The Chemical Composition of Extreme-Velocity Stars

Abstract

Little is known about the origin of the fastest stars in the Galaxy. Our understanding of the Milky Way and surrounding dwarf galaxies chemical evolution history allows us to use the chemical composition of a star to investigate its origin, and say whether a star was formed in-situ or was accreted. However, the fastest stars, the hypervelocity stars, are young and massive and their chemical composition has not yet been analyzed. Though it is difficult to analyze the chemical composition of a massive young star, we are well versed in the analysis of late-type stars. We have used high-resolution ARCES/3.5m Apache Point Observatory, MIKE/Magellan spectra to study the chemical details of 15 late-type hypervelocity stars candidates. With Gaia EDR3 astrometry and spectroscopically determined radial velocities we found total velocities with a range of $274$ - $520$ km s${}^{-1}$ and mean value of $381$ km s${}^{-1}$. Therefore, our sample stars are not fast enough to be classified as Hypervelocity stars, and are what is known as extreme-velocity stars. Our sample has a wide iron abundance range of $-2.5\le [Fe/H]\le -0.9$. Their chemistry indicate that at least 50\% of them are accreted extragalactic stars, with iron-peak elements consistent with prior sub-Chandrasekhar mass type Ia supernova enrichment. Without indication of binary companions, their chemical abundances and orbital parameters are indicative that they are the accelerated tidal debris of disrupted dwarf galaxies.

