Kohta 2008 High-energy cosmic-ray nuclei from GRB

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· arXiv e-print (arXiv:0801.2861)

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Title:		High-energy cosmic-ray nuclei from high- and low-luminosity gamma-ray bursts and implications for multi-messenger astronomy
Authors:		Murase, Kohta; Ioka, Kunihito; Nagataki, Shigehiro; Nakamura, Takashi
Publication:		eprint arXiv:0801.2861
Publication Date:		01/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		20 pages, 9 figures
Bibliographic Code:		2008arXiv0801.2861M

Abstract

Gamma-ray burst (GRB) is one of the candidates of high-energy cosmic-ray acceleration sites. They may be also ultra-high-energy (above 3 EeV) cosmic-ray (UHECR) sources. In this paper, we discuss possibilities and implications of high-energy cosmic-ray acceleration in GRBs. (1) First, we show that not only protons but also heavier nuclei can be accelerated up to ultra-high energies in both usual high-luminosity (HL) and low-luminosity (LL) GRBs by using the Geant4. LL GRBs may also make a significant contribution to the observed UHECR flux if they form a distinct population, and we investigate cosmic-ray acceleration in LL GRBs in detail. (2) Second, we discuss implications of the GRB-UHECR hypothesis (and Hypernova-UHECR hypothesis) to cosmic-ray astronomy. HL GRBs and LL GRBs will lead to different source number densities as UHECR sources, so that the determination of the number density of UHECR sources and strength of the mean extragalactic magnetic field (EGMF) will give us useful clues to test the hypothesis. If the EGMF is sufficiently weak, only LL GRBs can be dominant as UHECR sources. If the EGMF is sufficiently strong, HL GRBs would be more suitable UHECR sources to explain the observed anisotropy. (3) The detection of high-energy neutrinos and gamma rays will also give us important clues to high-energy cosmic-ray acceleration in GRBs. We show that, when ultra-high-energy heavy nuclei such as iron can survive in GRBs, the detection of high-energy neutrinos would become more difficult. However, since escape of high-energy gamma rays from the source is easier in such cases, the detection of very high-energy gamma rays and/or secondary delayed gamma rays can be more expected.

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