Dead zones around young stellar objects: FU Orionis outbursts and transition discs

Martin, Rebecca G.; Lubow, Stephen H.; Livio, Mario; Pringle, J. E.

doi:10.1111/j.1365-2966.2012.21076.x

Cited by 66 publications

(43 citation statements)

References 57 publications

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“…Hartmann (1998) argues that disc accretion is inherently intermittent and that the main difference between FUor and EXor outbursts is the evolutionary stage in which they take place, with FU Ori outburst occurring preferentially during the embedded stage and EXor outbursts occurring during the T Tauri phase. At least four outburst mechanisms have been proposed to date: 1) the coupling of magnetorotational and gravitational instabilities (MRI+GI, Armitage et al 2001, Zhu et al 2009, Martin et al 2012, 2) disc fragmentations followed by the inward migration of the resulting fragments (Vorobyov & Basu 2005, Zhu et al 2012), 3) Thermal-viscous instability (Bell et al 1995), and 4) instabilities induced by planets (Clarke et al 1990, Lodato & Clarke 2004 or stellar companions (Bonnell & Bastien 1992).…”

Section: Introductionmentioning

confidence: 99%

The ALMA early science view of FUor/EXor objects – V. Continuum disc masses and sizes

Cieza

Ruíz-Rodríguez

Pérez

et al. 2017

Monthly Notices of the Royal Astronomical Society

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Low-mass stars build a significant fraction of their total mass during short outbursts of enhanced accretion known as FUor and EXor outbursts. FUor objects are characterized by a sudden brightening of ∼5 magnitudes at visible wavelengths within one year and remain bright for decades. EXor objects have lower amplitude outbursts on shorter timescales. Here we discuss a 1.3 mm ALMA mini-survey of eight outbursting sources (three FUor, four EXor, and the borderline object V1647 Ori) in the Orion Molecular Cloud. While previous papers in this series discuss the remarkable molecular outflows observed in the three FUor objects and V1647 Ori, here we focus on the continuum data and the differences and similarities between the FUor and EXor populations. We find that FUor discs are significantly more massive (∼80-600 M JU P ) than the EXor objects (∼0.5-40 M JU P ). We also report that the EXor sources lack the prominent outflows seen in the FUor population. Even though our sample is small, the large differences in disc masses and outflow activity suggest that the two types of objects represent different evolutionary stages.The FUor sources seem to be rather compact (R c < 20-40 au) and to have a smaller characteristic radius for a given disc mass when compared to T Tauri stars. V1118 Ori, the only known close binary system in our sample, is shown to host a disc around each one of the stellar components. The disc around HBC 494 is asymmetric, hinting at a structure in the outer disc or the presence of a second disc.

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Section: Introductionmentioning

confidence: 99%

The ALMA early science view of FUor/EXor objects – V. Continuum disc masses and sizes

Cieza

Ruíz-Rodríguez

Pérez

et al. 2017

Monthly Notices of the Royal Astronomical Society

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“…Fleming 2000), and the viscosity parameter α. Martin et al (2012a) showed that in order to reproduce FU Orionis outbursts, ReM,crit must be a few 10…”

Section: Discussionmentioning

confidence: 99%

“…We use a one dimensional layered disc model described in Martin & Lubow (2011) and further developed in Martin et al (2012a) to evolve the total surface density, Σ(R, t) and mid-plane temperature, Tc(R, t). We take a solar mass star, M = 1 M⊙, with a disc that extends from a radius of R = 5 R⊙ up to R = 40 AU.…”

Section: Protoplanetary Disc Modelmentioning

confidence: 99%

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On the evolution of the Snow Line in Protoplanetary Discs

Martin¹,

Livio

2013

Proc. IAU

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We model the evolution of the snow line in a protoplanetary disc. If the magnetorotational instability (MRI) drives turbulence throughout the disc, there is a unique snow line outside of which the disc is icy. The snow line moves closer to the star as the infall accretion rate drops. Because the snow line moves inside the radius of the Earth's orbit, the formation of our water-devoid planet is difficult with this model. However, protoplanetary discs are not likely to be sufficiently ionised to be fully turbulent. A dead zone at the mid-plane slows the flow of material through the disc and a steady state cannot be achieved. We therefore model the evolution of the snow line also in a time-dependent disc with a dead zone. As the mass is accumulating, the outer parts of the dead zone become self gravitating, heat the massive disc and thus the outer snow line does not come inside the radius of the Earth's orbit, contrary to the fully turbulent disc model. There is a second, inner icy region, within the dead zone, that moves inwards of the Earth's orbit after a time of about 10 6 yr. With this model there is sufficient time and mass in the disc for the Earth to form from waterdevoid planetesimals at a radius of 1 AU. Furthermore, the additional inner icy region predicted by this model may allow for the formation of giant planets close to their host star without the need for much migration.

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“…2. The dead zone surface density is determined via a critical magnetic Reynolds number (e.g., Hawley et al 1995;Fleming et al 2000;Martin et al 2012aMartin et al , 2012b (Blaes & Balbus 1994) and x e is the electron fraction. We use the analytic approximations for the active layer surface density shown in Equations (27) and (28) in Martin et al (2012a) that include thermal ionization, cosmic ray ionization, and the effects of recombination.…”

Section: Disk Model With a Dead Zonementioning

confidence: 99%

On the Formation of Super-Earths With Implications for the Solar System

Martin

Livio

2016

ApJ

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We first consider how the level of turbulence in a protoplanetary disk affects the formation locations for the observed close-in super-Earths in exosolar systems. We find that a protoplanetary disk that includes a dead zone (a region of low turbulence) has substantially more material in the inner parts of the disk, possibly allowing for in situ formation. For the dead zone to last the entire lifetime of the disk requires the active layer surface density to be sufficiently small,  S -100 g cm crit 2 . Migration through a dead zone may be very slow and thus super-Earth formation followed by migration toward the star through the dead zone is less likely. For fully turbulent disks, there is not enough material for in situ formation. However, in this case, super-Earths can form farther out in the disk and migrate inward on a reasonable timescale. We suggest that both of these formation mechanisms operate in different planetary systems. This can help to explain the observed large range in densities of super-Earths because the formation location determines the composition. Furthermore, we speculate that super-Earths could have formed in the inner parts of our solar system and cleared the material in the region inside of Mercury's orbit. The super-Earths could migrate through the gas disk and fall into the Sun if the disk was sufficiently cool during the final gas disk accretion process. While it is definitely possible to meet all of these requirements, we don't expect them to occur in all systems, which may explain why the solar system is somewhat special in its lack of super-Earths.

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Dead zones around young stellar objects: FU Orionis outbursts and transition discs

Cited by 66 publications

References 57 publications

The ALMA early science view of FUor/EXor objects – V. Continuum disc masses and sizes

The ALMA early science view of FUor/EXor objects – V. Continuum disc masses and sizes

On the evolution of the Snow Line in Protoplanetary Discs

On the Formation of Super-Earths With Implications for the Solar System

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