  We explore the analogy between a rotating magnetized black hole and an
axisymmetric pulsar and derive its electromagnetic spindown after its formation
in the core collapse of a supermassive star. The spindown shows two
characteristic phases, an early Blandford-Znajek phase that lasts a few hundred
seconds, and a late pulsar-like afterglow phase that lasts much longer. During
the first phase, the spindown luminosity decreases almost exponentially,
whereas during the afterglow phase it decreases as t^{-a} with 1<a<1,5. We
associate our findings with long duration gamma-ray bursts (GRB) and compare
with observations.
