The origin of B-type runaway stars based on kinematics

Abstract

Runaway stars depart their birthplaces with high peculiar velocities. Two mechanisms are commonly invoked to explain their origin, the binary supernova scenario (BSS) and the dynamical ejection scenario (DES). Investigating the kinematic properties of runaway stars is key to understanding their origins.We intend to investigate the origins of 39 B-type runaway stars from LAMOST using orbital traceback analysis. From the catalog of LAMOST, we selected 39 B-type runaway stars and determined their spectral subtypes from key absorption lines. We then derived atmospheric parameters for each star using the Stellar Label Machine (SLAM), which is trained on TLUSTY synthetic spectra computed under the non-local thermodynamic equilibrium (NLTE) assumption. Using the derived atmospheric parameters as input, we estimated stellar masses and ages with a machine learning model trained on PARSEC evolutionary tracks. We finally performed orbital traceback with GALPY to analyze their origins. Through orbital traceback, we find that 29 stars have trajectories entirely within the Galactic disk, whereas 10 are disk-passing yet still trace back to the disk. Two stars have trajectories that intersect those of known clusters. Their orbits show similar morphologies in both the $X-Y$ and $R-Z$ planes, and their [M/H] values are comparable, suggesting possible cluster origins. However, definitive confirmation will require additional evidence. In addition, the $V_{\mathrm{Sp}}-v\sin i$ plane shows that runaway stars with low peculiar space velocities but high $v\sin i$ remain on the Galactic disk, whereas those with high peculiar space velocities but low $v\sin i$ pass through the disk, possibly reflecting two distinct origins.

References in corpus (21)

• Estimating distances from parallaxes. V: Geometric and photogeometric distances to 1.47 billion stars in Gaia Early Data Release 3
• galpy: A Python Library for Galactic Dynamics
• 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
• A Grid of NLTE Line-Blanketed Model Atmospheres of Early B-type Stars
• Improving PARSEC models for very low mass stars
• Improving the open cluster census. II. An all-sky cluster catalogue with Gaia DR3
• Hunting for open clusters in \textit{Gaia} DR2: $582$ new OCs in the Galactic disc
• Hunting for open clusters in \textit{Gaia} DR2: the Galactic anticentre
• Flare in the Galactic stellar outer disc detected in SDSS-SEGUE data
• A Catalogue of OB Stars from LAMOST Spectroscopic Survey
• The Century Survey Galactic Halo Project III: A Complete 4300 deg^2 Survey of Blue Horizontal Branch Stars in the Metal-Weak Thick Disk and Inner Halo
• Exploring open cluster properties with Gaia and LAMOST
• The Nature of the Hyper-Runaway Candidate HIP 60350
• Metallicities and Radial Velocities of Five Open Clusters Including a New Candidate Member of the Monoceros Stream
• Galactic runaway O and Be stars found using Gaia DR3
• The VLT-FLAMES Tarantula Survey: Observational evidence for two distinct populations of massive runaway stars in 30 Doradus
• Clean catalogues of blue horizontal-branch stars using Gaia EDR3
• A Catalog of Candidate Field Horizontal-Branch and A-Type Stars. III. A 2MASS-Cleaned Version
• The Origin of B-Type Runaway Stars: Non-LTE Abundances as a Diagnostic
• The binary fraction of Blue Horizontal-Branch (BHB) Stars
• The Binary Fraction of B-type Runaway Stars from LAMOST DR8