Rates of Energy Gain and Loss in the Circumstellar Envelopes of Be Stars: The Disk Model

Abstract

We have investigated the kinetic temperatures assumed by Waters, Cote, & Lamers for the circumstellar envelopes of a group of Be stars. Waters introduced a simple equatorial disk model with ρ ∝ r-n to describe the physical characteristics of Be star disks. Since this equatorial disk model was applied to a large number of stars, it is important to ensure that the kinetic temperatures assumed by Waters et al. were reasonable. We have investigated their choice of kinetic temperature in two ways. Initially we tested the appropriateness of the temperatures assumed by evaluating the rates of energy gain and loss. Then, based on equating the rates of energy gain and loss, we self-consistently determined the temperature structure for these envelopes. Our investigation included the stars γ Cas, δ Cen, ψ Per, and β CMi. For each of the stars examined we discovered that the constant temperature of the envelope assumed by Waters et al. was too high by a factor of 2-3.