Testing the Limits of Particle Acceleration in Cygnus OB2 with HAWC

TL;DR

This study uses HAWC gamma-ray data to investigate particle acceleration to very high energies in the Cygnus OB2 star-forming region, exploring its potential as a cosmic ray source.

Contribution

First detailed analysis of TeV gamma-ray emission from Cygnus OB2 using HAWC, extending understanding of cosmic ray acceleration in star-forming regions.

Findings

Gamma-ray emission extends from GeV to tens of TeV.

Spectral energy distribution indicates high-energy particle acceleration.

No clear TeV source association prior to this study.

Abstract

Star forming regions (SFRs) have been postulated as possible sources of cosmic rays (CRs) in our galaxy. One example of a gamma-ray source associated with an SFR is the Fermi-LAT cocoon, an extended region of gamma-ray emission in the Cygnus X region and attributed to a possible superbubble with freshly accelerated CRs. Because the emission region is surrounded by ionization fronts, it has been named the "Cygnus cocoon". CRs in the cocoon could have originated in the OB2 association and been accelerated at the interaction sites of stellar winds of massive O type stars. So far, there is no clear association at TeV energies. Spectral and morphological studies of TeV gamma-ray emission detected by the High Altitude Water Cherenkov (HAWC) observatory at the 2HWC J2031+415 region reveal that the spectral energy distribution of the cocoon extends from GeV to at least tens of TeV. Using HAWC data, we are able to study the acceleration of particles to highest energies in the Cygnus OB2 SFR.