On the Origin of Stochastic, Low-Frequency Photometric Variability in Massive Stars

TL;DR

This paper investigates the origin of stochastic low-frequency photometric variability in massive stars, proposing that subsurface convection, rather than core-driven gravity waves, is the primary cause of observed surface turbulence.

Contribution

The study demonstrates a strong correlation between subsurface convection properties and observed variability, challenging the gravity wave hypothesis as the main explanation.

Findings

Subsurface convection correlates with variability timescale and amplitude.

Surface turbulence is likely caused by subsurface convection.

Gravity wave explanation faces significant difficulties.

Abstract

High-precision photometric observations have revealed ubiquitous stochastic low-frequency photometric variability in early type stars. It has been suggested that this variability arises due to either subsurface convection or internal gravity waves launched by the convective core. Here we show that relevant properties of convection in subsurface convective layers correlate very well with the timescale and amplitude of stochastic low-frequency photometric variability, as well as with the amplitude of macroturbulence. We suggest that low-frequency, stochastic photometric variability and surface turbulence in massive stars are caused by the the presence of subsurface convection. We show that an explanation for the observed surface photometric variability and macroturbulence relying on convective core driven internal gravity waves encounters a number of difficulties and seems unlikely to be able to explain the observed trends.