White dwarfs in the UKIRT Infrared Deep Sky Survey Large Area Survey: the substellar companion fraction

Steele, P. R.; Burleigh, M. R.; Dobbie, P. D.; Jameson, R. F.; Barstow, M. A.; Satterthwaite, R. P.

doi:10.1111/j.1365-2966.2011.19225.x

Cited by 82 publications

(90 citation statements)

References 76 publications

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“…a Jupiter-like planet or a brown dwarf. The brown-dwarf option, as noted above, is apriori unlikely, because of the rarity of brown-dwarf companions to WDs (Steele et al 2011;Girven et al 2011). The insolation temperature of the companion side facing the WD, assuming it is tidally locked in this configuration, would be 1500-2300 K for a range of albedo values D = 0.9 to 0, making this a "hot" companion.…”

Section: Kic 6669882 = J18557+4207mentioning

confidence: 99%

“…Baraffe et al 2014) or brown dwarfs. The browndwarf reflection option, however, is unlikely to be relevant for more than one or two of the WDs in the sample, because there is a 2% fraction of brown-dwarf companions to WDs (Steele et al 2011;Girven et al 2011). A minimum companion radius above R2 ∼ 0.2R⊙ implies a hydrogenburning star with T eff 2800 K (e.g.…”

Section: Reflection From a Companionmentioning

confidence: 99%

“…summary in Debes et al 2011), but it is clear that such systems are rare, in analogy to the "brown-dwarf desert" of main-sequence stars. Based on near-infrared excesses in samples of WDs from SDSS, Steele et al (2011) and Girven et al (2011) have estimated that ∼ 0.5 to 2 per cent of WDs have brown-dwarf companions.…”

Section: Close Companions To Wdsmentioning

confidence: 99%

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Kepler and the seven dwarfs: detection of low-level day-time-scale periodic photometric variations in white dwarfs

Maoz

Mazeh

McQuillan

2014

Monthly Notices of the Royal Astronomical Society

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We make use of the high photometric precision of Kepler to search for periodic modulations among 14 normal (DA-and DB-type, likely non-magnetic) hot white dwarfs (WDs). In five, and possibly up to seven of the WDs, we detect periodic, ∼ 2 hr to 10 d, variations, with semi-amplitudes of 60-2000 ppm, lower than ever seen in WDs. We consider various explanations: WD rotation combined with magnetic cool spots; rotation combined with magnetic dichroism; rotation combined with hot spots from an interstellar-medium accretion flow; transits by size ∼ 50-200 km objects; relativistic beaming due to reflex motion caused by a cool companion WD; or reflection/reradiation of the primary WD light by a brown-dwarf or giant-planet companion, undergoing illumination phases as it orbits the WD. Each mechanism could be behind some of the variable WDs, but could not be responsible for all five to seven variable cases. Alternatively, the periodicity may arise from UV metal-line opacity, associated with accretion of rocky material, a phenomenon seen in ∼ 50% of hot WDs. Nonuniform UV opacity, combined with WD rotation and fluorescent optical re-emission of the absorbed UV energy, could perhaps explain our findings. Even if reflection by a planet is the cause in only a few of the seven cases, it would imply that hot Jupiters are very common around WDs. If some of the rotation-related mechanisms are at work, then normal WDs rotate as slowly as do peculiar WDs, the only kind for which precise rotation measurements have been possible to date.

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Section: Kic 6669882 = J18557+4207mentioning

confidence: 99%

Section: Reflection From a Companionmentioning

confidence: 99%

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Kepler and the seven dwarfs: detection of low-level day-time-scale periodic photometric variations in white dwarfs

Maoz

Mazeh

McQuillan

2014

Monthly Notices of the Royal Astronomical Society

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“…9.1, it hence appears that stellar wind accretion can occur onto white dwarfs in close binaries. One other known example of a very likely He-core that is metal-polluted and has a dusty debris disk is SDSSJ 155720.77+091624.7, suggesting that complex planetary systems in close binary systems can form Steele et al 2011;Farihi et al 2012a). …”