arXiv commentAccepted for publication at AJ; 23 pages; 6 Figures; 4 Tables

References in corpus (91)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Array Programming with NumPy
• Astropy: A Community Python Package for Astronomy
• Gaia Data Release 2. Summary of the contents and survey properties
• The Structure of Cold Dark Matter Halos
• The Wide-field Infrared Survey Explorer (WISE): Mission Description and Initial On-orbit Performance
• The Gaia mission
• Modules for Experiments in Stellar Astrophysics (MESA)
• Binary companions of evolved stars in APOGEE DR14: Search method and catalog of ~5,000 companions
• Modules for Experiments in Stellar Astrophysics (MESA): Giant Planets, Oscillations, Rotation, and Massive Stars
• Modules for Experiments in Stellar Astrophysics (MESA): Binaries, Pulsations, and Explosions
• MultiNest: an efficient and robust Bayesian inference tool for cosmology and particle physics
• MESA Isochrones and Stellar Tracks (MIST). I: Solar-Scaled Models
• Estimating distances from parallaxes. V: Geometric and photogeometric distances to 1.47 billion stars in Gaia Early Data Release 3
• MESA Isochrones and Stellar Tracks (MIST) 0: Methods for the construction of stellar isochrones
• Multimodal nested sampling: an efficient and robust alternative to MCMC methods for astronomical data analysis
• The Galaxy in Context: Structural, Kinematic and Integrated Properties
• X-ray spectral modelling of the AGN obscuring region in the CDFS: Bayesian model selection and catalogue
• galpy: A Python Library for Galactic Dynamics
• The Milky Way Tomography with SDSS: I. Stellar Number Density Distribution
• A 3D Dust Map Based on Gaia, Pan-STARRS 1 and 2MASS
• First stars V - Abundance patterns from C to Zn and supernova yields in the early Galaxy
• Gaia Early Data Release 3: Parallax bias versus magnitude, colour, and position
• Importance Nested Sampling and the MultiNest Algorithm
• Detection of the gravitational redshift in the orbit of the star S2 near the Galactic centre massive black hole
• Gaia Data Release 2: Photometric content and validation
• Optimal Techniques in Two-dimensional Spectroscopy: Background Subtraction for the 21st Century
• Two distinct halo populations in the solar neighborhood. Evidence from stellar abundance ratios and kinematics
• The Radial Velocity Experiment (RAVE): Fifth Data Release
• Determining stellar atmospheric parameters and chemical abundances of FGK stars with iSpec
• VLT/UVES Abundances in Four Nearby Dwarf Spheroidal Galaxies: I. Nucleosynthesis and Abundance Ratios
• NEOWISE Observations of Near-Earth Objects: Preliminary Results
• Ejection of hypervelocity stars by the (binary) black hole(s) in the Galactic center
• R-process enrichment from a single event in an ancient dwarf galaxy
• SkyMapper Southern Survey: First Data Release (DR1)
• The Cannon: A data-driven approach to stellar label determination
• 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
• Discovery of an Unbound Hyper-Velocity Star in the Milky Way Halo
• Chemical evolution with rotating massive star yields: I. The solar neighbourhood and the s-process elements
• Modern stellar spectroscopy caveats
• Three Hypervelocity White Dwarfs in Gaia DR2: Evidence for Dynamically Driven Double-Degenerate Double-Detonation Type Ia Supernovae
• Discovery of HE 1523-0901, a Strongly r-Process Enhanced Metal-Poor Star with Detected Uranium
• CERES: A Set of Automated Routines for Echelle Spectra
• The Evolution of Early-Type Galaxies in Distant Clusters II: Internal Kinematics of 55 Galaxies in the z=0.33 Cluster CL1358+62
• A high resolution VLT/FLAMES study of individual stars in the centre of the Fornax dwarf spheroidal galaxy
• Spectroscopic determination of masses (and implied ages) for red giants
• New Rare Earth Element Abundance Distributions for the Sun and Five r-Process-Rich Very Metal-Poor Stars
• 'Sculptor'-ing the Galaxy? The Chemical Compositions of Red Giants in the Sculptor Dwarf Spheroidal Galaxy
• The Solar Twin Planet Search. I. Fundamental parameters of the stellar sample
• Systematic non-LTE study of the $-2.6\le$ [Fe/H] $\le 0.2$ F and G dwarfs in the solar neighbourhood. II. Abundance patterns from Li to Eu
• Multi-Element Abundance Measurements from Medium-Resolution Spectra. I. The Sculptor Dwarf Spheroidal Galaxy
• The Ital-FLAMES survey of the Sagittarius dwarf Spheroidal galaxy. I. Chemical abundances of bright RGB stars
• The R-Process Alliance: First Release from the Northern Search for r-Process Enhanced Metal-Poor Stars in the Galactic Halo
• Disentangling the Galactic Halo with APOGEE: I. Chemical and Kinematical Investigation of Distinct Metal-Poor Populations
• Non-LTE aluminium abundances in late-type stars
• The Great Escape: Discovery of a nearby 1700 km/s star ejected from the Milky Way by Sgr A*
• New Type Ia supernova Yields and the Manganese and Nickel Problems in the Milky Way and Dwarf Spheroidal Galaxies
• High-Resolution Spectroscopic Study of Extremely Metal-Poor Star Candidates from the SkyMapper Survey
• The Lazy Giants: APOGEE Abundances Reveal Low Star Formation Efficiencies in the Magellanic Clouds
• An Alternative Origin for Hypervelocity Stars
• The GALAH Survey: Non-LTE departure coefficients for large spectroscopic surveys
• linemake: An Atomic and Molecular Line List Generator
• Stellar Abundances for Galactic Archaeology Database IV - Compilation of Stars in Dwarf Galaxies
• Revisiting hypervelocity stars after Gaia DR2
• The Southern Stellar Stream Spectroscopic Survey (S5): Chemical Abundances of Seven Stellar Streams
• Chemical evolution of the Galactic bulge as traced by microlensed dwarf and subgiant stars. II. Ages, metallicities, detailed elemental abundances, and connections to the Galactic thick disc
• Orbital Clustering Identifies the Origins of Galactic Stellar Streams
• The RAVE-on catalog of stellar atmospheric parameters and chemical abundances for chemo-dynamic studies in the Gaia era
• A hypervelocity star with a Magellanic origin
• Evidence from Disrupted Halo Dwarfs that $r$-process Enrichment via Neutron Star Mergers is Delayed by $\gtrsim 500$ Myrs
• Non-LTE analysis of K I in late-type stars
• Constraining cosmic scatter in the Galactic halo through a differential analysis of metal-poor stars
• Old, Metal-Poor Extreme Velocity Stars in the Solar Neighborhood
• Manganese Indicates a Transition from Sub- to Near-Chandrasekhar Type Ia Supernovae in Dwarf Galaxies
• A Dipole on the Sky: Predictions for Hypervelocity Stars from the Large Magellanic Cloud
• The Carnegie-Spitzer-IMACS Redshift Survey of Galaxy Evolution since z=1.5: I. Description and Methodology and More!
• Runaway Stars, Hypervelocity Stars, and Radial Velocity Surveys
• Predicting the hypervelocity star population in Gaia
• The Fastest Travel Together: Chemical Tagging of the Fastest Stars in Gaia DR2 to the Stellar Halo
• Evidence that the Hot Jupiter WASP-77 A b Formed Beyond Its Parent Protoplanetary Disk's H2O Ice Line
• Nearby high-speed stars in Gaia DR2
• Chasing Accreted Structures within Gaia DR2 using Deep Learning
• Evidence for sub-Chandrasekhar Type Ia supernovae from the last major merger
• The Metal-Poor Stellar Halo in RAVE-TGAS and its Implications for the Velocity Distribution of Dark Matter
• The Most Metal-poor Stars in the Inner Bulge
• Sc and neutron-capture abundances in Galactic low- and high-alpha field halo stars
• Evidences of extragalactic origin and planet engulfment in the metal-poor twin pair HD 134439/HD 134440
• Comparing hypervelocity star populations from the Large Magellanic Cloud and the Milky Way
• Blue extreme disk-runaway stars with Gaia EDR3
• Constraining Solar position and velocity with a Nearby Hypervelocity Star

Cited by in corpus (5)

• A non-interacting Galactic black hole candidate in a binary system with a main-sequence star
• Gaia DR3 in 6D: The search for fast hypervelocity stars and constraints on the Galactic Centre environment
• On the origins of extreme velocity stars as revealed by large-scale Galactic surveys
• High Velocity Stars in SDSS/APOGEE DR17
• Ancient, eclipsing, tidally-locked: A blue lurker progenitor in the population of extreme-velocity star candidates