Modeling of GeV-TeV gamma-ray emission of Cygnus Cocoon

• Main Authors: Bykov, A. M, Kalyashova, M. E
• Format: Journal Article
• Language: English
• Published: 18-03-2022
• Subjects: Physics - High Energy Astrophysical Phenomena
• DOI: 10.48550/arxiv.2203.09842

Advances in Space Research 70 (2022) 2685-2695 OB-associations and superbubbles being energetically essential galactic
powerhouses are likely to be the important acceleration sites of galactic
cosmic rays (CRs). The emission profile of gamma-ray sources related to
superbubbles and stellar clusters indicates on continuous particle acceleration
by winds of massive stars. One of the most luminous galactic gamma-ray sources
is Cygnus Cocoon superbubble, observed by multiple instruments, such as
Fermi-LAT, ARGO, and, recently, HAWC. We discuss a model of particle
acceleration and transport in a superbubble to explain GeV-TeV gamma-ray
spectrum of Cygnus Cocoon, which has a break at the energy of about 1 TeV. It
is shown that the gamma rays produced by hadronic interactions of high-energy
protons accelerated by an ensemble of shocks from winds of massive stars and
supernovae in the Cygnus Cocoon can explain the observations. The proton
spectral shape at the highest energies depends on the MHD-fluctuation spectrum
in the Cocoon. The viable solutions for Cygnus Cocoon may be applied to some
other associations showing similar behaviour. We briefly discuss the similarity
and differences of particle acceleration processes in extended superbubbles and
compact clusters of young massive stars as represented by Westerlund 1 and 2
gamma-ray sources.