Evolutionary tracks for Betelgeuse

TL;DR

This paper develops detailed evolutionary models for Betelgeuse, explaining its observed properties, surface variability, and pulsations, and estimates its progenitor mass and age based on observational constraints.

Contribution

It presents the first comprehensive non-rotating evolutionary models for Betelgeuse that incorporate multiple observational constraints and analyze surface variability and pulsations.

Findings

Progenitor mass estimated at 20 (+5, -3) solar masses.

Current age of Betelgeuse estimated at 8.0-8.5 million years.

Models successfully reproduce observed temperature, luminosity, and surface features.

Abstract

We have constructed a series of non-rotating quasi-hydrostatic evolutionary models for the M2 Iab supergiant Betelgeuse ($\alpha~Orionis$). Our models are constrained by multiple observed values for the temperature, luminosity, surface composition and mass loss for this star, along with the parallax distance and high resolution imagery that determines its radius. We have then applied our best-fit models to analyze the observed variations in surface luminosity and the size of detected surface bright spots as the result of up-flowing convective material from regions of high temperature in the surface convective zone. We also attempt to explain the intermittently observed periodic variability in a simple radial linear adiabatic pulsation model. Based upon the best fit to all observed data, we suggest a best progenitor mass estimate of $ 20 ^{+5}_{-3} M_\odot$ and a current age from the start of the zero-age main sequence of $8.0 - 8.5$ Myr based upon the observed ejected mass while on the giant branch.