Bibliographic Information: Peretti, E., Petropoulou, M., Vasilopoulos, G., & Gabici, S. (2024). Particle acceleration and multi-messenger radiation from Ultra-Luminous X-ray Sources -- A new class of Galactic PeVatrons. Astronomy & Astrophysics.
Research Objective: This research paper investigates the potential of Ultra-Luminous X-ray Sources (ULXs) as Galactic PeVatrons, focusing on particle acceleration mechanisms within wind bubbles created by ULX outflows.
Methodology: The authors develop a model of diffusive shock acceleration (DSA) occurring at the wind termination shock within ULX wind bubbles. They solve the energy-dependent and space-dependent transport equation to analyze the acceleration and propagation of high-energy protons. The model predicts multi-messenger emissions, including cosmic rays, gamma rays, radio waves, and neutrinos.
Key Findings: The model demonstrates that ULX wind bubbles can efficiently accelerate protons to PeV energies, making them viable PeVatron candidates. The study focuses on the Galactic source SS 433, a hidden ULX, and finds that the model's predictions align with recent high-energy gamma-ray observations, particularly those from LHAASO. The authors suggest that the high-energy photons (>100 TeV) and their morphology observed from SS 433 could originate from high-energy protons accelerated within the wind bubble.
Main Conclusions: The research concludes that ULX wind bubbles are promising sites for cosmic ray acceleration, potentially contributing significantly to the Galactic cosmic ray flux at PeV energies. The study proposes ULXs as a new class of PeVatron candidates, providing a plausible explanation for the origin of high-energy particles in the Milky Way.
Significance: This research significantly contributes to our understanding of particle acceleration mechanisms in the Galaxy and sheds light on the long-standing mystery surrounding the origin of Galactic PeVatrons. The findings have implications for high-energy astrophysics and cosmic ray physics.
Limitations and Future Research: The model primarily focuses on hadronic acceleration and radiation, with limited discussion on leptonic processes. Future research could explore the contribution of primary and secondary electrons to the multi-wavelength emission from ULX wind bubbles. Further investigation is warranted to constrain model parameters and refine predictions for multi-messenger observations, particularly in neutrinos and radio wavelengths.
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by Enrico Peret... a las arxiv.org 11-14-2024
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