  A new type of cosmological transient, dubbed fast radio bursts (FRBs), was
recently discovered. The source of FRBs is still unknown. One possible scenario
of an FRB is the collapse of a spinning supra-massive neutron star. Zhang
(2014) suggests that the collapse can happen shortly (hundreds to thousands of
seconds) after the birth of supra-massive neutron stars. The signatures can be
visible in X-ray afterglows of long and short gamma-ray bursts (GRBs). For
instance, a sudden drop (decay index steeper than -3 to -9) from a shallow
decay (decay index shallower than -1) in the X-ray afterglow flux can indicate
the event. We selected the X-ray afterglow light curves with a steep decay
after the shallow decay phase from the Swift/XRT GRB catalog. We analyzed when
the decay index changed suddenly by fitting these light curves to double
power-law functions and compared it with the onset of FRBs. We found none of
our GRB samples match the onset of FRBs.
