The gamma Cygni supernova remnant (SNR) is a middle-aged, Sedov-phase SNR in the Cygnus region. It is a known source of non-thermal emission at radio, X-ray, and gamma-ray energies. Very-high energy (VHE, >100 GeV) gamma-ray emission from gamma Cygni was first detected by the VERITAS observatory and it has since been observed by other experiments. Observations so far indicate that there must be a population of non-thermal particles present in the remnant which produces the observed emission. However, it is not clear what kind of particles (protons/ions or electrons) are accelerated in the remnant, how efficient the acceleration is, and up to which energy particles can be accelerated. Accurate measurements of the VHE gamma-ray spectrum are crucial to investigate particle acceleration above TeV energies.

This presentation will focus on multi-wavelength observations of the gamma Cygni SNR and their interpretation. We will present improved measurements of the VHE gamma-ray emission spectrum of gamma Cygni by the High-Altitude Water Cherenkov (HAWC) gamma-ray observatory, and use these results as well as measurements from other instruments to model the underlying particle populations producing this emission. HAWC's excellent sensitivity at TeV energies and above enables us to extend spectral measurements to higher energies and better constrain the maximum acceleration energy.