A Roche Lobe-filling hot Subdwarf and White Dwarf Binary: possible detection of an ejected common envelope

Abstract

Binaries consisting of a hot subdwarf star and an accreting white dwarf (WD) are sources of gravitational wave radiation at low frequencies and possible progenitors of type Ia supernovae if the WD mass is large enough. Here, we report the discovery of the third binary known of this kind: it consists of a hot subdwarf O (sdO) star and a WD with an orbital period of 3.495 hours and an orbital shrinkage of 0.1 s in 6 yr. The sdO star overfills its Roche lobe and likely transfers mass to the WD via an accretion disk. From spectroscopy, we obtain an effective temperature of $T_{\mathrm{eff}}=54240\pm 1840$ K and a surface gravity of $\log g=4.841\pm 0.108$ for the sdO star. From the light curve analysis, we obtain a sdO mass of $M_{\mathrm{sdO}}=0.55$ ${\mathrm{M}}_{\odot }$ and a mass ratio of $q=M_{\mathrm{WD}}/M_{\mathrm{sdO}}=0.738\pm 0.001$. Also, we estimate that the disk has a radius of $\sim 0.41R_{\odot }$ and a thickness of $\sim 0.18R_{\odot }$. The origin of this binary is probably a common envelope ejection channel, where the progenitor of the sdO star is either an RGB star or, more likely, an early AGB star; the sdO star will subsequently evolve into a WD and merge with its WD companion, likely resulting in an R CrB star. The outstanding feature in the spectrum of this object is strong Ca H&K lines, which are blueshifted by $\sim$200 km/s and likely originate from the recently ejected common envelope, and we estimated that the remnant CE material in the binary system has a density $\sim 6\times 10^{-10}g/c{\mathrm{m}}^3$.

13 pages, 15 figures, to be published in MNRAS

References in corpus (91)

