Optical detection of the 1.1-day variability at the white dwarf GD 394 with TESS

Abstract

Recent discoveries have demonstrated that planetary systems routinely survive the post-main sequence evolution of their host stars, leaving the resulting white dwarf with a rich circumsteller environment. Among the most intriguing of such hosts is the hot white dwarf GD 394, exhibiting a unique $1.150\pm 0.003$ d flux variation detected in Extreme Ultraviolet Explorer (EUVE) observations in the mid 1990s. The variation has eluded a satisfactory explanation, but hypotheses include channeled accretion producing a dark spot of metals, occultation by a gas cloud from an evaporating planet, or heating from a flux tube produced by an orbiting iron-cored planetesimal. We present observations obtained with the Transiting Exoplanet Survey Satellite (TESS) of GD 394. The space-based optical photometry demonstrates a $0.12\pm 0.01$ % flux variation with a period of $1.146\pm 0.001$ d, consistent with the EUVE period and the first re-detection of the flux variation outside of the extreme ultraviolet. We describe the analysis of the TESS light curve and measurement of the optical variation, and discuss the implications of our results for the various physical explanations put forward for the variability of GD 394.

Accepted for publication in ApJ Letters

References in corpus (7)

• 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
• Accretion of a giant planet onto a white dwarf
• Kepler and the seven dwarfs: detection of low-level day-timescale periodic photometric variations in white dwarfs
• TESS first look at evolved compact pulsators: asteroseismology of the pulsating helium-atmosphere white dwarf TIC 257459955
• A Comparative Study of Optical and Ultraviolet Effective Temperatures for DA White Dwarfs from the IUE Archive
• Survivability of radio-loud planetary cores orbiting white dwarfs
• Periodic optical variability and debris accretion in white dwarfs: a test for a causal connection

Cited by in corpus (3)

• Horizontal spreading of planetary debris accreted by white dwarfs
• Astrometric Gravitational-Wave Detection via Stellar Interferometry
• EPIC 206197016: A very hot white dwarf orbited by a strongly irradiated red dwarf