  We investigate one-dimensional (1D) Majorana bound states (MBSs) realized in
terms of the helical edge states of a 2D quantum spin-Hall insulator (QSHI) in
a heterostructure with a superconducting substrate and two ferromagnetic
insulators (FIs). By means of Bogoliubov-de Gennes approach we demonstrate that
there is a helical spin texture in the MBS wave function with a pitch
proportional to the Fermi momentum of the helical edge states of QSHI.
Moreover, simultaneous detection on local density of states by scanning
tunneling microscopy and spectroscopy at a position close to one FI edge and at
the midpoint between two FIs can not only map out the energy spectrum $\pm E
\cos(\phi/2)$, but also prove experimentally that the two quasiparticle
excitations do not mix with each other as protected by the parity conservation
associated with the MBSs.
