The first sub-70 min non-interacting WD–BD system: EPIC212235321

Casewell, Sarah L.; Braker, I. P.; Parsons, S. G.; Hermes, J. J.; Burleigh, M. R.; Belardi, Claudia; Chaushev, Alexander; Finch, Nicolle L.; Roy, Mervyn; Littlefair, S. P.; Goad, M. R.; Dennihy, E.

doi:10.1093/mnras/sty245

Cited by 37 publications

(38 citation statements)

References 58 publications

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“…The K-band flux is however brighter than that of the field dwarf, and slightly brighter than the intermediate gravity object. We see brightening in the K-band light curves of WD0137−349B and SDSS1411B (Casewell et al 2015(Casewell et al , 2018 compared to models of irradiated brown dwarfs, and so this discrepancy could be due to irradiation induced emission. However, the resolution of the SpeX spectrum is too low to search for H + 3 emission that could be causing this brightening.…”

Section: Indications Of Low Gravitymentioning

confidence: 59%

“…H α emission has been detected in other irradiated brown dwarf systems, both WD0137−349A (T eff = 16500 ± 500 K; Maxted et al 2006) and EPIC212235321A (T eff = 24490 ± 194 K; Casewell et al 2018) show emission from H α and other species (e.g. Na, K, Ca) in their spectra.…”

Section: Introductionmentioning

confidence: 98%

“…NLTT5306AB is one of five systems known with a period of around 2 h (P = 101.88 min; Steele et al 2013), similar to the 116 min of WD0137−349AB (Longstaff et al 2017) and 121 min of SDSSJ141126.20+200911.1 (Beuermann et al 2013). Indeed, until the recent discovery of three very short period white dwarf-brown dwarf binaries from the Kepler K2 mission (Parsons et al 2017;Casewell et al 2018) with periods of <72 min, NLTT5306AB was the shortest period white dwarf-brown dwarf binary known.…”

Section: Introductionmentioning

confidence: 99%

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NLTT5306B: an inflated, weakly irradiated brown dwarf

Casewell

Debes

Braker

et al. 2020

Monthly Notices of the Royal Astronomical Society

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We present Spitzer observations at 3.6 and 4.5 microns and a near-infrared IRTF SpeX spectrum of the irradiated brown dwarf NLTT5306B. We determine that the brown dwarf has a spectral type of L5 and is likely inflated, despite the low effective temperature of the white dwarf primary star. We calculate brightness temperatures in the Spitzer wavebands for both the model radius, and Roche Lobe radius of the brown dwarf, and conclude that there is very little day-night side temperature difference. We discuss various mechanisms by which NLTT5306B may be inflated, and determine that while low mass brown dwarfs (M<35 MJup) are easily inflated by irradiation from their host star, very few higher mass brown dwarfs are inflated. The higher mass brown dwarfs that are inflated may be inflated by magnetic interactions or may have thicker clouds.

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Section: Indications Of Low Gravitymentioning

confidence: 59%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

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NLTT5306B: an inflated, weakly irradiated brown dwarf

Casewell

Debes

Braker

et al. 2020

Monthly Notices of the Royal Astronomical Society

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“…At 10 11 cm from the center of an extreme-AGB star, the evaporation timescale is on the order of ∼10 3−4 years compared to an orbital decay timescale of a few years, suggesting that the planet likely shreds before significant evaporation occurs (Watson et al 1981;Murray-Clay et al 2009;Lopez et al 2012). Furthermore, brown dwarfs around white dwarfs in post-CE orbits show no evidence that the common envelope phase affected their masses (Maxted et al 2006;Casewell et al 2018;Longstaff et al 2019). In contrast to brown dwarfs, all but the most massive planets are unlikely to survive the common envelope phase based on theoretical arguments and observational searches for planets in white dwarf habitable zones (Nordhaus & Spiegel 2013;Sandhaus et al 2016;Xu et al 2015;van Sluijs & Van Eylen 2017;Vanderburg et al 2015).…”

