Super Eightbrane in Superspace

We present a superspace formulation for super eightbrane theory based on massive type IIA supergravity in ten-dimensions. Remarkably, in addition to the 10-form superfield strength originally needed for super eightbrane, we also need an `over-ranked' 11-form superfield strength $H_{A_1... A_{11}}$ with identically vanishing purely bosonic component, in order to satisfy all the Bianchi identities. As a natural super p-brane formulation for the 11-form superfield strength, we present a super ninebrane action on 10-dimensional super-worldvolume invariant under a local fermionic $\k$-symmetry. We also show that we can formulate such a superspace with an `over-ranked' superfield strength also in eleven-dimensions, and possibly in other lower dimensions as well.