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Journal articles on the topic 'High energy astrophysics and galactic cosmic rays'

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Author: Grafiati

Published: 10 December 2022

Last updated: 28 January 2023

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1

BIERMANN, P. L., J. K. BECKER, L. CARAMETE, L. GERGELY, I. C. MARIŞ, A. MELI, V. DE SOUZA, and T. STANEV. "ACTIVE GALACTIC NUCLEI: SOURCES FOR ULTRA HIGH ENERGY COSMIC RAYS." International Journal of Modern Physics D 18, no. 10 (October 2009): 1577–81. http://dx.doi.org/10.1142/s0218271809015369.

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Ultra high energy cosmic ray events presently show a spectrum, which we interpret here as galactic cosmic rays due to a starburst, in the radio galaxy Cen A which is pushed up in energy by the shock of a relativistic jet. The knee feature and the particles with energy immediately higher in galactic cosmic rays then turn into the bulk of ultra high energy cosmic rays. This entails that all ultra high energy cosmic rays are heavy nuclei. This picture is viable if the majority of the observed ultra high energy events come from the radio galaxy Cen A, and are scattered by intergalactic magnetic fields across much of the sky.

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2

Blandford, R. D. "The Phenomena of High Energy Astrophysics." Symposium - International Astronomical Union 214 (2003): 3–20. http://dx.doi.org/10.1017/s0074180900194124.

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A brief summary of some highlights in the study of high energy astrophysical sources over the past decade is presented. It is argued that the great progress that has been made derives largely from the application of new technology to observation throughout all of the electromagnetic and other spectra and that, on this basis, the next decade should be even more exciting. However, it is imperative to observe cosmic sources throughout these spectra in order to obtain a full understanding of their properties. In addition, it is necessary to learn the universal laws that govern the macroscopic and the microscopic behavior of cosmic plasma over a great range of physical conditions by combining observations of different classes of source. These two injunctions are illustrated by discussions of cosmology, hot gas, supernova remnants and explosions, neutron stars, black holes and ultrarelativistic outflows. New interpreations of the acceleration of Galactic cosmic rays, the cooling of hot gas in rich clusters and the nature of ultrarelativistic outflows are outlined. The new frontiers of VHE γ-ray astronomy, low frequency radio astronomy, neutrino astronomy, UHE cosmic ray physics and gravitational wave astronomy are especially promising.

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BLASI, PASQUALE. "ON THE ORIGIN OF VERY HIGH ENERGY COSMIC RAYS." Modern Physics Letters A 20, no. 40 (December 28, 2005): 3055–76. http://dx.doi.org/10.1142/s0217732305019213.

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We discuss the most recent developments in our understanding of the acceleration and propagation of cosmic rays up to the highest energies. In particular we specialize our discussion to three issues: (a) developments in the theory of particle acceleration at shock waves; (b) the transition from galactic to extragalactic cosmic rays; (c) implications of up-to-date observations for the origin of ultra high energy cosmic rays (UHECRs).

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Fukushima, Masaki. "The Highest Energy Cosmic Rays, A Review and Prospects." Symposium - International Astronomical Union 214 (2003): 399–408. http://dx.doi.org/10.1017/s007418090019480x.

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The existence of extremely high energy cosmic rays (EHECRs) with energy above 1020eV have been reported by several air shower experiments. The sources of these cosmic rays were considered to be extra-galactic. Relevant high energy astrophysical sources were searched in the arrival direction of these cosmic rays but no appropriate candidates were found. The origin of EHECRs stays unexplained. We review the present status of EHECR studies and introduce several new experiments aiming to unveil its mysterious origin.

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Palladino, Andrea, Arjen van Vliet, Walter Winter, and Anna Franckowiak. "Can astrophysical neutrinos trace the origin of the detected ultra-high energy cosmic rays?" Monthly Notices of the Royal Astronomical Society 494, no. 3 (April 15, 2020): 4255–65. http://dx.doi.org/10.1093/mnras/staa1003.

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ABSTRACT Since astrophysical neutrinos are produced in the interactions of cosmic rays, identifying the origin of cosmic rays using directional correlations with neutrinos is one of the most interesting possibilities of the field. For that purpose, especially the Ultra-High Energy Cosmic Rays (UHECRs) are promising, as they are deflected less by extragalactic and Galactic magnetic fields than cosmic rays at lower energies. However, photo-hadronic interactions of the UHECRs limit their horizon, while neutrinos do not interact over cosmological distances. We study the possibility to search for anisotropies by investigating neutrino-UHECR correlations from the theoretical perspective, taking into account the UHECR horizon, magnetic-field deflections, and the cosmological source evolution. Under the assumption that the neutrinos and UHECRs all come from the same source class, we demonstrate that the non-observation of neutrino multiplets strongly constrains the possibility to find neutrino-UHECR correlations.

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Armillotta, Lucia, Eve C. Ostriker, and Yan-Fei Jiang. "Cosmic-Ray Transport in Simulations of Star-forming Galactic Disks." Astrophysical Journal 922, no. 1 (November 1, 2021): 11. http://dx.doi.org/10.3847/1538-4357/ac1db2.

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Abstract Cosmic-ray transport on galactic scales depends on the detailed properties of the magnetized, multiphase interstellar medium (ISM). In this work, we postprocess a high-resolution TIGRESS magnetohydrodynamic simulation modeling a local galactic disk patch with a two-moment fluid algorithm for cosmic-ray transport. We consider a variety of prescriptions for the cosmic rays, from a simple, purely diffusive formalism with constant scattering coefficient, to a physically motivated model in which the scattering coefficient is set by the critical balance between streaming-driven Alfvén wave excitation and damping mediated by local gas properties. We separately focus on cosmic rays with kinetic energies of ∼1 GeV (high-energy) and ∼30 MeV (low energy), respectively important for ISM dynamics and chemistry. We find that simultaneously accounting for advection, streaming, and diffusion of cosmic rays is crucial for properly modeling their transport. Advection dominates in the high-velocity, low-density hot phase, while diffusion and streaming are more important in higher-density, cooler phases. Our physically motivated model shows that there is no single diffusivity for cosmic-ray transport: the scattering coefficient varies by four or more orders of magnitude, maximal at density n H ∼ 0.01 cm−3. The ion-neutral damping of Alfvén waves results in strong diffusion and nearly uniform cosmic-ray pressure within most of the mass of the ISM. However, cosmic rays are trapped near the disk midplane by the higher scattering rate in the surrounding lower-density, higher-ionization gas. The transport of high-energy cosmic rays differs from that of low-energy cosmic rays, with less effective diffusion and greater energy losses for the latter.

