The photometric variability of massive stars due to gravity waves excited by core convection

TL;DR

This study uses 3D simulations to predict photometric variability caused by gravity waves from core convection in massive stars, finding the observed red noise likely originates from other processes.

Contribution

First 3D simulations of massive star convection from core to surface with realistic luminosities, predicting gravity wave-induced photometric variability and comparing it to observations.

Findings

Gravity waves produce lower amplitude variability than observed red noise.

Predicted gravity wave signals are below current detection limits.

Red noise in observations likely arises from alternative processes.

Abstract

Massive stars die in catastrophic explosions, which seed the interstellar medium with heavy elements and produce neutron stars and black holes. Predictions of the explosion's character and the remnant mass depend on models of the star's evolutionary history. Models of massive star interiors can be empirically constrained by asteroseismic observations of gravity wave oscillations. Recent photometric observations reveal a ubiquitous red noise signal on massive main sequence stars; a hypothesized source of this noise is gravity waves driven by core convection. We present the first 3D simulations of massive star convection extending from the star's center to near its surface, with realistic stellar luminosities. Using these simulations, we make the first prediction of photometric variability due to convectively-driven gravity waves at the surfaces of massive stars, and find that gravity waves produce photometric variability of a lower amplitude and lower characteristic frequency than the observed red noise. We infer that the photometric signal of gravity waves excited by core convection is below the noise limit of current observations, so the red noise must be generated by an alternative process.