  We have developed a new method for calculating common envelope (CE) events
based on explicit consideration of the donor star's structural response to
adiabatic mass loss. In contrast to existing CE prescriptions, which specify a
priori the donor's remnant mass, we determine this quantity self-consistently
and find it depends on binary and CE parameters. This aspect of our model is
particularly important to realistic modeling for upper main sequence star
donors without strongly degenerate cores (and hence without a clear
core/envelope boundary). We illustrate the central features of our method by
considering CE events involving 10 solar mass donors on or before their red
giant branch. For such donors, the remnant core mass can be as much as 30%
larger than the star's He-core mass. Applied across a population of such
binaries, our methodology results in a significantly broader remnant mass and
final orbital separation distribution and a 20% increase in CE survival rates
as compared to previous prescriptions for the CE phase.
