The Betelgeuse Project II: Asteroseismology

TL;DR

This study investigates the potential of asteroseismology to probe the internal structures of massive red supergiant supernova progenitors by modeling their convective zones and wave generation during different burning stages.

Contribution

It provides the first detailed estimates of wave frequencies and surface luminosity modulations in massive red supergiants during key evolutionary phases, incorporating rotation effects.

Findings

Inner convective zones generate waves with periods of ~20 days during core helium burning.

Surface luminosity fluctuations could reach a few millimagnitudes early in core helium burning.

Wave signals are likely damped within the envelope, especially during shell carbon burning.

Abstract

We explore the question of whether the interior state of massive red supergiant supernova progenitors can be effectively probed with asteroseismology. We have computed a suite of ten models with ZAMS masses from 15 to 25 m_sun in intervals of 1 m_sun, including the effects of rotation, with the stellar evolutionary code MESA. We estimate characteristic frequencies and convective luminosities of convective zones at two illustrative stages, core helium burning and off-center convective carbon burning. We also estimate the power that might be delivered to the surface to modulate the luminous output considering various efficiencies and dissipation mechanisms. The inner convective regions should generate waves with characteristic periods of ~20 days in core helium burning, ~10 days in helium shell burning, and 0.1 to 1 day in shell carbon burning. Acoustic waves may avoid both shock and diffusive dissipation relatively early in core helium burning throughout most of the structure. In shell carbon burning, years before explosion, the signal generated in the helium shell might in some circumstances be weak enough to avoid shock dissipation, but is subject to strong thermal dissipation in the hydrogen envelope. Signals from a convective carbon-burning shell are very likely to be even more severely damped within the envelope. In the most optimistic case, early in core helium burning, waves arriving close to the surface could represent luminosity fluctuations of a few millimagnitudes, but the conditions in the very outer reaches of the envelope suggest severe thermal damping there.