http://arxiv.org/abs/2006.09837
We conduct a rigorous examination of the nearby red supergiant $\alpha$ Orionis, or Betelgeuse, by drawing on the synthesis of new observational data and three different modeling techniques. Our observational results include the release of new, processed photometric measurements collected with the space-based SMEI instrument prior to Betelgeuse’s recent, unprecedented dimming event. Our theoretical predictions include self-consistent results from multi-timescale evolutionary, oscillatory, and hydrodynamic simulations conducted with the Modules for Experiments in Stellar Astrophysics (MESA) software suite. Significant outcomes of our modeling efforts include a precise prediction for the star’s radius: $750^{+62}{-30}\,R{\odot}$. In concert with additional constraints, this allows us to derive a new, independent distance estimate of $165^ {+16}{-8}$\,pc and a parallax of $\pi=6.06^{+0.31}{-0.52}$\,mas, in good agreement with \textit{Hipparcos} but less so with recent radio measurements. Seismic results from both perturbed hydrostatic and evolving hydrodynamic simulations constrain the period and driving mechanisms of Betelgeuse’s dominant periodicities in new ways. Our analyses converge to the conclusion that Betelgeuse’s $388$ day period is the result of pulsation in the fundamental mode, driven by the $\kappa$-mechanism. Grid-based hydrodynamic modeling reveals that the behavior of the oscillating envelope is mass-dependent, and likewise suggests that the non-linear pulsation excitation time could serve as a mass constraint. Our results corroborate recent conclusions that Betelgeuse is the outcome of a past merger. We place it definitively in the core helium-burning phase near the base of the red supergiant branch, and we report a present-day mass of $16.5$–$19 ~M_{\odot}$—slightly lower than typical literature values.
M. Joyce, S. Leung, L. Molnár, et. al.
Thu, 18 Jun 20
43/84
Comments: Comments welcome