Numerical Simulations of the Onset and Stability of Dynamical Mass Transfer in Binaries

Abstract

Hydrodynamical simulations of semi-detached, polytropic binary stars are presented in an effort to study the onset and stability of dynamical mass transfer events. Initial, synchronously rotating equilibrium models are constructed using a self-consistent-field technique and then evolved with an Eulerian hydrodynamics code in a fully self-consistent manner. We describe code improvements introduced over the past few years that permit us to follow dynamical mass-transfer events through more than 30 orbits. Mass-transfer evolutions are presented for two different initial configurations: A dynamically unstable binary with initial mass ratio (donor/accretor) $q_0=1.3$ that leads to a complete merger in $\sim 10$ orbits; and a double-degenerate binary with initial mass ratio $q_0=0.5$ that, after some initial unstable growth of mass transfer, tends to separate as the mass-transfer rate levels off.

47 pages, 11 figures, submitted to the Astrophysical Journal. See http://www.phys.lsu.edu/faculty/tohline/astroph/dmtf05 for high resolution figures and mpeg animations