Impact of the finite life-time of UHECR sources

Abstract

The observational data on ultrahigh energy cosmic rays (UHECR), in particular their mass composition, show strong indications for extremely hard spectra of individual mass groups of CR nuclei at Earth. In this work, we show that such hard spectra can be the result of the finite life-time of UHECR sources, if a few individual sources dominate the UHECR flux at the highest energies. In this case, time delays induced by deflections in the turbulent extragalactic magnetic field as well as from the diffusive or advective escape from the source environment can suppress low-energy CRs, leading to a steepening of the observed spectrum. Considering radio galaxies as the main source of UHECRs, we discuss the necessary conditions that few individual sources dominate over the total contribution from the bulk of sources that have been active in the past. We provide two proof-of-principle scenarios showing that for a turbulent extragalactic magnetic field with a strength $B$ and a coherence length $l_{\mathrm{coh}}$, the life-time of a source at a distance $d_{\mathrm{src}}$ should satisfy $t_{\mathrm{act}}\sim {\left(B/1\text{nG}\right)}^2{\left(d_{\mathrm{src}}/10\text{Mpc}\right)}^2\left(l_{\mathrm{coh}}/1\text{Mpc}\right)\text{Myr}$ to obtain the necessary hardening of the CR spectrum at Earth.

References in corpus (16)

• Array Programming with NumPy
• The Cosmic Ray Energy Spectrum Observed with the Surface Detector of the Telescope Array Experiment
• Measurement of the cosmic-ray energy spectrum above $2.5\times 10^{18}$ eV using the Pierre Auger Observatory
• New facts about muon production in Extended Air Shower simulations
• Features of the energy spectrum of cosmic rays above $2.5\times 10^{18}$ eV using the Pierre Auger Observatory
• High-energy particle acceleration at the radio-lobe shock of Centaurus A
• A new view on Auger data and cosmogenic neutrinos in light of different nuclear disintegration and air-shower models
• CRPropa 3.2 -- an advanced framework for high-energy particle propagation in extragalactic and galactic spaces
• A representative survey of the dynamics and energetics of FRII radio galaxies
• Cycling of the powerful AGN in MS 0735.6+7421 and the duty cycle of radio AGN in Clusters
• The life cycle of radio galaxies in the LOFAR Lockman Hole field
• Ultrahigh energy cosmic rays from a nearby extragalactic source in the diffusive regime
• The flickering nuclear activity of Fornax A
• Particle acceleration in radio galaxies with flickering jets: GeV electrons to ultrahigh energy cosmic rays
• Cosmic ray anisotropies from transient extragalactic sources
• High Energy Cosmic Rays from Fanaroff-Riley Radio Galaxies

Cited by in corpus (4)

• Impact of the Magnetic Horizon on the Interpretation of the Pierre Auger Observatory Spectrum and Composition Data
• Impact of anisotropic cosmic-ray transport on the gamma-ray signatures in the Galactic Center
• Case for Centaurus A as the main source of ultrahigh-energy cosmic rays
• Revisiting Propagation Delays of Ultra-High-Energy Cosmic Rays from Long-lived Sources