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16 pages, 16584 KiB

Open AccessArticle

Performance of the RF Detectors of the Astroneu Array

by Stavros Nonis, Antonios Leisos, Apostolos Tsirigotis, Ioannis Gkialas, Kostas Papageorgiou and Spyros Tzamarias

Universe 2023, 9(1), 17; https://doi.org/10.3390/universe9010017 - 27 Dec 2022

Cited by 1 | Viewed by 1220

Abstract

Since 2014, the university campus of Hellenic Open University (HOU) has hosted the Astroneu array, which is dedicated to the detection of extensive air showers (EAS) induced by high-energy cosmic rays (CR). The Astroneu array incorporates 9 large particle scintillation detectors and 6 [...] Read more.

Since 2014, the university campus of Hellenic Open University (HOU) has hosted the Astroneu array, which is dedicated to the detection of extensive air showers (EAS) induced by high-energy cosmic rays (CR). The Astroneu array incorporates 9 large particle scintillation detectors and 6 antennas sensitive to the radio frequency (RF) range 1–200 MHz. The detectors are adjusted in three autonomous stations operating in an environment with a strong electromagnetic background. As shown by previous studies, EAS radio detection in such environments is possible using innovative noise rejection methods, as well as advanced analysis techniques. In this work, we present the analysis of the collected radio data corresponding to an operational period of approximately four years. We present the performance of the Astroneu radio array in reconstructing the EAS axis direction using different RF detector geometrical layouts and a technique for the estimation of the shower core by comparing simulation and experimental data. Moreover, we measure the relative amplitudes of the two mechanisms that give rise to RF emission (the Askaryan effect and geomagnetic emission) and show that they are in good agreement with previous studies as well as with the simulation predictions. Full article

(This article belongs to the Special Issue Astroparticle Physics)

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20 pages, 21570 KiB

Open AccessArticle

EAS Observation Conditions in the SPHERE-2 Balloon Experiment

by Elena Bonvech, Dmitry Chernov, Miroslav Finger, Michael Finger, Vladimir Galkin, Dmitry Podgrudkov, Tatiana Roganova and Igor Vaiman

Universe 2022, 8(1), 46; https://doi.org/10.3390/universe8010046 - 11 Jan 2022

Cited by 4 | Viewed by 1612

Abstract

The SPHERE project studies primary cosmic rays by detection of the Cherenkov light of extensive air showers reflected from the snow covered surface of the earth. Measurements with the aerial-based detector SPHERE-2 were performed in 2011–2013. The detector was lifted by a balloon [...] Read more.

The SPHERE project studies primary cosmic rays by detection of the Cherenkov light of extensive air showers reflected from the snow covered surface of the earth. Measurements with the aerial-based detector SPHERE-2 were performed in 2011–2013. The detector was lifted by a balloon to altitudes of up to 900 m above the snow covered surface of Lake Baikal, Russia. The results of the experiment are summarized now in a series of papers that opens with this article. An overview of the SPHERE-2 detector telemetry monitoring systems is presented along with the analysis of the measurements conditions including atmosphere profile. The analysis of the detector state and environment atmosphere conditions monitoring provided various cross-checks of detector calibration, positioning, and performance. Full article

(This article belongs to the Special Issue Astroparticle Physics)

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13 pages, 354 KiB

Open AccessArticle

Nonthermal Radiation of the Extreme TeV Blazar 1ES 0229+200 from Electromagnetic Cascades on Infrared Photon Field

by Timur Dzhatdoev, Vladimir Galkin and Egor Podlesnyi

Universe 2021, 7(12), 494; https://doi.org/10.3390/universe7120494 - 14 Dec 2021

Cited by 2 | Viewed by 2399

Abstract

Extreme TeV blazars (ETBs) are active galactic nuclei with jets presumably pointing towards the observer having their intrinsic (compensated for the effect of

γ

-ray absorption on extragalactic background light photons) spectral energy distributions (SEDs) peaked at an energy in excess of 1 [...] Read more.

Extreme TeV blazars (ETBs) are active galactic nuclei with jets presumably pointing towards the observer having their intrinsic (compensated for the effect of

γ

-ray absorption on extragalactic background light photons) spectral energy distributions (SEDs) peaked at an energy in excess of 1 TeV. These sources typically reveal relatively weak and slow variability as well as higher frequency of the low-energy SED peak compared to other classes of blazars. It proved to be exceedingly hard to incorporate all these peculiar properties of ETBs into the framework of conventional

γ

-ray emission models. ETB physics have recently attracted great attention in the astrophysical community, underlying the importance of the development of self-consistent ETB emission model(s). We propose a new scenario for the formation of X-ray and

