Young Binary Stars and Associated Disks

Abstract

The typical product of the star formation process is a binary star. Binaries have provided the first dynamical measures of the masses of pre-main-sequence (PMS) stars, providing support for the calibrations of PMS evolutionary tracks. Surprisingly, in some star-forming regions PMS binary frequencies are higher than among main-sequence solar-type stars. The difference in PMS and main-sequence binary frequencies is apparently not an evolutionary effect; recent attention has focussed on correlations between binary frequency and stellar density or cloud temperatures. Accretion disks are common among young binary stars. Binaries with separations between 1 AU and 100 AU have substantially less submillimeter emission than closer or wider binaries, suggesting that they have truncated their disks. Evidence of dynamical clearing has been seen in several binaries. Remarkably, PMS binaries of all separations show evidence of circumstellar disks and continued accretion. This suggests that the circumstellar disks are replenished from circumbinary disks or envelopes. The frequent presence of disks suggests that planet formation can occur in binary environments, and formation of planets in wide binaries is already established by their discovery. Circumbinary disk masses around very short period binaries are ample to form planetary systems such as our own. The nature of planetary systems among the most common binaries, with separations between 10 AU and 100 AU, is less clear given the observed reduction in disk mass, though they may have disk masses adequate for the formation of terrestrial-like planets.

32 pages, including 6 Postscript figures (TeX, uses psfig.sty); to appear in "Protostars & Planets IV". Gif figures with captions and high-res Postscript color figure available at http://hven.swarthmore.edu/~jensen/preprints/ppiv.html

References in corpus (8)

• NICMOS Imaging of the HR 4796A Circumstellar Disk
• The tidally induced warping, precession and truncation of accretion discs in binary systems: three-dimensional simulations
• The Connection between Submillimeter Continuum Flux and Binary Separation in Young Binaries: Evidence of Interaction between Stars and Disks
• Star Cluster Evolution, Dynamical Age Estimation and the Kinematical Signature of Star Formation
• Evolutionary models for solar metallicity low-mass stars: mass-magnitude relationships and color-magnitude diagrams
• The Stability of Planets in the Alpha Centauri system
• Star formation environments and the distribution of binary separations
• Physical Properties of 90 AU to 250 AU Pre-Main-Sequence Binaries