Time Dependent Models of Magnetospheric Accretion onto Young Stars

Abstract

Accretion onto Classical T Tauri stars is thought to take place through the action of magnetospheric processes, with gas in the inner disk being channeled onto the star's surface by the stellar magnetic field lines. Young stars are known to accrete material in a time-variable manner and the source of this variability remains an open problem, particularly on the shortest (~ day) timescales. Using one-dimensional time-dependent numerical simulations that follow the field line geometry, we find that for plausibly realistic young stars, steady-state transonic accretion occurs naturally in the absence of any other source of variability. However, we show that if the density in the inner disk varies smoothly in time with ~ day long time-scales (e.g., due to turbulence) this complication can lead to the development of shocks in the accretion column. These shocks propagate along the accretion column and ultimately hit the star, leading to rapid, large amplitude changes in the accretion rate. We argue that when these shocks hit the star the observed time-dependence will be a rapid increase in accretion luminosity followed by a slower decline and could be an explanation for some of the short period variability observed in accreting young stars. Our one-dimensional approach bridges previous analytic work to more complicated, multi-dimensional simulations, and observations.

16 Pages, 12 figures

References in corpus (11)

• Protoplanetary Disk Structures in Ophiuchus
• The Magnetic Fields of Classical T Tauri Stars
• Structure and evolution of pre-main sequence circumstellar disks
• Accretion to Magnetized Stars through the Rayleigh-Taylor Instability: Global Three-Dimensional Simulations
• Dust settling in local simulations of turbulent protoplanetary disks
• "Propeller" Regime of Disk Accretion to Rapidly Rotating Stars
• CSI 2264: Investigating rotation and its connection with disk accretion in the young open cluster NGC 2264
• A continuum of accretion burst behavior in young stars observed by K2
• Using FUV to IR Variability to Probe the Star-Disk Connection in the Transitional Disk of GM Aur
• Hot Jupiter Breezes: Time-dependent Outflows from Extrasolar Planets
• The multipolar magnetic fields of accreting pre-main-sequence stars: B at the inner disk, B along the accretion flow, and B at the accretion shock

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• Using Multiwavelength Variability to Explore the Connection between X-ray Emission, the Far-Ultraviolet H2 Bump, and Accretion in T Tauri Stars
• Synthetic Light Curves of Accretion Variability in T Tauri Stars
• Towards an understanding of YSO variability: A multi-wavelength analysis of bursting, dipping, and symmetrically varying light curves of disc-bearing YSOs
• Amplitude Modulation of Short-Timescale Hot Spot Variability
• Predicting the time variation of radio emission from MHD simulations of a flaring T-Tauri star