Rates of Energy Gain and Loss in the Circumstellar Envelopes of Be Stars: 1 Delphini

We have investigated the rates of energy gain and loss in the circum-stellar envelope of the cool B8-9e star, 1 Delphini , using the Poeckert-Marlborough model. We determined iteratively the kinetic temperature of the gas as a function of position in the circumstellar envelope by adjusting the temperature at each grid point until the rates of energy gain and loss there were equal. The gas was assumed to gain energy from photoionization, collisional de-excitation of bound levels and free-free absorption, and to lose energy by recombination, collisional excitation and free-free emission. The resultant temperatures are a self-consistent solution of the equation of energy conservation. We were also able to reproduce the gross features of the H line with this model and the corresponding temperature grid. Our investigation demonstrates that there is suucient continuum radiation present to ionize the circumstellar envelope and produce the relative line strength without any additional source of heating in the envelopes of cool Be stars.