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TOMOZAWA, YUKIO. "HIGH ENERGY COSMIC RAYS, GAMMA RAYS AND NEUTRINOS FROM AGN." Modern Physics Letters A 23, no. 24 (August 10, 2008): 1991–97. http://dx.doi.org/10.1142/s0217732308027278.

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The author reviews a model for the emission of high energy cosmic rays, gamma-rays and neutrinos from AGN (Active Galactic Nuclei) that he has proposed since 1985. Further discussion of the knee energy phenomenon of the cosmic ray energy spectrum requires the existence of a heavy particle with mass in the knee energy range. A possible method of detecting such a particle in the Pierre Auger Project is suggested. Also presented is a relation between the spectra of neutrinos and gamma-rays emitted from AGN. This relation can be tested by high energy neutrino detectors such as ICECUBE, the Mediterranean Sea Detector and possibly by the Pierre Auger Project.

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del Valle, Maria V. "Gamma-rays from reaccelerated cosmic rays in high-velocity clouds colliding with the Galactic disc." Monthly Notices of the Royal Astronomical Society 509, no. 3 (November 11, 2021): 4448–56. http://dx.doi.org/10.1093/mnras/stab3206.

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ABSTRACT High-velocity clouds moving towards the disc will reach the Galactic plane and will inevitably collide with the disc. In these collisions, a system of two shocks is produced, one propagating through the disc and the other develops within the cloud. The shocks produced within the clouds in these interactions have velocities of hundreds of kilometres per second. When these shocks are radiative they may be inefficient in accelerating fresh particles; however, they can reaccelerate and compress Galactic cosmic rays from the background. In this work, we investigate the interactions of Galactic cosmic rays within a shocked high-velocity cloud, when the shock is induced by the collision with the disc. This study is focused in the case of radiative shocks. We aim to establish under which conditions these interactions lead to significant non-thermal emission, especially gamma-rays. We model the interaction of cosmic ray protons and electrons reaccelerated and further energized by compression in shocks within the clouds, under very general assumptions. We also consider secondary electron–positron pairs produced by the cosmic ray protons when colliding with the material of the cloud. We conclude that nearby clouds reaccelerating Galactic cosmic rays in local shocks can produce high-energy radiation that might be detectable with existing and future gamma-ray detectors. The emission produced by electrons and secondary pairs is important at radio wavelengths, and in some cases it may be relevant at hard X-rays. Concerning higher energies, the leptonic contribution to the spectral energy distribution is significant at soft gamma-rays.

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Gorchakov, E., I. Kharchenko, Anvar Shukurov, and Dmitry Sokoloff. "Ultra-high energy cosmic rays in the galactic corona." Astrophysics and Space Science 179, no. 1 (1991): 141–45. http://dx.doi.org/10.1007/bf00642358.

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Learned, John G., and Karl Mannheim. "High-Energy Neutrino Astrophysics." Annual Review of Nuclear and Particle Science 50, no. 1 (December 2000): 679–749. http://dx.doi.org/10.1146/annurev.nucl.50.1.679.

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▪ Abstract High-energy (>100 MeV) neutrino astrophysics enters an era of opportunity and discovery as the sensitivity of detectors approaches astrophysically relevant flux levels. We review the major challenges for this emerging field, among which the nature of dark matter, the origin of cosmic rays, and the physics of extreme objects such as active galactic nuclei, gamma-ray bursts, pulsars, and supernova remnants are of prime importance. Variable sources at cosmological distances allow the probing of neutrino propagation properties over baselines up to about 20 orders of magnitude larger than those probed by terrestrial long-baseline experiments. We review the possible astrophysical sources of high-energy neutrinos, which also act as an irreducible background to searches for phenomena at the electroweak and grand-unified-theory symmetry-breaking scales related to possible supersymmetric dark matter and topological defects. Neutrino astronomy also has the potential to discover previously unimagined high-energy sources invisible in other channels and provides the only means for direct observations of the early universe prior to the era of decoupling of photons and matter. We conclude with a discussion of experimental approaches and a short report on present projects and prospects. We look forward to the day when it will be possible to see the universe through a new window in the light of what may be its most numerous particle, the elusive neutrino.

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Cooper, A. J., D. Gaggero, S. Markoff, and S. Zhang. "High-energy cosmic ray production in X-ray binary jets." Monthly Notices of the Royal Astronomical Society 493, no. 3 (February 11, 2020): 3212–22. http://dx.doi.org/10.1093/mnras/staa373.

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ABSTRACT As smaller analogues of active galactic nuclei, X-ray binaries (XRBs) are also capable of launching jets that accelerate particles to high energies. In this work, we re-examine XRB jets as potential sources of high-energy cosmic rays (CRs) and explore whether they could provide a significant second Galactic component to the CR spectrum. In the most intriguing scenario, XRB-CRs could dominate the observed spectrum above the so-called knee feature at ∼3 × 1015 eV, offering an explanation for several key issues in this transition zone from Galactic to extragalactic CRs. We discuss how such a scenario could be probed in the near future via multimessenger observations of XRB jets, as well as diffuse Galactic neutrino flux measurements.

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Desiati, Paolo. "ICECUBE OBSERVATORY: NEUTRINOS AND THE ORIGIN OF COSMIC RAYS." Acta Polytechnica 53, A (December 18, 2013): 770–75. http://dx.doi.org/10.14311/ap.2013.53.0770.

