Present and future gamma-ray probes of the Cygnus OB2 environment

Abstract

The MAGIC Collaboration has provided new observational data pertaining to the TeV J2032+4130 gamma-ray source (within the Cygnus OB2 region), for energies ${E}_{\ensuremath{\gamma}}g400\text{ }\text{ }\mathrm{GeV}$. It is then appropriate to update the impact of these data on gamma-ray production mechanisms in stellar associations. We consider two mechanisms of gamma-ray emission, pion production and decay (PION) and photoexcitation of high-energy nuclei followed by prompt photoemission from the daughter nuclei (${A}^{\ensuremath{\star}}$). We find that while the data can be accommodated with either scenario, the ${A}^{\ensuremath{\star}}$ features a spectral bump, corresponding to the threshold for exciting the giant dipole resonance, which can serve to discriminate between them. We comment on neutrino emission and detection from the region if the PION and/or ${A}^{\ensuremath{\star}}$ processes are operative. We also touch on the implications for this analysis of future Fermi and \ifmmode \check{C}\else \v{C}\fi{}erenkov Telescope array data.