Possible Signatures of Magnetospheric Accretion onto Young Giant Planets

Abstract

Magnetospheric accretion is an important process for a wide range of astrophysical systems, and may play a role in the formation of gas giant planets. Extending the formalism describing stellar magnetospheric accretion into the planetary regime, we demonstrate that magnetospheric processes may govern accretion onto young gas giants in the isolation phase of their development. Planets in the isolation phase have cleared out large gaps in their surrounding circumstellar disks, and settled into a quasi-static equilibrium with radii only modestly larger than their final sizes (i.e., $r\sim 1.4r_{\mathrm{final}}$). Magnetospheric accretion is less likely to play a role in a young gas giant's main accretion phase, when the planet's envelope is predicted to be much larger than the planet's Alfvén radius. For a fiducial 1 M${}_J$ gas giant planet with a remnant isolation phase accretion rate of ${\dot{M}}_{\odot }=$ 10${}^{-10}{M}_{\odot }{\mathrm{yr}}^{-1}=10^{-7}{M}_J{\mathrm{yr}}^{-1}$, the disk accretion will be truncated at $\sim 2.7r_J$ (with $r_J$ is Jupiter's radius) and drive the planet to rotate with a period of $\sim$7 hours. Thermal emission from planetary magnetospheric accretion will be difficult to observe; the most promising observational signatures may be non-thermal, such as gyrosynchrotron radiation that is clearly modulated at a period much shorter than the rotation period of the host star.

6 pages, 4 figures

References in corpus (9)

• On the Luminosity of Young Jupiters
• Spin-orbit angle measurements for six southern transiting planets; New insights into the dynamical origins of hot Jupiters
• UV excess measures of accretion onto young very low-mass stars and brown dwarfs
• On the formation of H-alpha line emission around classical T Tauri stars
• VLBA determination of the distance to nearby star-forming regions I. The distance to T Tauri with 0.4% accuracy
• Gas accretion onto planetary cores: three-dimensional self-gravitating radiation hydrodynamical calculations
• Type I Planet Migration in Nearly Laminar Disks
• Core Formation in Giant Gaseous Protoplanets
• X-Ray flares in Orion Young Stars. II. Flares, Magnetospheres, and Protoplanetary Disks

Cited by in corpus (22)

• Accreting Circumplanetary Disks: Observational Signatures
• Luminosity of young Jupiters revisited. Massive cores make hot planets
• Evolution of Gas Giant Entropy During Formation by Runaway Accretion
• The Planetary Accretion Shock: I. Framework for Radiation-hydrodynamical Simulations and First Results
• Shock-driven Accretion in Circumplanetary Disks: Observables and Satellite Formation
• Comparison of planetary Hα-emission models: A new correlation with accretion luminosity
• The Galilean Satellites Formed Slowly from Pebbles
• Accretion in giant planet circumplanetary disks
• Accreting protoplanets: Spectral signatures and magnitude of gas and dust extinction at H alpha
• Magnetic Coupling in the Disks Around Young Gas Giant Planets
• Tilting Ice Giants with a Spin-Orbit Resonance
• Characterizing the protolunar disk of the accreting companion GQ Lupi B
• Disk-fed giant planet formation
• A "Rosetta Stone" for protoplanetary disks: The synergy of multi-wavelength observations
• Searching for H${}_{\alpha }$-emitting sources in the gaps of five transitional disks. SPHERE/ZIMPOL high-contrast imaging
• The protoplanetary system HD 100546 in H$\alpha$ polarized light from SPHERE/ZIMPOL. A bar-like structure across the disk gap?
• The Planetary Accretion Shock. III. Smoothing-free 2.5D simulations and calculation of H alpha emission
• Tilting Uranus via the migration of an ancient satellite
• On the Terminal Spins of Accreting Stars and Planets: Boundary Layers
• A faint companion around CrA-9: protoplanet or obscured binary?
• High signal-to-noise spectral characterization of the planetary-mass object HD 106906 b
• Semianalytical Accretion-Tracer Emission: Forming Planets Are Intrinsically Faint