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The completed IceCube Observatory, the first km<sup>3</sup> neutrino telescope, is already providing the most stringent limits on the flux of high energy cosmic neutrinos from point-like and diffuse galactic and extra-galactic sources. The non-detection of extra-terrestrial neutrinos has important consequences on the origin of the cosmic rays. Here the current status of astrophysical neutrino searches, and of the observation of a persistent cosmic ray anisotropy above 100TeV, are reviewed.

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WIBIG, TADEUSZ, and ARNOLD W. WOLFENDALE. "COSMIC RAYS AND COSMOLOGY." International Journal of Modern Physics A 20, no. 29 (November 20, 2005): 6612–20. http://dx.doi.org/10.1142/s0217751x05029642.

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Two aspects of cosmic rays and cosmology are considered here. Firstly, the relevance of extragalactic cosmic rays to the radiation – and magnetic – fields in the Universe and secondly the contribution of Galactic cosmic rays (or other entities allied to them) to the 'foreground' in analysis of the cosmic microwave background (CMB). Concerning the latter, we present evidence strongly suggesting that the foreground is, indeed, important. Coupled with the demonstration of asymmetries, of Galactic form, in the CMB maps the case for changes to the presently-derived cosmological parameters is strong.

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Li, Zhuo, Giuseppe Di Sciascio, Quan-Bu Gou, Yi-Qing Guo, Hao-Ning He, Ruo-Yu Liu, and Kai Wang. "Chapter 6 Multimessenger Physics *." Chinese Physics C 46, no. 3 (March 1, 2022): 030006. http://dx.doi.org/10.1088/1674-1137/ac3fac.

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Abstract Combining observations of multi-messengers help in boosting the sensitivity of astrophysical source searches, and probe various aspects of the source physics. In this chapter we discuss how LHAASO observations of very high energy (VHE) gamma rays in combination with telescopes for the other messengers can help in solving the origins of VHE neutrinos and galactic and extragalactic cosmic rays.

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Mesquita, A. L., D. Rodgers-Lee, A. A. Vidotto, D. Atri, and B. E. Wood. "Galactic cosmic ray propagation through M dwarf planetary systems." Monthly Notices of the Royal Astronomical Society 509, no. 2 (October 29, 2021): 2091–101. http://dx.doi.org/10.1093/mnras/stab3131.

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ABSTRACT Quantifying the flux of cosmic rays reaching exoplanets around M dwarfs is essential to understand their possible effects on exoplanet habitability. Here, we investigate the propagation of Galactic cosmic rays as they travel through the stellar winds (astrospheres) of five nearby M dwarfs, namely: GJ 15A, GJ 273, GJ 338B, GJ 411, and GJ 887. Our selected stars each have one or two detected exoplanets and they all have wind mass-loss rates constrained by Lyman α observations. Our simulations use a combined 1D magnetohydrodynamic (MHD) Alfvén-wave-driven stellar wind model and 1D cosmic ray transport model. We find that GJ 411 and GJ 887 have Galactic cosmic rays fluxes comparable with Earth’s at their habitable zones. On the other hand, GJ 15A, GJ 273, and GJ 338B receive a lower Galactic cosmic ray flux in their habitable zones. All exoplanets in our sample, with exception of GJ 15A c and GJ 411 c, have a significantly lower flux of Galactic cosmic rays than values observed at the Earth because they orbit closer-in. The fluxes found here can be further used for chemical modelling of planetary atmospheres. Finally, we calculate the radiation dose at the surface of the habitable-zone planet GJ 273 b, assuming it has an Earth-like atmosphere. This planet receives up to 209 times less 15 MeV energy cosmic ray fluxes than values observed at Earth. However, for high-energy cosmic rays (∼GeV), the difference in flux is only 2.3 times smaller, which contributes to GJ 273 b receiving a significant surface radiation dose of 0.13 mSv yr−1 (40 per cent of the annual dose on Earth’s surface).

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Mirzoyan, Razmik. "Technological Novelties of Ground-Based Very High Energy Gamma-Ray Astrophysics with the Imaging Atmospheric Cherenkov Telescopes." Universe 8, no. 4 (March 29, 2022): 219. http://dx.doi.org/10.3390/universe8040219.

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In the past three decades, the ground-based technique of imaging atmospheric Cherenkov telescopes has established itself as a powerful discipline in science. Approximately 250 sources of very high gamma rays of both galactic and extra-galactic origin have been discovered largely due to this technique. The study of these sources is providing clues to many basic questions in astrophysics, astro-particle physics, physics of cosmic rays and cosmology. The currently operational generation of telescopes offer a solid performance. Further improvements of this technique led to the next-generation large instrument known as the Cherenkov Telescope Array. In its final configuration, the sensitivity of CTA will be several times higher than that of the currently best instruments VERITAS, H.E.S.S., and MAGIC. This article is devoted to outlining the technological developments that shaped this technique and led to today’s success.

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HÖRANDEL, JÖRG R. "OVERVIEW ON DIRECT AND INDIRECT MEASUREMENTS OF COSMIC RAYS." International Journal of Modern Physics A 20, no. 29 (November 20, 2005): 6753–64. http://dx.doi.org/10.1142/s0217751x05030016.

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An overview is given on results from direct and indirect measurements of galactic cosmic rays. Their implications on the contemporary understanding of the origin of cosmic rays and the knee in their energy spectrum are discussed.

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KACHELRIES, M., P. SERPICO, and M. TESHIMA. "The Galactic magnetic field as spectrograph for ultra-high energy cosmic rays." Astroparticle Physics 26, no. 6 (January 2007): 378–86. http://dx.doi.org/10.1016/j.astropartphys.2006.08.004.

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19

LAGUTIN, A. A., A. G. TYUMENTSEV, and A. V. YUSHKOV. "ENERGY SPECTRA AND MASS COMPOSITION OF COSMIC RAYS IN THE FRACTAL-LIKE GALACTIC MEDIUM." International Journal of Modern Physics A 20, no. 29 (November 20, 2005): 6834–36. http://dx.doi.org/10.1142/s0217751x05030235.

