English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

Supernova remnants are believed to be the main sites where Galactic cosmicrays originate. This scenario, however, fails to explain some of the featuresobserved in the cosmic-ray spectrum. Microquasars have been proposed asadditional candidates, because their non-thermal emission indicates theexistence of efficient particle acceleration mechanisms in their jets. Apromising scenario envisages the production of relativistic neutrons in thejets, that decay outside the system injecting relativistic protons to thesurroundings. The first investigations of this scenario suggest thatmicroquasars might be fairly alternative cosmic-ray sources.  We aim at assessing the role played by the degree of collimation of the jeton the cosmic-ray energetics in the neutron-carrier scenario, as well as theproperties of the emission region. Our goals are to explain the Galacticcomponent of the observed proton cosmic-ray spectrum at energies higher than$\sim 10$ GeV and to relate the mentioned jet properties with the power andspectral index of the produced cosmic rays. We find that collimated jets, withcompact acceleration regions close to the jet base, are very efficient sourcesthat could deliver a fraction of up to $\sim 0.01$ of their relativistic protonluminosity into cosmic rays. Collimation is the most significant featureregarding efficiency; a well collimated jet might be $\sim 4$ orders ofmagnitude more efficient than a poorly collimated one. The main feature of thepresented mechanism is the production of a spectrum with a steeper spectralindex ($\sim 2.3$ at energies up to $\sim 10$ TeV) than in the supernovascenario, and closer to what is observed. The predictions of our model may beused to infer the total contribution of the population of Galactic microquasarsto the cosmic ray population, and therefore to quantitatively assess theirsignificance as cosmic-ray sources.

Highly collimated microquasar jets as efficient cosmic-ray sources