Spectral studies of magnetic photon splitting in the March 5 event and SGR 1806-20

[[abstract]]Soft Gamma Repeaters (SGRs) have been proposed to be neutron stars with extremely strong magnetic fields of greater than or similar to 5 x 10(14) G. The spectra of SGR 1806-20 and the initial spike of the March 5 event can be fitted by a photon-splitting modified spectrum under such a strong magnetic field. A moderate beaming pattern is needed for the emission producing the initial spike of the March 5 event, and the strength of its magnetic field is not well constrained by spectral fitting. An extended emission region over the whole stellar surface is preferred for SGR 1806-20 rather than a localized equatorial region. The intrinsic emission of SGR 1806-20 should be nearly isotropic. The magnetic field near the surface of SGR 1806-20 should be > 10 B-c (B-c = 4.4 x 10(13) G) and its GM/c(2)R is greater than or similar to 0.25.[[fileno]]2010507010040[[department]]天文