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We consider the problem of the cosmic ray spectrum formation assuming that cosmic rays are produced by galactic sources. The fractional diffusion equation proposed in our recent papers is used to describe the cosmic rays propagation in interstellar medium. We show that in the framework of this approach it is possible to explain the locally observed basic features of the cosmic rays in the energy region 1010 ÷ 1020 eV : difference between spectral exponents of protons and other nuclei, mass composition variation, "knee" problem, flattening of the primary spectrum for E ≥ 1018 ÷ 1019 eV .

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20

Pohl, Martin, and David Eichler. "ORIGIN OF ULTRA-HIGH-ENERGY GALACTIC COSMIC RAYS: THE ISOTROPY PROBLEM." Astrophysical Journal 742, no. 2 (November 15, 2011): 114. http://dx.doi.org/10.1088/0004-637x/742/2/114.

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21

Tomassetti, Nicola, and Jie Feng. "The Curious Case of High-energy Deuterons in Galactic Cosmic Rays." Astrophysical Journal 835, no. 2 (January 30, 2017): L26. http://dx.doi.org/10.3847/2041-8213/835/2/l26.

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Escobar, G. J., L. J. Pellizza, and G. E. Romero. "Cosmic-ray production from neutron escape in microquasar jets." Astronomy & Astrophysics 650 (June 2021): A136. http://dx.doi.org/10.1051/0004-6361/202039860.

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Context. The origin of Galactic cosmic rays remains a matter of debate, but supernova remnants are commonly considered to be the main place where high-energy cosmic rays are accelerated. Nevertheless, current models predict cosmic-ray spectra that do not match observations and the efficiency of the acceleration mechanism is still undetermined. On the other hand, the contribution of other kinds of sources to the Galactic cosmic-ray population is still unclear, and merits investigation. Aims. In this work we explore a novel mechanism through which microquasars might produce cosmic rays. In this scenario, microquasar jets generate relativistic neutrons, which escape and decay outside the system; protons and electrons, created when these neutrons decay, escape to the interstellar medium as cosmic rays. Methods. We introduce the relativistic neutron component through a coupling term in the transport equation that governs the jet proton population. We compute the escape rate and decay distribution of these neutrons, and follow the propagation of the decay products until they escape the system and become cosmic rays. We then compute the spectra of these cosmic rays. Results. Neutrons can drain only a small fraction of the jet power as cosmic rays. The most promising scenarios arise in extremely luminous systems (Ljet ∼ 1040 erg s−1), in which the fraction of jet power deposited in cosmic rays can reach ∼0.001. Slow jets (Γ ≲ 2, where Γ is the bulk Lorentz factor) favour neutron production. The resulting cosmic-ray spectrum is similar for protons and electrons, which share the power in the ratio given by neutron decay. The spectrum peaks at roughly half the minimum energy of the relativistic protons in the jet; it is soft (spectral index ∼3) above this energy, and almost flat below. Conclusions. The proposed mechanism produces more energetic cosmic rays from microquasars than those presented by previous works in which the particles escape through the jet terminal shock. Values of spectral index steeper than 2 are possible for cosmic rays in our model and these indeed agree with those required to explain the spectral signatures of Galactic cosmic rays, although only the most extreme microquasars provide power comparable to that of a typical supernova remnant. The mechanism explored in this work may provide stronger and softer cosmic-ray sources in the early Universe, and therefore contribute to the heating and reionisation of the intergalactic medium.

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ZANINETTI, LORENZO. "MODELS OF DIFFUSION OF GALACTIC COSMIC RAYS FROM SUPERBUBBLES." International Journal of Modern Physics A 22, no. 05 (February 20, 2007): 995–1026. http://dx.doi.org/10.1142/s0217751x07035215.

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Superbubbles are shells in the interstellar medium produced by the simultaneous explosions of many supernova remnants. The solutions of the mathematical diffusion and of the Fourier expansion in 1D, 2D and 3D were deduced in order to describe the diffusion of nucleons from such structures. The mean number of visits in the the case of the Levy flights in 1D was computed with a Monte Carlo simulation. The diffusion of cosmic rays has its physical explanation in the relativistic Larmor gyro-radius which is energy dependent. The mathematical solution of the diffusion equation in 1D with variable diffusion coefficient was computed. Variable diffusion coefficient means magnetic field variable with the altitude from the Galactic plane. The analytical solutions allow us to calibrate the code that describes the Monte Carlo diffusion. The maximum energy that can be extracted from the superbubbles is deduced. The concentration of cosmic rays is a function of the distance from the nearest superbubble and the selected energy. The interaction of the cosmic rays on the target material allows us to trace the theoretical map of the diffuse Galactic continuum gamma-rays. The streaming of the cosmic rays from the Gould Belts that contains the sun at its internal was described by a Monte Carlo simulation. Ten new formulas are derived.

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Zhang, Pei-Pei, Yi-Qing Guo, Bing-Qiang Qiao, and Wei Liu. "Constraining the Position of the Knee in the Galactic Cosmic-Ray Spectrum with Ultra-high-energy Diffuse γ-Rays." Astrophysical Journal 940, no. 1 (November 1, 2022): 3. http://dx.doi.org/10.3847/1538-4357/ac98ff.

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Abstract The diffuse γ-ray emission was measured up to 957 TeV by the Tibet-ASγ experiment recently. Assuming that it is produced by the hadronic interaction between cosmic-ray nuclei and the interstellar medium, it requires that the cosmic-ray nuclei should be accelerated well beyond PeV energies. Measurements of the cosmic-ray spectra for different species show diverse results at present. The Tibet experiments showed that the spectrum of proton plus helium has an early knee below PeV. If this is correct, the diffuse γ-ray emission would suggest an additional component of Galactic cosmic rays above PeV energies. This second component may originate from a source population of so-called PeVatrons revealed by recent ultra-high-energy γ-ray observations and could contribute to the cosmic-ray fluxes up to the energy of the second knee. On the other hand, the KASCADE measurement showed that the knee of protons is higher than PeV. In this case, the diffuse γ-rays observed by Tibet-ASγ can be well accounted for by only one cosmic-ray component. These two scenarios (i.e., the Tibet and KASCADE knees) could be distinguished by the spectral structures of diffuse γ-rays and cosmic-ray nuclei. Future measurements of spectra of individual nuclei by HERD and LHAASO experiments and diffuse γ-rays by LHAASO can jointly constrain these two scenarios.

