  We apply a friends-of-friends algorithm to the HectoMAP redshift survey and
cross-identify associated X-ray emission in the ROSAT All-Sky Survey data
(RASS). The resulting flux limited catalog of X-ray cluster survey is complete
to a limiting flux of $\sim3 \times10^{-13}$ erg s$^{-1}$ cm$^{-2}$ and
includes 15 clusters (7 newly discovered) with redshift $z \leq 0.4$. HectoMAP
is a dense survey ($\sim1200$ galaxies deg$^{-2}$) that provides $\sim50$
members (median) in each X-ray cluster. We provide redshifts for the 1036
cluster members. Subaru/Hyper Suprime-Cam imaging covers three of the X-ray
systems and confirms that they are impressive clusters. The HectoMAP X-ray
clusters have an $L_{X} - {\sigma}_{cl}$ scaling relation similar to that of
known massive X-ray clusters. The HectoMAP X-ray cluster sample predicts $\sim
12000 \pm3000$ detectable X-ray clusters in the RASS to the limiting flux,
comparable with previous estimates.
