Wind Competing Against Settling: A Coherent Model of the GW Virginis Instability Domain

We examine in detail the proposition that GW Vir pulsators owe their existence to a residual stellar wind that competes against the settling of the carbon and oxygen atoms which 'fuel' pulsational instabilities via their opacity. With cooling, the fading wind progressively loses its capacity to maintain enough of these opaque atoms in the driving region, leading naturally to a red edge where pulsations disappear. We investigate, in particular, the effects of changing the mass-loss law and the initial envelope composition on the position of the red edge in the log g-T{sub eff} diagram. With this approach, we derive a coherent picture of the GW Vir instability domain.