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

Matteo Cantiello,Luca Grassitelli,Daniel Lecoanet,Adam S Jermyn

doi:10.3847/1538-4357/ac03b0

Abstract

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 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.

Highlights

Massive stars largely drive the dynamical and chemical evolution of gas in galaxies (e.g. Hopkins et al 2014)
It has been suggested that this variability arises due to either subsurface convection or internal gravity waves launched by the convective core
We show that one way to differentiate between the two proposed mechanisms is by examining macroturbulence and SLF in massive stars with surface magnetic fields, since magnetic effects have a larger impact on core internal gravity waves (IGWs) than on the FeCZ

Summary

Introduction

Massive stars largely drive the dynamical and chemical evolution of gas in galaxies (e.g. Hopkins et al 2014). They accomplish this via their stellar winds, eruptions, and explosive deaths, producing neutron stars and black holes (Langer 2012). These compact remnants can merge and generate the gravitational waves observed by LIGO/Virgo (Abbott et al 2016). The evolutionary trajectory starting with a massive star burning hydrogen in its core and ending with a compact remnant is understood only qualitatively. The picture is further complicated by the fact that the majority of massive stars are found in multiple systems (Sana et al 2012), with a large fraction expected to interact with their companions (de Mink et al 2014)

Methods

Results

Discussion

Conclusion