EXor outbursts from disk amplification of stellar magnetic cycles

Abstract

EXor outbursts - moderate-amplitude disk accretion events observed in Class I and Class II protostellar sources - have time scales and amplitudes that are consistent with the viscous accumulation and release of gas in the inner disk near the dead zone boundary. We suggest that outbursts are indirectly triggered by stellar dynamo cycles, via poloidal magnetic flux that diffuses radially outward through the disk. Interior to the dead zone the strength of the net field modulates the efficiency of angular momentum transport by the magnetorotational instability. In the dead zone changes in the polarity of the net field may lead to stronger outbursts because of the dominant role of the Hall effect in this region of the disk. At the level of simple estimates we show that changes to kG-strength stellar fields could stimulate disk outbursts on 0.1 AU scales, though this optimistic conclusion depends upon the uncertain efficiency of net flux transport through the inner disk. The model predicts a close association between observational tracers of stellar magnetic activity and EXor events.

arXiv commentApJL, in press

References in corpus (35)

• Spectral Energy Distributions of T Tauri Stars With Passive Circumstellar Disks
• Using FU Orionis Outbursts to Constrain Self-Regulated Protostellar Disk Models
• Wind-driven Accretion in Protoplanetary Disks. I: Suppression of the Magnetorotational Instability and Launching of the Magnetocentrifugal Wind
• Dynamics of Protoplanetary Disks
• Linear Analysis of the Hall Effect in Protostellar Disks
• Episodic accretion in magnetically layered protoplanetary discs
• Sustained Magnetorotational Turbulence in Local Simulations of Stratified Disks with Zero Net Magnetic Flux
• The Origin of Episodic Accretion Bursts in the Early Stages of Star Formation
• Thanatology in Protoplanetary Discs: the combined influence of Ohmic, Hall, and ambipolar diffusion on dead zones
• The Balbus-Hawley instability in weakly ionised discs
• Non-steady Accretion in Protostars
• Launching of Conical Winds and Axial Jets from the Disk-Magnetosphere Boundary: Axisymmetric and 3D Simulations
• Episodic Accretion on to Strongly Magnetic Stars
• Accretion Discs Trapped Near Corotation
• Unstable Disk Accretion to Magnetized Stars: First Global 3D MHD Simulations
• Magnetically driven accretion in protoplanetary discs
• Hall-effect Controlled Gas Dynamics in Protoplanetary Disks: I. Wind Solutions at the Inner Disk
• Accretion disc dynamo activity in local simulations spanning weak-to-strong net vertical magnetic flux regimes
• Emergent Mesoscale Phenomena in Magnetized Accretion Disc Turbulence
• High-Temperature Ionization in Protoplanetary Disks
• Accretion Outbursts in Self-gravitating Protoplanetary Disks
• Advection/Diffusion of Large-Scale B-Field in Accretion Disks
• The Gravo-Magneto Limit Cycle in Accretion Disks
• Fu Ori outbursts and the planet-disc mass exchange
• Boundary between Stable and Unstable Regimes of Accretion. Ordered and Chaotic Unstable Regimes
• Radial Transport of Large-Scale Magnetic Fields in Accretion Disks. I. Steady Solutions and an Upper Limit on the Vertical Field Strength
• Global evolution of the magnetic field in a thin disc and its consequences for protoplanetary systems
• Accretion disc-stellar magnetosphere interaction: field line inflation and the effect on the spin-down torque
• Simulations of the magnetospheres of accreting millisecond pulsars
• The Differential Rotation of FU Ori
• A multi-wavelength study of the young star V1118 Orionis in outburst
• X-raying the Beating Heart of a Newborn Star: Rotational Modulation of High-energy Radiation from V1647 Ori
• Magnetically modulated accretion in T Tauri stars
• Magnetic cycles and photometric variability of T Tauri stars
• Turbulence, Transport and Waves in Ohmic Dead Zones

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• Young Faithful: The Eruptions of EC 53 as It Cycles through Filling and Draining the Inner Disk
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• Radiative Transfer modeling of EC 53: An Episodically Accreting Class I Young Stellar Object
• The 2015-2016 outburst of the classical EXor V1118 Ori
• The circumstellar environment around the embedded protostar EC 53
• The Circumstellar Disk and Asymmetric outflow of the EX Lup Outburst System
• Inferring possible magnetic field strength of accreting inflows in EXor-type objects from scaled laboratory experiments
• Large amplitude periodic outbursts and long period variables in the VVV VIRAC2-$\beta$ database
• Accretion Burst Echoes as Probes of Protostellar Environments and Episodic Mass Assembly
• EXORCISM: a spectroscopic survey of young eruptive variables (EXor and candidates)
• The 2016-2017 peak luminosity of the pre-main sequence variable V2492 Cyg
• ALMA and VLA Observations of EX Lupi in its Quiescent State
• Close-in giant-planet formation via in-situ gas accretion and their natal disk properties
• JWST captures a sudden stellar outburst and inner disk wall destruction
• Halting Migration in Magnetospherically Sculpted Protoplanetary Disks