Section: Dependence On the Mass Of The White Dwarfs And Their Progenimentioning

confidence: 99%

The frequency of planetary debris around young white dwarfs

Koester

Gänsicke

Farihi

2014

A&A

442

531

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Context. Heavy metals in the atmospheres of white dwarfs are thought in many cases to be accreted from a circumstellar debris disk, which was formed by the tidal disruption of a rocky planetary body within the Roche radius of the star. The abundance analysis of photospheric elements and conclusions about the chemical composition of the accreted matter are a new and promising method of studying the composition of extrasolar planetary systems. However, ground-based searches for metal-polluted white dwarfs that rely primarily on the detection of the Ca ii K line become insensitive at T eff > 15 000 K because this ionization state depopulates.Aims. We present the results of the first unbiased survey for metal pollution among hydrogen-atmosphere (DA type) white dwarfs with cooling ages in the range 20-200 Myr and 17 000 K < T eff < 27 000 K. Methods. The sample was observed with the Cosmic Origins Spectrograph on board the Hubble Space Telescope in the far ultraviolet range between 1130 and 1435 Å. The atmospheric parameters were obtained using these spectra and optical observations from the literature. Element abundances were determined using theoretical models, which include the effects of element stratification due to gravitational settling and radiative levitation. Results. We find 48 of the 85 DA white dwarfs studied, or 56% show traces of heavy elements. In 25 stars (showing only Si and occasionally C), the elements can be explained by radiative levitation alone, although we argue that accretion has very likely occurred recently. The remaining 23 white dwarfs (27%), however, must be currently accreting. Together with previous studies from the ground and adopting bulk Earth abundances for the debris, accretion rates range from a few 10 5 g s −1 to a few 10 8 g s −1 , with no evident trend in cooling age from ≈40 Myr to ≈2 Gyr. Only a single, modest case of metal pollution (Ṁ < 10 6 g s −1 ) is found among ten white dwarfs with T eff > 23 000 K, in excellent agreement with the absence of infrared excess from dust around these warmer stars. The median, main sequence progenitor of our sample corresponds to an A-type star of ≈2 M , and we find 13 of 23 white dwarfs descending from main sequence 2-3 M , late B-and A-type stars to be currently accreting. Only one of 14 targets with M wd > 0.8 M is found to be currently accreting, which suggests a large fraction of these stars result from double-degenerate mergers, and the merger disks do not commonly reform large planetesimals or otherwise pollute the remnant. We reconfirm our previous finding that two 625 Myr Hyades white dwarfs are currently accreting rocky planetary debris. Conclusions. At least 27% of all white dwarfs with cooling ages 20-200 Myr are accreting planetary debris, but that fraction could be as high as ≈50%. At T eff > 23 000 K, the luminosity of white dwarfs is probably sufficient to vaporize circumstellar dust grains, so no stars with strong metal-pollution are found. Planetesimal disruption events should occur in this cooling age and temper...

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“…A long-term goal has been to combine these detections with the detection of an orbiting planet (Mullally et al 2008;Hogan, Burleigh & Clarke 2009;Debes et al 2011;Faedi et al 2011;Steele et al 2011;Fulton et al 2014;Sandhaus et al 2016). A recent success is WD 1145+017 (Vanderburg et al 2015), a white dwarf which is both polluted and bears a debris disc, and which has recently been shown to also host disintegrating planetesimals.…”

Section: Introductionmentioning

confidence: 99%

The fate of exomoons in white dwarf planetary systems

Payne

Veras

Gänsicke

et al. 2016

Mon. Not. R. Astron. Soc.

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Roughly 1000 white dwarfs are known to be polluted with planetary material, and the progenitors of this material are typically assumed to be asteroids. The dynamical architectures which perturb asteroids into white dwarfs are still unknown, but may be crucially dependent on moons liberated from parent planets during post-main-sequence gravitational scattering. Here, we trace the fate of these exomoons, and show that they more easily achieve deep radial incursions towards the white dwarf than do scattered planets. Consequently, moons are likely to play a significant role in white dwarf pollution, and in some cases may be the progenitors of the pollution itself.

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White dwarfs in the UKIRT Infrared Deep Sky Survey Large Area Survey: the substellar companion fraction

Cited by 82 publications

References 76 publications

Kepler and the seven dwarfs: detection of low-level day-time-scale periodic photometric variations in white dwarfs

Kepler and the seven dwarfs: detection of low-level day-time-scale periodic photometric variations in white dwarfs

The frequency of planetary debris around young white dwarfs

The fate of exomoons in white dwarf planetary systems

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