Prospects for the characterization of the VHE emission from the Crab nebula and pulsar with the Cherenkov Telescope Array

Abstract

The Cherenkov Telescope Array (CTA) will be the next generation instrument for the very high energy gamma-ray astrophysics domain. With its enhanced sensitivity in comparison with the current facilities, CTA is expected to shed light on a varied population of sources. In particular, we will achieve a deeper knowledge of the Crab nebula and pulsar, which are the best characterized pulsar wind nebula and rotation powered pulsar, respectively. We aim at studying the capabilities of CTA regarding these objects through simulations, using the main tools currently in development for the CTA future data analysis: gammapy and ctools. We conclude that, even using conservative Instrument Response Functions, CTA will be able to resolve many uncertainties regarding the spectrum and morphology of the pulsar and its nebula. The large energy range covered by CTA will allow us to disentangle the nebula spectral shape among different hypotheses, corresponding to different underlying emitting mechanisms. In addition, resolving internal structures (smaller than ∼0.02° in size) in the nebula and unveiling their location, would provide crucial information about the propagation of particles in the magnetized medium. We used a theoretical asymmetric model to characterize the morphology of the nebula and we showed that if predictions of such morphology exist, for instance as a result of hydrodynamical or magneto-hydrodynamical simulations, it can be directly compared with CTA results. We also tested the capability of CTA to detect periodic radiation from the Crab pulsar obtaining a precise measurement of different light curves shapes.

The Crab nebula variability at short time-scales with the Cherenkov telescope array

“…For that purpose, we performed a number of simulations to reproduce the ∼400 MeV emission detected by gamma-ray satellites, and derived the expected emission in the high energy regime, under different conditions of magnetic and photon fields, and particle spectral energy distribution. The comparison with the CTA simulated data (see Mestre et al 2020), and previous IACTs observations (H. E. S. S. Collaboration et al 2014) result in constraints on the physical parameters ruling the flare emission.…”

“…In our simulations, the background is dominated by the emission from the nebula, specially in the TeV regime. To account for that, we used the results from the simulations presented in our previous work (Mestre et al 2020). In particular, we used the spectral shape described as a log-parabola as in Aleksić et al 2015.…”

Testing source confusion and identification capability in Cherenkov telescope array data

“…The latter software was adopted as the Science Analysis Tools of the CTA by the CTA Observatory (CTAO), being this decision announced on 1 June 2021 5 . Both softwares were proven to be stable, providing nearly identical high-level analysis results (such as events sky maps or spectra) in different analyses (Mohrmann et al 2019;Mestre et al 2020). Hence, we do not expect significantly different results if implementing our simulation scheme in .…”

The Crab Pulsar and Nebula as Seen in Gamma-Rays

“…This can be seen in Figure 4, which also clearly shows how the jet-torus structure should become visible again at TeV energies. Probing the nebular morphology at this level of detail in VHE gamma-rays is however beyond the reach of current and planned instruments [82]. One thing that gamma-rays can readily probe, however, is the goodness of 2D MHD models at correctly describing the energy content of the nebula: in fact, the main limitations inherent to the assumption of axisymmetry become apparent as soon as one compares the IC spectrum computed from simulations with the available data.…”