Very-high energy emission from pulsars

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 veryhigh 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 groundbased 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.

New Advances in the Modelling of Pulsar Magnetospheres

“…There exist a number of complementary reviews, e.g., by Beskin [14] giving a chronological overview of the development of pulsar magnetosphere models, Caraveo [18] providing an observational γ-ray pulsar overview, Melrose & Yuen [71] as well as Cerutti & Beloborodov [22] relating progress in the development of pulsar electrodynamics, Hirotani [56] reviewing outer gap (OG) and slot gap (SG) models, Harding [52] reviewing polar cap (PC) and SG models, Venter & Harding [113] assessing the impact of geometric light curve modelling on pulsar emission characterisation, Grenier & Harding [43] focusing on the Fermi LAT legacy plus implications for theory, Harding [53] discussing the use of light curve modelling in vacuum, force-free (FF) and dissipative MHD magnetosphere models to probe pulsar magnetospheric structure as well as that of the emission region, Contopoulos [29] discussing the current sheet (CS), Y-point (Section 3), and dissipation of energy, and Breed et al [17] summarising the young field of very-high-energy pulsar science.…”