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Hinton, J. A., and R. L. C. Starling. "High-energy emission from transients." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 371, no. 1992 (June 13, 2013): 20120279. http://dx.doi.org/10.1098/rsta.2012.0279.

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Cosmic explosions dissipate energy into their surroundings on a very wide range of time scales: producing shock waves and associated particle acceleration. The historical culprits for the acceleration of the bulk of Galactic cosmic rays are supernova remnants: explosions on approximately 10 4 year time scales. Increasingly, however, time-variable emission points to rapid and efficient particle acceleration in a range of different astrophysical systems. Gamma-ray bursts have the shortest time scales, with inferred bulk Lorentz factors of approximately 1000 and photons emitted beyond 100 GeV, but active galaxies, pulsar wind nebulae and colliding stellar winds are all now associated with time-variable emission at approximately teraelectron volt energies. Cosmic photons and neutrinos at these energies offer a powerful probe of the underlying physical mechanisms of cosmic explosions, and a tool for exploring fundamental physics with these systems. Here, we discuss the motivations for high-energy observations of transients, the current experimental situation, and the prospects for the next decade, with particular reference to the major next-generation high-energy observatory, the Cherenkov Telescope Array.

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LEMOINE, MARTIN. "ON ACCELERATION AND PROPAGATION OF ULTRA-HIGH ENERGY COSMIC RAYS." International Journal of Modern Physics D 18, no. 10 (October 2009): 1583–86. http://dx.doi.org/10.1142/s0218271809015497.

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This paper discusses the correlation reported in 2008 by the Pierre Auger Observatory (PAO) of the arrival directions of the highest energy cosmic rays with active galactic nuclei (AGN). It is argued that these correlating AGN do not have the power required to be the sources of ultra-high energy protons. This current PAO dataset is further shown to disfavor giant radio-galaxies (both Fanaroff–Riley type I and II) as sources of ultra-high energy protons. The current data thus likely point to the local large scale structure, in which the actual sources of ultra-high energy cosmic rays camouflage. Finally, it is shown that the last gamma-ray burst in Centaurus A could explain, through rescattering on the Cen A lobes, the apparent cluster of events in this direction.

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Müller, Ana L., Gustavo E. Romero, and Markus Roth. "High-energy processes in starburst-driven winds." Monthly Notices of the Royal Astronomical Society 496, no. 2 (June 17, 2020): 2474–81. http://dx.doi.org/10.1093/mnras/staa1720.

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ABSTRACT Starburst galaxies generate large-scale winds powered by the activity in the star-forming regions located in the galactic discs. Fragmentation of the disc produced by the outbreak of the wind results in the formation of clouds. Bowshocks caused by the supersonic outflow appear around such clouds. In this paper, we discuss the acceleration of relativistic particles and the production of non-thermal radiation in such scenario. Cosmic rays accelerated at the bowshocks do not reach the highest energies, although the high-energy luminosity generated is significant. We show that up to ∼10 per cent of the gamma-ray emission in starbursts might come from these sources outside the galactic discs. Discrete X-ray sources with a power-law component are also expected.

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Kovalev, Y. Y., A. V. Plavin, and S. V. Troitsky. "Galactic Contribution to the High-energy Neutrino Flux Found in Track-like IceCube Events." Astrophysical Journal Letters 940, no. 2 (November 29, 2022): L41. http://dx.doi.org/10.3847/2041-8213/aca1ae.

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Abstract Astrophysical sources of neutrinos detected by large-scale neutrino telescopes remain uncertain. While there exist statistically significant observational indications that a part of the neutrino flux is produced by blazars, numerous theoretical studies suggest also the presence of potential Galactic point sources. Some of them have been observed in gamma rays above 100 TeV. Moreover, cosmic-ray interactions in the Galactic disk guarantee a diffuse neutrino flux. However, these Galactic neutrinos have not been unambiguously detected so far. Here we examine whether such a Galactic component is present among the observed neutrinos of the highest energies. We analyze public track-like IceCube events with estimated neutrino energies above 200 TeV. We examine the distribution of arrival directions of these neutrinos in the Galactic latitude b with the help of a simple unbinned, nonparametric test statistics, the median ∣b∣ over the sample. This distribution deviates from that implied by the null hypothesis of the neutrino flux isotropy, and is shifted toward lower ∣b∣ with the p-value of 4 × 10−5, corresponding to the statistical significance of 4.1σ. There exists a significant component of the high-energy neutrino flux of Galactic origin, matching well the multimessenger expectations from Tibet-ASγ observations of diffuse Galactic gamma rays at hundreds of TeV. Together with the previously established extragalactic associations, the Galactic component we report here implies that the neutrino sky is rich and is composed of contributions from various classes of sources.

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GHIA, P. L., and G. NAVARRA. "THE EXPERIMENTAL DATA ON THE HIGH ENERGY GALACTIC COSMIC RAYS FROM EAS-TOP." International Journal of Modern Physics A 20, no. 29 (November 20, 2005): 6817–20. http://dx.doi.org/10.1142/s0217751x05030181.

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We summarize the main results reported by EAS-TOP in the study of cosmic rays in the energy range 1012 – 1016 eV (from the direct measurements up to above the "knee"), i.e. the region which is generally considered to represent the high energy galactic radiation.

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Abbasi, R., M. Ackermann, J. Adams, J. A. Aguilar, M. Ahlers, M. Ahrens, J. M. Alameddine, et al. "Search for High-energy Neutrino Emission from Galactic X-Ray Binaries with IceCube." Astrophysical Journal Letters 930, no. 2 (May 1, 2022): L24. http://dx.doi.org/10.3847/2041-8213/ac67d8.

