A Very Metal-poor RR Lyrae Star with a Disk Orbit Found in the Solar Neighborhood
arXiv:2201.05402 · doi:10.3847/1538-4357/ac3483
Abstract
Metal-deficient stars are important tracers for understanding the early formation of the Galaxy. Recent large-scale surveys with both photometric and spectroscopic data have reported an increasing number of metal-deficient stars whose kinematic features are consistent with those of the disk stellar populations. We report the discovery of an RR~Lyrae variable (hereafter RRL) that is located within the thick disk and has an orbit consistent with the thick-disk kinematics. Our target RRL (HD 331986) is located at around 1 kpc from the Sun and, with V=11.3, is among the 130 brightest RRLs known so far. However, this object was scarcely studied because it is in the midplane of the Galaxy, the Galactic latitude around -1 deg. Its near-infrared spectrum (0.91-1.32 micron) shows no absorption line except hydrogen lines of the Paschen series, suggesting [Fe/H] less than -2.5. It is the most metal-deficient RRL, at least, among the RRLs whose orbits are consistent with the disk kinematics, although we cannot determine to which of the disk and the halo it belongs. This unique RRL would provide us with essential clues for studying the early formation of stars in the inner Galaxy with further investigations, including high-resolution optical spectroscopy.
arXiv comment13 pages, 7 figures, 6 tables, accepted for publication in ApJ
References in corpus (57)
- 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 Galaxy in Context: Structural, Kinematic and Integrated Properties
- galpy: A Python Library for Galactic Dynamics
- Understanding the Lomb-Scargle Periodogram
- The merger that led to the formation of the Milky Way's inner stellar halo and thick disk
- Co-formation of the Galactic disc and the stellar halo
- Preliminary Results from NEOWISE: An Enhancement to the Wide-field Infrared Survey Explorer for Solar System Science
- Initial Performance of the NEOWISE Reactivation Mission
- Gaia Data Release 2: Photometric content and validation
- Kinematics of Metal-Poor Stars in the Galaxy. III. Formation of the Stellar Halo and Thick Disk as Revealed from a Large Sample of Non-Kinematically Selected Stars
- Debris streams in the solar neighbourhood as relicts from the formation of the Milky Way
- AGAMA: Action-based galaxy modelling architecture
- Near-Field Cosmology with Metal-Poor Stars
- The Optical to Mid-Infrared Extinction Law Based on the APOGEE, Gaia DR2, Pan-STARRS1, SDSS, APASS, 2MASS and WISE Surveys
- The ASAS-SN Catalog of Variable Stars I: The Serendipitous Survey
- Streams, substructures and the early history of the Milky Way
- The birth of the Milky Way as uncovered by accurate stellar ages with Gaia
- The Pristine survey I: Mining the Galaxy for the most metal-poor stars
- New ATLAS9 And MARCS Model Atmosphere Grids for the Apache Point Observatory Galactic Evolution Experiment (APOGEE)
- Accuracy and precision of industrial stellar abundances
- The Absolute Magnitude and Kinematics of RR Lyrae Stars via Statistical Parallax
- Correcting for Telluric Absorption: Methods, Case Studies, and Release of the TelFit Code
- Oscillator Strengths and Damping Constants for Atomic Lines in the J and H Bands
- Wide-field Infrared Survey Explorer (WISE) Catalog of Periodic Variable Stars
- Chemo-kinematics of the RR Lyrae: the halo and the disc
- Analysis of RR Lyrae Stars in the Northern Sky Variability Survey
- Old-Aged Stellar Population Distance Indicators
- The Pristine survey X: a large population of low-metallicity stars permeates the Galactic disk
- Population Studies. XIII. A New Analysis of the Bidelman-MacConnell "Weak-Metal" Stars - Confirmation of Metal-Poor Stars in the Thick Disk of the Galaxy
- The Outer Stellar Halos of Galaxies: how Radial Merger Mass Deposition, Shells and Streams depend on Infall-Orbit Configurations
- Spectroscopic Comparison of Metal-Rich RRab Stars of the Galactic Field with Their Metal-Poor Counterparts
- The SkyMapper DR1.1 Search for Extremely Metal-Poor Stars
- Lessons from the Auriga discs: The hunt for the Milky Way's ex-situ disc is not yet over
- Reviving old controversies: is the early Galaxy flat or round? Investigations into the early phases of the Milky Way formation through stellar kinematics and chemical abundances
- On a new theoretical framework for RR Lyrae stars II: Mid--Infrared Period--Luminosity--Metallicity Relations
- Standard Galactic Field RR Lyrae II: A Gaia DR2 calibration of the period-Wesenheit-metallicity relation
- On the Use of Field RR Lyrae as Galactic Probes. II. A new S calibration to estimate their metallicity
- First stars XIII. Two extremely metal-poor RR Lyrae stars?
- Lines and continuum sky emission in the near infrared: observational constraints from deep high spectral resolution spectra with GIANO-TNG
- The RRC Stars: Chemical Abundances and Envelope Kinematics
- Evidence for Galactic disc RR~Lyrae stars in the Solar neighbourhood
- Metallicity of Galactic RR Lyrae from Optical and Infrared Light Curves: I. Period-Fourier-Metallicity Relations for Fundamental Mode RR Lyrae
- On the Use of Field RR Lyrae as Galactic Probes. III. The -element abundances
- The Pristine survey XIII: Uncovering the very metal-poor tail of the thin disc
- Local RR Lyrae Stars: native and alien
- On the use of field RR Lyrae as Galactic probes: IV. New insights into and around the Oosterhoff dichotomy
- Proper identification of RR Lyrae Stars brighter than 12.5 mag
- Chemical Compositions of Field and Globular Cluster RR~Lyrae Stars: II. omega Centauri
- Targeting Bright Metal-poor Stars in the Disk and Halo Systems of the Galaxy
- On the Use of Field RR Lyrae as Galactic Probes. V. Optical and radial velocity curve templates
- Seven New Carbon-Enhanced Metal-Poor RR Lyrae Stars
- Metal-Rich RRc stars in the Carnegie RR Lyrae Survey
- A New CEMP-s RR Lyrae Star
- Eclipsing Binary Populations across the Northern Galactic Plane from the KISOGP survey
- Spectroscopic and photometric time series of the bright RRc star T Sex
- Variable stars in the northern Galactic plane from KISOGP