The formation of close binary systems by dynamical interactions and orbital decay

By Matthew R. Bate, Ian A. Bonnell, Volker Bromm. 2002

232 citations recorded by the source corpus.

We present results from the first hydrodynamical star formation calculation to demonstrate that close binary stellar systems (separations 10 au) need not be formed directly by fragmentation. Instead, a high frequency of close binaries can be produced through a combination of dynamical interactions in unstable multiple systems and the orbital decay of initially wider binaries. Orbital decay may occur as a result of gas accretion and/or the interaction of a binary with its circumbinary disc. These three mechanisms avoid the problems associated with the fragmentation of optically thick gas to form close systems directly. They also result in a preference for close binaries to have roughly equal-mass components because dynamical exchange interactions and the accretion of gas with high specific angular momentum drive mass ratios towards unity. Furthermore, because of the importance of dynamical interactions, we find that stars with greater masses ought to have a higher frequency of close companions, and that many close binaries ought to have wide companions. These properties are in good agreement with the results of observational surveys.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/0bd52b73eb8e7c61dc177bf1a80f1dae38dd8893

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Citations in the corpus

Stellar, brown dwarf and multiple star properties from a radiation hydrodynamical simulation of star cluster formation (2011, background): “The mechanisms by which close binaries form have been discussed in detail by Bate et al. (2002b).”
Stellar, brown dwarf and multiple star properties from hydrodynamical simulations of star cluster formation (2008, background): “Bate et al. (2002b) discuss how close binaries (separations less than 10 AU) are formed from wider systems in the BBB2003 calculation through a combination of dynamical encounters with other protostars, their interactions with circumbinary and circumtriple discs, and accretion.”
On the diversity and statistical properties of protostellar discs (2018, background): “The observed small disc sizes would be consistent with brown dwarfs being ejected from multiple protostellar systems during their formation (Reipurth & Clarke 2001; Bate et al. 2002a; Goodwin & Whitworth 2007; Stamatellos et al. 2007; Bate 2009a, 2012).”
THE HIGH ANGULAR RESOLUTION MULTIPLICITY OF MASSIVE STARS (2008, background): “Instead, the initial angular momentum of the natal cloud may end up (through a variety of processes) in the orbital angular momentum of binaries among the more massive stars (Bate et al. 2002; Zinnecker & Yorke 2007; Gies 2007).”
MAPPING THE SHORES OF THE BROWN DWARF DESERT. II. MULTIPLE STAR FORMATION IN TAURUS–AURIGA (2011, methodology): “Any companion that forms via disk instability should be large enough to open a gap immediately, so subsequent migration should proceed via the Type II mechanism (Lin & Papaloizou 1985) and carry the companion inward; this tendency is born out by simulations (Bate et al. 2002; Clarke et al. 2009).”
Adaptive Optics Photometry and Astrometry of Binary Stars. II. A Multiplicity Survey of B Stars (2005, background): “Many massive stars are probably born in high density stellar environments where binaries may be formed through three-body interactions (Bate et al. 2002) and through the interactions with large proto-stellar accretion disks (Moeckel & Bally 2007).”
Tertiary Companions to Close Spectroscopic Binaries (2006, background): “Indeed, hydrodynamical simulations of Bate et al. (2002) show how such companions are formed and how accreting binaries become tighter by interacting with their distant companions or with fly-by members of a nascent cluster.”
Observational Evidence for Tidal Interaction in Close Binary Systems (2007, background): “Common primordial spin-orbit misalignment can rule out some binary formation scenarios (e.g., Durisen et al. 2001; Bate et al. 2002; Bonnell & Bate 2005; Machida 2005).”
The origin of the initial mass function and its dependence on the mean Jeans mass in molecular clouds (2004, methodology): “In thissection,we investigate in detailwhy the second calculation form sm ore brown dwarfsthan the rst.From Calculation 1,Bate et al.(2002a) found that the m echanism forbrown dwarfform ation wasthata fragm entwasejected from the region ofdense m olecular gas in which it form ed c 0000 R A S,M N R…”
The importance of radiative feedback for the stellar initial mass function (2008, background): “As was found by Bate et al. (2002), although two objects can form well separated from each other, the combination of dynamical interactions, gas accretion, and interactions with circumbinary and circum-multiple discs is very effective at producing multiple systems and even close binaries.”