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Abstract We present the first comprehensive search for high-energy neutrino emission from high- and low-mass X-ray binaries conducted by IceCube. Galactic X-ray binaries are long-standing candidates for the source of Galactic hadronic cosmic rays and neutrinos. The compact object in these systems can be the site of cosmic-ray acceleration, and neutrinos can be produced by interactions of cosmic rays with radiation or gas, in the jet of a microquasar, in the stellar wind, or in the atmosphere of the companion star. We study X-ray binaries using 7.5 yr of IceCube data with three separate analyses. In the first, we search for periodic neutrino emission from 55 binaries in the Northern Sky with known orbital periods. In the second, the X-ray light curves of 102 binaries across the entire sky are used as templates to search for time-dependent neutrino emission. Finally, we search for time-integrated emission of neutrinos for a list of 4 notable binaries identified as microquasars. In the absence of a significant excess, we place upper limits on the neutrino flux for each hypothesis and compare our results with theoretical predictions for several binaries. In addition, we evaluate the sensitivity of the next generation neutrino telescope at the South Pole, IceCube-Gen2, and demonstrate its power to identify potential neutrino emission from these binary sources in the Galaxy.

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Neronov, A., and D. Semikoz. "Galactic diffuse gamma-ray emission at TeV energy." Astronomy & Astrophysics 633 (January 2020): A94. http://dx.doi.org/10.1051/0004-6361/201936368.

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Context. Measuring the diffuse Galactic γ-ray flux in the TeV range is difficult for ground-based γ-ray telescopes because of the residual cosmic-ray background, which is higher than the γ-ray flux by several orders of magnitude. Its detection is also challenging for space-based telescopes because of low signal statistics. Aims. We characterise the diffuse TeV flux from the Galaxy using decade-long exposures of the Fermi Large Area Telescope. Methods. Considering that the level of diffuse Galactic emission in the TeV band approaches the level of residual cosmic-ray background, we estimated the level of residual cosmic-ray background in the SOURCEVETO event selection and verified that the TeV diffuse Galactic emission flux is well above the residual cosmic-ray background up to high Galactic latitude regions. Results. We study spectral and imaging properties of the diffuse TeV signal from the Galactic plane. We find much stronger emission from the inner Galactic plane than in previous HESS telescope estimates (lower bound). We also find a significant difference in the measurement of the Galactic longitude and latitude profiles of the signal measured by Fermi and HESS. These discrepancies are presumably explained by the fact that regions of background estimate in HESS have non-negligible γ-ray flux. Comparing Fermi measurements with those of ARGO-YBJ, we find better agreement, with the notable exception of the Cygnus region, where we find much higher flux (by a factor 1.5). We also measure the TeV diffuse emission spectrum up to high Galactic latitude and show that the spectra of different regions of the sky have spectral slopes consistent with Γ = 2.34 ± 0.04, which is harder than the slope of the locally observed spectrum of cosmic rays with energies 10–100 TeV, which produce TeV diffuse emission on their way through the interstellar medium. We discuss the possible origin of the hard slope of the TeV diffuse emission. Conclusions. Fermi/LAT provides reliable measurements of the diffuse Galactic emission spectrum in the TeV range, which are almost background free at low Galactic latitudes. The diffuse flux becomes comparable to the residual cosmic-ray background at Galactic latitudes |b| > 50°. Its measurement in these regions might suffer from systematic uncertainty stemming from the uncertainty of our phenomenological model of the residual cosmic-ray background in the Pass 8 Fermi/LAT data.

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Goto, Miwa. "The cosmic ray ionization rate in the central parsec of the Galaxy." Proceedings of the International Astronomical Union 9, S303 (October 2013): 429–33. http://dx.doi.org/10.1017/s1743921314001070.

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AbstractCosmic rays represent a unique crossing point of high-energy astrophysics and astrochemistry. The cosmic ray ionization rate of molecular hydrogen (ζ2) measured by H3+ spectroscopy in the central parsec of the Galaxy is 2 orders of magnitude higher than that in the dense clouds outside the Galactic center. However, it is still too short, by the factor of 10,000, to agree with an extremely high ζ2 that accommodates the new γ-ray observations of Sgr A* and its environment.

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33

Prouza, M., and R. Šmída. "The Galactic magnetic field and propagation of ultra-high energy cosmic rays." Astronomy & Astrophysics 410, no. 1 (October 2003): 1–10. http://dx.doi.org/10.1051/0004-6361:20031281.

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George, M. R., A. C. Fabian, W. H. Baumgartner, R. F. Mushotzky, and J. Tueller. "On active galactic nuclei as sources of ultra-high energy cosmic rays." Monthly Notices of the Royal Astronomical Society: Letters 388, no. 1 (July 21, 2008): L59—L63. http://dx.doi.org/10.1111/j.1745-3933.2008.00499.x.

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35

Erdmann, Martin, Lukas Geiger, David Schmidt, Martin Urban, and Marcus Wirtz. "Origins of Extragalactic Cosmic Ray Nuclei by Contracting Alignment Patterns induced in the Galactic Magnetic Field." EPJ Web of Conferences 210 (2019): 04004. http://dx.doi.org/10.1051/epjconf/201921004004.

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We present a novel approach to search for origins of ultra-high energy cosmic rays. In a simultaneous fit to all observed cosmic rays we use the galactic magnetic field as a mass spectrometer and adapt the nuclear charges such that their extragalactic arrival directions are concentrated in as few directions as possible. During the fit the nuclear charges are constraint by the individual energy and shower depth measurements. We show in a simulated astrophysical scenario that source directions can be reconstructed even within a substantial isotropic background.

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36

Rieger, Frank M. "Active Galactic Nuclei as Potential Sources of Ultra-High Energy Cosmic Rays." Universe 8, no. 11 (November 17, 2022): 607. http://dx.doi.org/10.3390/universe8110607.

