ON THE ROLE OF DISKS IN THE FORMATION OF STELLAR SYSTEMS: A NUMERICAL PARAMETER STUDY OF RAPID ACCRETION

By K. Kratter, C. Matzner, Mark R. Krumholz, Richard Klein. 2009

216 citations recorded by the source corpus.

We study rapidly accreting, gravitationally unstable disks with a series of idealized global, numerical experiments using the code ORION. Our numerical parameter study focuses on protostellar disks, showing that one can predict disk behavior and the multiplicity of the accreting star system as a function of two dimensionless parameters which compare the infall rate to the disk sound speed and orbital period. Although gravitational instabilities become strong, we find that fragmentation into binary or multiple systems occurs only when material falls in several times more rapidly than the canonical isothermal limit. The disk-to-star accretion rate is proportional to the infall rate and governed by gravitational torques generated by low-m spiral modes. We also confirm the existence of a maximum stable disk mass: disks that exceed ∼50% of the total system mass are subject to fragmentation and the subsequent formation of binary companions.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/1b80347fe8bcdd3009510d0f76edb405692d1fc4

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CHALLENGES IN FORMING PLANETS BY GRAVITATIONAL INSTABILITY: DISK IRRADIATION AND CLUMP MIGRATION, ACCRETION, AND TIDAL DESTRUCTION (2011, methodology): “D: ANALYTIC ESTIMATE FOR THE CRITICAL FRAGMENTATION RADIUS The parameter space for GI disk fragmentation has been explored analytically by several authors (Rafikov 2005, 2007, 2010; Levin 2007; Kratter et al. 2008, 2010a; Cossins et al. 2010; Zhu et al. 2010b).”
The VAST Survey - III. The multiplicity of A-type stars within 75 pc (2013, background): “This process may lead to a significa t number of disc-born lower mass companions to more massive stars (Kratter et al. 2010; Stamatellos et al. 2011), with the prefer ntial equalisation of the mass ratios of those binaries formed at close separations (Bate & Bonnell 1997; Bate 2000).”
Gravitational Instabilities in Circumstellar Disks (2016, methodology): “In this case, simulations suggest that disk undergo strong m = 1 dominated transport, and in many cases fragmentation into stellar companions (Adams et al. 1989; Kratter et al. 2010a).”
A COMPLETE SPECTROSCOPIC SURVEY OF THE MILKY WAY SATELLITE SEGUE 1: THE DARKEST GALAXY (2010, background): “10 AU) are expected to form via disk fragmentation (e.g., Kratter et al. 2010) or interactions between protostellar cores (e.g., Bate 2009), neither of which should be very sensitive to metallicity (M. Krumholz 2010, private communication).”
The Close Binary Fraction of Solar-type Stars Is Strongly Anticorrelated with Metallicity (2018, methodology): “We begin with an expression for the disk midplane equilibrium temperature (see Kratter et al. 2008, 2010b), s t t = + +⎜ ⎟ ⎛ ⎝ ⎞ ⎠ ( )T F F 3 8 1 2 , 64 visc irrad where p = W˙ ( )F M3 4 , 7visc 2 * *s m p = ⎜ ⎟ ⎡ ⎣ ⎢⎢ ⎛ ⎝⎜ ⎞ ⎠⎟ ⎛ ⎝ ⎞ ⎠ ⎤ ⎦ ⎥⎥ ( )F k G M L r4 1 , 8birrad 3 1 7 2 7 3 7 4 * * = ˙ (…”
THE FORMATION MECHANISM OF GAS GIANTS ON WIDE ORBITS (2009, unknown): “Furthermore, A star disks experience the highest infall rates during formation and are better candidates than lower-mass G or M stars for triggered gravitational instability (Kratter et al. 2009).”
SOUTHERN MASSIVE STARS AT HIGH ANGULAR RESOLUTION: OBSERVATIONAL CAMPAIGN AND COMPANION DETECTION (2014, background): “High infall rates can lead to massive, gravitationally unstable disks, which in turn fragment to produce one or more bound objects that typically grow to stellar masses (Kratter & Matzner 2006; Krumholz et al. 2007; Kratter et al. 2010).”
Stellar, brown dwarf and multiple star properties from a radiation hydrodynamical simulation of star cluster formation (2011, background): “Later in the star formation process, it may perhaps be assumed that the mass of the disc is less than that of the stellar object (i.e. the stellar mass should be wrong by less than a factor of 2; Kratter & Matzner 2006; Kratter, Matzner & Krumholz 2008; Kratter et al. 2010).”
LIMITING ACCRETION ONTO MASSIVE STARS BY FRAGMENTATION-INDUCED STARVATION (2010, methodology): “This is also supported by analytic estimates comparing typical accretion rates onto the disk with its ability to transport matter inwards through viscous and gravitational torques (Kratter & Matzner 2006; Kratter et al. 2010).”
Mass Loss: Its Effect on the Evolution and Fate of High-Mass Stars (2014, background): “In the end we may find that observed trends with Z hinge upon the formation of massive binaries (Kratter et al. 2010) and its dependence on fragmentation and cooling as a function of Z. 5.”
THE MASS–METALLICITY RELATION FOR GIANT PLANETS (2015, background): “Assuming that gas accretion through the gap becomes inefficient for Δ/RH=fS∼5 (Lissauer et al. 2009; Kratter et al. 2010), a planet mass Mp set by gap truncation implies the disk viscosity parameter (Shakura & Sunyaev 1973; Armitage 2011) ( ) * a p = - ⎜ ⎟⎛⎝ ⎞ ⎠ f f M M H r .”
On the diversity and statistical properties of protostellar discs (2018, background): “Rapid accretion can be important for driving fragmentation (Bonnell 1994; Bonnell & Bate 1994; Hennebelle et al. 2004; Kratter et al. 2008, 2010), adding another complication.”
THE FORMATION OF LOW-MASS BINARY STAR SYSTEMS VIA TURBULENT FRAGMENTATION (2010, background): “…suggested that Electronic address: soffner@cfa.harvard.edu this process was limited to large mass ratio systems, recent work such as Stamatellos & Whitworth (2009) and Kratter et al. (2010a) has shown that when disks continue to be fed at their outer edges, the companions can grow substantially.”
THE VLA NASCENT DISK AND MULTIPLICITY SURVEY OF PERSEUS PROTOSTARS (VANDAM). II. MULTIPLICITY OF PROTOSTARS IN THE PERSEUS MOLECULAR CLOUD (2016, background): “Fragmentation of the protostellar disk via gravitational instability can also directly form close companion systems (e.g., Adams et al. 1989; Bonnell & Bate 1994a; Kratter et al. 2010; Zhu et al. 2012).”
THE BURST MODE OF ACCRETION AND DISK FRAGMENTATION IN THE EARLY EMBEDDED STAGES OF STAR FORMATION (2010, background): “The time-averaged rate of mass accretion onto the disk 〈Ṁd〉 is greater than the time-averaged mass accretion onto the star 〈Ṁ∗〉 so that Σ quickly increases with time and may reach the unstable regime (Vorobyov & Basu 2006, 2007; Vorobyov 2009b; Kratter et al. 2010; Boley 2009).”
The First Stars: Mass Growth Under Protostellar Feedback (2011, background): “As discussed in Kratter et al. (2010), the actual minimum value of Q can vary with disk properties such as scale height, and from Figures 5 and 6 we see this varies throughout the disk evolution for both cases.”