A photon splitting cascade model of soft gamma repeaters
Abstract
The spectra of soft gamma 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 (1) found that cascades due to photon splitting in a very strong, homogeneous magnetic field can soften spectra and produce good fits to SGR spectra. Magnetic field strengths somewhat above the QED critical field strength Bcr, where Bcr=4.413×1013 G, are 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.
- Publication:
-
Gamma-ray Bursts: 3rd Huntsville Symposium
- Pub Date:
- August 1996
- DOI:
- 10.1063/1.51622
- arXiv:
- arXiv:astro-ph/9603095
- Bibcode:
- 1996AIPC..384..941H
- Keywords:
-
- 98.70.Rz;
- 95.30.Gv;
- 97.60.Jd;
- gamma-ray sources;
- gamma-ray bursts;
- Radiation mechanisms;
- polarization;
- Neutron stars;
- Astrophysics
- E-Print:
- 5 pages in LATEX using REVTEX aipbook.sty + 4 figures (uuencoded, compressed postscript), to appear in the proceedings of the Third Huntsville Workshop on Gamma-Ray Bursts, eds. C. Kouveliotou, M. S. Briggs and G. J. Fishman (New York, AIP)