  We analyzed in a systematic way the public INTEGRAL observations spanning
from December 2002 to September 2016, to investigate the hard X-ray properties
of about 60 High Mass X-ray Binaries (HMXBs). We considered both persistent and
transient sources, hosting either a Be star (Be/XRBs) or a blue supergiant
companion (SgHMXBs, including Supergiant Fast X-ray Transients, SFXTs), a
neutron star or a black hole. INTEGRAL X-ray light curves (18-50 keV), sampled
at a bin time of about 2 ks, were extracted for all HMXBs to derive the
cumulative distribution of their hard X-ray luminosity, their duty cycle, the
range of variability of their hard X-ray luminosity. This allowed us to obtain
an overall and quantitative characterization of the long-term hard X-ray
activity of the HMXBs in our sample. Putting the phenomenology observed with
INTEGRAL into context with other known source properties (e.g. orbital
parameters, pulsar spin periods) together with observational constraints coming
from softer X-rays (1-10 keV), enabled the investigation of the way the
different HMXB sub-classes behave (and sometimes overlap). For given source
properties, the different sub-classes of massive binaries seem to cluster in a
suggestive way. However, for what concerns supergiant systems (SgHMXBs versus
SFXTs), several sources with intermediate properties exist, suggesting a smooth
transition between the two sub-classes.
