PoS - Proceedings of Science
Volume 444 - 38th International Cosmic Ray Conference (ICRC2023) - Gamma-ray Astronomy (GA)
Detection of Diffuse γ-Ray Emission toward a Massive Star-forming Region Hosting Wolf-Rayet Stars
K. Wang
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Pre-published on: August 14, 2023
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Massive star clusters hosting WR and OB-type stars have been proposed as potential Galactic cosmic-ray accelerators for decades, in particular via diffusive shock acceleration at wind termination shocks. Here we report the analysis of Fermi Large Area Telescope's data towards the direction of Masgomas-6a, a young massive star cluster candidate hosting two WR stars. We detect an extended $\gamma$-ray source with $\rm{TS}=183$ in the vicinity of Masgomas-6a, spatially coincident with two unassociated Fermi 4FGL sources.
The $\gamma$-ray emission intensity correlates well with the distribution of molecular gas at the distance of Masgomas-6a, indicating that these gamma rays may be produced by CRs accelerated by massive stars in Masgomas-6a. At the distance of $3.9{\rm \ kpc}$ of Masgomas-6a, the luminosity of the extended source is $(1.81\pm0.02)\times 10^{35}{\rm \ erg \ s^{-1}}$. With a kinetic luminosity of $\sim 10^{37}{\rm erg \ s^{-1}}$ in the stellar winds, the WR stars are capable of powering the $\gamma$-ray emission via neutral pion decay resulted from cosmic ray $pp$ interactions. The size of the GeV source and the energetic requirement suggests a CR diffusion coefficient smaller than that in the Galactic interstellar medium, indicating strong suppression of CR diffusion in the molecular cloud.
DOI: https://doi.org/10.22323/1.444.0835
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