Self-lensing Discovery of a $0.2M_{\odot }$ White Dwarf in an Unusually Wide Orbit Around a Sun-like Star

Abstract

We report the discovery of the fifth self-lensing binary in which a low-mass white dwarf (WD) gravitationally magnifies its 15th magnitude G-star companion, KIC 8145411, during eclipses. The system was identified from a pair of such self-lensing events in the Kepler photometry, and was followed up with the Tillinghast Reflector Echelle Spectrograph (TRES) on the 1.5m telescope at the Fred Lawrence Whipple Observatory and the High-Dispersion Spectrograph (HDS) on the Subaru 8.2m telescope. A joint analysis of the TRES radial velocities, the HDS spectrum, and the Kepler photometry of the primary star determines the WD mass $0.20\pm 0.01M_{\odot }$, orbital semi-major axis $1.28\pm 0.03\mathrm{au}$, and orbital eccentricity $0.14\pm 0.02$. Because such extremely low-mass WDs cannot be formed in isolation within the age of the Galaxy, their formation is believed to involve binary interactions that truncated evolution of the WD progenitor. However, the observed orbit of the KIC 8145411 system is at least ten times wider than required for this scenario to work. The presence of this system in the Kepler sample, along with its similarities to field blue straggler binaries presumably containing WDs, may suggest that some 10% of post-AGB binaries with Sun-like primaries contain such anomalous WDs.

accepted for publication in ApJ Letters

References in corpus (15)

• Modules for Experiments in Stellar Astrophysics (MESA)
• The Dartmouth Stellar Evolution Database
• A Search for Stars of Very Low Metal Abundance. VI. Detailed Abundances of 313 Metal-Poor Stars
• Precision Stellar Characterization of FGKM Stars using an Empirical Spectral Library
• Found: The missing blue opacity in atmosphere models of cool hydrogen white dwarfs
• PyTransit: Fast and Easy Exoplanet Transit Modelling in Python
• The ELM Survey. I. A Complete Sample of Extremely Low Mass White Dwarfs
• RR-Lyrae-type pulsations from a 0.26-solar-mass star in a binary system
• Finding binaries from phase modulation of pulsating stars with Kepler: V. Orbital parameters, with eccentricity and mass-ratio distributions of 341 new binaries
• The Future is Now: the Formation of Single Low Mass White Dwarfs in the Solar Neighborhood
• KOI-3278: A Self-Lensing Binary Star System
• ZASPE: A Code to Measure Stellar Atmospheric Parameters and their Covariance from Spectra
• Characterizing the Cool KOIs. V. KOI-256: A Mutually Eclipsing Post-Common Envelope Binary
• Discovery of Two New Thermally Bloated Low-Mass White Dwarfs Among the Kepler Binaries
• Discovery of a Compact Companion to a Nearby Star

Cited by in corpus (32)

• The ELM Survey. VIII. 98 Double White Dwarf Binaries
• Weighing the Darkness: Astrometric Mass Measurement of Hidden Stellar Companions using Gaia
• Unicorns and Giraffes in the binary zoo: stripped giants with subgiant companions
• Common-Envelope Episodes that lead to Double Neutron Star formation
• The White Dwarf Binary Pathways Survey IV: Three close white dwarf binaries with G-type secondary stars
• Wide post-common envelope binaries from Gaia: orbit validation and formation models
• The White Dwarf Binary Pathways Survey VI: two close post common envelope binaries with TESS light curves
• Lithium abundance is a gravitational model dependent quantity
• Studies of RR Lyrae Variables in Binary Systems. I.: Evidence of a Trimodal Companion Mass Distribution
• Metric-affine effects in crystallization processes of white dwarfs
• White dwarf stars in modified gravity
• UOCS.VI. UVIT/AstroSat detection of low-mass white dwarf companions to 4 more blue stragglers in M67
• The White Dwarf Binary Pathways Survey -- IX. Three long period white dwarf plus subgiant binaries
• The White Dwarf Binary Pathways Survey VII: Evidence for a bi-modal distribution of post mass transfer systems?
• Predicting the self-lensing population in optical surveys
• No longer impossible: the self-lensing binary KIC 8145411 is a triple
• Detectability of Sub-Solar Mass Neutron Stars Through a Template Bank Search
• Searching for Anomalies in the ZTF Catalog of Periodic Variable Stars
• Early evolution of fully convective stars in scalar-tensor gravity
• WIYN Open Cluster Study. XC. Radial-velocity Measurements and Spectroscopic Binary Orbits in the Open Cluster NGC 2506
• Population demographics of white dwarf binaries with intermediate separations: Gaia constraints on post-AGB mass transfer
• Dynamically Forming Extremely Low-Mass White Dwarf Binaries in Wide Orbits
• Cosmology and nuclear-physics implications of a subsolar gravitational-wave event
• Finding binaries from phase modulation of pulsating stars with \textit{Kepler}: VI. Orbits for 10 new binaries with mischaracterised primaries
• Common envelope evolution and triple dynamics as potential pathways to form the inner white dwarf + brown dwarf binary of the triple star system Gaia 0007-1605
• Crystallized white dwarf stars in scalar-tensor gravity
• Analysis of Previously Classified White Dwarf-Main Sequence Binaries Using Data from the APOGEE Survey
• One of Everything: The Breakthrough Listen Exotica Catalog
• Apparently ultra-long period radio sources from self-lensed pulsar-black hole binaries
• Effects of modified gravity on microscopic properties and cooling timescale of white dwarfs
• Two unseen massive white dwarf candidates in close binaries
• Parameter estimation from the transit light curve including gravitational lensing effects