Prospects for Observations of Pulsars and Pulsar Wind Nebulae with CTA

The last few years have seen a revolution in very-high gamma-ray astronomy (VHE; E>100 GeV) driven largely by a new generation of Cherenkov telescopes (namely the H.E.S.S. telescope array, the MAGIC and MAGIC-II large telescopes and the VERITAS telescope array). The Cherenkov Telescope Array (CTA) project foresees a factor of 5 to 10 improvement in sensitivity above 0.1 TeV, extending the accessible energy range to higher energies up to 100 TeV, in the Galactic cut-off regime, and down to a few tens GeV, covering the VHE photon spectrum with good energy and angular resolution. As a result of the fast development of the VHE field, the number of pulsar wind nebulae (PWNe) detected has increased from one PWN in the early ’90s to more than two dozen firm candidates today. Also, the low energy threshold achieved and good sensitivity at TeV energies has resulted in the detection of pulsed emission from the Crab Pulsar (or its close environment) opening new and exiting expectations about the pulsed spectra of the high energy pulsars powering PWNe. Here we discuss the physics goals we aim to achieve with CTA on pulsar and PWNe physics evaluating the response of the instrument for different configurations.

💡 Research Summary

The paper “Prospects for Observations of Pulsars and Pulsar Wind Nebulae with CTA” presents a comprehensive assessment of how the upcoming Cherenkov Telescope Array (CTA) will advance our understanding of pulsars and their associated pulsar wind nebulae (PWNe) in the very‑high‑energy (VHE) gamma‑ray regime. The authors begin by summarising the rapid progress made over the past decade with the current generation of imaging atmospheric Cherenkov telescopes (IACTs) – H.E.S.S., MAGIC, and VERITAS – which have increased the known population of PWNe from a single object in the early 1990s to more than two dozen firm candidates today. They note that the detection of pulsed emission from the Crab pulsar at energies up to several hundred GeV has opened a new window on pulsar magnetospheric physics.

CTA is described as a next‑generation facility that will improve sensitivity by a factor of five to ten above 0.1 TeV, lower the energy threshold to a few tens of GeV, and extend the observable band up to ~100 TeV. In addition, CTA will deliver an angular resolution better than 3 arcmin, a systematic pointing accuracy of ~5 arcsec, and a field of view (FoV) of at least 1.5 degrees. These capabilities are crucial for two broad scientific goals: (1) detailed studies of PWNe, and (2) exploration of the VHE pulsed spectra of pulsars.

For PWNe, the authors outline several key objectives. First, the large FoV will allow CTA to image the full spatial extent of many PWNe, which can be as large as 1°–1.2° in gamma‑rays, while the fine angular resolution will enable the separation of sub‑structures (e.g., torii, jets, and relic halos). Second, the wide energy coverage will make it possible to trace the cooling of relativistic electrons through both synchrotron and inverse‑Compton (IC) processes, distinguishing between radiative and adiabatic losses. Third, CTA’s resolution will help disentangle emission from composite systems where a supernova remnant shell coexists with a PWN (e.g., Kes 75, G21.5‑0.9), a task that is currently limited by the ≈3′ resolution of existing IACTs. Fourth, the improved sensitivity for extended sources (which scales as 1/d rather than 1/d²) will permit a homogeneous Galactic survey of PWNe out to distances of ~50 kpc, including objects in the Large Magellanic Cloud. Finally, the wealth of spectral and morphological data will provide stringent constraints for magnetohydrodynamic (MHD) simulations, allowing direct estimates of magnetic field evolution, particle injection spectra, and energy conversion efficiencies.

Regarding pulsars, the paper emphasizes the need to probe the VHE extension of the pulsed spectra beyond the few‑GeV cutoffs observed by Fermi‑LAT. Current models (polar‑cap, outer‑gap, slot‑gap, striped‑wind, force‑free magnetosphere) predict markedly different spectral shapes at tens to hundreds of GeV, ranging from super‑exponential cutoffs to double‑power‑law tails. The detection of pulsed emission from the Crab pulsar up to ~400 GeV by VERITAS and MAGIC already challenges simple polar‑cap scenarios. CTA’s low energy threshold (≈20 GeV) and excellent phase‑resolved sensitivity will enable systematic searches for VHE pulsations from a large sample of Fermi‑LAT pulsars, including millisecond pulsars and those in globular clusters. Precise phase‑resolved spectra will constrain the location of the acceleration gaps (e.g., the outer boundary relative to the light cylinder) and test whether additional IC components from secondary pairs contribute at the highest energies.

The authors evaluate three representative CTA configurations, varying telescope size distribution, FoV, and pixelization, and simulate their performance for both extended PWNe and point‑like pulsar signals. The simulations show that a configuration combining a large FoV with sub‑3′ angular resolution maximizes the detection of extended PWNe and resolves internal structures, while a configuration with the lowest possible energy threshold is essential for detecting pulsed emission below 30 GeV.

In conclusion, the paper argues that CTA will transform VHE studies of pulsars and PWNe. By acting as a “calorimeter” for relativistic electrons, CTA will reveal the time‑dependent energy budget of PWNe, clarify particle transport mechanisms, and provide the first systematic VHE pulsar population study. These observations will feed directly into theoretical models of particle acceleration in relativistic winds and magnetospheric gap physics, thereby opening a new era in high‑energy astrophysics.