γ

-ray spectra of ETBs assuming that electromagnetic cascades develop in the infrared photon field surrounding the central blazar engine. This scenario does not invoke compact fast-moving sources of radiation (so-called “blobs”), in agreement with the apparent absence of fast and strong variability of ETBs. For the case of the extreme TeV blazar 1ES 0229+200 we propose a specific emission model in the framework of the considered scenario. We demonstrate that this model allows to obtain a good fit to the measured SED of 1ES 0229+200. Full article

(This article belongs to the Special Issue Astroparticle Physics)

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8 pages, 602 KiB

Open AccessArticle

Interpretation of the Spectral Inhomogeneity in the 10 TV Region in Terms of a Close Source

by Ilya Kudryashov, Farid Gasratov, Vladimir Yurovskiy and Vasilii V. Latonov

Universe 2021, 7(12), 460; https://doi.org/10.3390/universe7120460 - 24 Nov 2021

Cited by 2 | Viewed by 1297

Abstract

The description of the inhomogeneity of the cosmic ray spectrum in the region of 10 TV, which is observed in experimental data, in terms of isotropic diffusion from a single close source is considered. It is shown that such a description is possible, [...] Read more.

The description of the inhomogeneity of the cosmic ray spectrum in the region of 10 TV, which is observed in experimental data, in terms of isotropic diffusion from a single close source is considered. It is shown that such a description is possible, and the area of possible localization of the source in space and time and its energy are found. The method of penalty functions is used to account for the data on the spectrum of all particles. Full article

(This article belongs to the Special Issue Astroparticle Physics)

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13 pages, 745 KiB

Open AccessArticle

Mass Composition of UHECRs from X_max Distributions Recorded by the Pierre Auger and Telescope Array Observatories

by Nicusor Arsene

Universe 2021, 7(9), 321; https://doi.org/10.3390/universe7090321 - 30 Aug 2021

Cited by 9 | Viewed by 2158

Abstract

In this paper we infer the mass composition of the ultra high energy cosmic rays (UHECRs) from measurements of

X_{\max}

distributions recorded at the Pierre Auger (2014) and Telescope Array (TA) (2016) Observatories, by fitting them with all possible combinations of Monte [...] Read more.

In this paper we infer the mass composition of the ultra high energy cosmic rays (UHECRs) from measurements of

X_{\max}

distributions recorded at the Pierre Auger (2014) and Telescope Array (TA) (2016) Observatories, by fitting them with all possible combinations of Monte Carlo (MC) templates from a large set of primary species (p, He, C, N, O, Ne, Si and Fe), as predicted by EPOS-LHC, QGSJETII-04 and Sibyll 2.1 hadronic interaction models. We use the individual fractions of nuclei reconstructed from one experiment in each energy interval to build equivalent MC

X_{\max}

distributions, which we compare with the experimental

X_{\max}

distributions of the other experiment, applying different statistical tests of compatibility. The results obtained from both experiments confirm that the mass composition of the UHECRs is dominated (≳

70 %

) by protons and He nuclei in the energy range investigated

lg E (eV)

= [17.8–19.3] (Auger) and

lg E (eV)

= [18.2–19.0] (TA). The indirect comparisons between the

X_{\max}

distributions recorded by the two experiments show that the degree of compatibility of the two datasets is good, even excellent in some high energy intervals, especially above the ankle (

lg E (eV) \sim 18.7

). However, our study reveals that, at low energies, further effort in data analysis is required in order to harmonize the results of the two experiments. Full article

(This article belongs to the Special Issue Astroparticle Physics)

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7 pages, 357 KiB

Open AccessArticle

Studying Cosmic Ray Sources Using Intergalactic Electromagnetic Cascades

by Anna Uryson

Universe 2021, 7(8), 287; https://doi.org/10.3390/universe7080287 - 6 Aug 2021

Cited by 1 | Viewed by 1519

Abstract

In this paper, intergalactic electromagnetic cascades are used as a probe of cosmic ray sources. This is achieved as follows. In extragalactic space, cosmic rays initiate electromagnetic cascades, in which gamma-ray and neutrino emission arises. We used the joint analysis of cosmic ray [...] Read more.

