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

Matther R Bate, Ian Alexander Bonnell, Volker Bromm

Research output: Contribution to journalArticlepeer-review

234 Citations (Scopus)

Abstract

We present results from the first hydrodynamical star formation calculation to demonstrate that close binary stellar systems (separations less than or similar to 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.

Original languageEnglish
Pages (from-to)pp.705-713.
Number of pages9
JournalMonthly Notices of the Royal Astronomical Society
Volume336
Issue number3
Publication statusPublished - 1 Nov 2002

Keywords

  • accretion, accretion discs
  • hydrodynamics
  • binaries : close
  • binaries : spectroscopic
  • circumstellar matter
  • stars : formation
  • ROTATING INTERSTELLAR CLOUDS
  • SMOOTHED PARTICLE HYDRODYNAMICS
  • ELONGATED CYLINDRICAL CLOUDS
  • MASS-RATIO DISTRIBUTION
  • STAR-FORMATION
  • SPECTROSCOPIC BINARIES
  • PROTOSTELLAR FORMATION
  • FORMATION MECHANISM
  • STELLAR-SYSTEMS
  • PROTOBINARY SYSTEMS

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