Predicting the properties of binary stellar systems: the evolution of accreting protobinary systems

By Matthew R. Bate. 2000

215 citations recorded by the source corpus.

We investigate the formation of binary stellar systems. We consider a model where a ‘seed’ protobinary system forms, via fragmentation, within a collapsing molecular cloud core and evolves to its final mass by accreting material from an infalling gaseous envelope. This accretion alters the mass ratio and orbit of the binary, and is largely responsible for forming the circumstellar and/or circumbinary discs. Given this model for binary formation, we predict the properties of binary systems and how they depend on the initial conditions within the molecular cloud core. We predict that there should be a continuous trend such that closer binaries are more likely to have equal-mass components and are more likely to have circumbinary discs than wider systems. Comparing our results with observations, we find that the observed mass-ratio distributions of binaries and the frequency of circumbinary discs as a function of separation are most easily reproduced if the progenitor molecular cloud cores have radial density profiles between uniform and 1/r (e.g., Gaussian) with near-uniform rotation. This is in good agreement with the observed properties of pre-stellar cores. Conversely, we find that the observed properties of binaries cannot be reproduced if the cloud cores are in solid-body rotation and have initial density profiles which are strongly centrally condensed. Finally, in agreement with the radial-velocity searches for extrasolar planets, we find that it is very difficult to form a brown dwarf companion to a solar-type star with a separation ≲10 au, but that the frequency of brown dwarf companions should increase with larger separations or lower mass primaries.

Subfields: Astronomy and Astrophysics, Spectroscopy

View Paper: https://www.semanticscholar.org/paper/7a8f08c5fa48f5c6506eafe6b61da81e6828c677

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Citations in the corpus

Mind Your Ps and Qs: The Interrelation between Period (P) and Mass-ratio (Q) Distributions of Binary Stars (2016, background): “…companion migrates inward through the primordial disk, it most likely accretes additional mass. Competitive accretion in the circumbinary disk tends to drive the binary mass ratio toward unity (Kroupa 1995a; Bate & Bonnell 1997; Bate 2000; Tokovinin 2000; White & Ghez 2001; Marks & Kroupa 2011).”
THE RUNTS OF THE LITTER: WHY PLANETS FORMED THROUGH GRAVITATIONAL INSTABILITY CAN ONLY BE FAILED BINARY STARS (2009, background): “The trend toward continued growth and even mass equalization following disk fragmentation is observed in numerous simulations with ongoing accretion (Bonnell & Bate 1994; Bate 2000; Matsumoto & Hanawa 2003; Walch et al. 2009; Kratter et al. 2010; Krumholz et al. 9 2009).”
Disintegrating Multiple Systems in Early Stellar Evolution (2000, background): “In principle, the resulting ejection event may lead to escape already during the Ðrst close triple approach, in which case the remaining close binary settles down to follow the evolution analyzed in many recent numerical studies (e.g., Artymowicz & Lubow 1994, 1996 ; Bate 2000).”
The formation of close binary systems by dynamical interactions and orbital decay (2002, background): “…specific angular momentum that accretes from a circumbinary disc or a gaseous envelope on to a binary, is preferentially captured by the secondary and, thus, also drives the mass ratio towards unity (Artymowicz 1983; Bonnell & Bastien 1992; Whitworth et al. 1995; Bate & Bonnell 1997; Bate 2000).”
Toward Understanding Massive Star Formation (2007, background): “Nonhomologous gravitational collapse of portions of the cores into opti- cally thick, pressure-supported protostellar embryos with initial masses of the order of 10−3 M (Larson 1969, Bate 2000).”
Competitive accretion in embedded stellar clusters (2001, background): “Previous studies have explored the physics of accretion in binary systems (Bate & Bonnell 1997; Bate 2000) and in small stellar clusters (Bonnell et al. 1997).”
Pseudo-viscous modelling of self-gravitating discs and the formation of low mass ratio binaries (2009, background): “This tendency for simulations to produce nearly equal mass pairs is driven by the late accretion of high specific angular momentum material onto the proto-binary pair, which favours preferential accretion onto the secondary (Whitworth et al 1995, Bate & Bonnell 1997, Bate 2000, Delgado et al 2004).”
How Dry is the Brown Dwarf Desert? Quantifying the Relative Number of Planets, Brown Dwarfs, and Stellar Companions around Nearby Sun-like Stars (2004, background): “Larson 2003, Kroupa & Bouvier 20 03, Bate 20 00, Matzner & Levin 2004, Boss 2002, Rice et al. 2003).”
Comparative statistics and origin of triple and quadruple stars (2008, background): “Bate (2000) studied the evolution of the separation and mass ratio of an accreting proto-binary under the assumption that there is no angular momentum transport in the accreted gas.”
MAPPING THE SHORES OF THE BROWN DWARF DESERT. II. MULTIPLE STAR FORMATION IN TAURUS–AURIGA (2011, methodology): “This process typically is modelled using smoothed-particle hydrodynamic (SPH) simulations (Bate 2000; Bate et al. 2002; DelgadoDonate et al. 2004); the most recent simulations of larger-scale star formation implicitly include this process by extending down to much smaller angular scales (∼5 AU;…”
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).”
Stellar, brown dwarf and multiple star properties from a radiation hydrodynamical simulation of star cluster formation (2011, background): “In addition to dynamical interactions, accretion on to a binary from an envelope decreases the binary’s separation unless the specific angular momentum of the accreted material is significantly greater than that of the binary (Artymowicz 1983; Bate 1997, 2000; Bate & Bonnell 1997).”
The origin of the initial mass function and its dependence on the mean Jeans mass in molecular clouds (2004, background): “Any com panion would likely becom e a staralso because the long term e ectofaccretion onto a binary is generally to drive the system to equalm ass com - ponents(Bate 2000;W hitworth etal.1995).”
The formation of a star cluster: predicting the properties of stars and brown dwarfs (2002, background): “Accretion onto a binary from an envelope decreases the binary’s separation unless the specific angular momentum of the accreted material is significantly greater than that of the binary (Artymowicz 1983; Bate 1997; Bate & Bonnell 1997; Bate 2000).”
Stellar, brown dwarf and multiple star properties from hydrodynamical simulations of star cluster formation (2008, background): “A trend of more unequal mass binaries with increasing separation is expected from the evolution of protobinary systems accreting gas from an envelope (Bate 2000).”
Observational Constraints on the Formation and Evolution of Binary Stars (2001, background): “%) of the final stellar masses are contained in the initial protobinary fragments for systems of separation less than ∼ 100 AU (Boss 1988; Bate 2000).”
The physics of star formation (2003, background): “…simulations have shown the formation of trailing spiral wave patterns in tidally perturbed disks, typically with a two-armed symmetry reflecting the symmetry of the tidal distortion (Sawada et al 1987; Różyczka and Spruit 1993; Savonije et al 1994; Bate 2000; Makita et al 2000; Blondin 2000).”
LIMITING ACCRETION ONTO MASSIVE STARS BY FRAGMENTATION-INDUCED STARVATION (2010, methodology): “The key to the process, as already discussed by Bate (2000), is that fragments that form later at larger radii will preferentially accrete larger-angular momentum material.”