  The Swift X-Ray Telescope often observes a rapidly decaying X-ray emission
stretching to as long as $ t \sim 10^3$ seconds after a conventional prompt
phase. This component is most likely due to a prompt emission viewed at large
observer angles $\theta > 1/\Gamma$, where $\theta\sim 0.1$ is a typical
viewing angle of the jet and$\Gamma\geq 100$ is the Lorentz factor of the flow
during the prompt phase. This can be used to estimate the prompt emission
radii, $r_{em} \geq 2 t c/\theta^2 \sim 6 \times 10^{15}$ cm. These radii are
much larger than is assumed within a framework of a fireball model. Such large
emission radii can be reconciled with a fast variability, on time scales as
short as milliseconds, if the emission is beamed in the bulk outflow frame,
e.g. due to a random relativistic motion of ''fundamental emitters''. This may
also offer a possible explanation for X-ray flares observed during early
afterglows.
