The Fate of Close-in Planets: Tidal or Magnetic Migration?

Strugarek, Antoine; Bolmont, Émeline; Mathis, S.; Brun, Allan Sacha; Réville, Victor; Gallet, F.; Charbonnel, C.

doi:10.3847/2041-8213/aa8d70

Cited by 72 publications

(62 citation statements)

References 50 publications

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“…7. This could have interesting consequences for the innermost Trappist-1 planets, as to whether there is another unseen planet, with a high inclination, or whether there was another planet at the formation of the system, but has since disappeared as the system has evolved over time, possibly due to tidal or magnetic migration (Strugarek et al 2017). It is also interesting to note that we find a number of co-orbitals in both the pebble and planetesimal accretion scenarios, with approximately 2.2% and 2.6% of the planet pairs with periods less than 20 days.…”

Section: Mean Motion Resonancesmentioning

confidence: 99%

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Pebbles versus planetesimals: the case of Trappist-1

Coleman

Leleu

Alibert

et al. 2019

A&A

107

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We present a study into the formation of planetary systems around low mass stars similar to Trappist-1, through the accretion of either planetesimals or pebbles. The aim is to determine if the currently observed systems around low mass stars could favour one scenario over the other. To determine these differences, we ran numerous N-body simulations, coupled to a thermally evolving viscous 1D disc model, and including prescriptions for planet migration, photoevaporation, and pebble and planetesimal dynamics. We mainly examine the differences between the pebble and planetesimal accretion scenarios, but we also look at the influences of disc mass, size of planetesimals, and the percentage of solids locked up within pebbles. When comparing the resulting planetary systems to Trappist-1, we find that a wide range of initial conditions for both the pebble and planetesimal accretion scenarios can form planetary systems similar to Trappist-1, in terms of planet mass, periods, and resonant configurations. Typically these planets formed exterior to the water iceline and migrated in resonant convoys into the inner region close to the central star. When comparing the planetary systems formed through pebble accretion to those formed through planetesimal accretion, we find a large number of similarities, including average planet masses, eccentricities, inclinations and period ratios. One major difference between the two scenarios was that of the water content of the planets. When including the effects of ablation and full recycling of the planets' envelope with the disc, the planets formed through pebble accretion were extremely dry, whilst those formed through planetesimal accretion were extremely wet. If the water content is not fully recycled and instead falls to the planets' core, or if ablation of the water is neglected, then the planets formed through pebble accretion are extremely wet, similar to those formed through planetesimal accretion. Should the water content of the Trappist-1 planets be determined accurately, this could point to a preferred formation pathway for planetary systems, or to specific physics that may be at play.

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Section: Mean Motion Resonancesmentioning

confidence: 99%

“…Hence, it is unsurprising that the Trappist-1 planets are also found to be in three-body resonance. These resonant chains can be modified over time through tidal evolution, which can affect their stability and two-body appearance (Strugarek et al 2017;Papaloizou et al 2018).…”

Section: Mean Motion Resonancesmentioning

confidence: 99%

Pebbles versus planetesimals: the case of Trappist-1

Coleman

Leleu

Alibert

et al. 2019

A&A

107

View full text Add to dashboard Cite

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“…Planets on short-period orbit are expected to interact strongly with their host star (Cuntz et al 2000) due to the strong irradiation they receive (Yelle et al 2008;Trammell et al 2014;Matsakos et al 2015;Bourrier et al 2016;Daley-Yates & Stevens 2018), the strong tidal forces they experience (Mathis 2017;Bolmont et al 2017;Strugarek et al 2017b), and the strong interplanetary magnetic field they orbit in (see Lanza 2010;Cohen et al 2011;Strugarek 2016, 2017b, andreferences therein). Such close-in planets will generally orbit in the sub-alfvénic region of the accelerating wind of their star.…”

Section: Introductionmentioning

confidence: 99%

Chasing Star–Planet Magnetic Interactions: The Case of Kepler-78

Strugarek

Brun

Donati

et al. 2019

ApJ

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Observational evidence of star-planet magnetic interactions (SPMI) in compact exo-systems have been looked for in the past decades. Indeed planets in close-in orbit can be magnetically connected to their host star, and channel Alfvén waves carrying large amounts of energy towards the central star. The strength and temporal modulation of SPMIs are primarily set by the magnetic topology of the host star and the orbital characteristics of the planet. As a result, SPMI signals can be modulated over the rotational period of the star, the orbital period of the planet, or a complex combination of the two. The detection of SPMI thus have to rely on multiple-epochs and multiple-wavelengths observational campaigns. We present a new method to characterize SPMIs and apply it to Kepler-78, a late G star with a super-Earth on an 8.5 hours orbit. We model the corona of Kepler-78 using the large-scale magnetic topology of the star observed with Zeeman-Doppler-Imaging. We show that the closeness of Kepler-78b allows the interaction to channel energy flux densities up to a few kW m −2 towards the central star. We show that this flux is large enough to be detectable in classical activity tracers such as Hα. It is nonetheless too weak to explain the modulation observed by Moutou et al. (2016). We furthermore demonstrate how to predict the temporal modulation of SPMI signals in observed systems such as Kepler-78. The methodology presented here thus paves the road towards denser, specific observational campaigns that would allow a proper identification of SPMIs in compact star-planet systems.

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“…The set of equations we used to obtain our results may also be applied to other planetary systems where a unipolar inductor circuit has been established between a star and a solid planet that can both be characterised with Maxwell rheologies. Our model can thus help characterise planetary systems which do not fall under the remit of the few other investigations which have so far considered the interplay between gravitational tides and magnetic torques (Bouvier & Cébron 2015;Strugarek et al 2017). These studies focused on protostars and hot Jupiters, T-Tauri stars and hot Jupiters, K stars and hot Jupiters, and M-dwarfs and Earths.…”

Section: Applicability To Other Planetary Systemsmentioning

confidence: 99%

Survivability of radio-loud planetary cores orbiting white dwarfs

Veras

Wolszczan

2019

Monthly Notices of the Royal Astronomical Society

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The discovery of the intact metallic planetary core fragment orbiting the white dwarf SDSS J1228+1040 within one Solar radius highlights the possibility of detecting larger, unfragmented conducting cores around magnetic white dwarfs through radio emission. Previous models of this decades-old idea focussed on determining survivability of the cores based on their inward Lorentz drift towards the star. However, gravitational tides may represent an equal or dominant force. Here, we couple both effects by assuming a Maxwell rheological model and performing simulations over the entire range of observable white dwarf magnetic field strengths (10 3 -10 9 G) and their potential atmospheric electrical conductivities (10 −1 -10 4 S/m) in order to more accurately constrain survivability lifetimes. This force coupling allows us to better pinpoint the physical and orbital parameters which allow planetary cores to survive for over a Gyr, maximizing the possibility that they can be detected. The most robust survivors showcase high dynamic viscosities ( 10 24 Pa·s) and orbit within kG-level magnetic fields.

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The Fate of Close-in Planets: Tidal or Magnetic Migration?

Cited by 72 publications

References 50 publications

Pebbles versus planetesimals: the case of Trappist-1

Pebbles versus planetesimals: the case of Trappist-1

Chasing Star–Planet Magnetic Interactions: The Case of Kepler-78

Survivability of radio-loud planetary cores orbiting white dwarfs

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