  The occurrence rates of bright X-ray flares in z<1 gamma-ray bursts (GRBs)
with or without observed supernovae (SNe) association were compared. Our Sample
I: the z<1 long GRBs (LGRBs) with SNe association (SN-GRBs) and with early
Swift/X-Ray Telescope (XRT) observations, consists of 18 GRBs, among which only
two GRBs have bright X-ray flares. Our Sample II: for comparison, all the z<1
LGRBs without observed SNe association and with early Swift/XRT observations,
consists of 45 GRBs, among which 16 GRBs present bright X-ray flares. Thus, the
study indicates a lower occurrence rate of bright X-ray flares in Sample I
(11.1%) than in Sample II (35.6%). In addition, if dim X-ray fluctuations are
included as flares, then 16.7% of Sample I and 55.6% of Sample II are found to
have flares, again showing the discrepancy between these two samples. We
examined the physical origin of these bright X-ray flares and found that most
of them are probably related to the central engine reactivity. To understand
the discrepancy, we propose that such a lower occurrence rate of flares in the
SN-GRB sample may hint at an energy partition among the GRB, SNe, and X-ray
flares under a saturated energy budget of massive star explosion.
