A Transparent Window into Early-type Stellar Variability

Abstract

Abstract Subsurface convection zones are ubiquitous in early-type stars. Driven by narrow opacity peaks, these thin convective regions transport little heat but play an important role in setting the magnetic properties and surface variability of stars. Here we demonstrate that these convection zones are not present in as wide a range of stars as previously believed. In particular, there are regions which 1D stellar evolution models report to be convectively unstable but which fall below the critical Rayleigh number for onset of convection. For sub-solar metallicity this opens up a stability window in which there are no subsurface convection zones. For Large Magellanic Cloud metallicity this surface stability region extends roughly between 8 and 16M ⊙, increasing to 8–35M ⊙ for Small Magellanic Cloud metallicity. Such windows are then an excellent target for probing the relative influence of subsurface convection and other sources of photometric variability in massive stars.