Radial velocity variability and evolution of hot subdwarf stars

Abstract

Hot subdwarf stars represent a late and peculiar stage in the evolution of low-mass stars, because they are likely formed by close binary interactions. Here we performed a radial velocity (RV) variability study of a sample of 646 hot subdwarfs with multi-epoch radial velocities from Sloan Digital Sky Survey (SDSS) and Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) spectra [...] As diagnostics we used the fraction of RV-variable stars and the distribution of the maximum RV variations $\Delta R{V}_{\max }$. Both indicators turned out to be quite inhomogeneous across the studied parameter ranges. A striking feature is the completely different behaviour of He-poor and He-rich hot subdwarfs. While the former have a high fraction of close binaries, almost no significant RV variations could be detected for the latter. This led us to the conclusion that there likely is no evolutionary connection between these subtypes. Intermediate He-rich- and extreme He-rich sdOB/Os on the other hand are likely related. We conclude further that the vast majority of this population is formed via one or several binary merger channels. Hot subdwarfs with temperatures cooler than $\sim 24000\mathrm{K}$ tend to show less and smaller RV-variations. These objects might constitute a new subpopulation of binaries with longer periods and late-type or compact companions. The RV-variability properties of the extreme horizontal branch (EHB) and corresponding post-EHB populations of the He-poor hot subdwarfs match and confirm the predicted evolutionary connection between them. Stars found below the canonical EHB at somewhat higher surface gravities show large RV-variations and a high RV-variability fraction, which is consistent with most of them being low-mass EHB stars or progenitors of low-mass helium white dwarfs in close binaries.

arXiv comment28 pages, A&A accepted

References in corpus (102)