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Active Galactic Nuclei (AGNs) and their relativistic jets belong to the most promising class of ultra-high-energy cosmic ray (UHECR) accelerators. This compact review summarises basic experimental findings by recent instruments, and discusses possible interpretations and astrophysical constraints on source energetics. Particular attention is given to potential sites and mechanisms of UHECR acceleration in AGNs, including gap-type particle acceleration close to the black hole, as well as first-order Fermi acceleration at trans-relativistic shocks and stochastic shear particle acceleration in large-scale jets. It is argued that the last two represent the most promising mechanisms given our current understanding, and that nearby FR I type radio galaxies provide a suitable environment for UHECR acceleration.

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ARAKIDA, HIDEYOSHI, and SHUICHI KURAMATA. "DIFFUSIVE PROPAGATION OF HIGH ENERGY COSMIC RAYS IN GALAXY: EFFECT OF HALL DRIFT." International Journal of Modern Physics A 26, no. 05 (February 20, 2011): 911–23. http://dx.doi.org/10.1142/s0217751x11051378.

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We phenomenologically developed a propagation model of high energy galactic cosmic rays. We derived the analytical solutions by adopting the semi-empirical diffusion equation, proposed by Berezinskii et al. (1990) and the diffusion tensor proposed by Ptuskin et al. (1993). This model takes into account both the symmetric diffusion and the antisymmetric diffusion due to the particle Hall drift. Our solutions are an extension of the model developed by Ptuskin et al. to a two-dimensional two-layer (galactic disk and halo) model, and they coincide completely with the solution derived by Berezinskii et al. in the absence of antisymmetric diffusion due to Hall drift. We showed that this relatively simple toy model can be used to explain the variation in the exponent of the cosmic ray energy spectrum, γ, around the knee E ≈1015 eV .

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Cirkovic, Milan, and I. Damjanov. "On determination of the cosmic ray flux using molecular hydrogen absorption lines." Serbian Astronomical Journal, no. 167 (2003): 15–20. http://dx.doi.org/10.2298/saj0367015c.

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We outline a procedure for estimating the cosmic ray flux at remote locations where molecular hydrogen absorption lines have been detected. The method relies on several assumptions whose validity in the local Galactic ISM has been independently verified, so it might be useful for much less accessible objects, especially damped Ly? absorption systems. Since most of low-energy cosmic rays in the Galactic environment are thought to originate in supernovae remnants, the link to the rate of high-mass star formation could in principle, be established. We applied the method to a particular case of high redshift damped Ly? absorption system towards 0528?250 and obtained an estimate of proton density and some useful constraints.

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Neronov, A., D. Semikoz, and Ie Vovk. "New limit on high Galactic latitude PeV γ-ray flux from Tibet ASγ data." Astronomy & Astrophysics 653 (September 2021): L4. http://dx.doi.org/10.1051/0004-6361/202141800.

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The Tibet ASγ collaboration has recently reported the detection of γ-rays with energies up to Peta-electronvolt from parts of the Galactic plane. We note that the analysis of γ-ray flux by the Tibet-ASγ experiment also implies an upper bound on the diffuse γ-ray flux from high Galactic latitudes (|b|> 20°) in the energy range between 100 TeV and 1 PeV. This bound is up to an order of magnitude stronger than previously derived bounds from GRAPES3, KASCADE, and CASA-MIA experiments. We discuss the new Tibet-ASγ limit on the high Galactic latitude γ-ray flux in the context of possible mechanisms of multi-messenger (γ-ray and neutrino) emission from nearby cosmic ray sources, dark matter decays, and the large-scale cosmic ray halo of the Milky Way.

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40

Bérat, Corinne, Carla Bleve, Olivier Deligny, François Montanet, Pierpaolo Savina, and Zoé Torrès. "Diffuse Flux of Ultra-high-energy Photons from Cosmic-Ray Interactions in the Disk of the Galaxy and Implications for the Search for Decaying Super-heavy Dark Matter." Astrophysical Journal 929, no. 1 (April 1, 2022): 55. http://dx.doi.org/10.3847/1538-4357/ac5cbe.

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Abstract An estimate of the expected photon flux above 1017 eV from the interactions of ultra-high-energy cosmic rays with the matter in the Galactic disk is presented. Uncertainties arising from the distribution of the gas in the disk, the absolute level of the cosmic-ray flux, and the composition of the cosmic rays are taken into account. Within these uncertainties, the integrated photon flux above 1017 eV is averaged out over Galactic latitude less than 5°, between ≃3.2 × 10−2 km−2 yr−1 sr−1 and ≃8.7 × 10−2 km−2 yr−1 sr−1. The all-sky average value amounts to ≃1.1 ×10−2 km−2 yr−1 sr−1 above 1017 eV and decreases roughly as E −2, making this diffuse flux the dominant one from cosmic-ray interactions for energy thresholds between 1017 and 1018 eV. Compared to the current sensitivities of detection techniques, a gain of between two and three orders of magnitude in exposure is required for a detection below ≃1018 eV. The implications for searches for photon fluxes from the Galactic center that would be indicative of the decay of super-heavy dark matter particles are discussed, as the photon flux presented in this study can be considered as a floor below which other signals would be overwhelmed.

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41

de Naurois, Mathieu. "TeV observations of the Galactic center and starburst galaxies." Proceedings of the International Astronomical Union 9, S303 (October 2013): 29–42. http://dx.doi.org/10.1017/s1743921314000118.

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AbstractThe vicinity of the Galactic center harbors many potential accelerators of cosmic rays (CR) that could shine in very-high-energy (VHE) γ-rays, such as pulsar wind nebulae, supernova remnants, binary systems and the central black hole Sgr A*, and is characterized by high gas density, large magnetic fields and a high rate of starburst activity similar to that observed in the core of starburst galaxies. In addition to these astrophysical sources, annihilation of putative WIMPs concentrated in the gravitational well could lead to significant high-energy emission at the Galactic center. The Galactic center region has been observed by atmospheric Cherenkov telescopes, and in particular by the H. E. S. S. array in Namibia for the last ten years above 150 GeV. This large data set, comprising more than 200 hours of observations, led to the discovery of a point-like source spatially compatible with the supermassive black hole Sgr A*, and to an extended diffuse emission, correlated with molecular clouds and attributed to the interaction of cosmic rays with the interstellar medium. Over the same time period, two starburst galaxies, namely M 82 and NGC 253, were detected at TeV energies after very deep exposures. Results from these ten years of observations of the Galactic center region and starburst galaxies at TeV energies are presented, and implications for the various very-high-energy emission mechanisms are discussed.

