WISE J072003.20-084651.2B is a Massive T Dwarf<sup>∗</sup>
                  <sup>†</sup>

Dupuy, Trent J.; Liu, Mengmeng; Best, William M. J.; Mann, Andrew W.; Tucker, M. A.; Zhang, Zhoujian; Baraffe, I.; Chabrier, G.; Forveille, T.; Metchev, Stanimir; Tremblin, Pascal; Do, A.; Payne, A. V.; Shappee, B. J.; Bond, C.; Cetre, Sylvain; Chun, Mark; Delorme, Jacques-Robert; Jovanović, Nemanja; Lilley, Scott; Mawet, Dimitri; Ragland, Sam; Wetherell, Ed; Wizinowich, Peter

doi:10.3847/1538-3881/ab3cd1

Cited by 37 publications

(31 citation statements)

References 78 publications

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“…This measurement joins a growing list of massive T dwarfs that are challenging evolutionary models (e.g. Bowler et al (2018); Dieterich et al (2018); Dupuy et al (2019)). We note, however, that the dynamical mass measurement of Gl 229 B should be considered with caution until confirmed unambiguously (the paper is only on ArXiv for now) (R. Oppenheimer priv.…”

Section: Comparison With Dynamical Massesmentioning

confidence: 76%

A new set of atmosphere and evolution models for cool T–Y brown dwarfs and giant exoplanets

Phillips

Tremblin

Baraffe

et al. 2020

A&A

193

262

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We present a new set of solar metallicity atmosphere and evolutionary models for very cool brown dwarfs and self-luminous giant exoplanets, which we term ATMO 2020. Atmosphere models are generated with our state-of-the-art 1D radiative-convective equilibrium code ATMO, and are used as surface boundary conditions to calculate the interior structure and evolution of 0.001 − 0.075 M objects. Our models include several key improvements to the input physics used in previous models available in the literature. Most notably, the use of a new H-He equation of state including ab initio quantum molecular dynamics calculations has raised the mass by ∼ 1 − 2% at the stellar-substellar boundary and has altered the cooling tracks around the hydrogen and deuterium burning minimum masses. A second key improvement concerns updated molecular opacities in our atmosphere model ATMO, which now contains significantly more line transitions required to accurately capture the opacity in these hot atmospheres. This leads to warmer atmospheric temperature structures, further changing the cooling curves and predicted emission spectra of substellar objects. We present significant improvement for the treatment of the collisionally broadened potassium resonance doublet, and highlight the importance of these lines in shaping the red-optical and near-infrared spectrum of brown dwarfs. We generate three different grids of model simulations, one using equilibrium chemistry and two using non-equilibrium chemistry due to vertical mixing, all three computed self-consistently with the pressure-temperature structure of the atmosphere. We show the impact of vertical mixing on emission spectra and in colourmagnitude diagrams, highlighting how the 3.5 − 5.5 µm flux window can be used to calibrate vertical mixing in cool T-Y spectral type objects.

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Section: Comparison With Dynamical Massesmentioning

confidence: 76%

A new set of atmosphere and evolution models for cool T–Y brown dwarfs and giant exoplanets

Phillips

Tremblin

Baraffe

et al. 2020

A&A

193

262

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“…Currently, only one even closer flyby is known in the recent past, which is that of WISE J072003.20-084651.2 . This already mentioned UCD binary with lacking Gaia DR2 astrometry passed, according to the most recent results of Dupuy et al (2019), at a distance of 0.33 pc from the Sun just 80 000 years ago.…”

Section: Discussion and Outlookmentioning

confidence: 80%

“…The Gaia DR2 provided full astrometry of the M8.5 primary (with G≈14.0 mag) but no other object within an angular separation of 3.5 arcsec. A very similar system of a late-M dwarf with a close mid-T dwarf companion is WISE J072003.20-084651.2 (M9.5+T5.5 at 6.8 pc ;Scholz 2014;Burgasser et al 2015;Dupuy et al 2019). At the expected position of this system, Gaia DR2 contained only an unresolved source (G≈15.3 mag) lacking the parallax and proper motion.…”

Section: Discussion and Outlookmentioning

confidence: 90%

“…At the expected position of this system, Gaia DR2 contained only an unresolved source (G≈15.3 mag) lacking the parallax and proper motion. This binary had, according to Dupuy et al (2019), separations of the order of only 0.2 arcsec at the Gaia DR2 epochs. Some known WDs within 20 pc, including four within 10 pc, are missing from Gaia DR2, or are listed without parallax and proper motion measurements.…”

Section: Discussion and Outlookmentioning

confidence: 99%

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New ultracool dwarf neighbours within 20 pc fromGaiaDR2

