Viscous decretion discs around rapidly rotating stars

Abstract: We discuss steady viscous Keplerian decretion discs around rapidly rotating stars. We assume that low frequency modes, which may be excited by the opacity bump mechanism, convective motion in the core, or tidal force if the star is in a binary system, can transport an enough amount of angular momentum to the region close to the stellar surface. Under this assumption, we construct a star-disc system, in which there forms a viscous decretion disc around a rapidly rotating star because of the angular momentum supply. We find a series of solutions of steady viscous decretion discs around a rapidly rotating star that extend to $R_{\rm disc}\gtsim~10R_$ with $R_$ being the equatorial radius of the star, depending on the amount of angular momentum supply.