EPIC 206197016: A very hot white dwarf orbited by a strongly irradiated red dwarf

Abstract

Very precise satellite photometry has revealed a large number of variable stars whose variability is caused either by surface spots or by binarity. Detailed studies of such variables provide insights into the physics of these objects. We study the nature of the periodic light variability of the white dwarf EPIC 206197016 that was observed by the K2 mission. We obtain phase-resolved medium-resolution spectroscopy of EPIC 206197016 using XSHOOTER spectrograph at VLT to understand the nature of the white dwarf variability. We use NLTE model atmospheres to determine stellar parameters at individual phases. EPIC 206197016 is a hot DA white dwarf with $T_{\text{eff}}=78$kK. The analysis of the spectra reveals periodic radial velocity variations that can result from gravitational interaction with an invisible secondary whose mass corresponds to a red dwarf. The close proximity of the two stars where the semimajor axis is about $3R_{\odot }$ results in the irradiation of the companion with temperatures more than twice as high on the illuminated side compared to the nonilluminated hemisphere. This effect can explain the observed light variations. The spectra of the white dwarf show a particular feature of the Balmer lines called the Balmer line problem, where the observed cores of the lower Balmer lines are deeper than predicted. This can be attributed to either weak pollution of hydrogen in the white dwarf atmosphere by heavy elements or to the presence of a circumstellar cloud or disk.

arXiv comment8 pages, accepted for publication in Astronomy & Astrophysics

References in corpus (71)

