Evidence of an Upper Bound on the Masses of Planets and Its Implications for Giant Planet Formation

Schlaufman, Kevin C.

doi:10.3847/1538-4357/aa961c

Cited by 149 publications

(138 citation statements)

References 222 publications

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“…Previous studies have also searched for evidence of a correlation between planet occurrence rate and stellar metallicity in order to distinguish between core accretion and other formation mechanisms. There is compelling evidence to suggest that relatively close-in (<10 AU) and low-mass (<10 M Jup ) gas giant planets likely form via core accretion, as they are preferentially found around more metal-rich stars (Fischer & Valenti 2005;Schlaufman 2018). This metallicity correlation disappears for transiting planets larger than ∼8 M Jup , indicating that more massive companions may form via an alternative mechanism, most likely gravitational instability (Schlaufman 2018).…”

Section: Introductionmentioning

confidence: 99%

A Rotation Rate for the Planetary-mass Companion DH Tau b

Xuan

Bryan

Knutson

et al. 2020

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DH Tau b is a young planetary-mass companion orbiting at a projected separation of 320 AU from its ∼2 Myr old host star DH Tau. With an estimated mass of 8 − 22 M Jup this object straddles the deuterium-burning limit, and might have formed via core or pebble accretion, disk instability, or molecular cloud fragmentation. To shed light on the formation history of DH Tau b, we obtain the first measurement of rotational line broadening for this object using high-resolution (R ∼25,000) near-infrared spectroscopy from Keck/NIRSPEC. We measure a projected rotational velocity (vsini) of 9.6 ± 0.7 km/s, corresponding to a rotation rate that is between 9-15% of DH Tau b's predicted break-up speed. This low rotation rate is in good agreement with scenarios in which magnetic coupling between the companion and its circumplanetary disk during the late stages of accretion reduces angular momentum and regulates spin. We compare the rotation rate of DH Tau b to published values for other planetary-mass objects with masses between 0.3 − 20 M Jup and find no evidence of a correlation between mass and rotation rate in this mass regime. Finally, we search for evidence of individual molecules in DH Tau b's spectrum and find that it is dominated by CO and H 2 O, with no evidence for the presence of CH 4 . This agrees with expectations given DH Tau b's relatively high effective temperature (∼2300 K).

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Section: Introductionmentioning

confidence: 99%

A Rotation Rate for the Planetary-mass Companion DH Tau b

Xuan

Bryan

Knutson

et al. 2020

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“…The Spitzer data are taken from Kirkpatrick et al (2019); Leggett et al (2017); Martin et al (2018) and references therein, the trigonometric parallaxes are taken from Kirkpatrick et al (2019); Leggett et al (2017); Martin et al (2018); Smart et al (2018); Theissen (2018) and references therein. In addition, for this work, we determined W1 magnitudes from images downloaded from the unWISE database 2 (Schlafly et al 2019) for four Y dwarfs, WISE J033605.05-014350.4 with W 1 = 18.20 ± 0.10, WISEA J035000.31-565830.5 with W 1 = 18.3 ± 0.2, WISE J064723.23-623235.5 with W 1 = 18.8 ± 0.2, and WISEA J235402.79+024014.1 with W 1 = 18.1 ± 0.3. Figures 11 and 12 are color-magnitude diagrams for the 4 µm and 5 µm filters.…”

Section: Resultsmentioning

confidence: 99%

3.8 μm Imaging of 400–600 K Brown Dwarfs and Orbital Constraints for WISEP J045853.90+643452.6AB

Leggett

Dupuy

Morley

et al. 2019

ApJ

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Half of the energy emitted by late-T-and Y-type brown dwarfs emerges at 3.5 ≤ λ µm ≤ 5.5. We present new L (3.43 ≤ λ µm ≤ 4.11) photometry obtained at the Gemini North telescope for nine late-T and Y dwarfs, and synthesize L from spectra for an additional two dwarfs. The targets include two binary systems which were imaged at a resolution of 0. 25. One of these, WISEP J045853.90+643452.6AB, shows significant motion, and we present an astrometric analysis of the binary using Hubble Space Telescope, Keck Adaptive Optics, and Gemini images. We compare λ ∼ 4 µm observations to models, and find that the model fluxes are too low for brown dwarfs cooler than ∼700 K. The discrepancy increases with decreasing temperature, and is a factor of ∼2 at T eff = 500 K and ∼4 at T eff = 400 K. Warming the upper layers of a model atmosphere generates a spectrum closer to what is observed. The thermal structure of cool brown dwarf atmospheres above the radiative-convective boundary may not be adequately modelled using pure radiative equilibrium; instead heat may be introduced by thermochemical instabilities (previously suggested for the L-to Ttype transition) or by breaking gravity waves (previously suggested for the solar system giant planets). One-dimensional models may not capture these atmospheres, which likely have both horizontal and vertical pressure/temperature variations.

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“…We also compared our results to observations: DI constraints on the frequency of wide orbit companions (Vigan et al 2017), RV constraints on gas giants inside 5 AU (Cumming et al 2008), and correlations with host metallicity from Fischer & Valenti (2005), Santos et al (2017) and Schlaufman (2018). To assess the implications of these constraints we tested two extreme models for gap opening that we named quenched and super migration.…”

Section: Discussionmentioning

confidence: 95%

Constraining the initial planetary population in the gravitational instability model

Humphries

Vazan

Bonavita

et al. 2019

Monthly Notices of the Royal Astronomical Society

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Direct imaging (DI) surveys suggest that gas giants beyond 20 AU are rare around FGK stars. However, it is not clear what this means for the formation frequency of Gravitational Instability (GI) protoplanets due to uncertainties in gap opening and migration efficiency. Here we combine state-of-the-art calculations of homogeneous planet contraction with a population synthesis code. We find DI constraints to be satisfied if protoplanet formation by GI occurs in tens of percent of systems if protoplanets 'super migrate' to small separations. In contrast, GI may occur in only a few percent of systems if protoplanets remain stranded at wide orbits because their migration is 'quenched' by efficient gap opening. We then use the frequency of massive giants in radial velocity surveys inside 5 AU to break this degeneracy -observations recently showed that this population does not correlate with the host star metallicity and is therefore suspected to have formed via GI followed by inward migration. We find that only the super-migration scenario can sufficiently explain this population whilst simultaneously satisfying the DI constraints and producing the right mass spectrum of planets inside 5 AU. If massive gas-giants inside 5 AU formed via GI, then our models imply that migration must be efficient and that the formation of GI protoplanets occurs in at least a tens of percent of systems.

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Evidence of an Upper Bound on the Masses of Planets and Its Implications for Giant Planet Formation

Cited by 149 publications

References 222 publications

A Rotation Rate for the Planetary-mass Companion DH Tau b

A Rotation Rate for the Planetary-mass Companion DH Tau b

3.8 μm Imaging of 400–600 K Brown Dwarfs and Orbital Constraints for WISEP J045853.90+643452.6AB

Constraining the initial planetary population in the gravitational instability model

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