| Abstract: | To search for giant X-ray pulses correlated with the giant radio pulses
(GRPs) from the Crab pulsar, we performed a simultaneous observation of the
Crab pulsar with the X-ray satellite Hitomi in the 2 -- 300 keV band and the
Kashima NICT radio observatory in the 1.4 -- 1.7 GHz band with a net exposure
of about 2 ks on 25 March 2016, just before the loss of the Hitomi mission.The
timing performance of the Hitomi instruments was confirmed to meet the timing
requirement and about 1,000 and 100 GRPs were simultaneously observed at the
main and inter-pulse phases, respectively, and we found no apparent correlation
between the giant radio pulses and the X-ray emission in either the main or
inter-pulse phases.All variations are within the 2 sigma fluctuations of the
X-ray fluxes at the pulse peaks, and the 3 sigma upper limits of variations of
main- or inter- pulse GRPs are 22\% or 80\% of the peak flux in a 0.20 phase
width, respectively, in the 2 -- 300 keV band.The values become 25\% or 110\%
for main or inter-pulse GRPs, respectively, when the phase width is restricted
into the 0.03 phase.Among the upper limits from the Hitomi satellite, those in
the 4.5-10 keV and the 70-300 keV are obtained for the first time, and those in
other bands are consistent with previous reports.Numerically, the upper limits
of main- and inter-pulse GRPs in the 0.20 phase width are about (2.4 and 9.3)
$ imes 10^{-11}$ erg cm$^{-2}$, respectively. No significant variability in
pulse profiles implies that the GRPs originated from a local place within the
magnetosphere and the number of photon-emitting particles temporally
increases.However, the results do not statistically rule out variations
correlated with the GRPs, because the possible X-ray enhancement may appear due
to a $>0.02$\% brightening of the pulse-peak flux under such conditions. |
REGISTER
Did you like this article? 
