Approaches to Mass-loss Modeling, and the Bowen Code

The Bowen code, developed in the 1980s and 1990s, was optimized for studying the mass loss mechanism as a system. It allowed inclusion of pulsation with shock development, non-LTE coupling of the gas to the radiation field and departures from radiative equilibrium, grain formation and acceleration by radiation, and radiative acceleration on molecules. Most of these were found to play important roles in the development of,a massive wind. All were treated by simple parameterized relations that could be adjusted to test the effects using information from more detailed calculations. The advantage of the Bowen code is that it may easily be adapted to study any process suspected of playing a role in driving and accelerating the wind from these stars. The disadvantages are that it cannot be used as a basis for spectrum synthesis without violating conservation of energy. It has also been suggested that (a) the mean opacity used is too low, giving an atmosphere that is too massive; and (b) that the grey approximation will not take into account essential physics of the wind mechanism. We are in the process of working up the code to include more of the physics suspected of playing a role, while preserving its essential nature as a code for the study of the mass loss rather than the details of one or more processes that are involved in driving the wind. We here present a summary of how the code works and outline our plans for improvements.