Evolutionary Tracks of Betelgeuse

We have constructed a series of quasi-hydrostatic evolutionary models for the M2 Iab supergiant Betelgeuse (α Orionis). Our models are constrained by the observed temperature, luminosity, surface composition and mass loss for this star, along with recent parallax measurements and high resolution imagery which directly determine its radius. The surface convective zone obtained in our model roughly accounts for observed variations in surface luminosity and the size of detected surface bright spots. In our models these result from upflowing convective material from regions of high temperature in the surface convective zone. We also account for the observed periodic variability as the result of the equation of state in a simple linear pulsation model. Based upon a best fit to all observed data we suggest a mass estimate of ≈ 21±2 M⊙.