Open Questions in Cosmic-Ray Research at Ultrahigh Energies

Batista, Rafael Alves; Biteau, J.; Bustamante, Mauricio; Dolag, K.; Engel, R.; Fang, Ke; Kampert, K. H.; Kostunin, D.; Mostafá, M.; Murase, Kohta; Oikonomou, Foteini; Olinto, Angela V.; Panasyuk, M. I.; Sigl, Guenter; Taylor, A. M.; Unger, Michael

doi:10.3389/fspas.2019.00023

Cited by 211 publications

(139 citation statements)

References 418 publications

(682 reference statements)

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“…From the table it can be seen that for E min = 10 20 eV, P rej is smaller than 0.5 for the two sets of pixels considered (0.34 and 0.26 for S GC and S M 31 , respectively). Note that the Auger exposure at present is approximately 8 × 10 4 km 2 yr sr [40] and it can reach values of order of 2 × 10 5 km 2 yr sr at the end of its life [41]. Therefore, with Auger data it will be possible to performed the proposed test for E min = 10 20 eV.…”

Section: )mentioning

confidence: 97%

Ultra high energy cosmic rays from super-heavy dark matter in the context of large exposure observatories

Supanitsky

Medina‐Tanco

2019

J. Cosmol. Astropart. Phys.

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The origin of the ultra high energy cosmic rays (UHECRs, E > 10 18 eV) is still uncertain. However, great progress has been achieved due to the data taken by The Pierre Auger and Telescope Array observatories. The UHECR flux presents two main features, a hardening of the spectrum known as the ankle and a suppression at higher energies. The experimental data suggest that above the ankle the UHECRs flux is dominated by an extragalactic component of astrophysical origin. However, a minority component of exotic origin that dominates the flux beyond the suppression is still compatible with current data. Therefore, there exist the possibility that part of the UHECR flux originates from the decay of super-heavy dark matter particles clustered in the halos of the galaxies. In these scenarios the main contribution comes from the halo of our galaxy. In this article the possibility of identifying these scenarios in the context of the future very large exposure cosmic rays observatories is studied. It is worth mentioning that the contribution of the extragalactic halos located in the nearby universe is also included in these studies.

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Section: )mentioning

confidence: 97%

Ultra high energy cosmic rays from super-heavy dark matter in the context of large exposure observatories

Supanitsky

Medina‐Tanco

2019

J. Cosmol. Astropart. Phys.

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“…Although the nearest extreme blazar, Mkn 501, is at a luminosity distance of ∼ 150 Mpc, misaligned counterparts could satisfy the local proximity constraint. Because of a tight lower bound on the magnetic luminosity (e.g., [59]), only the most luminous sources should be able to reach the highest energies, so that nearby ones could already be identified in electromagnetic surveys [60].…”

Section: (Lepto-)hadronic Modelsmentioning

confidence: 99%

Progress in unveiling extreme particle acceleration in persistent astrophysical jets

Biteau

Prandini

Costamante³

et al. 2020

Nat Astron

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The most powerful persistent accelerators in the Universe are jetted active galaxies. Galaxies whose jets are directed towards Earth, so called blazars, dominate the extragalactic γ-ray sky. Still, most of the highest-energy accelerators likely elude detection. These extreme blazars, whose radiated energy can peak beyond 10 TeV, are ideal targets to study particle acceleration and radiative processes, and may provide links to cosmic rays and astrophysical neutrinos. The growing number of extreme blazars observed at TeV energies has been critical for the emergence of γ-ray cosmology, including measurements of the extragalactic background light, tight bounds on the intergalactic magnetic field, and constraints on exotic physics at energies inaccessible with human-made accelerators. Tremendous progress is expected in the decade to come, particularly with the deployment of the Cherenkov Telescope Array.

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“…Given the observed level of isotropy in arrival directions, these CRs have to be of extragalactic (possibly AGN-type) origin so as to avoid a large anisotropy towards the Galactic Plane. With increasing energy the composition then seems to become more heavier (log(E t [eV])=18.3 transition), with a trend that protons are gradually replaced by helium, helium by nitrogen etc, an iron contribution possibly emerging above log(E[eV]) = 19.4 (e.g., see Alves Batista et al 2019;Kachelriess & Semikoz 2019, for reviews).…”

Section: Maximum Energiesmentioning

confidence: 99%

Particle Acceleration in Shearing Flows: Efficiencies and Limits

Rieger

Duffy

2019

ApJL

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We examine limits to the efficiency for particles acceleration in shearing flows, showing that relativistic flow speeds are required for efficient gradual shear acceleration. We estimate maximum achievable particle energies for parameters applicable to relativistic AGN jets. The implications of our estimates is that if large-scale jets are relativistic, then efficient electron acceleration up to several PeV, and proton acceleration up to several EeV energies appears feasible. This suggests that shear particle acceleration could lead to a continued energization of synchrotron X-ray emitting electrons, and be of relevance for the production of ultra-high-energy cosmic-ray particles.

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Open Questions in Cosmic-Ray Research at Ultrahigh Energies

Cited by 211 publications

References 418 publications

Ultra high energy cosmic rays from super-heavy dark matter in the context of large exposure observatories

Ultra high energy cosmic rays from super-heavy dark matter in the context of large exposure observatories

Progress in unveiling extreme particle acceleration in persistent astrophysical jets

Particle Acceleration in Shearing Flows: Efficiencies and Limits

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