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Medvedev, Mikhail V. "Extragalactic shocks as cosmic accelerators." Proceedings of the International Astronomical Union 2, no. 14 (August 2006): 95–96. http://dx.doi.org/10.1017/s1743921307009970.

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AbstractIt is quite well established that shocks accelerate particles via the Fermi mechanism. We discuss common features of various extragalactic sources, ranging from Gamma-Ray Bursts and jets of Active Galactic Nuclei to Large-Scale Structure shocks and address how they affect particle acceleration. In particular, we address constraints on the maximum energy of ultra-high-energy cosmic rays. Interestingly, some recent studies indicate that Fermi acceleration in relativistic shocks (and GRBs, in particular) faces severe difficulties. We will address this issue and demonstrate that the ‘observed’ shock acceleration of electrons may have nothing to do with Fermi acceleration, but may rather be associated with micro-physics of collisionless shocks.

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CHANG, FENG-YIN, PISIN CHEN, GUEY-LIN LIN, ROBERT NOBLE, and RICHARD SYDORA. "MAGNEOWAVE INDUCED PLASMA WAKEFIELD ACCELERATION AS A MECHANISM FOR UHECR." International Journal of Modern Physics: Conference Series 01 (January 2011): 151–56. http://dx.doi.org/10.1142/s2010194511000201.

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Magnetowave induced plasma wakefield acceleration (MPWA) in a relativistic astrophysical outflow has been proposed as a viable mechanism for the acceleration of cosmic particles to ultra high energies. In this paper we present the relativistic MPWA theory and confirm such a concept via the plasma simulation. Invoking Active Galactic Nuclei (AGN) as the site, we show that MPWA production of ultra high energy cosmic rays (UHECR) beyond ZeV (1021 eV) is possible.

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44

Maurin, David, Michel Cassé, and Elisabeth Vangioni-Flam. "Heavy nuclei enrichment of the galactic cosmic rays at high energy: astrophysical interpretation." Astroparticle Physics 18, no. 5 (February 2003): 471–86. http://dx.doi.org/10.1016/s0927-6505(02)00163-9.

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45

Barghouty, A. F., and D. A. Schnee. "ANOMALOUS TRANSPORT OF HIGH-ENERGY COSMIC RAYS IN GALACTIC SUPERBUBBLES. I. NUMERICAL SIMULATIONS." Astrophysical Journal 749, no. 2 (April 5, 2012): 178. http://dx.doi.org/10.1088/0004-637x/749/2/178.

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46

Fraschetti, F., and F. Melia. "Ultra-high-energy cosmic rays from the radio lobes of active galactic nuclei." Monthly Notices of the Royal Astronomical Society 391, no. 3 (December 11, 2008): 1100–1106. http://dx.doi.org/10.1111/j.1365-2966.2008.13987.x.

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47

Jokipii, J. R., and G. Morfill. "Ultra-high-energy cosmic rays in a galactic wind and its termination shock." Astrophysical Journal 312 (January 1987): 170. http://dx.doi.org/10.1086/164857.

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KIM, HANG BAE. "CONSTRAINING SHDM MODEL OF UHECR WITH SUGAR DATA." Modern Physics Letters A 19, no. 13n16 (May 30, 2004): 1137–44. http://dx.doi.org/10.1142/s0217732304014483.

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We focus on the arrival direction distributions of the ultra-high energy cosmic rays (UHECR) in search of their possible origins. Models which associate the origin of UHECR with decays of relic superheavy dark matter particles (SHDM) predict the anisotropy of UHECR flux toward the Galactic center. We use the existing SUGAR data, which cover the Galactic center, to look for such a signal and limit the fraction of UHECR produced by this mechanism.

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MURASE, KOHTA, SUSUMU INOUE, and KATSUAKI ASANO. "COSMIC RAYS ABOVE THE 2ND KNEE FROM CLUSTERS OF GALAXIES." International Journal of Modern Physics D 18, no. 10 (October 2009): 1609–14. http://dx.doi.org/10.1142/s0218271809015564.

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In clusters of galaxies, accretion and merger shocks are potential accelerators of high energy protons, as well as intracluster active galactic nuclei. We discuss the possibility that protons from cluster shocks make a significant contribution to the observed cosmic rays in the energy range between the second knee at ~1017.5 eV and the ankle at ~1018.5 eV. The accompanying neutrino and gamma-ray signals could be detectable by upcoming telescopes such as IceCube/KM3Net and CTA, providing a test of this scenario as well as a probe of cosmic-ray confinement properties in clusters.

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Ebisuzaki, T., and T. Tajima. "Wakefield acceleration towards ZeV from a black hole emanating astrophysical jets." International Journal of Modern Physics A 34, no. 34 (December 10, 2019): 1943018. http://dx.doi.org/10.1142/s0217751x19430188.

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We consider that electromagnetic pulses produced in the jets of this innermost part of the accretion disk accelerate charged particles (protons, ions, electrons) to very high energies via wakefield acceleration, including energies above 10[Formula: see text] eV for the case of protons and nucleus and 10[Formula: see text] eV for electrons by electromagnetic wave-particle interaction. Thereby, the wakefield acceleration mechanism supplements the pervasive Fermi’s stochastic acceleration mechanism (and overcomes its difficulties in the highest energy cosmic ray generation). The episodic eruptive accretion in the disk by the magneto-rotational instability gives rise to the strong Alfvenic pulses, which acts as the driver of the collective accelerating pondermotive force. This pondermotive force drives the wakes. The accelerated hadrons (protons and nuclei) are released to the intergalactic space to be ultra-high energy cosmic rays. The high-energy electrons, on the other hand, emit photons to produce various non-thermal emissions (radio, IR, visible, UV, and gamma-rays) of active galactic nuclei in an episodic manner, giving observational telltale signatures.

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