Search for pulsed VHE gamma-ray emission from young pulsars with HESS

Aims.We present the results of a search for pulsed very-high-energy (VHE) $\gamma$-ray emission from young pulsars using data taken with the HESS imaging atmospheric Cherenkov telescope system. Methods.Data on eleven pulsars, selected according to their spin-down luminosity relative to distance, are searched for $\gamma$-ray signals with periodicity at the respective pulsar spin period. Special analysis efforts were made to improve the sensitivity in the 100 GeV $\gamma$-ray energy domain in an attempt to reduce the gap between satellite and ground-based $\gamma$-ray instruments. Results.No significant evidence for pulsed emission is found in any data set. Differential upper limits on pulsed energy flux are determined for all selected pulsars in the approximate $\gamma$-ray energy range between 100 GeV and 50 TeV, using different limit determination methods, testing a wide range of possible pulsar light curves and energy spectra. Conclusions.The limits derived here imply that the magnetospheric VHE $\gamma$-ray production efficiency in young pulsars is less than 10-4 of the pulsar spin-down luminosity, requiring spectral turnovers for the high-energy emission of four established $\gamma$-ray pulsars, and constrain the inverse Compton radiation component predicted by several outer gap models.