Pulsar Emission above the Spectral Break - A Stacked Approach

NASA's Fermi space telescope has provided us with a bountiful new population of gamma-ray sources following its discovery of 150 new gamma-ray pulsars. One common feature exhibited by all of these pulsars is the form of their spectral energy distribution, which can be described by a power law followed by a spectral break occurring between $\sim$1 and $\sim$8 GeV. The common wisdom is that the break is followed by an exponential cut-off driven by radiation/reaction-limited curvature emission. The discovery of pulsed gamma rays from the Crab pulsar, the only pulsar so far detected at very high energies (E$>$100GeV), contradicts this "cutoff" picture. Here we present a new stacked analysis with an average of 4.2 years of data on 115 pulsars published in the 2nd LAT catalog of pulsars. This analysis is sensitive to low-level $\sim$100 GeV emission which cannot be resolved in individual pulsars but can be detected from an ensemble.