• The Eleventh and Twelfth Data Releases of the Sloan Digital Sky Survey: Final Data from SDSS-III
• SEGUE: A Spectroscopic Survey of 240,000 stars with g=14-20
• The Origin of Subdwarf B Star (I): the Formation Channels
• A Grid of NLTE Line-Blanketed Model Atmospheres of O-type Stars
• The origin of sdB stars (II)
• Spectral Classification and Redshift Measurement for the SDSS-III Baryon Oscillation Spectroscopic Survey
• Ultraviolet Radiation from Evolved Stellar Populations -- I. Models
• Binarity in Brown Dwarfs: T Dwarf Binaries Discovered with the Hubble Space Telescope WPFC2
• Hot subluminous stars
• The binary fraction of extreme horizontal branch stars
• The Origin of Extreme Horizontal Branch Stars
• New evolutionary sequences for extremely low mass white dwarfs: Homogeneous mass and age determinations, and asteroseismic prospects
• Flash Mixing on the White Dwarf Cooling Curve: Understanding Hot Horizontal Branch Anomalies in NGC 2808
• Spectral models for binary products: Unifying Subdwarfs and Wolf-Rayet stars as a sequence of stripped-envelope stars
• Models of low-mass helium white dwarfs including gravitational settling, thermal and chemical diffusion, and rotational mixing
• Can Planets Influence the Horizontal Branch Morphology?
• Close binary EHB stars from SPY
• A selection of hot subluminous stars in the GALEX survey II. Subdwarf atmospheric parameters
• Orbital periods of twenty two subdwarf B stars
• 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 subdwarfs from the ESO Supernova Ia Progenitor Survey - I. Atmospheric parameters and cool companions of sdB stars
• Spectral analysis of sdB stars from the Hamburg Quasar Survey
• The hot subdwarf B + white dwarf binary KPD 1930+2752 - a Supernova Type Ia progenitor candidate
• Hot subdwarf binaries from the MUCHFUSS project - Analysis of 12 new systems and a study of the short-period binary population
• A progenitor binary and an ejected mass donor remnant of faint type Ia supernovae
• Radial velocity measurements of Subdwarf B stars
• Abundance studies of sdB stars using UV echelle HST/STIS spectroscopy
• 2M1938+4603: A rich, multimode pulsating sdB star with an eclipsing dM companion observed with Kepler
• First full evolutionary computation of the He-flash induced mixing in Population II stars
• The ESO supernovae type Ia progenitor survey (SPY)
• Slowing down atomic diffusion in subdwarf B stars: mass loss or turbulence?
• Population of hot subdwarf stars studied with Gaia III. Catalogue of known hot subdwarf stars: Data Release 2
• Testing common classical LTE and NLTE model atmosphere and line-formation codes for quantitative spectroscopy of early-type stars
• The orbital periods of subdwarf B binaries produced by the first stable Roche overflow channel
• Flash Mixing on the White Dwarf Cooling Curve: FUSE Observations of three He-rich sdB Stars
• Hot subdwarf stars in close-up view I. Rotational properties of subdwarf B stars in close binary systems and nature of their unseen companions
• A survey for pulsating subdwarf B stars with the Nordic Optical Telescope
• Mass-loss and diffusion in subdwarf B stars and hot white dwarfs: do weak winds exist?
• The first ultracompact Roche lobe-filling hot subdwarf binary
• Single and Composite Hot Subdwarf Stars in the Light of 2MASS Photometry
• On the formation of single and binary helium-rich sdO stars
• New binaries among UV-selected, hot subdwarf stars and population properties
• A hot subdwarf-white dwarf super-Chandrasekhar candidate supernova Ia progenitor
• Discovery of extremely lead-rich subdwarfs: does heavy metal signal the formation of subdwarf B stars?
• The catalogue of radial velocity variable hot subluminous stars from the MUCHFUSS project
• Alone but not lonely: Observational evidence that binary interaction is always required to form hot subdwarf stars
• Hot subdwarf stars in close-up view - III. Metal abundances of subdwarf B stars
• A Neutral Beam Model for High-Energy Neutrino Emission from the Blazar TXS 0506+056
• The orbital period -- mass ratio relation of wide sdB+MS binaries and its application to the stability of RLOF
• On helium-dominated stellar evolution: the mysterious role of the O(He)-type stars
• Hot subdwarf stars in close-up view - II. Rotational properties of single and wide binary subdwarf B stars
• The EREBOS project -- Investigating the effect of substellar and low-mass stellar companions on late stellar evolution
• Sirius A: turbulence or mass loss?
• Hot Subdwarf Stars Observed in LAMOST DR1 - Atmospheric parameters from single-lined spectra
• Observed binary populations reflect the Galactic history. Explaining the orbital period-mass ratio relation in wide hot subdwarf binaries
• Subdwarf B stars from the common envelope ejection channel
• Formation of sdB-stars via common envelope ejection by substellar companions
• How to Make a Singleton sdB Star via Accelerated Stellar Evolution
