Very-high energy emission from pulsars

TL;DR

Recent observations of pulsars in the very-high energy regime (>100 GeV) challenge previous models, revealing pulsed emissions from the Crab and Vela pulsars, and prompting updates to theoretical models and future predictions.

Contribution

This paper reviews recent VHE pulsar observations, discusses model refinements, and explores implications for understanding pulsar electrodynamics and future detections.

Findings

Detection of pulsed emission from the Vela pulsar up to tens of GeV.

Confirmation of pulsed emission from the Crab pulsar up to 1.5 TeV.

Deep upper limits set for the Geminga pulsar by VERITAS and MAGIC.

Abstract

The vast majority of pulsars detected by the Fermi Large Area Telescope (LAT) display exponentially cutoff spectra with cutoffs falling in a narrow band around a few GeV. Early spectral modelling predicted spectral cutoffs at energies of up to 100 GeV, assuming curvature radiation. It was therefore not expected that pulsars would be visible in the very-high energy (VHE) regime (>100 GeV). The VERITAS announcement of the detection of pulsed emission from the Crab pulsar at energies up to 400 GeV (and now up to 1.5 TeV as detected by MAGIC) therefore raised important questions about our understanding of the electrodynamics and local environment of pulsars. H.E.S.S. has now detected pulsed emission from the Vela pulsar down to tens of GeV, making this the second pulsar detected by a ground-based Cherenkov telescope. Deep upper limits have also been obtained by VERITAS and MAGIC for the Geminga pulsar. We will review the latest developments in VHE pulsar science, including an overview of the latest observations, refinements, and extensions to radiation models and magnetic field structures, and the implementation of new radiation mechanisms. This will assist us in understanding the VHE emission detected from the Crab pulsar, and predicting the level of VHE emission expected from other pulsars, which is very important for the upcoming CTA.