AAS 197, January 2001
Session 10. Low Mass Star Formation
Display, Monday, January 8, 2001, 9:30am-7:00pm, Exhibit Hall

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[10.04] The Formation of Close Binary Stellar Systems

M. R. Bate (Institute of Astronomy, Cambridge, United Kingdom)

The formation of close binary systems is an unsolved problem. Whereas binaries with intermediate and wide separations can be explained by fragmentation during the isothermal collapse phase of a molecular cloud core, when the central part of the cloud becomes optically-thick and begins to heat up, fragmentation is inhibited. A second chance for fragmentation occurs inside the optically-thick region when molecular hydrogen dissociates, initiating the second collapse phase.

We present results from three-dimensional hydrodynamic calculations which follow the collapse of a molecular cloud core (~10-18 g cm-3) to stellar densities (> 0.01 g cm-3). The calculations resolve structures over 7 orders of magnitude in spatial extent (~5000 AU - 0.1 R\odot), and over 17 orders of magnitude in density contrast. With these calculations, we consider whether fragmentation to form a close binary stellar system (separation <1 AU) can occur during the second collapse phase.

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