We have examined 40 NuSTAR light curves (LCs) of five TeV emitting high
synchrotron peaked blazars: 1ES 0229+200, Mrk 421, Mrk 501, 1ES 1959+650 and
PKS 2155-304. Four of the blazars showed intraday variability in the NuSTAR
energy range of 3-79 keV. Using an auto correlation function analysis we
searched for intraday variability timescales in these LCs and found indications
of several between 2.5 and 32.8 ks in eight LCs of Mrk 421, a timescale around
8.0 ks for one LC of Mrk 501, and timescales of 29.6 ks and 57.4 ks in two LCs
of PKS 2155-304. The other two blazars' LCs do not show any evidence for
intraday variability timescales shorter than the lengths of those observations,
however, the data was both sparser and noisier, for them. We found positive
correlations with zero lag between soft (3-10 keV) and hard (10-79 keV) bands
for most of the LCs, indicating that their emissions originate from the same
electron population. We examined spectral variability using a hardness ratio
analysis and noticed a general "harder-when-brighter" behavior. The 22 LCs of
Mrk 421 observed between July 2012 and April 2013 show that this source was in
a quiescent state for an extended period of time and then underwent an
unprecedented double peaked outburst while monitored on a daily basis during 10
- 16 April 2013. We briefly discuss models capable of explaining these blazar
emissions.Comment: 21 pages, 4 figures, 4 tables, Accepted for Publication in Ap
