Hot molecular bullets in HH 111 and Cep E

Many protostellar outflows show high velocity molecular bullets, in additio n to a low velocity molecular outflow and shocked H-2 knots. The velocities of these bullets suggets that they are closely related to the protostellar wind. We demonstrate from (CO)-C-12 4-3 and lower-J (CO)-C-12 and (CO)-C-1 3 observations that the CO bullets are hot, as expected for actively shocke d molecular material. This upwardly revised temperature estimate implies th at the bullets are more massive than was previously considered. The high ma sses have consequences for models of the origin of the bullets. They cannot consist of locally swept up material; they can form of material swept up a long their path only if that path is much longer than the distance between the bullets; alternatively, if they consist of jet material then the jet mu st have a density of similar to 10(4)cm(-3).