Scholz

2020

A&A

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Aims. The Gaia data release 2 (DR2) contains >6000 objects with parallaxes (Plx + 3 × e_Plx) > 50 mas placing them within 20 pc from the Sun. Since the expected numbers extrapolating the well-known 10 pc census are much lower, nearby Gaia stars need a quality assessment. The 20 pc sample of white dwarfs (WDs) had already been verified and completed with Gaia DR2. We aimed to check and complete the 20 pc sample of ultracool dwarfs (UCDs) with spectral types M7 and given Gaia DR2 parallaxes. Methods. Dividing the Gaia DR2 20 pc sample into subsamples of various astrometric and photometric quality, we studied their distribution on the sky, in the M G vs. G−RP colour-magnitude diagram (CMD), and as a function of G magnitude and total proper motion. After excluding 139 known WDs and 263 known UCDs from the CMD, we checked all remaining ≈3500 candidates with M G > 14 mag (used to define UCDs in this study) for the correctness of their Gaia DR2 proper motions via visual inspection of finder charts, comparison with proper motion catalogues, and comparison with our own proper motion measurements. For confirmed UCD candidates we estimated spectral types photometrically using Gaia and near-infrared absolute magnitudes and colours. Results. We failed to confirm new WDs, but found 50 new UCD candidates not mentioned in three previous studies using Gaia DR2. They have relatively small proper motions and tangential velocities and are concentrated towards the Galactic plane. Half of them have spectral types in SIMBAD and/or previous non-Gaia distance estimates that placed them already within 20 pc. For 20 of the 50 objects, we estimated photometric spectral types of M6-M6.5, slightly below the classical UCD spectral type limit. However, seven L4.5-L6.5, four L0-L1, five M8.5-M9.5, and three M7-M8 dwarfs can be considered as completely new UCDs discoveries within 20 pc based on Gaia DR2. Four M6.5 and two L4.5 dwarfs have high membership probabilities (64%-99%) in the ARGUS, AB Doradus, or Carina Near young moving groups.

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“…To better understand the role that gravity plays in the L/T transition, a large sample of benchmarks spanning a wide range in surface gravities (or equivalently ages) is essential. Since the most recent large photometric analyses (e.g., Faherty et al 2016;Liu et al 2016), the census of planetary and substellar benchmarks has been expanded, as (1) new young moving group members and companions to stars or white dwarfs have been discovered, whose ages can be determined from their host associations or primary stars (e.g., COCONUTS-1 in this work; Bowler et al 2017;Deacon et al 2017;Gagné et al 2017Gagné et al , 2018Gauza et al 2019), and (2) more substellar binaries and companions have measured dynamical masses thanks to ongoing astrometric monitoring programs (e.g., Dupuy & Liu 2017;Dupuy et al 2019). In addition, the current census of benchmarks can now have very precise absolute magnitudes and physical properties (e.g., bolometric luminosities and effective temperatures), as a result of the high-precision parallaxes from Gaia DR2 (Gaia Collaboration et al 2016).…”

Section: The Surface-gravity Dependence Of the L/t Transitionmentioning

confidence: 99%

COol Companions ON Ultrawide orbiTS (COCONUTS). I. A High-gravity T4 Benchmark around an Old White Dwarf and a Re-examination of the Surface-gravity Dependence of the L/T Transition

Zhang

Liu

Hermes

et al. 2020

ApJ

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We present the first discovery from the COol Companions ON Ultrawide orbiTS (COCONUTS) program, a large-scale survey for wide-orbit planetary and substellar companions. We have discovered a co-moving system COCONUTS-1, composed of a hydrogen-dominated white dwarf (PSO J058.9855 + 45.4184; d = 31.5 pc) and a T4 companion (PSO J058.9869 + 45.4296) at a 40.6 (1280 au) projected separation. We derive physical properties for COCONUTS-1B from (1) its near-infrared spectrum using cloudless Sonora atmospheric models, and (2) its luminosity and the white dwarf's age (7.3 +2.8 −1.6 Gyr) using Sonora evolutionary models. The two methods give consistent temperatures and radii, but atmospheric models infer a lower surface gravity and therefore an unphysically young age. Assuming evolutionary model parameters (T eff = 1255 +6 −8 K, log g = 5.44 +0.02 −0.03 dex, R = 0.789 +0.011 −0.005 R Jup ), we find cloudless model atmospheres have brighter Y -and J-band fluxes than the data, suggesting condensate clouds have not fully dispersed around 1300 K. The W2 flux (4.6 µm) of COCONUTS-1B is fainter than models, suggesting non-equilibrium mixing of CO. To investigate the gravity dependence of the L/T transition, we compile all 60 known L6−T6 benchmarks and derive a homogeneous set of temperatures, surface gravities, and masses. As is wellknown, young, low-gravity late-L dwarfs have significantly fainter, redder near-infrared photometry and ≈ 200 − 300 K cooler temperatures than old, high-gravity objects. Our sample now reveals such gravity dependence becomes weaker for T dwarfs, with young objects having comparable near-infrared photometry and ≈ 100 K cooler temperatures compared to old objects. Finally, we find that young objects have a larger amplitude J-band brightening than old objects, and also brighten at H band as they cross the L/T transition.

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WISE J072003.20-084651.2B is a Massive T Dwarf^∗ ^†

Cited by 37 publications

References 78 publications

A new set of atmosphere and evolution models for cool T–Y brown dwarfs and giant exoplanets

A new set of atmosphere and evolution models for cool T–Y brown dwarfs and giant exoplanets

New ultracool dwarf neighbours within 20 pc fromGaiaDR2

COol Companions ON Ultrawide orbiTS (COCONUTS). I. A High-gravity T4 Benchmark around an Old White Dwarf and a Re-examination of the Surface-gravity Dependence of the L/T Transition

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WISE J072003.20-084651.2B is a Massive T Dwarf∗ †

Cited by 37 publications

References 78 publications

A new set of atmosphere and evolution models for cool T–Y brown dwarfs and giant exoplanets

A new set of atmosphere and evolution models for cool T–Y brown dwarfs and giant exoplanets

New ultracool dwarf neighbours within 20 pc fromGaiaDR2

COol Companions ON Ultrawide orbiTS (COCONUTS). I. A High-gravity T4 Benchmark around an Old White Dwarf and a Re-examination of the Surface-gravity Dependence of the L/T Transition

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WISE J072003.20-084651.2B is a Massive T Dwarf^∗ ^†