Gamma-ray bursts from blast waves around Galactic neutron stars

If gamma-ray bursts originate in our Galaxy, they probably involve violentdisturbances in the magnetospheres of neutron stars. Any event of this kind islikely to trigger the sudden expulsion of magnetic flux and plasma atrelativistic speed. We show that such ejecta would be braked by theinterstellar medium (ISM), and that a gamma-ray flash with duration $\sim 0.1 -100 $ s may result from this interaction. We suggest that thestronger,``smooth"class of bursts, recently identified from analyses of BATSEdata, could result from the deceleration of such a blast wave by the ISM. Theradiative efficiency,and hence the detectability, of such bursts would dependon the density of the circumstellar ISM. Therefore, even if the neutron star``triggers" were uniformly distributed in space (at least within 1--2 kpc ofthe Sun), the bserved locations of bursts would correlate with regions ofabove-average ISM density.Comment: 7pages, te