Ghoreyshi, M. R.
Carciofi, A. C.
Rimulo, L. R.
Vieira, R. G.
Faes, D. M.
Bjorkman, J. E.
Total Authors: 9
 Univ Sao Paulo, Inst Astron Geofis & Ciencias Atmosfer, Rua Matao 1226, BR-05508900 Sao Paulo, SP - Brazil
 RIAAM, Maragha 55134441 - Iran
 European Org Astron Res Southern Hemisphere ESO, Karl Schwarzschild Str 2, D-85748 Garching - Germany
 Univ Toledo, Dept Phys Astron, MS111 2801 West Bancroft St, Toledo, OH 43606 - USA
 AAVSO, Cambdrige, MA - USA
 European Org Astron Res Southern Hemisphere ESO, Casilla 19001, Santiago 19 - Chile
Total Affiliations: 6
Monthly Notices of the Royal Astronomical Society;
Web of Science Citations:
We analysed V-band photometry of the Be star omega CMa, obtained during the last four decades, during which the star went through four complete cycles of disc formation and dissipation. The data were simulated by hydrodynamic models based on a time-dependent implementation of the viscous decretion disc (VDD) paradigm, in which a disc around a fast-spinning Be star is formed by material ejected by the star and driven to progressively larger orbits by means of viscous torques. Our simulations offer a good description of the photometric variability during phases of disc formation and dissipation, which suggests that the VDD model adequately describes the structural evolution of the disc. Furthermore, our analysis allowed us to determine the viscosity alpha, as well as the net mass and angular momentum (AM) loss rates. We find that alpha is variable, ranging from 0.1 to 1.0, not only from cycle to cycle but also within a given cycle. Additionally, build-up phases usually have larger values of a than the dissipation phases. Furthermore, during dissipation the outward AM flux is not necessarily zero, meaning that omega CMa does not experience a true quiescence (b)ut, instead, switches between a high to a low AM loss rate during which the disc quickly assumes an overall lower density but never zero. We confront the average AM loss rate with predictions from stellar evolution models for fast-rotating stars, and find that our measurements are smaller by more than one order of magnitude. (AU)