Discovery of Galactic center ejected star in DESI DR1

Abstract

Hypervelocity stars (HVSs) are stars ejected from the Galactic Centre (GC) through tidal interactions with the central supermassive black hole. Formed in the immediate vicinity of Sgr~A${}^{\ast }$, these stars are accelerated to velocities high enough to escape the GC and be observable in the Galactic halo. Using spectroscopy from the Dark Energy Spectroscopic Instrument (DESI) and astrometry from Gaia, we conducted a six-dimensional search for HVSs and identified a compelling candidate, hereafter DESI-312, whose bound trajectory can be confidently traced back to the central 2 kpc of our galaxy. The star resides in the inner halo and exhibits supersolar metallicity ([Fe/H] $=0.27\pm 0.09$), distinct from other known stellar populations with radial orbits. Its inferred GC ejection velocity of $698_{-27}^{+35}$ is consistent with a Hills mechanism ejection, supporting an origin in the innermost regions of the Milky Way. We considered alternative origins for the star, including disk ejections from young clusters and globular clusters, but these scenarios fail to explain both its orbit and metallicity. Unlike previously identified A- and B-type HVSs, DESI-312 is a $\sim 1M_{\odot }$ star on the main sequence or early subgiant branch, thus enabling a detailed chemical analysis of its atmosphere and offering a rare window - unobscured by dust and crowding - into the composition of the central regions of the Galaxy.

12 pages, 5 figures, submitted to A&A, comments are welcome!

References in corpus (35)

• Array Programming with NumPy
• The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
• Modules for Experiments in Stellar Astrophysics (MESA)
• Gaia Data Release 3: Summary of the content and survey properties
• The mass distribution and gravitational potential of the Milky Way
• Photo-astrometric distances, extinctions, and astrophysical parameters for Gaia EDR3 stars brighter than G=18.5
• Interaction of massive black hole binaries with their stellar environment: I. Ejection of hypervelocity stars
• APOGEE Chemical Abundance Patterns of the Massive Milky Way Satellites
• Orbits of Massive Satellite Galaxies: I. A Close Look at the Large Magellanic Cloud and a New Orbital History for M33
• All-Sky Dynamical Response of the Galactic Halo to the Large Magellanic Cloud
• The last breath of the Sagittarius dSph
• $S^5$: Probing the Milky Way and Magellanic Clouds potentials with the 6-D map of the Orphan-Chenab stream
• The Star Formation Rate of the Milky Way as seen by Herschel
• The effect of the LMC on the Milky Way system
• Kinematics of hypervelocity stars in the triaxial halo of the Milky Way
• Proper Motions and Trajectories for 16 Extreme Runaway and Hypervelocity Stars
• On the origin of the Galactic thin and thick discs, their abundance gradients and the diagnostic potential of their abundance ratios
• The Quintuplet Cluster III. Hertzsprung-Russell diagram and cluster age
• Testing kinematic distances under a realistic Galactic potential
• Core-Collapse Supernovae in Binaries as the Origin of Galactic Hyper-Runaway Stars
• Gaia DR3 in 6D: The search for fast hypervelocity stars and constraints on the Galactic Centre environment
• Gaia EDR3 in 6D: Searching for unbound stars in the Galaxy
• Ejection of hypervelocity binary stars by a black hole of intermediate mass orbiting Sgr A*
• Archetype-Based Redshift Estimation for the Dark Energy Spectroscopic Instrument Survey
• Global survey of star clusters in the Milky Way -- VII. Tidal parameters and mass function
• Gaia-Sausage-Enceladus star formation history as revealed by detailed elemental abundances
• Comparing hypervelocity star populations from the Large Magellanic Cloud and the Milky Way
• DESI Data Release 1: Stellar Catalogue
• Bar-driven dispersal of Galactic substructure
• Metallicity and $\alpha$-abundance for 48 million stars in low-extinction regions in the Milky Way
• Probing the shape of the Milky Way dark matter halo with hypervelocity stars: a new method
• Double progenitor origin of the S-star cluster
• Stellar ejection velocities from the binary supernova scenario: A comparison across population synthesis codes
• Searching for stars ejected from the Galactic Centre in DESI
• The large-scale kinematics of young stars in the Milky Way disc: first results from SDSS-V