Abstract
Localized stationary structures that are embedded at supercritical driving in a convectively unstable homogeneous surrounding are investigated by numerical simulations of convection in binary fluid mixtures with weakly negative separation ratios. Bistability of pinned and moving fronts is found in a finite driving interval. The pinning mechanism and the different transition scenarios between pinned and moving fronts at the two ends of the pinning interval is identified to be strongly influenced by the concentration field. Its advective lateral redistribution acting on a sub-wavelength scale allows to explain the observed behavior.