Age dating of an early Milky Way merger via asteroseismology of the naked-eye star $\nu$ Indi

Abstract

Over the course of its history, the Milky Way has ingested multiple smaller satellite galaxies. While these accreted stellar populations can be forensically identified as kinematically distinct structures within the Galaxy, it is difficult in general to precisely date the age at which any one merger occurred. Recent results have revealed a population of stars that were accreted via the collision of a dwarf galaxy, called \textit{Gaia}-Enceladus, leading to a substantial pollution of the chemical and dynamical properties of the Milky Way. Here, we identify the very bright, naked-eye star $\nu$\,Indi as a probe of the age of the early in situ population of the Galaxy. We combine asteroseismic, spectroscopic, astrometric, and kinematic observations to show that this metal-poor, alpha-element-rich star was an indigenous member of the halo, and we measure its age to be $11.0\pm 0.7$ (stat) $\pm 0.8$ (sys)$\mathrm{Gyr}$. The star bears hallmarks consistent with it having been kinematically heated by the \textit{Gaia}-Enceladus collision. Its age implies that the earliest the merger could have begun was 11.6 and 13.2 Gyr ago at 68 and 95% confidence, respectively. Input from computations based on hierarchical cosmological models tightens (i.e. reduces) slightly the above limits.

Accepted for publication as a Letter in Nature Astronomy (26 pages, 7 figures, including main article and methods section)

References in corpus (31)

• A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
• galpy: A Python Library for Galactic Dynamics
• Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics
• Evidence for Two Early Accretion Events That Built the Milky Way Stellar Halo
• Standing on the shoulders of Dwarfs: the Kepler asteroseismic LEGACY sample II - radii, masses, and ages
• Target Selection for the SDSS-IV APOGEE-2 Survey
• NLTE abundances of Mn in a sample of metal-poor stars
• Eclipsing Binary Stars as Benchmarks for Trigonometric Parallaxes in the Gaia Era
• Asteroseismology for "à la carte" stellar age-dating and weighing: Age and mass of the CoRoT exoplanet host HD 52265
• Disentangling the Galactic Halo with APOGEE: I. Chemical and Kinematical Investigation of Distinct Metal-Poor Populations
• The Gaia FGK Benchmark Stars - High resolution spectral library
• The Fall of a Giant. Chemical evolution of Enceladus, alias the Gaia Sausage
• The First APOKASC Catalog of Kepler Dwarf and Subgiant Stars
• DIAMONDS: a new Bayesian Nested Sampling tool. Application to Peak Bagging of solar-like oscillations
• 18 Sco: a solar twin rich in refractory and neutron-capture elements. Implications for chemical tagging
• AIMS - A new tool for stellar parameter determinations using asteroseismic constraints
• Bayesian peak bagging analysis of 19 low-mass low-luminosity red giants observed with Kepler
• Synthetic Stellar Photometry - II. Testing the bolometric flux scale, and tables of bolometric corrections for the Hipparcos/Tycho, Pan-STARRS1, SkyMapper and JWST systems
• Red Supergiant Stars as Cosmic Abundance Probes: KMOS Observations in NGC 6822
• The Asteroseismic Target List (ATL) for solar-like oscillators observed in 2-minute cadence with the Transiting Exoplanet Survey Satellite (TESS)
• Why should we correct reported pulsation frequencies for stellar line-of-sight Doppler velocity shifts?
• Solar-like oscillations in the metal-poor subgiant nu Indi: constraining the mass and age using asteroseismology
• Helium signature in red giant oscillation patterns observed by Kepler
• Atmospheric parameters and chemical properties of red giants in the CoRoT asteroseismology fields
• Fundamental properties of Kepler and CoRoT targets: III. Tuning scaling relations using the first adiabatic exponent
• Solar-like oscillations in the metal-poor subgiant nu Indi: II. Acoustic spectrum and mode lifetime
• Mode width fitting with a simple bayesian approach. Application to CoRoT targets HD 181420 and HD 49933
• The central spheroids of Milky Way mass-sized galaxies
• Automated asteroseismic peak detections
• Limits on radial differential rotation in Sun-like stars from parametric fits to oscillation power spectra
• Anomalies in the Kepler Asteroseismic Legacy Project Data. A re-analysis of 16 Cyg A&B, KIC8379927 and 6 solar-like stars

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