silicon Lines
• Descendants of the first stars: the distinct chemical signature of second generation stars
• The role of binaries in the enrichment of the early Galactic halo. II. Carbon-Enhanced Metal-Poor Stars - CEMP-no 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
• Galactic Archaeology. The dwarfs that survived and perished
• 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
• The R-Process Alliance: A Comprehensive Abundance Analysis of HD 222925, a Metal-Poor Star with an Extreme R-Process Enhancement of [Eu/H] = -0.14
• 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
• Metal-Poor Stars Observed with the Magellan Telescope. III. New Extremely and Ultra Metal-Poor Stars from SDSS/SEGUE and Insights on the Formation of Ultra Metal-Poor Stars
• SD 1313-0019 -- Another second-generation star with [Fe/H] = -5.0, observed with the Magellan Telescope
• Faint Population III supernovae as the origin of the most iron-poor stars
• The Most Metal-Poor Stars. I. Discovery, Data, and Atmospheric Parameters
• Galactic Archaeology with Gaia
• The Gaia DR3 view of dynamical substructure in the stellar halo near the Sun
• Metal-Poor Stars Observed with the Magellan Telescope II. Discovery of Four Stars with [Fe/H] < -3.5
• 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
• Red Supergiant Stars as Cosmic Abundance Probes. III. NLTE effects in J-band Magnesium lines
• A New Type of Extremely Metal Poor Star
• Zero-metallicity hypernova uncovered by an ultra metal-poor star in the Sculptor dwarf spheroidal galaxy
• Tracing the first stars and galaxies of the Milky Way
• A new candidate for probing Population III nucleosynthesis with carbon-enhanced damped Lyman-alpha systems
• Detection of a population of carbon-enhanced metal-poor stars in the Sculptor dwarf spheroidal galaxy
• Spectroscopic Validation of Low-Metallicity Stars from RAVE
• Searches for Metal-Poor Stars from the Hamburg/ESO Survey using the CH G-band
• The stellar content of the Hamburg/ESO survey VI. The metallicity distribution of main-sequence turnoff stars in the Galactic halo
• 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
• 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
• Phase-space Properties and Chemistry of the Sagittarius Stellar Stream Down to the Extremely Metal-poor ($[Fe/H]\lesssim -3$) Regime
• A Search for Unrecognized Carbon-Enhanced Metal-Poor Stars in the Galaxy
• 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