  The BATSE experiment has now observed more than 1100 gamma-ray bursts. The
observed angular distribution is isotropic, while the brightness distribution
of bursts shows a reduced number of faint events. These observations favor a
cosmological burst origin. Alternatively, very extended Galactic Halo (EGH)
models have been considered. In the latter scenario, the currently favored
source of gamma-ray bursts involves high velocity pulsars ejected from the
Galactic disk. To be compatible with the observed isotropy, most models invoke
a sampling distance of 300 kpc, a turn-on delay of 30 Myrs, and a source life
time of about 1 Gyr. We consider the global energy requirements of such models
and show that the largest known resource. rotational kinetic energy, is
insufficient by orders of magnitude to provide the observed burst rate. More
exotic energy sources or differently tuned pulsar models may be able to get
around the global energy constraint but at the cost of becoming contrived.
Thus, while extended halo models are not ruled out, our arguments place a
severe obstacle for such models and we encourage proponents of EGH models to
clearly address the issue of global energetics.
