NLTT5306B: an inflated, weakly irradiated brown dwarf

Casewell, Sarah L.; Debes, John H.; Braker, I. P.; Cushing, Michael C.; Mace, Gregory N.; Marley, Mark S.; Kirkpatrick, J. Davy

doi:10.1093/mnras/staa3184

Cited by 23 publications

(37 citation statements)

References 45 publications

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“…Based on the given mass ratio (0.1), orbital separation (0.003au), and brown dwarf radius (0.7 R Jup ), the modeled distortion for SDSS1411-B is around 0.67%. The model calculation is the same as that in Casewell et al (2020a). The fitted orbital period of 2.02863 ± 0.00008 hours, or 121.718 ± 0.005 minutes is within 2-σ of the reported period of 121.73 minutes in Beuermann et al (2013).…”

Section: Day-night Contrast and Mid-eclipse Timementioning

confidence: 66%

Mapping the pressure-dependent day-night temperature contrast of a strongly irradiated atmosphere with HST spectroscopic phase curve

Lew,

Apai,

Zhou

et al. 2021

Preprint

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Many brown dwarfs are on ultra-short period and tidally-locked orbits around white dwarf hosts. Because of these small orbital separations, the brown dwarfs are irradiated at levels similar to hot Jupiters. Yet, they are easier to observe than hot Jupiters because white dwarfs are fainter than main-sequence stars at near-infrared wavelengths. Irradiated brown dwarfs are, therefore, ideal hot Jupiter analogs for studying the atmospheric response under strong irradiation and fast rotation. We present the 1.1-1.67 µm spectroscopic phase curve of the irradiated brown dwarf (SDSS1411-B) in the SDSS J141126.20+200911.1 brown-dwarf white-dwarf binary with the near-infrared G141 grism of Hubble Space Telescope Wide Field Camera 3. SDSS1411-B is a 50M Jup brown dwarf with an irradiation temperature of 1300K and has an orbital period of 2.02864 hours. Our best-fit model suggests a phase-curve amplitude of 1.4% and places an upper limit of 11 degrees for the phase offset from the secondary eclipse. After fitting the white-dwarf spectrum, we extract the phase-resolved brown-dwarf emission spectra. We report a highly wavelength-dependent day-night spectral variation, with the water-band flux variation of about 360 ± 70% and a comparatively small J-band flux variation of 37 ± 2%. By combining the atmospheric modeling results and the day-night brightness-temperature variations, we derive a pressure-dependent temperature contrast. We discuss the difference in the spectral features of SDSS1411-B and hot Jupiter WASP-43b, and the lower-than-predicted day-night temperature contrast of J4111-BD. Our study provides the high-precision observational constraints on the atmospheric structures of an irradiated brown dwarf at different orbital phases.

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Section: Day-night Contrast and Mid-eclipse Timementioning

confidence: 66%

Mapping the pressure-dependent day-night temperature contrast of a strongly irradiated atmosphere with HST spectroscopic phase curve

Lew,

Apai,

Zhou

et al. 2021

Preprint

View full text Add to dashboard Cite

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“…However given the long period of the system, and the high mass of the brown dwarf, we determine it to be unlikely that these effects would transfer enough heat into the brown dwarf to inflate it. Casewell et al (2020) consider the white-dwarf brown-dwarf binary NLTT5036, which also shows signs of inflation. They show that regardless of the level or irradiation experienced, low mass brown-dwarfs (M<35M Jup ) are able to be inflated when heated by their host star.…”

Section: Inflated Brown Dwarf Radiimentioning

confidence: 99%

“…However with so few transiting brown dwarfs yet discovered, whether this relationship continues into the substellar regime is unclear. It has been suggested that brown dwarfs may be able to be inflated if they orbit host stars that are particularly active (Casewell et al 2020). A comparison with evolutionary models would suggest that high mass brown dwarfs are much less likely to be inflated, regardless of the effect of their host star.…”

Section: Introductionmentioning

confidence: 99%

NGTS-19b : A high mass transiting brown dwarf in a 17-day eccentric orbit

Acton,

Goad,

Burleigh

et al. 2021

Preprint

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We present the discovery of NGTS-19b a high mass transiting brown dwarf discovered by the Next Generation Transit Survey (NGTS). We investigate the system using follow up photometry from the South African Astronomical Observatory, as well as sector 11 TESS data, in combination with radial velocity measurements from the CORALIE spectrograph to precisely characterise the system. We find that NGTS-19b is a brown dwarf companion to a Kstar, with a mass of 69.5 +5.7 −5.4 M Jup and radius of 1.034 +0.055 −0.053 R Jup . The system has a reasonably long period of 17.84 days, and a high degree of eccentricity of 0.3767 +0.0061 −0.0061 . The mass and radius of the brown dwarf imply an age of 0.46 +0.26 −0.15 Gyr, however this is inconsistent with the age determined from the host star SED, suggesting that the brown dwarf may be inflated. This is unusual given that its large mass and relatively low levels of irradiation would make it much harder to inflate. NGTS-19b adds to the small, but growing number of brown dwarfs transiting main sequence stars, and is a valuable addition as we begin to populate the so called brown dwarf desert.

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“…While NLTT 5306 B does not fill its Roche lobe, near-IR spectra from SpeX on the NASAInfraRed Telescope Facility have shown evidence of intermediate gravity, with ( ) g log 4.8, suggesting the brown dwarf is inflated (Casewell et al 2020a). In exoplanets, significant levels of UV irradiation onto a planet from its host can cause the planetary atmosphere to inflate and evaporate (e.g., Demory & Seager 2011).…”

Section: Introductionmentioning

confidence: 99%

Near-infrared Spectra of the Inflated Post-common Envelope Brown Dwarf NLTT 5306 B

Buzard¹,

Casewell²,

Lothringer³

et al. 2022

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NLTT 5306 is a post-common envelope binary made up of a white dwarf host and brown dwarf companion that has shown evidence of inflation and active mass donation despite not filling its Roche lobe. Two proposed mechanisms for the brown dwarf’s inflation are magnetic interactions and a high-metallicity, cloudy atmosphere. We present moderate-resolution (R ≲ 2000) J-band Keck/NIRSPEC observations of this system. These phase-resolved data allow us to constrain differences between atmospheric parameters of the day- and nightside of the brown dwarf. Our day- and nightside effective temperature measurements are consistent, in agreement with the brightness temperatures measurements from Casewell et al. The dayside favors a slightly lower surface gravity, perhaps stemming from the material streaming between the two objects. Finally, our data show a preference for low-metallicity models. This would be expected from the system’s old age, but provides direct evidence that a high-metallicity, cloudy brown dwarf atmosphere is not responsible for the witnessed inflation. These results strengthen the case for magnetic interactions leading to inflation of NLTT 5306 B.

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NLTT5306B: an inflated, weakly irradiated brown dwarf

Cited by 23 publications

References 45 publications

Mapping the pressure-dependent day-night temperature contrast of a strongly irradiated atmosphere with HST spectroscopic phase curve

Mapping the pressure-dependent day-night temperature contrast of a strongly irradiated atmosphere with HST spectroscopic phase curve

NGTS-19b : A high mass transiting brown dwarf in a 17-day eccentric orbit

Near-infrared Spectra of the Inflated Post-common Envelope Brown Dwarf NLTT 5306 B

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