Prospects of testing an UHECR single source class model with the K-EUSO orbital telescope

Oleg Kalashev,Maxim Pshirkov,Mikhail Zotov,I Lhenry-Yvon,O Deligny,P Ghia,J Biteau

doi:10.1051/epjconf/201921006011

Abstract

KLYPVE-EUSO (K-EUSO) is a planned orbital detector of ultra-high energy cosmic rays (UHECRs), which is to be deployed on board the International Space Station. K-EUSO is expected to have a uniform exposure over the celestial sphere and register from 120 to 500 UHECRs at energies above 57 EeV in a 2-year mission. We employed the TransportCR and CRPropa 3 packages to estimate prospects of testing a minimal single source class model for extragalactic cosmic rays and neutrinos by Kachelrieß, Kalashev, Ostapchenko and Semikoz (2017) with K-EUSO in terms of the large-scale anisotropy. Nearby active galactic nuclei Centaurus A, M82, NGC 253, M87 and Fornax A were considered as possible sources of UHECRs. We demonstrate that an observation of more than 200 events will allow testing predictions of the model with a high confidence level providing the fraction of events arriving from any of the sources is ^10-15%, with a smaller contribution for larger samples. These numbers agree with theoretical expectations of a possible contribution of a single source in the UHECR flux. Thus, K-EUSO can provide good opportunities for verifying the minimal model basing on an analysis of the large-scale anisotropy of arrival directions of UHECRs.

Highlights

Ultra-high energy cosmic rays (UHECRs) with energies above ∼ 50 EeV, sometimes called extreme-energy cosmic rays, were first registered almost 60 years ago [1] but their nature and sources still remain an open problem of astrophysics and cosmic ray physics
It was shown that a good fit to the CR energy spectrum can be obtained assuming only hadronic interactions of ultra-high energy cosmic rays (UHECRs) with gas around their sources, but it is difficult to reproduce the observed distribution of Xmax of CR-induced air showers
We study if K-EUSO will be able to verify the KKOS model basing on an analysis of the large-scale anisotropy of arrival directions of UHECRs with energies above 57 EeV

Summary

Introduction

Ultra-high energy cosmic rays (UHECRs) with energies above ∼ 50 EeV, sometimes called extreme-energy cosmic rays, were first registered almost 60 years ago [1] but their nature and sources still remain an open problem of astrophysics and cosmic ray physics. A minimal single source class model for extragalactic cosmic rays and neutrinos was proposed by Kachelrieß, Kalashev, Ostapchenko and Semikoz [18] (KKOS in what follows), which can explain the observed energy spectrum and mass composition of cosmic rays (CRs) with energies above ∼ 1017 eV, and matches the high-energy neutrino flux measured by IceCube. It is possible to reduce significantly the fraction of heavy nuclei in the primary fluxes and fit satisfactorily both the spectrum and composition data on UHECRs only after adding photo-nuclear interactions with a relatively large interaction depth, which suggests that UHECRs are accelerated close to a supermassive black hole. The secondary high-energy neutrino flux obtained in the scenario matches the IceCube measurements [19], while the contribution of unresolved UHECR sources to the extragalactic γ-ray background [20] is of the order of 30%

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