The R-Process Alliance: Discovery of a low-alpha, r-Process-Enhanced Metal-Poor Star in the Galactic Halo

Abstract

A new moderately r-process-enhanced metal-poor star, RAVE J093730.5-062655, has been identified in the Milky Way halo as part of an ongoing survey by the R-Process Alliance. The temperature and surface gravity indicate that J0937-0626 is likely a horizontal branch star. At [Fe/H] = -1.86, J0937-0626 is found to have subsolar [X/Fe] ratios for nearly every light, alpha, and Fe-peak element. The low [alpha/Fe] ratios can be explained by an ~0.6 dex excess of Fe; J0937-0626 is therefore similar to the subclass of "iron-enhanced" metal-poor stars. A comparison with Milky Way field stars at [Fe/H] = -2.5 suggests that J0937-0626 was enriched in material from an event, possibly a Type Ia supernova, that created a significant amount of Cr, Mn, Fe, and Ni and smaller amounts of Ca, Sc, Ti, and Zn. The r-process enhancement of J0937-0626 is likely due to a separate event, which suggests that its birth environment was highly enriched in r-process elements. The kinematics of J0937-0626, based on Gaia DR2 data, indicate a retrograde orbit in the Milky Way halo; J0937-0626 was therefore likely accreted from a dwarf galaxy that had significant r-process enrichment.

arXiv commentAccepted for publication in the Astrophysical Journal

References in corpus (89)

• GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral
• The chemical composition of the Sun
• Gaia Data Release 2. Summary of the contents and survey properties
• Measuring Reddening with SDSS Stellar Spectra and Recalibrating SFD
• The Gaia mission
• The Nucleosynthetic Signature of Population III
• Nucleosynthesis in Chandrasekhar Mass Models for Type Ia Supernovae and Constraints on Progenitor Systems and Burning-Front Propagation
• The merger that led to the formation of the Milky Way's inner stellar halo and thick disk
• Star Formation Histories, Abundances and Kinematics of Dwarf Galaxies in the Local Group
• The Radial Velocity Experiment (RAVE): first data release
• Neutron capture in low mass Asymptotic Giant Branch stars: cross sections and abundance signatures
• Elemental Abundance Survey of The Galactic Thick Disk
• Light Curves of the Neutron Star Merger GW170817/SSS17a: Implications for R-Process Nucleosynthesis
• Stellar Chemical Signatures And Hierarchical Galaxy Formation
• An absolutely calibrated effective temperature scale from the InfraRed Flux Method
• Nucleosynthesis and Evolution of Massive Metal-Free Stars
• The effective temperature scale of FGK stars. II. Teff : color : [Fe/H] calibrations
• The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/VIRGO GW170817. IV. Detection of Near-infrared Signatures of r-process Nucleosynthesis with Gemini-South
• Two distinct halo populations in the solar neighborhood. Evidence from stellar abundance ratios and kinematics
• Magnetorotationally driven Supernovae as the origin of early galaxy $r$-process elements?
• The Radial Velocity Experiment (RAVE): Fifth Data Release
• VLT/UVES Abundances in Four Nearby Dwarf Spheroidal Galaxies: I. Nucleosynthesis and Abundance Ratios
• A Search for Stars of Very Low Metal Abundance. VI. Detailed Abundances of 313 Metal-Poor Stars
• The RAdial Velocity Experiment (RAVE): Fourth data release
• Non-LTE calculations for neutral Na in late-type stars using improved atomic data
• The Most Metal-Poor Stars. II. Chemical Abundances of 190 Metal-Poor Stars Including 10 New Stars With [Fe/H] < -3.5
• Early Spectra of the Gravitational Wave Source GW170817: Evolution of a Neutron Star Merger
• Carbon-Enhanced Metal-Poor Star Frequencies in the Galaxy: Corrections for the Effect of Evolutionary Status on Carbon Abundances
• The Abundances of Neutron Capture Species in the Very Metal-Poor Globular Cluster M15: An Uniform Analysis of RGB and RHB Stars
• Abundances of Baade's Window Giants from Keck/HIRES Spectra: II. The Alpha- and Light Odd Elements
• The long-term evolution of neutron star merger remnants - I. The impact of r-process nucleosynthesis
• DAOSPEC: an automatic code for measuring equivalent widths in high-resolution stellar spectra
• $s$-process production in rotating massive stars at solar and low metallicities
• NLTE abundances of Mn in a sample of metal-poor stars
• Thin disc, Thick Disc and Halo in a Simulated Galaxy
• Non-standard s process in low metallicity massive rotating stars
• Normal and Outlying Populations of the Milky Way Stellar Halo at [Fe/H] < -2
• Signatures of hypermassive neutron star lifetimes on r-process nucleosynthesis in the disk ejecta from neutron star mergers
• Abundances of Baade's Window Giants from Keck/HIRES Spectra: I. Stellar Parameters and [Fe/H] Values
• Non-LTE line formation of Fe in late-type stars - III. 3D non-LTE analysis of metal-poor stars
• The intermediate r-process in core-collapse supernovae driven by the magneto-rotational instability
• Chromium: NLTE abundances in metal-poor stars and nucleosynthesis in the Galaxy
• Chemistry of the Sagittarius Dwarf Galaxy: a Top-Light IMF, Outflows and the R-Process
• Complete element abundances of nine stars in the r-process galaxy Reticulum II
• One large blob and many streams frosting the nearby stellar halo in Gaia DR2
• Neutrino-driven wind simulations and nucleosynthesis of heavy elements
• Nucleosynthesis and the Inhomogeneous Chemical Evolution of the Carina Dwarf Galaxy
• The $R$-Process Alliance: First Release from the Southern Search for $r$-Process-Enhanced Stars in the Galactic Halo
• Detailed Chemical Abundances in the r-Process-Rich Ultra-Faint Dwarf Galaxy Reticulum 2
• NLTE analysis of Co I/Co II lines in spectra of cool stars with new laboratory hyperfine splitting constants
• Chemical Abundances and Rotation Velocities of Blue Horizontal-Branch Stars in Six Globular Clusters
• Where are the most ancient stars in the Milky Way?
• The R-Process Alliance: First Release from the Northern Search for r-Process Enhanced Metal-Poor Stars in the Galactic Halo
• Non-LTE aluminium abundances in late-type stars
• APASS Landolt-Sloan BVgri photometry of RAVE stars. I. Data, effective temperatures and reddenings
• The Chemical Evolution of the Ursa Minor Dwarf Spheroidal Galaxy
• The role of neutron star mergers in the chemical evolution of the Galactic halo
• Thermal X-ray emission from shocked ejecta in Type Ia Supernova Remnants. Prospects for explosion mechanism identification
• The s-process in the Galactic halo: the fifth signature of spinstars in the early Universe?
• 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
• The R-Process Alliance: 2MASS J09544277+5246414, the Most Actinide-Enhanced R-II Star Known
• Kinematics of Highly R-Process-Enhanced Field Stars: Evidence for an Accretion Origin and Detection of Several Groups from Disrupted Satellites
• The Persistence of Memory, or How the X-Ray Spectrum of SNR 0509-67.5 Reveals the Brightness of its Parent Type Ia Supernova
• Ultrafaint Dwarf Galaxies - the lowest mass relics from before reionization
• Nine New Metal-Poor Stars on the Subgiant and Red Horizontal Branches with High Levels of r-process Enhancement
• Broadband UBVRI Photometry of Horizontal-Branch and Metal-Poor Candidates from the HK and Hamburg/ESO Surveys. I
• RAVE J203843.2-002333: The first highly r-process-enhanced star identified in the RAVE survey
• The Spatial Distribution of the Galactic First Stars II: SPH Approach
• Chemical and kinematical properties of BSSs and HB stars in NGC 6397
• Chemistry of the Most Metal-poor Stars in the Bulge and the z > 10 Universe
• A comparison of the s- and r-process element evolution in local dwarf spheroidal galaxies and in the Milky Way
• Chemical Abundance Analysis of Three $\alpha$-Poor, Metal-Poor Stars in the Ultra-Faint Dwarf Galaxy Horologium I
• The r-Process Pattern of a Bright, Highly r-Process-Enhanced, Metal-Poor Halo Star at [Fe/H] ~ -2
• Ultra metal-poor stars: Spectroscopic determination of stellar atmospheric parameters using iron Non-LTE line abundances
• Very metal-poor stars observed by the RAVE survey
• Evidence for a Sub-Chandrasekhar Mass Type~Ia Supernova in the Ursa Minor Dwarf Galaxy
• Spectroscopic Validation of Low-Metallicity Stars from RAVE
• uvby(-$\beta$) photometry of high-velocity and metal-poor stars X. Stars of very low metal abundance: observations, reddenings, metallicities, classifications, distances, and relative ages
• Retainment of r-process material in dwarf galaxies
• Influence of departures from LTE on calcium, titanium, and iron abundance determinations in cool giants of different metallicities
• The origin of low [alpha/Fe] ratios in extremely metal-poor stars
• The R-Process Alliance: Discovery of the first metal-poor star with a combined r- and s-process element signature
• Color Classification of Extrasolar Giant Planets: Prospects and Cautions
• The R-Process Alliance: Chemical Abundances for a Trio of R-Process-Enhanced Stars -- One Strong, One Moderate, One Mild
• Disk-Like Chemistry of the Triangulum-Andromeda Overdensity as Seen by APOGEE
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters -- XI. The horizontal branch in NGC\,6388 and NGC\,6441
• Star Formation in Ultrafaint Dwarfs: Continuous or Single-age Bursts?
• Early chemical evolution of Zn driven by magnetorotational supernovae and the pathway to the solar Zn composition
• Non-LTE iron abundances in cool stars: The role of hydrogen collisions

