X-ray flares in the early swift observations of the possible naked burst GRB 050421

We present the Swift observations of the faint burst GRB 050421. The X-ray light-curve shows two flares: the first flare peaking at ∼ 110 s after the BAT trigger (T₀) and the second one peaking at ∼154 s. We argue that the mechanism producing these flares is probably late internal shocks. The X-ray light-curve shows a rapid decline with a temporal index α ∼ 3.1. The X-ray source disappears completely less than 1 hour after the trigger. An X-ray spectral softening is also observed with time from β ∼ 0.1 to ∼ 1.2. A good joint fit to the BAT and XRT spectra indicates that the early X-ray and Gamma-ray emissions are produced by the same mechanism. The X-ray spectral softening is likely due to a shift down to lower energies of the peak of the prompt emission, and the rapid decline of the X-ray emission is probably the tail of the prompt emission. This suggests that the X-ray emission is completely dominated by high latitude radiation and the external shock, if any, is below the detection threshold.