Investigating the multiband nonthermal emission of the 100 TeV source eHWC J2019$+$368 with a pulsar wind nebula scenario

TL;DR

This paper models the multiband nonthermal emission of the TeV source eHWC J2019+368, suggesting it originates from a pulsar wind nebula powered by PSR J2021+3651, with particles reaching energies up to 0.4 PeV.

Contribution

It provides a theoretical PWN model that explains the observed multiband emission of eHWC J2019+368, supporting its origin from a pulsar wind nebula.

Findings

The model reproduces radio, X-ray, and TeV gamma-ray fluxes.

Particles in the nebula can reach energies up to 0.4 PeV.

The PWN can account for the TeV gamma-ray emission.

Abstract

eHWC J2019+368 is one of the sources emitting $\gamma$-rays with energies higher than 100 TeV based on the recent measurement with the High Altitude Water Cherenkov Observatory (HAWC), and the origin is still in debate. The pulsar PSR J2021$+$3651 is spatially coincident with the TeV source. We investigate theoretically whether the multiband nonthermal emission of eHWC J2019+368 can originate from the pulsar wind nebula (PWN) G75.2$+$0.1 powered by PSR J2021$+$3651. In the model, the spin-down power of the pulsar is transferred to high-energy particles and magnetic field in the nebula. As the particles with an energy distribution of either a broken power-law or a power-law continually injected into the nebula, the multiband nonthermal emission is produced via synchrotron radiation and inverse Compton scattering. The spectral energy distribution of the nebula from the model with the reasonable parameters is generally consistent with the detected radio, X-ray and TeV $\gamma$-ray fluxes. Our study supports that the PWN has the ability to produce the TeV $\gamma$-rays of eHWC J2019+368, and the most energetic particles in the nebula have energies up to about $0.4$ PeV.