Numerical evolutions of nonlinear r-modes in neutron stars

Nonlinear evolution of the gravitational radiation (GR) driven instability in the r-modes of neutron stars is studied by full numerical 3D hydrodynamical simulations. The growth of the r-mode instability is found to be limited by the formation of shocks and breaking waves when the dimensionless amplitude of the mode grows to about three in value. This maximum mode amplitude is shown by numerical tests to be rather insensitive to the strength of the GR driving force. Upper limits on the strengths of possible nonlinear mode--mode coupling are inferred. Previously unpublished details of the numerical techniques used are presented, and the results of numerous calibration runs are discussed.Comment: RevTeX 4, 17 pages, 26 figures. Slightly revised. To be published in PRD (April 2002

Fragmentation in rotating isothermal protostellar clouds

Results of an extensive set of 3-D hydrodynamic calculations that have been performed to investigate the susceptibility of rotating clouds to gravitational fragmentation are presented. (GHT

The Formation of Common-Envelope, Pre-Main-Sequence Binary Stars

This article, authored by Joel Edward Tohline of Louisiana State University, investigates if binaries can form by spontaneous fission of rapidly rotating protostars. The authors present a classical fission hypothesis, then point out the flaws in it and offer solutions