The Spectrum of the Crab Nebula and Highest Energy Photons Measured by HAWC

TL;DR

This paper introduces a new neural network-based energy reconstruction method for HAWC, enabling precise measurement of very high energy gamma rays from the Crab Nebula and other sources, including photons above 200 TeV.

Contribution

The paper presents a novel neural network approach for event-by-event gamma-ray energy estimation in HAWC, improving accuracy over previous methods and extending the energy range of observed photons.

Findings

Detection of photons above 200 TeV at 95% confidence

Measurement of the Crab Nebula spectrum at unprecedented energies

Comparison with models shows consistency with acceleration theories

Abstract

HAWC has developed new energy algorithms using an artificial neural network for event-by-event reconstruction of Very High Energy (VHE) primary gamma ray energies. Unlike previous estimation methods for HAWC photons, these estimate photon energies with good energy precision and accuracy in a range from 1 TeV to greater than 100 TeV. Photon emission at the highest energies is of interest in understanding acceleration mechanisms of astrophysical sources and where the acceleration might cut off. We apply the new HAWC reconstruction to present the preliminary measurement of the highest energies at which photons are emitted by the Crab Nebula and by six additional sources in the galactic plane which emit above 50 TeV. We have observed photons above 200 TeV at 95% confidence. We also compare fits to the HAWC Crab spectrum with other measurements and theoretical models of the Crab spectrum.