• Gaia Data Release 2. Summary of the contents and survey properties
• The Wide-field Infrared Survey Explorer (WISE): Mission Description and Initial On-orbit Performance
• Measuring Reddening with SDSS Stellar Spectra and Recalibrating SFD
• The Gaia mission
• Modules for Experiments in Stellar Astrophysics (MESA)
• Modules for Experiments in Stellar Astrophysics (MESA): Giant Planets, Oscillations, Rotation, and Massive Stars
• Modules for Experiments in Stellar Astrophysics (MESA): Binaries, Pulsations, and Explosions
• Modules for Experiments in Stellar Astrophysics (MESA): Convective Boundaries, Element Diffusion, and Massive Star Explosions
• The Zwicky Transient Facility: System Overview, Performance, and First Results
• Local Kinematics and the Local Standard of Rest
• Modules for Experiments in Stellar Astrophysics (MESA): Pulsating Variable Stars, Rotation, Convective Boundaries, and Energy Conservation
• Comprehensive analytic formulae for stellar evolution as a function of mass and metallicity
• The K2 Mission: Characterization and Early results
• A 3D Dust Map Based on Gaia, Pan-STARRS 1 and 2MASS
• The Zwicky Transient Facility: Data Processing, Products, and Archive
• Planetary Candidates Observed by Kepler, III: Analysis of the First 16 Months of Data
• Characteristics of planetary candidates observed by Kepler, II: Analysis of the first four months of data
• The Zwicky Transient Facility: Science Objectives
• The Origin of Subdwarf B Star (I): the Formation Channels
• Cosmic Distances Calibrated to 1% Precision with Gaia EDR3 Parallaxes and Hubble Space Telescope Photometry of 75 Milky Way Cepheids Confirm Tension with LambdaCDM
• A Grid of NLTE Line-Blanketed Model Atmospheres of O-type Stars
• The origin of sdB stars (II)
• The construction and use of LISA sensitivity curves
• RadVel: The Radial Velocity Modeling Toolkit
• Determining stellar atmospheric parameters and chemical abundances of FGK stars with iSpec
• The Evolution of Compact Binary Star Systems
• The Optical to Mid-Infrared Extinction Law Based on the APOGEE, Gaia DR2, Pan-STARRS1, SDSS, APASS, 2MASS and WISE Surveys
• Faint Thermonuclear Supernovae from AM Canum Venaticorum Binaries
• SkyMapper Southern Survey: First Data Release (DR1)
• Hot subluminous stars
• Progenitors of type Ia supernovae
• The Zwicky Transient Facility: Surveys and Scheduler
• The binary fraction of extreme horizontal branch stars
• Sub-Chandrasekhar Mass Models For Type Ia Supernovae
• Physics Of Eclipsing Binaries. II. Towards the Increased Model Fidelity
• Modern stellar spectroscopy caveats
• The Wide Field Spectrograph (WiFeS)
• Galactic Rotation and Solar Motion from Stellar Kinematics
• Mass Transfer between Double White Dwarfs
• SkyMapper Southern Survey: Second Data Release (DR2)
• Surface Detonations in Double Degenerate Binary Systems Triggered by Accretion Stream Instabilities
• The Wide Field Spectrograph (WiFeS): Performance and Data Reduction
• Helium star donor channel for the progenitors of type Ia supernovae
• Physics of Eclipsing Binaries. V. General Framework for Solving the Inverse Problem
• LISA verification binaries with updated distances from Gaia Data Release 2
• Close binary EHB stars from SPY
• General relativistic orbital decay in a seven-minute-orbital-period eclipsing binary system
• PyWiFeS: A Rapid Data Reduction Pipeline for the Wide Field Spectrograph (WiFeS)
• Mass accumulation efficiency in helium shell flashes for various white dwarf masses
• The Ignition of Carbon Detonations via Converging Shock Waves in White Dwarfs
• 3D kinematics of white dwarfs from the SPY project II
• On the brightness distribution of Type Ia supernovae from violent white dwarf mergers
• The fastest unbound star in our Galaxy ejected by a thermonuclear supernova
• Mass-accreting white dwarfs and type Ia supernovae
• The population of hot subdwarf stars studied with Gaia II. The Gaia DR2 catalogue of hot subluminous stars
• A progenitor binary and an ejected mass donor remnant of faint type Ia supernovae
• A systematic search of Zwicky Transient Facility data for ultracompact binary LISA-detectable gravitational-wave sources
• Binary Population Synthesis
• Blackbody radiation shift, multipole polarizabilities, oscillator strengths, lifetimes, hyperfine constants, and excitation energies in Ca+
• Circumbinary disks and cataclysmic variable evolution
• Formation of Extremely Low-mass White Dwarfs in Double Degenerates
• The Sizes and Kinematic Structure of Absorption Systems Towards the Lensed Quasar APM08279+5255
• Evolutionary Models for the Remnant of the Merger of Two Carbon-Oxygen Core White Dwarfs
• Episodic mass ejections from common-envelope objects
• The orbits of subdwarf-B + main-sequence binaries. II. Three eccentric systems; BD+29 3070, BD +34 1543 and Feige 87
• The shortest period sdB plus white dwarf binary CD-30 11223 (GALEX J1411-3053)
• Post-merger evolution of carbon-oxygen + helium white dwarf binaries and the origin of R Coronae Borealis and extreme helium stars
• Most Double Degenerate Low Mass White Dwarf Binaries Merge
• The first ultracompact Roche lobe-filling hot subdwarf binary
• The orbits of subdwarf-B + main-sequence binaries: III. The period - eccentricity distribution
• A hot subdwarf-white dwarf super-Chandrasekhar candidate supernova Ia progenitor
• The orbits of subdwarf B + main-sequence binaries. I: The sdB+G0 system PG 1104+243
• Angular momentum losses and the orbital period distribution of cataclysmic variables below the period gap: effects of circumbinary disks
• An 8.8 minute orbital period eclipsing detached double white dwarf binary
• Orbital Decay in a 20 Minute Orbital Period Detached Binary with a Hydrogen Poor Low Mass White Dwarf
• A new class of Roche lobe-filling hot subdwarf binaries
• Population synthesis of Galactic subdwarf B stars
• Calcium H & K and sodium D absorption induced by the interstellar and circumgalactic media of the Milky Way
• The helium star donor channel for the progenitors of type Ia supernovae with different metallicities
• Evolutionary models for R Coronae Borealis stars
• Hot subdwarf stars observed in Gaia DR2 and LAMOST DR5
• Accretion-Induced Collapse From Helium Star + White Dwarf Binaries
• PTF1 J082340.04+081936.5: A hot subdwarf B star with a low mass white dwarf companion in an 87 minute orbit
• Models for the evolution of close binaries with He-Star and WD components towards Type Ia supernova explosions
• Phases of Mass Transfer from Hot Subdwarfs to White Dwarf Companions and Their Photometric Properties
• 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
• Helium ignition in rotating magnetized CO white dwarfs leading to fast and faint rather than classical type Ia supernovae
• Electron Captures on ${}^{14}\mathrm{N}$ as a Trigger for Helium Shell Detonations
• Hot subdwarf B stars with neutron star components II: Binary population synthesis
• Pre-Explosion Properties of Helium Star Donors to Thermonuclear Supernovae

Cited by in corpus (8)

• Binary Stars in the New Millennium
• A Systematic Search for Short-period Close White Dwarf Binary Candidates Based on Gaia EDR3 Catalog and Zwicky Transient Facility Data
• Evolution and final fate of massive post-common-envelope binaries
• Compact Objects in close orbits as Gravitational Wave Sources: Formation Scenarios and Properties
• He-star donor AM CVn stars and their progenitors as LISA sources
• Detection of Ubiquitous Circumbinary Matter in Hot Subdwarfs Formed from Common-Envelope Ejections
• Discovery of periodic variables in the hot subdwarf catalogue through a systematic search in Zwicky Transient Facility data
• Discovery of the first outbursting hot subdwarf binary: ZTF J0007+4804