Formation of intermediate-mass planets via magnetically controlled disk fragmentation

Deng, Hongping; Mayer, Lucio; Helled, Ravit

doi:10.1038/s41550-020-01297-6

Cited by 29 publications

(33 citation statements)

References 35 publications

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“…The grand-design spirals in galaxies and some circumstellar disks are believed to be global spiral density waves. Spirals can further regulate the formation of stars in galaxies (Roberts 1969) and collapse to form planets in circumstellar disks (see, e.g., Durisen et al 2007;Deng et al 2021). In this Letter, we study the development of spiral structures through the gravitational instability (GI) of a massive gaseous disk orbiting in a central potential.…”

Section: Introductionmentioning

confidence: 95%

Standing Solitary Waves as Transitions to Spiral Structures in Gravitationally Unstable Accretion Disks

Deng¹,

Ogilvie²

2022

ApJL

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Astrophysical disks that are sufficiently cold and dense are linearly unstable to the formation of axisymmetric rings as a result of the disk’s gravity. In practice, spiral structures are formed, which may in turn produce bound fragments. We study a nonlinear dynamical path that can explain the development of spirals in a local model of a gaseous disk on the subcritical side of the gravitational instability bifurcation. Axisymmetric equilibria can be radially periodic or localized, in the form of standing solitary waves. The solitary solutions have energy slightly larger than a smooth disk. They are further unstable to nonaxisymmetric perturbations with a wide range of azimuthal wavenumbers. The solitary waves may act as a pathway to spirals and fragmentation.

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Section: Introductionmentioning

confidence: 95%

Standing Solitary Waves as Transitions to Spiral Structures in Gravitationally Unstable Accretion Disks

Deng¹,

Ogilvie²

2022

ApJL

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“…Yet several simulations find that clumps form at systematically smaller sizes, even differing by an order of magnitude from the predictions of perturbation theory (e.g. Boley et al 2010;Galvagni et al 2012;Galvagni & Mayer 2014;Müller et al 2018;Deng et al 2021;Forgan & Rice 2011). Differences arise due to finite disc thickness, departure from axisymmetry, and nonlinear effects in the gas flow dynamics immediately prior to fragmentation.…”

Section: Astrophysical Rationalementioning

confidence: 94%

In-situ extreme mass ratio inspirals via sub-parsec formation and migration of stars in thin, gravitationally unstable AGN discs

Derdzinski¹,

Mayer²

2022

Preprint

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We investigate the properties of stars born via gravitational instability in accretion discs around supermassive black holes (SMBHs) in active galactic nuclei (AGN), and how this varies with the SMBH mass, accretion rate, or viscosity. We show with geometrically thin, steady-state disc solutions that fragmentation results in different populations of stars when one considers the initial conditions (e.g. densities and temperature of the gravitationally unstable regions). We find that opacity gaps in discs around 10 6 M SMBHs can trigger fragmentation at radii 10 −2 pc, although the conditions lead to the formation of initially low stellar masses primarily at 0.1 − 0.5M . Discs around more massive SMBHs (𝑀 BH = 10 7−8 M ) form moderately massive or supermassive stars (the majority at 10 0−2 M ). Using linear migration estimates, we discuss three outcomes: stars migrate till they are tidally destroyed, accreted as extreme mass ratio inspirals (EMRIs), or leftover after disc dispersal. For a single AGN activity cycle, we find a lower-limit for the EMRI rate 𝑅 emri ∼ 0 − 10 −4 yr −1 per AGN assuming a SF efficiency of 𝜖 = 1%. In cases where EMRIs occur, this implies a volumetric rate up to 0.5 − 10yr −1 Gpc −3 in the local Universe. The rates are particularly sensitive to model parameters for 𝑀 BH = 10 6 M , for which EMRIs only occur if stars can accrete to 10s of solar masses. Our results provide further evidence that gas-embedded EMRIs can contribute a substantial fraction of events detectable by milliHz gravitational wave detectors such as LISA. Our disc solutions suggest the presence of migration traps, as has been found for more massive SMBH discs. Finally, the surviving population of stars after the disc lifetime leaves implications for stellar disc populations in galactic nuclei.

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“…This is at odds with the low density of WASP-193 b. Alternatively, the planet could have formed by disk instability, as it was recently shown by ref. 29 that magnetically controlled disk fragmentation could lead to intermediate-mass clumps of H-He. The formation mechanism of planets like WASP-193 b remains uncertain, including its potential orbital evolution and we hope that future formation models can address its formation mechanism.…”

Section: Planet Interiormentioning

confidence: 99%

WASP-193b: An extremely low-density super-Neptune

Barkaoui

Pozuelos

Hellier

et al. 2022

Preprint

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Gas giants transiting bright nearby stars are key objects for our understanding of planetary system formation and evolution mechanisms. This paper presents a new transiting exoplanet discovered by the WASP-South transit survey, WASP-193b. WASP-193b orbits its Vmag = 12.0 F9 main-sequence host star every 6.25d. Our analyses found that WASP-193b has a mass of Mp = 0.146 ± 0.033 M_Jup, a radius of R_p = 1.58 ± 0.14R_Jup, translating into an extremely low density of rho_p = 0.049 ± 0.015g/cm3. The planet was confirmed photometrically by the 0.6-m TRAPPIST-South and 1.0-m SPECULOOS-South telescopes and spectroscopically by the ESO-3.6-m/HARPS and Euler-1.2-m/CORALIE spectrographs. The combination of its large transit depth (dF≈1.4%), its super-low density, its high-equilibrium temperature (T_eq = 1275 ± 40K), and the infrared brightness of its host star (magnitude Kmag=10.7) makes WASP-193b an exquisite target for a detailed atmospheric characterization by transmission spectroscopy.

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Formation of intermediate-mass planets via magnetically controlled disk fragmentation

Cited by 29 publications

References 35 publications

Standing Solitary Waves as Transitions to Spiral Structures in Gravitationally Unstable Accretion Disks

Standing Solitary Waves as Transitions to Spiral Structures in Gravitationally Unstable Accretion Disks

In-situ extreme mass ratio inspirals via sub-parsec formation and migration of stars in thin, gravitationally unstable AGN discs

WASP-193b: An extremely low-density super-Neptune

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