Pulsar Wind Nebulae: The GeV to TeV Connection

摘要

In this paper we focus on pulsar wind nebulae (PWN) which show both GeV and TeV emission. In the case of the Crab Nebula we discuss the implications of the synchrotron cutoff of the Nebula as seen by Fermi-Lat and the implications thereof for particle acceleration at the highest energies. We also show that the emission from almost all PWN as seen in the TeV domain are consistent with electrons that have mostly cooled as a result of synchrotron losses in the extended volume of the PWN, whereas flatter spectrum GeV emission is expected as a result of the relatively long cooling times for these GeV emitting electrons. Such GeV emission is also expected to show a clear scaling with the birth period of the pulsar. This predicted GeV-TeV connection is clearly seen for the PWN of PSR B1509-58. Finally, PWN with two spectral components (radio and X-ray) are also expected to show discontinuous GeV to TeV spectra as seen for Vela X and possibly also for HESS J1640-465. In the case of Vela X we also see this two-component behaviour in the spectrum and morphology of the region close to the pulsar wind termination shock.