  In certain field theoretical models, composite solitons consisting of a
domain wall and vortex lines attached to the wall have been referred to as
D-brane solitons. We show that similar composite solitons can be realized in
phase-separated two-component Bose-Einstein condensates. We discuss the
similarities and differences between topological solitons in the Abelian-Higgs
model and those in two-component Bose-Einstein condensates. Based on the
formulation of gauge theory, we introduce the "boojum charge" to characterize
the "D-brane soliton" in Bose-Einstein condensates.
