Pseudo-viscous modelling of self-gravitating discs and the formation of low mass ratio binaries

By C. Clarke. 2009

160 citations recorded by the source corpus.

We present analytic models for the local structure of self-regulated self-gravitating accretion discs that are subject to realistic cooling. Such an approach can be used to predict the secular evolution of self-gravitating discs (which can usefully be compared with future radiation hydrodynamical simulations) and to define various physical regimes as a function of radius and equivalent steady state accretion rate. We show that fragmentation is inevitable, given realistic rates of infall into the disc, once the disc extends to radii >70 au (in the case of a solar mass central object). Owing to the outward redistribution of disc material by gravitational torques, we also predict fragmentation at >70 au even in the case of low angular momentum cores which initially collapse to a much smaller radius. We point out that 70 au is close to the median binary separation and propose that such delayed fragmentation, at the point that the disc expands to >70 au, ensures the creation of low mass ratio companions that can avoid substantial further growth and consequent evolution towards unit mass ratio. We thus propose this as a promising mechanism for producing low mass ratio binaries, which, while abundant observationally, are severely underproduced in hydrodynamical models.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/83cb916f178472fbf74e6445b6261aa0e09328dd

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

1. K. Kratter
2. Matthew R. Bate
3. S. Andrews
4. D. Wilner
5. Philip Armitage
6. L. Hartmann
7. Zhaohuan Zhu
8. G. Lodato

Citations in the corpus

• THE BURST MODE OF ACCRETION AND DISK FRAGMENTATION IN THE EARLY EMBEDDED STAGES OF STAR FORMATION (2010, unknown): “2009; Clarke 2009).”
• THE ROLE OF MULTIPLICITY IN DISK EVOLUTION AND PLANET FORMATION (2011, background): “Finally, theoretical modeling has begun to provide new context for disk formation, evolution, and destruction (Alexander et al. 2006; Clarke 2009; Alexander & Armitage 2009).”
• THE FORMATION OF LOW-MASS BINARY STAR SYSTEMS VIA TURBULENT FRAGMENTATION (2010, background): “Otherwise disks become unstable outside of a much smaller radius, within which cooling times are too long and viscous heating alone suffices to suppress fragmentation (Rafikov 2005; Matzner & Levin 2005; Clarke 2009)”
• Dynamics of Protoplanetary Disks (2010, methodology): “…of Lin & Pringle 1987), in which ν(r,Σ) is completely determined by the requirement of thermal equilibrium, and seek either steady-state analytic (Clarke 2009; Cossins, Lodato & Clarke 2010; Matzner & Levin 2005; Rafikov 2009) or time-dependent numerical solutions (Rice & Armitage 2009; Zhu,…”
• RESOLVED IMAGES OF LARGE CAVITIES IN PROTOPLANETARY TRANSITION DISKS (2011, background): “Moreover, this disk instability mechanism seems to naturally favor formation at wide separations from the primary (Boss 2006; Boley 2009; Rafikov 2009; Clarke 2009; Dodson-Robinson et al. 2009).”
• Rapid inward migration of planets formed by gravitational instability (2011, background): “…be gravitationally unstable, and other sources of turbulence such as the magnetorotational instability could prevail (see e.g., Zhu et al. 2009; Rice & Armitage 2009; Clarke 2009, who studied the radial dependence of the alpha viscosity parameter in self-gravitating discs with realistic cooling).”
• RESOLVING THE LUMINOSITY PROBLEM IN LOW-MASS STAR FORMATION (2011, background): “…that this is the minimum distance from the star at which gravitational instability and fragmentation can occur (e.g. Stamatellos & Whitworth 2008; Clarke 2009; Vorobyov & Basu 2010, Meru & Bate 2010), suggesting a causal link between the disk gravitational instability and accretion variability…”
• TRANSITIONAL DISKS AS SIGNPOSTS OF YOUNG, MULTIPLANET SYSTEMS (2011, background): “For planets formed by disk fragmentation, the characteristic Phase I mass is much higher (e.g. Clarke 2009).”
• THE FORMATION MECHANISM OF GAS GIANTS ON WIDE ORBITS (2009, unknown): “Clarke (2009) argues that companions formed by disk fragmentation typically have at least 10% of the primary star mass.”
• CHALLENGES IN FORMING PLANETS BY GRAVITATIONAL INSTABILITY: DISK IRRADIATION AND CLUMP MIGRATION, ACCRETION, AND TIDAL DESTRUCTION (2011, methodology): “This critical radius has been derived by several authors before (Levin 2007; Rafikov 2005, 2010; Clarke 2009; Cossins et al. 2010; Kratter et al. 2010a; Zhu et al. 2010b).”
• MAPPING THE SHORES OF THE BROWN DWARF DESERT. II. MULTIPLE STAR FORMATION IN TAURUS–AURIGA (2011, methodology): “…collapse (e.g. Bodenheimer & Burkert 2001), while close (.100 AU) binary compan- ion can form via gravitational instability and fragmentation in the protostellar accretion disk of the primary star (Toomre 1964; Boss 2001; Clarke 2009), most likely modified by subsequent migration through the disk.”
• Gravitational Instabilities in Circumstellar Disks (2016, methodology): “Clarke (2009) use an α model for GI to estimate the relevant cooling time as a function of radius, and show that fragmentation occurs beyond ∼ 70 AU, while self-regulation is expected between ∼ 20 − 70 AU.”