Hot subdwarf Atmospheric parameters, Kinematics, and Origins -- Based on 1587 hot subdwarf stars observed in Gaia DR2 and LAMOST DR7

Abstract

Based on the Gaia DR2 catalogue of hot subdwarf star candidates, we identified 1587 hot subdwarf stars with spectra in LAMOST DR7. We present atmospheric parameters for these stars by fitting the LAMOST spectra with {\sc Tlusty/Synspec} non-LTE synthetic spectra. Combining LAMOST radial velocities and Gaia Early Data Release 3 (EDR3) parallaxes and proper motions, we also present the Galactic space positions, velocity vectors, orbital parameters and the Galactic population memberships of the stars. With our He classification scheme, we identify four groups of He rich hot subdwarf stars in the $T_{\mathrm{eff}}-\log g$ and $T_{\mathrm{eff}}-\log (n\mathrm{He}/n\mathrm{H})$ diagrams. We find two extreme He-rich groups ($e$He-1 and $e$He-2) for stars with $\log (n\mathrm{He}/n\mathrm{H})\ge 0$ and two intermediate He-rich groups ($i$He-1 and $i$He-2) for stars with $-1\le \log (n\mathrm{He}/n\mathrm{H})<0$. We also find that over half of the stars in Group $e$He-1 are thick disk stars, while over half of the stars in Group $e$He-2 correspond to thin disk stars. The disk population fractions of Group $i$He-1 are between those of Group $e$He-1 and $e$He-2. Almost all stars in Group $i$He-2 belong to the thin disk. These differences indicate that the four groups probably have very different origins. Comparisons between hot subdwarf stars in the halo and in the Galactic globular cluster $\omega$ Cen show that only He-deficient stars with $-2.2\le \log (n\mathrm{He}/n\mathrm{H})<-1$ have similar fractions. Hot subdwarfs with $\log (n\mathrm{He}/n\mathrm{H})\ge 0$ in $\omega$ Cen have no counterparts in the thick disk and halo populations, but they appear in the thin disk.

34 pages, 17 figures, Accepted for publication in APJS

References in corpus (30)

• The Gaia mission
• 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
• A binary model for the UV-upturn of elliptical galaxies (MNRAS version)
• The Structure and Dynamical Evolution of the Stellar Disk of a Simulated Milky Way-Mass Galaxy
• A selection of hot subluminous stars in the GALEX survey II. Subdwarf atmospheric parameters
• Hot subdwarfs from the ESO Supernova Ia Progenitor Survey: II. Atmospheric parameters of subdwarf O stars
• Modeling He-rich subdwarfs through the hot-flasher Scenario
• White dwarf and subdwarf stars in the Sloan Digital Sky Survey Data Release 14
• The fastest unbound star in our Galaxy ejected by a thermonuclear supernova
• Hot subdwarf binaries from the MUCHFUSS project - Analysis of 12 new systems and a study of the short-period binary population
• On type Ia supernovae and the formation of single low-mass white dwarfs
• A possible solution for the lack of EHB binaries in globular clusters
• Ages and masses of million Galactic disk main sequence turn-off and sub-giant stars from the LAMOST Galactic spectroscopic surveys
• New binaries among UV-selected, hot subdwarf stars and population properties
• The catalogue of radial velocity variable hot subluminous stars from the MUCHFUSS project
• Discovery of extremely lead-rich subdwarfs: does heavy metal signal the formation of subdwarf B stars?
• Asteroseismology revealing trapped modes in KIC 10553698A
• Discovery of a variable lead-rich hot subdwarf: UVO 0825+15
• A new class of pulsating hot subdwarfs
• Evolution models of helium white dwarf--main sequence star merger remnants
• Hot subdwarf stars identified in Gaia DR2 with spectra of LAMOST DR6 and DR7 I. Single-lined spectra
• The SALT survey of helium-rich hot subdwarfs: methods, classification, and coarse analysis
• A possible formation channel for blue hook stars in globular cluster
• A search for heavy-metal stars: abundance analyses of hot subdwarfs with Subaru
• Hot Subdwarf Stars Identified in Gaia DR2 with Spectra of LAMOST DR6 and DR7. II. Kinematics
• Spectral analysis of four surprisingly similar hot hydrogen-rich subdwarf O stars
• Opacity modelling of heavy-metal hot subdwarfs. Photoionization of Sr${}^0$, Y${}^{+}$ and Zr${}^{2+}$
• Hot subdwarf B stars with neutron star components II: Binary population synthesis
• TESS photometry of helium-rich hot subdwarfs: r modes in BD+37 442 and BD+37 1977

Cited by in corpus (18)

• The population of hot subdwarf stars studied with Gaia -- IV. Catalogues of hot subluminous stars based on Gaia EDR3
• The Common Envelope Evolution Outcome -- A Case Study on Hot Subdwarf B Stars
• Radial velocity variability and evolution of hot subdwarf stars
• Hot subdwarf stars identified in LAMOST DR8 with single-lined and composite spectra
• Extremely low-mass white dwarf stars observed in Gaia DR2 and LAMOST DR8
• Discovery of hot subdwarfs with extremely high carbon and oxygen abundances
• A seven-Earth-radius helium-burning star inside a 20.5-min detached binary
• Minute-Cadence Observations of the LAMOST Fields with the TMTS: II. Catalogues of Short-Period Variable Stars from the First Two-Year Surveys
• Mass distribution for single-lined hot subdwarf stars in LAMOST
• A spectroscopic and kinematic survey of fast hot subdwarfs
• FX UMa: A New Heartbeat Binary System with Linear and Non-linear Tidal Oscillations and delta Sct Pulsations
• Advanced Classification of Hot Subdwarf Binaries Using Artificial Intelligence Techniques and Gaia DR3 data
• A 500 pc volume-limited sample of hot subluminous stars II. Atmospheric parameters, mass distribution, and kinematics
• Detection of Ubiquitous Circumbinary Matter in Hot Subdwarfs Formed from Common-Envelope Ejections
• Detection of hot subdwarf binaries and sdB stars using machine learning methods and a large sample of Gaia XP spectra
• Hot subdwarf stars from the Hamburg Quasar Survey
• Stars on the ascending helium giant branch I. From white dwarf merger to helium giant: the evolutionary state of the rapidly rotating hot subdwarf HE 1518-0948
• Discovery and analysis of three magnetic hot subdwarf stars: evidence for merger-induced magnetic fields