Accretion Outbursts in Self-gravitating Protoplanetary Disks

Abstract

We improve on our previous treatments of long-term evolution of protostellar disks by explicitly solving disk self-gravity in two dimensions. The current model is an extension of the one-dimensional layered accretion disk model of Bae et al. We find that gravitational instability (GI)-induced spiral density waves heat disks via compressional heating (i.e. $P\mathrm{d}\mathrm{V}$ work), and can trigger accretion outbursts by activating the magnetorotational instability (MRI) in the magnetically inert disk dead-zone. The GI-induced spiral waves propagate well inside of gravitationally unstable region before they trigger outbursts at $R\lesssim 1$ AU where GI cannot be sustained. This long-range propagation of waves cannot be reproduced with the previously used local $\alpha$ treatments for GI. In our standard model where zero dead-zone residual viscosity (${\alpha }_{\mathrm{rd}}$) is assumed, the GI-induced stress measured at the onset of outbursts is locally as large as $0.01$ in terms of the generic $\alpha$ parameter. However, as suggested in our previous one-dimensional calculations, we confirm that the presence of a small but finite ${\alpha }_{\mathrm{rd}}$ triggers thermally-driven bursts of accretion instead of the GI + MRI-driven outbursts that are observed when ${\alpha }_{\mathrm{rd}}=0$. The inclusion of non-zero residual viscosity in the dead-zone decreases the importance of GI soon after mass feeding from the envelope cloud ceases. During the infall phase while the central protostar is still embedded, our models stay in a quiescent accretion phase with ${\dot{M}}_{acc}\sim 10^{-8}-10^{-7}{M}_{\odot }\mathrm{y}{\mathrm{r}}^{-1}$ over $60\%$ of the time and spend less than $15\%$ of the infall phase in accretion outbursts.

16 pages, 17 figures, 1 table, Accepted for publication in ApJ

References in corpus (6)

• The Burst Mode of Protostellar Accretion
• Characterising the Gravitational Instability in Cooling Accretion Discs
• Type I planetary migration in a self-gravitating disk
• The Hot Inner Disk of FU Ori
• Grain growth in the envelopes and disks of Class I protostars
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Cited by in corpus (3)

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• EXor outbursts from disk amplification of stellar magnetic cycles
• One-armed spirals in locally isothermal, radially structured self-gravitating discs