In this paper, intergalactic electromagnetic cascades are used as a probe of cosmic ray sources. This is achieved as follows. In extragalactic space, cosmic rays initiate electromagnetic cascades, in which gamma-ray and neutrino emission arises. We used the joint analysis of cosmic ray data, along with extragalactic gamma-ray and neutrino emissions, to study particle acceleration in the vicinity of supermassive black holes. Particle injection spectra depend on processes of particle acceleration, and here we discuss models with various injection spectra. The computations of the propagation of cosmic rays in space were performed using the publicly available TransportCR code. It was found that a new subclass of sources might exist that does not contribute to the particle flux on Earth, instead to gamma-ray and neutrino emissions arising in electromagnetic cascades. In addition, the upper limit of the relative number of ‘exotic’ supermassive black holes surrounded by a superstrong magnetic field is derived. Full article

(This article belongs to the Special Issue Astroparticle Physics)

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12 pages, 366 KiB

Open AccessArticle

Modeling Gamma-Ray SEDs and Angular Extensions of Extreme TeV Blazars from Intergalactic Proton-Initiated Cascades in Contemporary Astrophysical EGMF Models

by Emil Khalikov

Universe 2021, 7(7), 220; https://doi.org/10.3390/universe7070220 - 30 Jun 2021

Cited by 1 | Viewed by 1651

Abstract

The intrinsic spectra of some distant blazars known as “extreme TeV blazars” have shown a hint at an anomalous hardening in the TeV energy region. Several extragalactic propagation models have been proposed to explain this possible excess transparency of the Universe to gamma-rays [...] Read more.

The intrinsic spectra of some distant blazars known as “extreme TeV blazars” have shown a hint at an anomalous hardening in the TeV energy region. Several extragalactic propagation models have been proposed to explain this possible excess transparency of the Universe to gamma-rays starting from a model which assumes the existence of so-called axion-like particles (ALPs) and the new process of gamma-ALP oscillations. Alternative models suppose that some of the observable gamma-rays are produced in the intergalactic cascades. This work focuses on investigating the spectral and angular features of one of the cascade models, the Intergalactic Hadronic Cascade Model (IHCM) in the contemporary astrophysical models of Extragalactic Magnetic Field (EGMF). For IHCM, EGMF largely determines the deflection of primary cosmic rays and electrons of intergalactic cascades and, thus, is of vital importance. Contemporary Hackstein models are considered in this paper and compared to the model of Dolag. The models assumed are based on simulations of the local part of large-scale structure of the Universe and differ in the assumptions for the seed field. This work provides spectral energy distributions (SEDs) and angular extensions of two extreme TeV blazars, 1ES 0229+200 and 1ES 0414+009. It is demonstrated that observable SEDs inside a typical point spread function of imaging atmospheric Cherenkov telescopes (IACTs) for IHCM would exhibit a characteristic high-energy attenuation compared to the ones obtained in hadronic models that do not consider EGMF, which makes it possible to distinguish among these models. At the same time, the spectra for IHCM models would have longer high energy tails than some available spectra for the ALP models and the universal spectra for the Electromagnetic Cascade Model (ECM). The analysis of the IHCM observable angular extensions shows that the sources would likely be identified by most IACTs not as point sources but rather as extended ones. These spectra could later be compared with future observation data of such instruments as Cherenkov Telescope Array (CTA) and LHAASO. Full article

(This article belongs to the Special Issue Astroparticle Physics)

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Review

Jump to: Research

33 pages, 1592 KiB

Open AccessReview

A Short Review on the Latest Neutrinos Mass and Number Constraints from Cosmological Observables

by Ziad Sakr

Universe 2022, 8(5), 284; https://doi.org/10.3390/universe8050284 - 16 May 2022

Cited by 10 | Viewed by 2570

Abstract

We review the neutrino science, focusing on its impact on cosmology along with the latest constraints on its mass and number of species. We also discuss its status as a possible solution to some of the recent cosmological tensions, such as the Hubble [...] Read more.

We review the neutrino science, focusing on its impact on cosmology along with the latest constraints on its mass and number of species. We also discuss its status as a possible solution to some of the recent cosmological tensions, such as the Hubble constant or the matter fluctuation parameter. We end by showing forecasts from next-generation planned or candidate surveys, highlighting their constraining power, alone or in combination, but also the limitations in determining neutrino mass distribution among its species. Full article

(This article belongs to the Special Issue Astroparticle Physics)

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72 pages, 5786 KiB

Open AccessReview

Axion-like Particles Implications for High-Energy Astrophysics

by Giorgio Galanti and Marco Roncadelli

Universe 2022, 8(5), 253; https://doi.org/10.3390/universe8050253 - 20 Apr 2022

Cited by 25 | Viewed by 3066

Abstract

We offer a pedagogical introduction to axion-like particles (ALPs) as far as their relevance for high-energy astrophysics is concerned, from a few MeV to 1000 TeV. This review is self-contained, in such a way to be understandable even to non-specialists. Among other things, [...] Read more.

We offer a pedagogical introduction to axion-like particles (ALPs) as far as their relevance for high-energy astrophysics is concerned, from a few MeV to 1000 TeV. This review is self-contained, in such a way to be understandable even to non-specialists. Among other things, we discuss two strong hints at a specific ALP that emerge from two very different astrophysical situations. More technical matters are contained in three Appendices. Full article

(This article belongs to the Special Issue Astroparticle Physics)

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