An in-depth study of magnetospheric emission in soft gamma-ray repeaters

The association of soft gamma-ray repeaters (SGRs) with supernova remnants strongly suggests that these transient events are produced in young neutron star environments, thereby supporting the view that SGR bursts result when these stars undergo structural adjustments. Observations at X-ray and radio wavelengths of the plerions which surround two of the three known SGR sources suggest that bursts are accompanied by an outflow of energized particles. In our previous work, we showed that crustal disturbances associated with glitching activity occurring on a neutron star excite a spectrum of outwardly propagating sheared Alfven waves. Since these waves load and energize the stellar magnetosphere, an ensuing mildly relativistic stellar wind is produced. This preliminary work reproduced some of the key SGR burst features. We extend here our study of the underlying physical processes and apply our results to the three known SGR sources, thereby determining the magnetospheric conditions during bursting events. The results of our calculations allow us to determine whether SGR bursts can have an observable impact on their surrounding plerion environments. In light of the similarity between G10.0-0.3 and the Crab Nebula, we consider the possibility that glitching activity on the Crab pulsar produces SGR-like bursts and show that the wisp activity correlated with a 1969 glitching event can be explained within the framework of our model. If this scenario is correct, then a neutron star glitch, which we associate with an SGR event, can indeed produce observable flux changes in the surrounding medium, but apparently only if the total released energy is greater than or similar to 10(41) ergs for a source distance of similar to 1.5 kpc. Although the numerical estimates that lead to this conclusion are uncertain, they nonetheless point to a potentially interesting observational signature that could support the glitch and sheared Alfven wave scenario developed here.