Deneb's variability: a hint of a deep-lying convection zone?

Abstract

During their post - main-sequence evolution, massive star models harbor a convection zone on top of their hydrogen burning shell. This physical property helps, under suitable circumstances, to destabilize low-degree nonradial modes that might explain the cyclic light variability of $\alpha $ Cygni variables. The results of first exploratory computations demonstrate that modes with periods ranging from about one dozen to several dozen days can be overstable in star models at about the position on the HR diagram where the prototype of the class, Deneb, is observed.