Spatial and Time Clustering of the High-Energy Photons collected by the Fermi LAT

The past decade has seen a dramatic improvement in the quality of data available at both high (HE, > 10 GeV ) and very high (VHE, > 100 GeV ) gamma-ray energies. Thanks to the latest Pass8 data release by Fermi LAT which increases the overlap in energy coverage with Cherenkov Telescopes, we can extend the observation in gamma rays until few TeV. We developed, applied and tested a new time and spatial clustering algorithm, which is able to analyse the whole Fermi LAT data set (about 7 years) as well as sets of shorter time intervals. Using time and spatial clusters of HE photons collected by the Fermi LAT data we both provide new candidates for VHE experiments and study the variability of gamma-ray properties of known HE sources.