Giant planets and brown dwarfs on wide orbits: a code comparison project

Fletcher, M.; Nayakshin, Sergei; Stamatellos, Dimitris; Dehnen, Walter; Meru, Farzana; Mayer, Lucio; Deng, Hongping; Rice, Ken

doi:10.1093/mnras/stz1123

Cited by 23 publications

(23 citation statements)

References 102 publications

(228 reference statements)

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“…The top panel of Figure 5 charts the orbital distance between the star and the dust only sink particle for several simulations with a variety of initial dust to gas ratios and feedback timescales. In all cases, the planet migrates inwards rapidly in the type I regime as expected from previous simulations (Baruteau et al 2011;Nayakshin 2017b) and begins to open a gap since it is relatively massive (Malik et al 2015;Fletcher et al 2019). The upper middle panel shows the mass inside the half Hill sphere of the protoplanet.…”

Section: Feedback From Dust Protocoressupporting

confidence: 67%

“…It is now widely believed that the gaps in the ∼ 1 mm dust discs observed by the Atacama Large Millimeter Array (ALMA) are the signatures of young planets (ALMA Partnership et al 2015;Isella et al 2016;Long et al 2018;Andrews et al 2018;Zhang et al 2018). Modelling suggests that these planets are often wide-orbit Saturn analogues (Dipierro et al 2016;Clarke et al 2018;Lodato et al 2019). Such planets present a challenge for both of the primary planet formation theories, albeit for different reasons.…”

Section: Introductionmentioning

confidence: 99%

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On the origin of wide-orbit ALMA planets: giant protoplanets disrupted by their cores

Humphries

Nayakshin

2019

Monthly Notices of the Royal Astronomical Society

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Recent ALMA observations may indicate a surprising abundance of sub-Jovian planets on very wide orbits in protoplanetary discs that are only a few million years old. These planets are too young and distant to have been formed via the Core Accretion (CA) scenario, and are much less massive than the gas clumps born in the classical Gravitational Instability (GI) theory. It was recently suggested that such planets may form by the partial destruction of GI protoplanets: energy output due to the growth of a massive core may unbind all or most of the surrounding pre-collapse protoplanet.Here we present the first 3D global disc simulations that simultaneously resolve grain dynamics in the disc and within the protoplanet. We confirm that massive GI protoplanets may self-destruct at arbitrarily large separations from the host star provided that solid cores of mass ∼10-20 M ⊕ are able to grow inside them during their precollapse phase. In addition, we find that the heating force recently analysed by Masset & Velasco Romero (2017) perturbs these cores away from the centre of their gaseous protoplanets. This leads to very complicated dust dynamics in the protoplanet centre, potentially resulting in the formation of multiple cores, planetary satellites, and other debris such as planetesimals within the same protoplanet. A unique prediction of this planet formation scenario is the presence of sub-Jovian planets at wide orbits in Class 0/I protoplanetary discs.

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Section: Feedback From Dust Protocoressupporting

confidence: 67%

Section: Introductionmentioning

confidence: 99%

On the origin of wide-orbit ALMA planets: giant protoplanets disrupted by their cores

Humphries

Nayakshin

2019

Monthly Notices of the Royal Astronomical Society

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“…Protoplanets formed through disc instability have super-Jovian masses (2−5 M J ) and orbit at distances 10−100 AU. These protoplanet properties are expected to change due to interactions with the disc and with other protoplanets (Forgan & Rice 2013;Nayakshin 2017a,b;Hall et al 2017;Forgan et al 2018;Stamatellos & Inutsuka 2018;Fletcher et al 2019). Protoplanets may migrate inwards rapidly until they open up a gap (Stamatellos 2015;Stamatellos & Inutsuka 2018).…”