Section: Additional Aspects Of the Formation Scenariomentioning

confidence: 99%

Hydrodynamic simulations of disrupted planetary accretion discs inside the core of an AGB star

Guidarelli

Nordhaus

Chamandy

et al. 2019

Monthly Notices of the Royal Astronomical Society

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Volume complete sky surveys provide evidence for a binary origin for the formation of isolated white dwarfs with magnetic fields in excess of a MegaGauss. Interestingly, not a single high-field magnetic white dwarf has been found in a detached system suggesting that if the progenitors are indeed binaries, the companion must be removed or merge during formation. An origin scenario consistent with observations involves the engulfment, inspiral, and subsequent tidal disruption of a low-mass companion in the interior of a giant star during a common envelope phase. Material from the shredded companion forms a cold accretion disc embedded in the hot ambient around the proto-white dwarf. Entrainment of hot material may evaporate the disc before it can sufficiently amplify the magnetic field, which typically requires at least a few orbits of the disc. Using three-dimensional hydrodynamic simulations of accretion discs with masses between 1 and 10 times the mass of Jupiter inside the core of an Asymptotic Giant Branch star, we find that the discs survive for at least 10 orbits (and likely for 100 orbits), sufficient for strong magnetic fields to develop.

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“…In both phase curves, 0 and 1 represent the times when the brown dwarf's dayside is aimed toward Earth, whereas phase 0.5 and 1.5 represent times when its nightside is aimed toward Earth. From EPIC 21223532 (Casewell et al 2018a), WD1202-024 (Rappaport et al 2017) and SDSS J141126.20+200911.1 (Littlefair et al 2014;Casewell et al 2018b).…”

Section: Irradiated Brown Dwarfsmentioning

confidence: 99%

Atmospheric Dynamics of Hot Giant Planets and Brown Dwarfs

2020

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Groundbased and spacecraft telescopic observations, combined with an intensive modeling effort, have greatly enhanced our understanding of hot giant planets and brown dwarfs over the past ten years. Although these objects are all fluid, hydrogen worlds with stratified atmospheres overlying convective interiors, they exhibit an impressive diversity of atmospheric behavior. Hot Jupiters are strongly irradiated, and a wealth of observations constrain the day-night temperature differences, circulation, and cloudiness. The intense stellar irradiation, presumed tidal locking and modest rotation leads to a novel regime of strong day-night radiative forcing. Circulation models predict large day-night temperature differences, global-scale eddies, patchy clouds, and, in most cases, a fast eastward jet at the equator—equatorial superrotation. The warm Jupiters lie farther from their stars and are not generally tidally locked, so they may exhibit a wide range of rotation rates, obliquities, and orbital eccentricities, which, along with the weaker irradiation, leads to circulation patterns and observable signatures predicted to differ substantially from hot Jupiters. Brown dwarfs are typically isolated, rapidly rotating worlds; they radiate enormous energy fluxes into space and convect vigorously in their interiors. Their atmospheres exhibit patchiness in clouds and temperature on regional to global scales—the result of modulation by large-scale atmospheric circulation. Despite the lack of irradiation, such circulations can be driven by interaction of the interior convection with the overlying atmosphere, as well as self-organization of patchiness due to cloud-dynamical-radiative feedbacks. Finally, irradiated brown dwarfs help to bridge the gap between these classes of objects, experiencing intense external irradiation as well as vigorous interior convection. Collectively, these diverse objects span over six orders of magnitude in intrinsic heat flux and incident stellar flux, and two orders of magnitude in rotation rate—thereby placing strong constraints on how the circulation of giant planets (broadly defined) depend on these parameters. A hierarchy of modeling approaches have yielded major new insights into the dynamics governing these phenomena.

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The first sub-70 min non-interacting WD–BD system: EPIC212235321

Cited by 37 publications

References 58 publications

NLTT5306B: an inflated, weakly irradiated brown dwarf

NLTT5306B: an inflated, weakly irradiated brown dwarf

Hydrodynamic simulations of disrupted planetary accretion discs inside the core of an AGB star

Atmospheric Dynamics of Hot Giant Planets and Brown Dwarfs

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