Michelle Tsirou (MPIK-Heidelberg, Germany)

The flaring behaviour of the Crab pulsar wind nebula in high-energy gamma-rays : signatures originating from lepton acceleration in pulsar winds (?)

The Crab pulsar wind nebula system is one of the brightest gamma-ray sources in our galaxy, observed across the electromagnetic spectrum. Its extreme behaviour has repeatedly challenged several theoretical models and predictions over the last decades, demanding further insight on acceleration mechanisms and radiation processes. Recent studies purport intermittent flaring events deviating from the continuous flux associated with its synchrotron spectrum in energy ranges below a few hundreds of MeV, straining the theoretical synchrotron burn-off limit.
By analysing available Fermi-LAT data across a thirteen-year-long monitoring, we study the energy-dependence of several observed high-energy flares in a few hundred MeV up to a few GeV energy ranges. We attempt preliminary comparison of acceleration models behind the variability of the emission and discuss observational signatures prone to distinguish competing mechanisms for the small-flare modes.