Optical Confirmation of X-ray selected Galaxy clusters from the Swift
  AGN and Cluster survey with MDM and Pan-STARRS Data (Paper III)
  To understand structure formation in the universe and impose stronger
constraints on the cluster mass function and cosmological models, it is
important to have large galaxy cluster catalogs. The Swift AGN and Cluster
Survey is a serendipitous X-ray survey aimed at building a large statistically
selected X-ray cluster catalog with 442 cluster candidates in its first
release. Our initial SDSS follow-up study confirmed $50\%$ of clusters in the
SDSS footprint as z $<$ 0.5 clusters. Here, we present further optical
follow-up analysis of 248 (out of 442) cluster candidates from the Swift
cluster catalog using multi-band imaging from the MDM $2.4m$ telescope and the
Pan-STARRS survey. We report the optical confirmation of 55 clusters with $>
3\sigma$ galaxy overdensities and detectable red sequences in the
color-magnitude space. The majority of these confirmed clusters have redshifts
z $<$ 0.6. The remaining candidates are potentially higher redshift clusters
that are excellent targets for infrared observations. We report the X-ray
luminosity and the optical richness for these confirmed clusters. We also
discuss the distinction between X-ray and optical observables for the detected
and non-detected cluster candidates.
