What it is
The LHAASO observatory recently detected gamma-ray emission extending beyond 100 TeV from 4 sources associated with powerful microquasars (binary star systems in which a black hole or neutron star draws matter from a companion and launches jets). The authors propose that such sources are the Galaxy's main PeVatrons, the accelerators that push cosmic rays to petaelectronvolt energies, and investigate their contribution to the proton and gamma-ray fluxes by modelling the entire population. They find that the presence of only about 10 active powerful microquasars in the Galaxy at any given time is sufficient to account for the proton flux around the knee (a steepening of the cosmic-ray energy spectrum) and to give a very good explanation of cosmic-ray and gamma-ray data in a self-consistent picture. In the model the 10 TeV bump and the 300 TeV hardening in the cosmic-ray spectrum appear naturally, and the diffuse background measured by LHAASO above a few tens of TeV is accounted for. The authors read this as support for the paradigm in which cosmic rays around the knee are predominantly accelerated in a very limited number of powerful microquasars.
Why it matters
A population model finds that about 10 powerful microquasars active in the Galaxy at any time would be enough to account for the cosmic-ray proton flux around the knee. LHAASO recently detected gamma rays beyond 100 TeV from 4 sources associated with powerful microquasars, and the authors propose that such systems are the Galaxy's main PeVatrons. Modelling the whole population, they find that the 10 TeV bump and the 300 TeV hardening in the cosmic-ray spectrum appear naturally and that the diffuse background LHAASO measured above a few tens of TeV is accounted for, in one self-consistent picture of cosmic-ray and gamma-ray data.
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Filed underAstrophysics and Cosmic Phenomena, Gamma-ray bursts and supernovae, Astrophysical Phenomena and Observations