• New hot subdwarf stars identified in Gaia DR2 with LAMOST DR5 spectra
• Massive unseen companions to hot faint underluminous stars from SDSS (MUCHFUSS) - Analysis of seven close subdwarf B binaries
• Hot subdwarf Atmospheric parameters, Kinematics, and Origins -- Based on 1587 hot subdwarf stars observed in Gaia DR2 and LAMOST DR7
• New hot subdwarf stars identified in Gaia DR2 with LAMOST DR5 spectra -- II
• Hot subdwarf stars observed in Gaia DR2 and LAMOST DR5
• Binary Central Stars of Planetary Nebulae Discovered Through Photometric Variability V: The Central Stars of HaTr 7 and ESO 330-9
• PTF1 J082340.04+081936.5: A hot subdwarf B star with a low mass white dwarf companion in an 87 minute orbit
• Discovery of a double detonation thermonuclear supernova progenitor
• A quantitative spectral analysis of 14 hypervelocity stars from the MMT survey
• Stellar wind models of subluminous hot stars
• A quantitative in-depth analysis of the prototype sdB+BD system SDSS J08205+0008 revisited in the Gaia era
• Common Envelope Mergers: A Possible Channel for Forming Single sdB Stars
• The helium-rich subdwarf CPD-20 1123: a post-common envelope binary evolving onto the extended horizontal branch
• Hydrogen in hot subdwarfs formed by double helium white dwarf mergers
• Heavy metals in intermediate He-rich hot subdwarfs: The chemical composition of HZ44 and HD127493
• Formation of hot subdwarf B stars with neutron star components
• The OmegaWhite survey for short-period variable stars - V. Discovery of an ultracompact hot subdwarf binary with a compact companion in a 44 minute orbit
• SHOTGLAS I: The ultimate spectroscopic census of extreme horizontal branch stars in $\omega$ Centauri
• Orbital properties of an unusually low-mass sdB star in a close binary system with a white dwarf
• The subdwarf B star SB 290 - A fast rotator on the extreme horizontal branch
• The blue-edge problem of the V1093 Her instability strip revisited using evolutionary models with atomic diffusion
• Orbital solutions of eight close sdB binaries and constraints on the nature of the unseen companions
• The effects of diffusion in hot subdwarf progenitors from the common envelope channel
• The fast rotating, low gravity subdwarf B star EC 22081-1916 - Remnant of a common envelope merger event
• The MUCHFUSS photometric campaign
• An in-depth reanalysis of the alleged type Ia supernova progenitor Henize 2-428
• Hot Subdwarf Stars Identified in Gaia DR2 with Spectra of LAMOST DR6 and DR7. II. Kinematics
• Discovery of hot subdwarfs with extremely high carbon and oxygen abundances
• Spectroscopic Orbital Elements for the Helium-Rich Subdwarf Binary PG1544+488
• Validation of LAMOST Stellar Parameters with the PASTEL Catalog
• A quantitative NLTE analysis of visual and ultraviolet spectra of four helium-rich subdwarf O stars
• The first heavy-metal hot subdwarf composite binary SB 744
• Quantitative spectral analysis of the sdB star HD 188112: a helium-core white dwarf progenitor
• Looking into the cradle of the grave: J22564-5910, a young post-merger hot subdwarf?
• A new HW Vir binary from the Palomar Transient Factory: PTF1 J072455.75+125300.3 - An eclipsing subdwarf B binary with a M-star companion
• EVR-CB-004: An Inflated Hot Subdwarf O star + Unseen WD Companion in a Compact Binary Discovered with the Evryscope
• NLTE spectroscopic analysis of the ${}^3$He anomaly in subluminous B-type stars
• Confirming new white dwarf-ultracool dwarf binary candidates
• Improved determination of the atmospheric parameters of the pulsating sdB star Feige 48
• No close companions to a sample of bright sdB stars
• NLTE spectral analysis of the intermediate helium-rich subdwarf B star CPD-20°1123

Cited by in corpus (15)

• The population of hot subdwarf stars studied with Gaia -- IV. Catalogues of hot subluminous stars based on Gaia EDR3
• Hot subdwarf stars identified in LAMOST DR8 with single-lined and composite spectra
• Birth of a Be star: an APOGEE search for Be stars forming through binary mass transfer
• Extremely low-mass white dwarf stars observed in Gaia DR2 and LAMOST DR8
• Shell helium-burning hot subdwarf B stars as candidates for blue large-amplitude pulsators
• Mass distribution for single-lined hot subdwarf stars in LAMOST
• A spectroscopic and kinematic survey of fast hot subdwarfs
• The first massive compact companion in a wide orbit around a hot subdwarf star
• 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
• Where are the binaries? -- Searching for blue horizontal-branch stars in binary systems in the inner Galactic Halo
• Identifying and characterising the population of hot sub-luminous stars with multi-colour MeerLICHT data
• Hot subdwarf stars from the Hamburg Quasar Survey
• Onset of common envelope evolution during a core helium flash by rapid envelope expansion
• 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