An analysis of the V-band light curve of the Be star omega CMa with the viscous decretion disk model

Abstract: We analyze the V-band photometry data of the Be star omega CMa, observed during the last four decades. The data is fitted by hydrodynamic models based on the viscous decretion disk (VDD) theory, in which a disk around a fast-spinning Be star is formed by material ejected by the central star and driven to progressively wider orbits by means of viscous torques. For the first time, we apply the model for both the disk build up and the dissipation phases. Our simulations offer a good description of the photometric variability in both phases, which suggests that the VDD model adequately describes the disk structural evolution. Furthermore, our analysis allowed us to determine the viscosity parameter (alpha) of the gas, as well as the net mass loss rate. We find that alpha is variable, ranging from 0.1 to 1.0, and that build up phases have larger values of alpha than the dissipation phases. Additionally, we find that, contrary to what is generally assumed, even during quiescence the outward mass flux is never zero, suggesting that the star alternates between a high mass-loss phase (outburst) and a low mass-loss phase (quiescence).