• 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
• The Gaia mission
• The Eleventh and Twelfth Data Releases of the Sloan Digital Sky Survey: Final Data from SDSS-III
• The K2 Mission: Characterization and Early results
• New evolutionary models for pre-main sequence and main sequence low-mass stars down to the hydrogen-burning limit
• Gaia Early Data Release 3: The astrometric solution
• X-shooter, the new wide band intermediate resolution spectrograph at the ESO Very Large Telescope
• A Grid of NLTE Line-Blanketed Model Atmospheres of O-type Stars
• A Grid of NLTE Line-Blanketed Model Atmospheres of Early B-type Stars
• A Tidally-Disrupted Asteroid Around the White Dwarf G29-38
• VOSA: Virtual Observatory SED Analyzer. An application to the Collinder 69 open cluster
• Reevaluating Old Stellar Populations
• A Possible Bifurcation in Atmospheres of Strongly Irradiated Stars and Planets
• An Improved Spectroscopic Analysis of DA White Dwarfs from the Sloan Digital Sky Survey Data Release 4
• Dynamical Simulations of Magnetically Channeled Line-Driven Stellar Winds: I. Isothermal, Nonrotating, Radially Driven Flow
• Post-Asymptotic Giant Branch Evolution of Low- and Intermediate-Mass Stars. Preliminary Results
• New models for the evolution of Post-Asymptotic Giant Branch stars and Central Stars of Planetary Nebulae
• On the Spectral Evolution of Hot White Dwarf Stars. I. A Detailed Model-Atmosphere Analysis of Hot White Dwarfs from SDSS DR12
• The White Dwarf Initial-Final Mass Relation for Progenitor Stars From 0.85 to 7.5 M${}_{\odot }$
• Interrelated Main-Sequence Mass-Luminosity, Mass-Radius and Mass-Effective Temperature Relations
• A Magnetic Confinement vs. Rotation Classification of Massive-Star Magnetospheres
• Dynamical Simulations of Magnetically Channeled Line-Driven Stellar Winds: II. The Effects of Field-Aligned Rotation
• Periodic Flux Variability of Stars due to the Reflex Doppler Effect Induced by Planetary Companions
• The VISTA Science Archive
• White Dwarf Rotation as a Function of Mass and a Dichotomy of Mode Linewidths: Kepler Observations of 27 Pulsating DA White Dwarfs Through K2 Campaign 8
• Rotation Periods, Variability Properties and Ages for Kepler Exoplanet Candidate Host Stars
• The Atmospheric Circulation of Ultra-hot Jupiters
• The Rigidly Rotating Magnetosphere of Sigma Ori E
• A simple model of the reflection effect for the interacting binaries and extrasolar planets
• 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
• New binaries among UV-selected, hot subdwarf stars and population properties
• MOBSTER - II. Identification of rotationally variable A stars observed with \emph{TESS} in Sectors 1 to 4
• The Carlsberg Meridian Telescope CCD Drift Scan Survey
• Kepler and the seven dwarfs: detection of low-level day-timescale periodic photometric variations in white dwarfs
• Formation of starspots in self-consistent global dynamo models: Polar spots on cool stars
• White Dwarf - Red Dwarf Systems Resolved with the Hubble Space Telescope. II. Full Snapshot Survey Results
• Rotation and pulsation in Ap stars: first light results from TESS sectors 1 and 2
• Magnetic flux transport on active cool stars and starspot lifetimes
• The White Dwarf Binary Pathways Survey I: A sample of FGK stars with white dwarf companions
• The Magnetic Early B-type Stars IV: Breakout or Leakage? H$\alpha$ emission as a diagnostic of plasma transport in centrifugal magnetospheres
• Close detached white dwarf + brown dwarf binaries: further evidence for low values of the common envelope efficiency
• Deposition of steeply infalling debris around white dwarf stars
• The EREBOS project -- Investigating the effect of substellar and low-mass stellar companions on late stellar evolution
• Formation of sdB-stars via common envelope ejection by substellar companions
• The first sub-70 minute non-interacting WD-BD system: EPIC212235321
• New Photometrically Variable Magnetic Chemically Peculiar Stars in the ASAS-3 Archive
• 15000 Ellipsoidal Binary Candidates in TESS: Orbital Periods, Binary Fraction, and Tertiary Companions
• Discovery of a hot ultramassive rapidly rotating DBA White Dwarf
• An Isolated White Dwarf with 317-Second Rotation and Magnetic Emission
• When flux standards go wild: white dwarfs in the age of Kepler
• Spectral analysis of the extremely hot DA white dwarf PG0948+534
• A Dark Spot on a Massive White Dwarf
• Asymmetry in the number of L4 and L5 Jupiter Trojans driven by jumping Jupiter
• Metal abundances in hot white dwarfs with signatures of a superionized wind
• On the Spectral Evolution of Hot White Dwarf Stars. IV. The Diffusion and Mixing of Residual Hydrogen in Helium-rich White Dwarfs
• New Variable Hot Subdwarf Stars Identified from Anomalous Gaia Flux Errors, Observed by TESS, and Classified via Fourier Diagnostics
• A grid of Synthetic Spectra for Hot DA White Dwarfs and Its Application in Stellar Population Synthesis
• A Plague of Magnetic Spots Among the Hot Stars of Globular Clusters
• Photometric variability in a warm, strongly magnetic DQ white dwarf, SDSS J103655.39+652252.2
• Atmosphere Models of Brown Dwarfs Irradiated by White Dwarfs: Analogues for Hot and Ultra-Hot Jupiters
• Stellar wind models of central stars of planetary nebulae
• Four new deeply-eclipsing white dwarfs in ZTF
• A new sdO+dM binary with extreme eclipses and reflection effect
• Distribution of magnetically confined circumstellar matter in oblique rotators
• The nearby magnetic cool DZ white dwarf PM J08186-3110
• Properties and nature of Be stars 31. The binary nature, light variability, physical elements, and emission-line changes of HD~81357
• V772 Cas: an ellipsoidal HgMn star in an eclipsing binary
• Optical detection of the 1.1-day variability at the white dwarf GD 394 with TESS
• Understanding the rotational variability of K2 targets. HgMn star KIC 250152017 and blue horizontal branch star KIC 249660366

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