Multiband Nonthermal Radiative Properties of the Pulsar Wind Nebula CTB 87

Abstract: The pulsar wind nebula CTB 87 (G74.9+1.2) is one of the sources emitting $\gamma$-rays with energies higher than 10 TeV, as measured by the Very Energetic Radiation Imaging Telescope Array System telescope (VERITAS). In this study, we undertake a reanalysis of the GeV emission from the CTB 87 region, utilising $\sim$16 years of high-energy $\gamma$-ray data collected with the Fermi Large Area Telescope. In the energy range of 0.03--1 TeV, the spectrum can be adequately described by a power-law model with an index of 1.34 $\pm$ 0.18, and the integral energy flux is calculated to be (7.25 $\pm$ 1.36) $\times$ 10$^{-13}$ erg cm$^{-2}$ s$^{-1}$. Based on the multiband data, we have employed a time-dependent model to investigate the non-thermal emission properties of CTB 87. In the model, it is assumed that particles with broken power-law energy distributions are continuously injected into the nebula. This results in multiband non-thermal emission being produced by relativistic leptons via synchrotron radiation and inverse Compton processes. Furthermore, the model suggests an energy of approximately 2.4 PeV for the most energetic particle in the nebula.