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

Lai, Samuel; Dennihy, E.; Xu, Siyi; Nitta, A.; Kleinman, S. J.; Leggett, S. K.; Bonsor, Amy; Hodgkin, S. T.; Rebassa‐Mansergas, A.; Rogers, Laura K.

doi:10.3847/1538-4357/ac1354

“…The unTimely Catalog provides multiple science opportunities with regard to infrared excesses around white dwarfs (WDs). Many WISE-based searches for WD infrared excesses have been performed (e.g., Dennihy et al 2017;Xu et al 2020;Lai et al 2021). However, a common problem with such studies is WISE blending/confusion, which might artificially cause a mistaken infrared excess identification (e.g., Dennihy et al 2020).…”

Section: White Dwarf Sciencementioning

confidence: 99%

unTimely: a Full-sky, Time-domain unWISE Catalog

Meisner

¹

,

Caselden

²

,

Schlafly

³

et al. 2023

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We present the unTimely Catalog, a deep time-domain catalog of detections based on Wide-field Infrared Survey Explorer (WISE) and NEOWISE observations spanning the 2010 through 2020 time period. Detections are extracted from “time-resolved unWISE coadds,” which stack together each biannual sky pass of WISE imaging to create a set of ∼16 all-sky maps (per band), each much deeper and cleaner than individual WISE exposures. unTimely incorporates the W1 (3.4 μm) and W2 (4.6 μm) channels, meaning that our data set effectively consists of ∼32 full-sky unWISE catalogs. We run the crowdsource crowded-field point-source photometry pipeline (Schlafly et al. 2018) on each epochal coadd independently, with low detection thresholds: S/N = 4.0 (2.5) in W1 (W2). In total, we tabulate and publicly release 23.5 billion (19.9 billion) detections at W1 (W2). unTimely is ∼1.3 mag deeper than the WISE/NEOWISE Single Exposure Source Tables near the ecliptic, with further enhanced depth toward higher ecliptic latitudes. The unTimely Catalog is primarily designed to enable novel searches for faint, fast-moving objects, such as Y dwarfs and/or late-type (T/Y) subdwarfs in the Milky Way’s thick disk or halo. unTimely will also facilitate other time-domain science applications, such as all-sky studies of quasar variability at mid-infrared wavelengths over a decade-long time baseline.

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“…b The WD was confirmed to have Spitzer excess by Lai et al (2021). 11)-( 13) best-fit inner radius and inclination of the dust disk, and minimum reduced-χ 2 .…”

Section: Wd+dust Disk Candidatesmentioning

confidence: 99%

White Dwarfs with Infrared Excess from LAMOST Data Release 5

Wang¹,

Zhang²,

Wang³

et al. 2023

ApJ

4

0

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Infrared (IR) excess is an important probe for substellar companions and/or debris disks around white dwarfs (WDs). Such systems are still rare, so an in-depth understanding of their formation and long-term evolution has yet to be developed. One of the largest spectroscopic surveys, carried out by the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST), has recently released more than 3000 WDs, a significant fraction of which have not been searched for IR excess. Here, we present a cross-correlation between the LAMOST Data Release 5 WD catalog and Pan-STARRS, the Sloan Digital Sky Survey (SDSS), the UKIRT Infrared Deep Sky Survey, the Two-Micron All Sky Survey (2MASS), and the Wide-field Infrared Survey Explorer (WISE). By performing spectral energy distribution fittings for 846 WDs with WISE detections, we identify 50 candidates with IR excess, including seven candidate WD+M dwarf binaries, 31 candidate WD+brown dwarf (BD) binaries, and 12 candidate WD+dust disk systems. Eight of the dust disk systems are our new identifications. By utilizing a systematic survey with accurate stellar parameters derived from spectral fitting, our work is an important addition to previous searches for IR excess from SDSS and Gaia WDs, and it provides a significant (≳8%) complement to the current database of WDs with candidate BD companions and dust disks. The frequencies of the WD+BD binaries and the WD+dust disk systems are constrained to be ≲3.7% and ∼1.4%, respectively. The properties of the candidate dust disk systems are discussed. All of our candidates require follow-up observations for confirmation, owing to the limited spatial resolution of WISE.

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“…To determine the white dwarf parameters, we performed a photometric fit following methods described in Vanderburg et al (2020) with updated JHK photometry of WD 1856+534 (Lai et al 2021). The white dwarf atmosphere was computed using the latest grids of cool white dwarf models (Blouin et al 2019).…”

Section: White Dwarf Parametersmentioning

confidence: 99%

Gemini/GMOS Transmission Spectroscopy of the Grazing Planet Candidate WD 1856+534 b

Xu

¹

,

Diamond-Lowe

²

,

Macdonald

³

et al. 2021

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WD 1856+534 b is a Jupiter-sized, cool giant planet candidate transiting the white dwarf WD 1856+534. Here, we report an optical transmission spectrum of WD 1856+534 b obtained from ten transits using the Gemini Multi-Object Spectrograph. This system is challenging to observe due to the faintness of the host star and the short transit duration. Nevertheless, our phase-folded white light curve reached a precision of 0.12%. WD 1856+534 b provides a unique transit configuration compared to other known exoplanets: the planet is 8× larger than its star and occults over half of the stellar disk during mid-transit. Consequently, many standard modeling assumptions do not hold. We introduce the concept of a “limb darkening corrected, time-averaged transmission spectrum” and propose that this is more suitable than ( R p , λ / R s ) 2 for comparisons to atmospheric models for planets with grazing transits. We also present a modified radiative transfer prescription. Though the transmission spectrum shows no prominent absorption features, it is sufficiently precise to constrain the mass of WD 1856+534 b to be >0.84 M J (to 2σ confidence), assuming a clear atmosphere and a Jovian composition. High-altitude cloud decks can allow lower masses. WD 1856+534 b could have formed either as a result of common envelope evolution or migration under the Kozai–Lidov mechanism. Further studies of WD 1856+534 b, alongside new dedicated searches for substellar objects around white dwarfs, will shed further light on the mysteries of post-main-sequence planetary systems.

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

Cited by 18 publications

References 49 publications

unTimely: a Full-sky, Time-domain unWISE Catalog

unTimely: a Full-sky, Time-domain unWISE Catalog

White Dwarfs with Infrared Excess from LAMOST Data Release 5

Gemini/GMOS Transmission Spectroscopy of the Grazing Planet Candidate WD 1856+534 b

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