X-ray plateaus followed by sharp drops in GRBs 060413, 060522, 060607A
  and 080330: Further evidences for central engine afterglow from Gamma-ray
  Bursts
  The X-ray afterglows of GRBs 060413, 060522, 060607A and 080330 are
characterized by plateaus that are followed by very sharp drops. An X-ray
plateau is interpretable within the framework of the external forward shock
model but the sharp drop is not. In this work we interpret these peculiar X-ray
afterglow data as the central engine afterglows from some magnetized central
engines, plausibly magnetars. In this model, the X-ray afterglows are powered
by the internal magnetic energy dissipation and the sudden drop is caused by
the collapse of the magnetar. Accordingly, the X-ray plateau photons should
have a high linear polarization, which can be tested by the future X-ray
polarimetry.
