The binary fraction of Blue Horizontal-Branch (BHB) Stars

Abstract

Blue horizontal-branch (BHB) stars are old, low-mass, metal-poor stars that serve as important tracers of the Galactic halo structure, kinematics, and evolution.Understanding their binary properties provides key insights into their formation channels and the role of binary interactions in the evolution of horizontal branch stars. We intend to investigate the intrinsic binary fraction $f_{\mathrm{b}}^{\mathrm{in}}$ of BHB stars and its dependencies on metallicity, kinematics, and effective temperature. We collect \GG{299} BHB stars from LAMOST with multiple radial velocity (RV) measurements and classify the sample into halo-like and disk-like BHBs based on their kinematics and metallicity, as well as into bluer and redder BHBs based on their \G{effective temperature}. We then investigate the observed binary fraction for each group based on the radial velocity variations and apply a set of Monte Carlo simulations, assuming distributions of $f(P)\propto P^{\pi }$ and $f(q)\propto q^{\kappa }$, to correct the observed binary fraction for observational biases and derive the intrinsic binary fraction. After correcting for observational biases, the intrinsic binary fraction increases to 31% for n > 2 and 32% for n > 3. A clear contrast is observed between halo-like and disk-like BHB stars, with halo-like BHBs exhibiting a lower intrinsic binary fraction (28% for n > 2 and 29% for n> 3) compared to disk-like BHBs (46% and 51%, respectively), indicating different formation pathways. Additionally, we find that bluer BHB stars exhibit a significantly higher binary fraction (42% for n > 2 and 45% for n> 3) than redder BHB stars (24% and 23%, respectively), which suggests a possible link between binarity and the effective temperature, although more samples are required to confirm this.

References in corpus (39)

• The Sloan Digital Sky Survey: Technical Summary
• Binary interaction dominates the evolution of massive stars
• Estimating distances from parallaxes. V: Geometric and photogeometric distances to 1.47 billion stars in Gaia Early Data Release 3
• A Survey of Stellar Families: Multiplicity of Solar-Type Stars
• Stellar Multiplicity
• Mind your Ps and Qs: the Interrelation between Period (P) and Mass-ratio (Q) Distributions of Binary Stars
• The Origin of Subdwarf B Star (I): the Formation Channels
• The Milky Way's Circular Velocity Curve to 60 kpc and an Estimate of the Dark Matter Halo Mass from Kinematics of ~2400 SDSS Blue Horizontal Branch Stars
• The origin of sdB stars (II)
• LAMOST Experiment for Galactic Understanding and Exploration (LEGUE) The survey science plan
• The VLT-FLAMES Tarantula Survey VIII. Multiplicity properties of the O-type star population
• Ultraviolet Radiation from Evolved Stellar Populations -- I. Models
• Hot subluminous stars
• The binary fraction of extreme horizontal branch stars
• Horizontal Branch Stars: The Interplay between Observations and Theory, and Insights into the Formation of the Galaxy
• The Biggest Splash
• The Close Binary Fraction of Solar-type Stars is Strongly Anti-correlated with Metallicity
• Discovery of Extended Blue Horizontal Branches in Two Metal-Rich Globular Clusters
• On the galactic disc age-metallicity relation
• The VLT-FLAMES Tarantula Survey XXII. Multiplicity properties of the B-type stars
• Quantifying Kinematic Substructure in the Milky Way's Stellar Halo
• The Absolute Magnitude and Kinematics of RR Lyrae Stars via Statistical Parallax
• Chemical Abundances and Rotation Velocities of Blue Horizontal-Branch Stars in Six Globular Clusters
• Gaia Data Release 2: Variable stars in the colour-absolute magnitude diagram
• Binary Population Synthesis
• Self-consistent Stellar Radial Velocities from LAMOST Medium-Resolution Survey (MRS) DR7
• Hot Stars in Globular Cluster - A Spectroscopist's View
• A possible solution for the lack of EHB binaries in globular clusters
• Binary Stars in the New Millennium
• The Structure of the Sagittarius Stellar Stream as Traced by Blue Horizontal Branch Stars
• Multiplicity of Galactic Luminous Blue Variable stars
• KIC 1718290: A Helium-rich V1093-Her-like Pulsator on the Blue Horizontal Branch
• The binarity of Galactic dwarf stars along with effective temperature and metallicity
• Rotating halo traced by the K giant stars from LAMOST and Gaia
• The Binarity of Early-type Stars from LAMOST Medium-resolution Spectroscopic Survey
• The statistical properties of early-type stars from LAMOST DR8
• A high resolution study of isotopic composition and chemical abundances of blue horizontal branch stars in the globular clusters NGC6397 and NGC6752
• Clean catalogues of blue horizontal-branch stars using Gaia EDR3
• Spectroscopy of blue horizontal branch stars in NGC 6656 (M22)

Cited by in corpus (2)

• Where are the binaries? -- Searching for blue horizontal-branch stars in binary systems in the inner Galactic Halo
• The origin of B-type runaway stars based on kinematics