Relatore
Descrizione
Recently, the Large High-Altitude Air Shower Observatory (LHAASO) collaboration reported ultra-high-energy gamma-rays from six microquasar systems.
For five of these sources, the emission exceeds $100$ TeV, making microquasars promising Galactic PeVatrons.
In this work, we investigate whether gamma-rays around $100$ TeV can originate from hadronic interactions of accelerated cosmic rays with the ambient medium and estimate the contribution of these sources to the CR proton knee.
Two transport scenarios are considered: one in which particle transport around the source is dominated by advection with the velocity of the jet, and another in which it is dominated by diffusion, with the diffusion coefficient reduced with respect to the Galactic value. In both scenarios, the diffusion coefficient matches the Galactic value at large distances from the source.
We find that in both advection and diffusion scenarios, hadrons alone cannot fully explain the observed emission in most sources, allowing us to place upper limits on the hadronic contribution to the observed gamma-ray flux.
Finally, we estimate the contribution of these sources to the Galactic cosmic-ray spectrum; this quantity strongly depends on source age and injection history.
| Sessione | Oggetti compatti |
|---|