  Context. The Cygnus OB2 association, the central engine of the Cygnus X
star-forming region, is the subject of an extensive INTEGRAL Key Project that
will accumulate 6Ms of observations. Analysis of 2Ms of observations by De
Becker and co-workers provides the most sensitive limit yet obtained on hard
X-ray emission from the cluster. Aims. We investigate the X-ray emission in the
20-40 keV band expected from the flaring low-mass stellar population in Cygnus
OB2. We discuss whether such emission needs to be considered in the
interpretation of existing and future X-ray observations of the region, and
whether such observations might provide insight into the high-energy processes
on low-mass pre-main sequence stars. Methods. The total hard X-ray flux from
low-mass stars is estimated by assuming the observed soft X-ray emission stems
from a superposition of flares. We further assume the ratio of hard X-ray to
soft X-ray emission is described by a scaling found for solar flares by Isola
and co-workers. Results. We estimate the low-mass stellar hard X-ray flux in
the 20-40 keV band to lie in the range ~2x10^31-6x10^32 erg/s and discuss some
potential biases that might affect this result. Conclusions. Hard X-ray
emission could lie at a level not much below the current observed flux upper
limits for Cygnus OB2. If this emission could be detected, it would provide
insight into the hard X-ray production of large flares on pre-main sequence
stars. We highlight the penetrating power of hard X-rays from low-mass stellar
populations as a possible pointer to our Galaxy's hidden star-forming clusters
and super-clusters using more sensitive observations from future missions.
