A comparative study of the evolution of a close binary using a standard and an improved technique for computing mass transfer.

The evolution of a close binary (M1 = 2 solar masses, M2 = 1 solar mass, and a = 8 solar radii) is computed using a standard and an improved technique for calculating mass transfer. The results obtained are not significantly different. It is concluded that the standard technique yields acceptable results when the following conditions are satisfied: (1) the mass transfer rate is a sensitive function of the difference between the stellar radius and the corresponding critical Roche radius; (2) the density/pressure scale height H in the outer layers of the donor is small compared to its radius R (i.e., H/R is much less than 1); and (3) the phases of turning on or off mass transfer are not important.