Section: Comparison With the Observed Properties Of Exoplanets Aroundmentioning

confidence: 99%

Planet formation around M dwarfs via disc instability

Mercer

Stamatellos

2020

A&A

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Context. Around 30 per cent of the observed exoplanets that orbit M dwarf stars are gas giants that are more massive than Jupiter. These planets are prime candidates for formation by disc instability. Aims. We want to determine the conditions for disc fragmentation around M dwarfs and the properties of the planets that are formed by disc instability. Methods. We performed hydrodynamic simulations of M dwarf protostellar discs in order to determine the minimum disc mass required for gravitational fragmentation to occur. Different stellar masses, disc radii, and metallicities were considered. The mass of each protostellar disc was steadily increased until the disc fragmented and a protoplanet was formed. Results. We find that a disc-to-star mass ratio between ~0.3 and ~0.6 is required for fragmentation to happen. The minimum mass at which a disc fragment increases with the stellar mass and the disc size. Metallicity does not significantly affect the minimum disc fragmentation mass but high metallicity may suppress fragmentation. Protoplanets form quickly (within a few thousand years) at distances around ~50 AU from the host star, and they are initially very hot; their centres have temperatures similar to the ones expected at the accretion shocks around planets formed by core accretion (up to 12 000 K). The final properties of these planets (e.g. mass and orbital radius) are determined through long-term disc-planet or planet–planet interactions. Conclusions. Disc instability is a plausible way to form gas giant planets around M dwarfs provided that discs have at least 30% the mass of their host stars during the initial stages of their formation. Future observations of massive M dwarf discs or planets around very young M dwarfs are required to establish the importance of disc instability for planet formation around low-mass stars.

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“…Given current uncertainties on the initial masses of fragments formed by gravitational instability and on their subsequent growth and migration (Kratter & Lodato 2016;Fletcher et al 2019), we evaluate the prospects for formation by disc instability using simple analytical prescriptions. We use the disc model of Ida et al (2016), where the disc structure is determined by the viscosity, α, and the mass flux through the disc,Ṁ disc .…”

Section: Appendix A: Additional Table and Figuresmentioning

confidence: 99%

Greening of the brown-dwarf desert

Persson

Csizmadia

Mustill

et al. 2019

A&A

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Context. Although more than 2000 brown dwarfs have been detected to date, mainly from direct imaging, their characterisation is difficult due to their faintness and model-dependent results. In the case of transiting brown dwarfs, however, it is possible to make direct high-precision observations. Aims. Our aim is to investigate the nature and formation of brown dwarfs by adding a new well-characterised object, in terms of its mass, radius and bulk density, to the currently small sample of less than 20 transiting brown dwarfs. Methods. One brown dwarf candidate was found by the KESPRINT consortium when searching for exoplanets in the K2 space mission Campaign 16 field. We combined the K2 photometric data with a series of multicolour photometric observations, imaging, and radial velocity measurements to rule out false positive scenarios and to determine the fundamental properties of the system. Results. We report the discovery and characterisation of a transiting brown dwarf in a 5.17-day eccentric orbit around the slightly evolved F7 V star EPIC 212036875. We find a stellar mass of 1.15 ± 0.08 M⊙, a stellar radius of 1.41 ± 0.05 R⊙, and an age of 5.1 ± 0.9 Gyr. The mass and radius of the companion brown dwarf are 51 ± 2 MJ and 0.83 ± 0.03 RJ, respectively, corresponding to a mean density of 108−13+15 g cm−3. Conclusions. EPIC 212036875 b is a rare object that resides in the brown-dwarf desert. In the mass-density diagram for planets, brown dwarfs, and stars, we find that all giant planets and brown dwarfs follow the same trend from ~0.3 MJ to the turn-over to hydrogen burning stars at ~ 73 MJ. EPIC 212036875 b falls close to the theoretical model for mature H/He dominated objects in this diagram as determined by interior structure models. We argue that EPIC 212036875 b formed via gravitational disc instabilities in the outer part of the disc, followed by a quick migration. Orbital tidal circularisation may have started early in its history for a brief period when the brown dwarf’s radius was larger. The lack of spin–orbit synchronisation points to a weak stellar dissipation parameter (Q⋆′ ≳ 108), which implies a circularisation timescale of ≳23 Gyr, or suggests an interaction between the magnetic and tidal forces of the star and the brown dwarf.

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Giant planets and brown dwarfs on wide orbits: a code comparison project

Cited by 23 publications

References 102 publications

On the origin of wide-orbit ALMA planets: giant protoplanets disrupted by their cores

On the origin of wide-orbit ALMA planets: giant protoplanets disrupted by their cores

Planet formation around M dwarfs via disc instability

Greening of the brown-dwarf desert

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