Infrared Excesses around Bright White Dwarfs from Gaia and unWISE. II

Abstract

Infrared excesses around white dwarf stars indicate the presence of various astrophysical objects of interest, including companions and debris disks. In this second paper of a series, we present follow-up observations of infrared excess candidates from Gaia and unWISE discussed in the first paper, Paper I. We report space-based infrared photometry at 3.6 and 4.5 micron for 174 white dwarfs from the Spitzer Space Telescope and ground-based near-infrared J, H, and K photometry of 235 white dwarfs from Gemini Observatory with significant overlap between Spitzer and Gemini observations. This data is used to confirm or rule-out the observed unWISE infrared excess. From the unWISE-selected candidate sample, the most promising infrared excess sample comes from both colour and flux excess, which has a Spitzer confirmation rate of 95%. We also discuss a method to distinguish infrared excess caused by stellar or sub-stellar companions from potential dust disks. In total, we confirm the infrared excess around 62 white dwarfs, 10 of which are likely to be stellar companions. The remaining 52 bright white dwarf with infrared excess beyond two microns has the potential to double the known sample of white dwarfs with dusty exoplanetary debris disks. Follow-up high-resolution spectroscopic studies of a fraction of confirmed excess white dwarfs in this sample have discovered emission from gaseous dust disks. Additional investigations will be able to expand the parameter space from which dust disks around white dwarfs are found.

23 pages, 8 figures, 8 tables, 3 of the tables are available digitally, and 329 SEDs are available as digital content

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• The Geometry of the G29-38 White Dwarf Dust Disk from Radiative Transfer Modeling
• Astrometric Gravitational-Wave Detection via Stellar Interferometry
• White Dwarfs with Infrared Excess from LAMOST Data Release 5
• Disk or Companion: Characterizing Excess Infrared Flux in Seven White Dwarf Systems with Near-Infrared Spectroscopy
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• Can tidal evolution lead to close-in planetary bodies around white dwarfs II: volcanism and transits
• Characterizing planetary material accreted by cool helium atmosphere white dwarfs using an exponentially decaying disc model
• A candidate giant planet companion to the massive, young white dwarf GALEX J071816.4+373139 informs the occurrence of giant planets orbiting B stars
• Tracing Planetary Accretion in a 3 Gyr-old Hydrogen-Rich White Dwarf: The Extremely Polluted Atmosphere of LSPM J0207+3331
• Gaia white dwarfs with infrared excess I. The 100 pc catalogue
• Seismic test of the mass-radius relationship of hydrogen-atmospheric white dwarf stars
• PHL 5038AB: Is the brown dwarf causing pollution of its white dwarf host star?