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Open AccessArticle

The Multimessenger Contribution of Ultra-High-Energy Cosmic Rays from Gamma-Ray Bursts

by Zhenjiang Li, Fangsheng Min, Yi Jin and Yiqing Guo

Universe 2025, 11(1), 22; https://doi.org/10.3390/universe11010022 - 15 Jan 2025

Cited by 1 | Viewed by 1485

It has long been debated whether gamma-ray bursts (GRBs) could serve as potential sources of ultra-high-energy cosmic rays (UHECRs). In this study, we consider GRBs as sources of UHECR injection with an injection index of

α = 2

and propagate them through the [...] Read more.

α = 2

and propagate them through the extragalactic magnetic field within the framework of CRPropa 3. The baryon loading factor

f_{C R}

is taken into account to quantify the rate of UHECR energy injection. In the benchmark case with a jet opening angle of

θ_{j} = 1

and

f_{C R} = 1

, we find that both high- and low-luminosity populations contribute to less than 10% of the UHECR spectrum. The most constrained scenario suggests

f_{C R} \leq 15

, indicating that GRBs are less efficient in producing the all-sky UHECR intensity. The high-energy diffuse neutrinos and gamma rays resulting from interactions between UHECRs from GRBs and extragalactic background photons do not dominate the observations of Fermi-LAT or IceCube. Full article

(This article belongs to the Special Issue Ultra-High-Energy Cosmic Rays)

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13 pages, 3218 KB

Open AccessArticle

Source Count Distribution of Fermi LAT Gamma-Ray Blazars Using Novel Nonparametric Methods

by Xuhang Yin and Houdun Zeng

Universe 2024, 10(9), 340; https://doi.org/10.3390/universe10090340 - 26 Aug 2024

Cited by 2 | Viewed by 1356

Abstract

We utilized a sample from the Fermi-LAT 14-year Source Catalog by adjusting the flux detection threshold, enabling us to derive the intrinsic source count distribution

d N / d F_{25}

of extragalactic blazars using nonparametric, unbinned methods developed by Efron and Petrosian [...] Read more.

We utilized a sample from the Fermi-LAT 14-year Source Catalog by adjusting the flux detection threshold, enabling us to derive the intrinsic source count distribution

d N / d F_{25}

of extragalactic blazars using nonparametric, unbinned methods developed by Efron and Petrosian and Lynden-Bell. Subsequently, we evaluated the contribution of blazars to the extragalactic gamma-ray background. Our findings are summarized as follows: (1) There is no significant correlation between flux and spectral index values among blazars and their subclasses FSRQs and BL Lacs. (2) The intrinsic differential distributions of flux values exhibit a broken-power-law form, with parameters that closely match previous findings. The intrinsic photon index distributions are well described by a Gaussian form for FSRQs and BL Lacs individually, while a dual-Gaussian model provides a more appropriate fit for blazars as a whole. (3) Blazars contribute 34.5% to the extragalactic gamma-ray background and 16.8% to the extragalactic diffuse gamma-ray background. When examined separately, FSRQs and BL Lacs contribute 19.6% and 13% to the extragalactic gamma-ray background, respectively. Full article

(This article belongs to the Special Issue Focus on Active Galactic Nuclei)

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6 pages, 786 KB

Open AccessCommunication

Influence of Extragalactic Magnetic Fields on Extragalactic Cascade Gamma-Ray Emission

by Anna Uryson

Universe 2022, 8(11), 569; https://doi.org/10.3390/universe8110569 - 29 Oct 2022

Viewed by 1576

Abstract

We discuss the influence of extragalactic magnetic fields on the intensity of gamma-ray emission produced in electromagnetic cascades from ultra-high energy cosmic rays propagating in extragalactic space. Both cosmic rays and cascade particles propagate mostly out of galaxies, galactic clusters, and large-scale structures, as their relative volume is small. Therefore, their magnetic fields weakly affect emission produced in cascades. Yet, estimates of this influence can be useful in searching for dark matter particles when components of extragalactic gamma-ray background should be known, including cascade gamma-ray emission. To study magnetic field influence on cascade emission, we calculated cosmic particle propagation in fields of ~10⁻⁶ and 10⁻¹² G (the former is typical inside galaxies and clusters and the latter is common in voids and outside galaxies and clusters). The calculated spectra of cascade gamma-ray emissions are similar in the range of ~10⁷–10⁹ eV, so analyzing cascade emission in this range it is not necessary to specify models of an extragalactic magnetic field. Full article

(This article belongs to the Special Issue Elementary Particles in Astrophysics and Cosmology)

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