Cited by in corpus (18)

• Four-hundred Very Metal-Poor Stars Studied with LAMOST and Subaru. II. Elemental abundances
• The $R$-Process Alliance: Fourth Data Release from the Search for $r$-Process-Enhanced Stars in the Galactic Halo
• The R-process Alliance: First Magellan/MIKE Release from the Southern Search for R-Process-enhanced Stars
• Abundances in the Milky Way across five nucleosynthetic channels from 4 million LAMOST stars
• Cosmological Insights into the Early Accretion of \textit{r}-Process-Enhanced stars. I. A Comprehensive Chemo-dynamical Analysis of LAMOST J1109+0754
• The R-Process Alliance: J1521-3538, a very metal-poor, extremely r-process-enhanced star with [Eu/Fe]=+2.2, and the class of r-III stars
• Origin of highly $r$-process-enhanced stars in a cosmological zoom-in simulation of a Milky Way-like galaxy
• R-process-rich stellar streams in the Milky Way
• The R-Process Alliance: Chemo-Dynamically Tagged Groups II. An Extended Sample of Halo $r$-Process-Enhanced Stars
• The Pristine survey -- XV. A CFHT ESPaDOnS view on the Milky Way halo and disc populations
• The metal-poor end of the Spite plateau. II. Detailed chemical investigation
• Finding $r$-II sibling stars in the Milky Way with the Greedy Optimistic Clustering algorithm
• Discovery of an Extremely r-process-enhanced Thin-disk Star with [Eu/H] = +0.78
• RR Lyrae stars as probes of the outer Galactic halo: Chemical and kinematic analysis of a pilot sample
• A Nuclear Equation of State Inferred from Stellar r-process Abundances
• Combining Astrometry and Elemental Abundances: The Case of the Candidate Pre-Gaia Halo Moving Groups G03-37, G18-39, and G21-22
• Detection of the actinide Th in an r-process-enhanced star with accretion origin
• Chemical abundances of field halo stars -- Implications for the building blocks of the Milky Way