Highly collimated microquasar jets as efficient cosmic-ray sources

Abstract

Supernova remnants are believed to be the main sites where Galactic cosmic rays originate. This scenario, however, fails to explain some of the features observed in the cosmic-ray spectrum. Microquasars have been proposed as additional candidates, because their non-thermal emission indicates the existence of efficient particle acceleration mechanisms in their jets. A promising scenario envisages the production of relativistic neutrons in the jets, that decay outside the system injecting relativistic protons to the surroundings. The first investigations of this scenario suggest that microquasars might be fairly alternative cosmic-ray sources. We aim at assessing the role played by the degree of collimation of the jet on the cosmic-ray energetics in the neutron-carrier scenario, as well as the properties of the emission region. Our goals are to explain the Galactic component of the observed proton cosmic-ray spectrum at energies higher than $\sim 10$ GeV and to relate the mentioned jet properties with the power and spectral index of the produced cosmic rays. We find that collimated jets, with compact acceleration regions close to the jet base, are very efficient sources that could deliver a fraction of up to $\sim 0.01$ of their relativistic proton luminosity into cosmic rays. Collimation is the most significant feature regarding efficiency; a well collimated jet might be $\sim 4$ orders of magnitude more efficient than a poorly collimated one. The main feature of the presented mechanism is the production of a spectrum with a steeper spectral index ($\sim 2.3$ at energies up to $\sim 10$ TeV) than in the supernova scenario, and closer to what is observed. The predictions of our model may be used to infer the total contribution of the population of Galactic microquasars to the cosmic ray population, and therefore to quantitatively assess their significance as cosmic-ray sources.

arXiv comment11 pages, 14 figures

References in corpus (27)

• The Origin of Galactic Cosmic Rays
• A relativistic jet from Cygnus X-1 in the low/hard X-ray state
• Parametrization of gamma-ray production cross-sections for pp interactions in a broad proton energy range from the kinematic threshold to PeV energies
• Cygnus X-1 contains a 21-solar mass black hole -- implications for massive star winds
• Neutral Beams from Blazar Jets
• Stellar black holes at the dawn of the universe
• Cosmic Rays from Microquasars: a Narrow Component to the CR Spectrum?
• Iron Emission Lines from Extended X-ray Jets in SS 433: Reheating of Atomic Nuclei
• Particle acceleration in winds of star clusters
• Baryons in the relativistic jets of the stellar-mass black hole candidate 4U 1630-47
• The proton low-mass microquasar: high-energy emission
• X-ray binary formation in low-metallicity blue compact dwarf galaxies
• Metallicity dependence of HMXB populations
• X-rays from Blue Compact Dwarf Galaxies
• A new lepto-hadronic model applied to the first simultaneous multiwavelength data set for Cygnus X--1
• TeV neutrinos from microquasars in compact massive binaries
• Lepto-hadronic model for the broadband emission of Cygnus X-1
• Do Cosmic Rays Heat the Early Intergalactic Medium?
• Particle acceleration and multimessenger emission from starburst-driven galactic winds
• Cosmic rays from Galactic pulsars
• Production of neutrons, neutrinos and gamma-rays by a very fast pulsar in the Galactic Center region
• The Origin of Matter at the Base of Relativistic Jets in Active Galactic Nuclei
• Microquasars as heating sources of the intergalactic medium during reionisation of the Universe
• Cosmic reionization by primordial cosmic rays
• Nonthermal processes and neutrino emission from the black hole GRO J0422+32 in a bursting state
• On the nature of the AGILE galactic transient sources
• Cosmic-ray production from neutron escape in microquasar jets

Cited by in corpus (5)

• Acceleration and transport of relativistic electrons in the jets of the microquasar SS 433
• Particle acceleration and multi-messenger radiation from Ultra-Luminous X-ray Sources: A new class of Galactic PeVatrons
• NuSTAR and XMM-Newton observations of the binary 4FGL J1405.1-6119. A $\gamma$-ray emitting microquasar?
• X-ray Binaries: a potential dominant contributor to the cosmic ray spectral knee structure
• Simulated Radio and Neutrino Imaging of a Microquasar