  The spectra of soft gamma-ray repeaters (SGRs), with the exception of the
March 5, 1979 main burst, are characterized by high-energy cutoffs around 30
keV and low-energy turnovers that are much steeper than a Wien spectrum. Baring
(1995) found that the spectra of cascades due to photon splitting in a very
strong, homogeneous magnetic field can soften spectra and produce good fits to
the soft spectra of SGRs. Magnetic field strengths somewhat above the QED
critical field strength $B_{\rm cr}$, where $B_{\rm cr} = 4.413 \times 10^{13}$
G, is required to produce cutoffs at 30-40 keV. We have improved upon this
model by computing Monte Carlo photon splitting cascade spectra in a neutron
star dipole magnetic field, including effects of curved space-time in a
Schwarzschild metric. We investigate spectra produced by photons emitted at
different locations and observer angles. We find that the general results of
Baring hold for surface emission throughout most of the magnetosphere, but that
emission in equatorial regions can best reproduce the constancy of SGR spectra
observed from different bursts.
