EL CVn-type binaries - Discovery of 17 helium white dwarf precursors in bright eclipsing binary star systems

Abstract

The star 1SWASP J024743.37-251549.2 was recently discovered to be a binary star in which an A-type dwarf star eclipses the remnant of a disrupted red giant star (WASP0247-25B). The remnant is in a rarely-observed state evolving to higher effective temperatures at nearly constant luminosity prior to becoming a very low-mass white dwarf composed almost entirely of helium, i.e., it is a pre-He-WD. We have used the WASP photometric database to find 17 eclipsing binary stars with orbital periods P=0.7 to 2.2 days with similar lightcurves to 1SWASP J024743.37-251549.2. The only star in this group previously identified as a variable star is the brightest one, EL CVn, which we adopt as the prototype for this class of eclipsing binary star. The characteristic lightcurves of EL CVn-type stars show a total eclipse by an A-type dwarf star of a smaller, hotter star and a secondary eclipse of comparable depth to the primary eclipse. We have used new spectroscopic observations for 6 of these systems to confirm that the companions to the A-type stars in these binaries have very low masses (approximately 0.2 solar masses). This includes the companion to EL CVn which was not previously known to be a pre-He-WD. EL CVn-type binary star systems will enable us to study the formation of very low-mass white dwarfs in great detail, particularly in those cases where the pre-He-WD star shows non-radial pulsations similar to those recently discovered in WASP0247-25B.

Accepted for publication in MNRAS. 18 pages

References in corpus (7)

• The Dartmouth Stellar Evolution Database
• WASP-4b: a 12th-magnitude transiting hot-Jupiter in the Southern hemisphere
• RR-Lyrae-type pulsations from a 0.26-solar-mass star in a binary system
• Multi-periodic pulsations of a stripped red giant star in an eclipsing binary
• Stellar Exotica in 47 Tucanae
• Radial velocity mapping of Paczyński's star AW UMa: Not a contact binary
• The Clusters AgeS Experiment (CASE). I. V209 omega Cen - An Eclipsing Post-Common Envelope Binary in the Globular Cluster omega Cen

Cited by in corpus (72)

