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Title: Can We Reconcile the TA Excess and Hotspot with Auger Observations?

Abstract

The Telescope Array (TA) shows a 20° hotspot as well as an excess of ultra-high-energy cosmic-rays (UHECRs) above 50 EeV when compared with the Auger spectrum. We consider the possibility that both the TA excess and hotspot are due to a dominant source in the northern sky. We carry out detailed simulations of UHECR propagation in both the intergalactic medium and the Galaxy, using different values for the intergalactic magnetic field. We consider two general classes of sources: transients and steady, adopting a mixed UHECR composition that is consistent with the one found by Auger. The spatial location of the sources is drawn randomly. We generate Auger-like and TA-like data sets from which we determine the spectrum, the sky maps, and the level of anisotropy. We find that, while steady sources are favored over transients, it is unlikely to account for all the currently available observational data. While we reproduce fairly well the Auger spectrum for the vast majority of the simulated data sets, most of the simulated data sets with a spectrum compatible with that of TA (at most a few percent depending on density model tested) show a much stronger anisotropy than the one observed. We find thatmore » the rare cases in which both the spectrum and the anisotropy are consistent require a steady source within ∼10 Mpc, to account for the flux excess, and a strong extragalactic magnetic field ∼10 nG, to reduce the excessive anisotropy.« less

Authors:
;  [1]; ; ;  [2]
  1. Racah Institute of Physics, The Hebrew University of Jerusalem, 91904 Jerusalem (Israel)
  2. Laboratoire Astroparticule et Cosmologie, Université Paris Diderot/CNRS, 10 rue A. Domon et L. Duquet, F-75205 Paris Cedex 13 (France)
Publication Date:
OSTI Identifier:
22663784
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 836; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ANISOTROPY; AUGER ELECTRON SPECTROSCOPY; COMPARATIVE EVALUATIONS; COSMIC RADIATION; DENSITY; EEV RANGE; GALAXIES; MAGNETIC FIELDS; RANDOMNESS; SIMULATION; SPECTRA; TELESCOPES

Citation Formats

Globus, Noemie, Piran, Tsvi, Allard, Denis, Parizot, Etienne, and Lachaud, Cyril. Can We Reconcile the TA Excess and Hotspot with Auger Observations?. United States: N. p., 2017. Web. doi:10.3847/1538-4357/836/2/163.
Globus, Noemie, Piran, Tsvi, Allard, Denis, Parizot, Etienne, & Lachaud, Cyril. Can We Reconcile the TA Excess and Hotspot with Auger Observations?. United States. doi:10.3847/1538-4357/836/2/163.
Globus, Noemie, Piran, Tsvi, Allard, Denis, Parizot, Etienne, and Lachaud, Cyril. Mon . "Can We Reconcile the TA Excess and Hotspot with Auger Observations?". United States. doi:10.3847/1538-4357/836/2/163.
@article{osti_22663784,
title = {Can We Reconcile the TA Excess and Hotspot with Auger Observations?},
author = {Globus, Noemie and Piran, Tsvi and Allard, Denis and Parizot, Etienne and Lachaud, Cyril},
abstractNote = {The Telescope Array (TA) shows a 20° hotspot as well as an excess of ultra-high-energy cosmic-rays (UHECRs) above 50 EeV when compared with the Auger spectrum. We consider the possibility that both the TA excess and hotspot are due to a dominant source in the northern sky. We carry out detailed simulations of UHECR propagation in both the intergalactic medium and the Galaxy, using different values for the intergalactic magnetic field. We consider two general classes of sources: transients and steady, adopting a mixed UHECR composition that is consistent with the one found by Auger. The spatial location of the sources is drawn randomly. We generate Auger-like and TA-like data sets from which we determine the spectrum, the sky maps, and the level of anisotropy. We find that, while steady sources are favored over transients, it is unlikely to account for all the currently available observational data. While we reproduce fairly well the Auger spectrum for the vast majority of the simulated data sets, most of the simulated data sets with a spectrum compatible with that of TA (at most a few percent depending on density model tested) show a much stronger anisotropy than the one observed. We find that the rare cases in which both the spectrum and the anisotropy are consistent require a steady source within ∼10 Mpc, to account for the flux excess, and a strong extragalactic magnetic field ∼10 nG, to reduce the excessive anisotropy.},
doi = {10.3847/1538-4357/836/2/163},
journal = {Astrophysical Journal},
number = 2,
volume = 836,
place = {United States},
year = {Mon Feb 20 00:00:00 EST 2017},
month = {Mon Feb 20 00:00:00 EST 2017}
}