• The Evolution of Compact Binary Star Systems
• Hot subluminous stars
• Gaia Data Release 3: Stellar multiplicity, a teaser for the hidden treasure
• New white dwarf and subdwarf stars in the Sloan Digital Sky Survey Data Release 12
• Pulsating white dwarfs: new insights
• Models of low-mass helium white dwarfs including gravitational settling, thermal and chemical diffusion, and rotational mixing
• White dwarf and subdwarf stars in the Sloan Digital Sky Survey Data Release 14
• The formation of low-mass helium white dwarfs orbiting pulsars: Evolution of low-mass X-ray binaries below the bifurcation period
• The EBLM Project IV. Spectroscopic orbits of over 100 eclipsing M dwarfs masquerading as transiting hot-Jupiters
• Formation of Extremely Low-mass White Dwarfs in Double Degenerates
• The timescale of low-mass proto-helium white dwarf evolution
• Evolution of Cataclysmic Variables and Related Binaries Containing a White-Dwarf
• Precise Atmospheric Parameters for the Shortest Period Binary White Dwarfs: Gravitational Waves, Metals, and Pulsations
• The BEBOP radial-velocity survey for circumbinary planets I. Eight years of CORALIE observations of 47 single-line eclipsing binaries and abundance constraints on the masses of circumbinary planets
• Gaia Data Release 2 Catalogue of Extremely-low Mass White Dwarf Candidates
• New binaries among UV-selected, hot subdwarf stars and population properties
• Detection of the Ultraviolet Spectrum of the Hot Subdwarf Companion of 60 Cygni (B1 Ve) from a Survey of IUE Spectra of Be Stars
• WASP 1628+10 - an EL CVn-type binary with a very-low-mass stripped-red-giant star and multi-periodic pulsations
• Unicorns and Giraffes in the binary zoo: stripped giants with subgiant companions
• The White Dwarf Binary Pathways Survey I: A sample of FGK stars with white dwarf companions
• A Catalogue of Potential Post Common Envelope Binaries
• WASP-167b/KELT-13b: Joint discovery of a hot Jupiter transiting a rapidly-rotating F1V star
• The Formation of EL CVn-type Binaries
• UVIT Open Cluster Study. II. Detection of extremely low mass white dwarfs and post-mass transfer binaries in M67
• The occurrence of Binary Evolution Pulsators in the classical instability strip of RR Lyrae and Cepheid variables
• KIC 8262223: A Post-Mass Transfer Eclipsing Binary Consisting of a Delta Scuti Pulsator and a Helium White Dwarf Precursor
• Discovery of 36 eclipsing EL CVn binaries found by the Palomar Transient Factory
• BEER analysis of Kepler and CoRoT light curves: IV. Discovery of four new low-mass white dwarf companions in the Kepler data
• Towards a volumetric census of close white dwarf binaries I.Reference samples
• White dwarf and subdwarf stars in the Sloan Digital Sky Survey Data Release 16
• Discovery of Three Pulsating, Mixed-atmosphere, Extremely Low-mass White Dwarf Precursors
• The sdA problem - II. Photometric and Spectroscopic Follow-up
• A proto-helium white dwarf stripped by a substellar companion via common-envelope ejection -- Uncovering the true nature of a candidate hypervelocity B-type star
• Pulsation in faint blue stars
• The Physical Nature of Subdwarf A Stars: White Dwarf Impostors
• What are the spectroscopic binaries with high mass functions near the Gaia DR3 main sequence?
• Absolute Properties of the Pulsating Post-mass Transfer Eclipsing Binary OO Draconis
• The sdA problem I: Physical Properties
• The EBLM Project VI. The mass and radius of five low-mass stars in F+M binaries discovered by the WASP survey
• Reversing the verdict: Cataclysmic variables could be the dominant progenitors of AM CVn binaries after all
• KIC 6206751: the first R CMa-type eclipsing binary with $\gamma$ Doradus pulsations
• A double white dwarf with a paradoxical origin?
• Forming merging double compact objects with stable mass transfer
• Extremely low-mass white dwarf stars observed in Gaia DR2 and LAMOST DR8
• A close-in giant planet escapes engulfment by its star
• Discovery and characterisation of long-period eclipsing binary stars from Kepler K2 campaigns 1, 2 and 3
• Most EL CVn systems are inner binaries of hierarchical triples
• The White Dwarf Binary Pathways Survey -- IX. Three long period white dwarf plus subgiant binaries
• Convection and rotation boosted prescription of magnetic braking: application to the formation of extremely low-mass white dwarfs
• The Pre-He White Dwarfs in Eclipsing Binaries. I. WASP 0131+28
• GlobULeS-IV. UVIT/AstroSat detection of extremely low mass white dwarf companions to blue straggler stars in NGC 362
• V1224 Cas - an EL CVn-type Eclipsing Binary Consisting of a Helium White Dwarf Precursor and a Delta Scuti Pulsator
• A Model of the Pulsating Extremely Low-Mass White Dwarf Precursor WASP 0247-25B
• Pulsating White Dwarfs
• The formation of subdwarf A-type stars
• Spectroscopic Detection of the Pre-White Dwarf Companion of Regulus
• Discovery of a pre-cataclysmic binary with unusual chromaticity of the eclipsed white dwarf by the GPX Survey
• A long-period pre-ELM system discovered from LAMOST medium-resolution survey
• Luminaries in the Sky: The TESS Legacy Sample of Bright Stars. I. Asteroseismic detections in naked-eye main-sequence and sub-giant solar-like oscillators
• 4FGL J1120.0-2204: A Unique Gamma-ray Bright Neutron Star Binary with an Extremely Low Mass Proto-White Dwarf
• The Pre-He White Dwarfs in Eclipsing Binaries. IV. WASP 1814+48 with Multiperiodic Pulsations
• The Araucaria Project. Precise physical parameters of the eclipsing binary IO Aqr
• The Pre-He White Dwarfs in Eclipsing Binaries. III. WASP 1625-04
• Discovery of four new EL CVn-type binaries in the Gaia eclipsing binaries
• WASP 0639-32: a new F-type subgiant/K-type main-sequence detached eclipsing binary from the WASP project
• White Dwarf Stars
• Asteroseismic Determination of Stellar Rotation: On Synchronization in the Close Eclipsing Binaries AB Cas and OO Dra
• KIC 12268220: A $\delta$ Scuti Pulsating Star and an Active Protohelium White Dwarf in an Eclipsing Binary System
• The Head-on Collision of a Neutron Star with a White Dwarf
• Evryscope-South Survey of Upper- and Pre-main Sequence Solar Neighborhood Stars
• Pulsation and Rotation of the EL CVn-type Eclipsing Binary 1SWASP J024743.37-251549.2
• Discovery and Characterization of White Dwarf-FGK Main-Sequence Binaries within the Optical Main-Sequence Locus