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Blazars are the most extreme subclass of active galactic nuclei with relativistic jets emerging from a super-massive black hole and forming a small angle with respect to our line of sight. Blazars are also known to be related to flaring…

High Energy Astrophysical Phenomena · Physics 2021-08-02 Stamatios I. Stathopoulos , Maria Petropoulou , Paolo Giommi , Georgios Vasilopoulos , Paolo Padovani , Apostolos Mastichiadis

Supermassive black holes in the centers of galaxies are very common. They are known to rotate, accrete, spin down and eject highly relativistic jets; those jets pointed at us all seem to show a spectrum with two strong bumps, one in the TeV…

Astrophysics of Galaxies · Physics 2015-05-20 P. L. Biermann , J. K. Becker , L. I. Caramete , F. Fraschetti , T. Kneiske , A. Meli , T. Stanev

On July 30th, 2019 IceCube detected a high-energy astrophysical muon neutrino candidate, IC-190730A, with a $67\%$ probability of astrophysical origin. The flat spectrum radio quasar (FSRQ) PKS 1502+106 is in the error circle of the…

High Energy Astrophysical Phenomena · Physics 2022-02-09 Foteini Oikonomou , Maria Petropoulou , Kohta Murase , Aaron Tohuvavohu , Georgios Vasilopoulos , Sara Buson , Marcos Santander

In this paper I review recent results on high-energy neutrino astronomy and what they can reveal about some of the most extreme cosmic accelerators. I discuss recent measurements of the diffuse TeV-PeV cosmic neutrino spectrum by the…

High Energy Astrophysical Phenomena · Physics 2026-03-12 Xavier Rodrigues

Microquasars are laboratories for the study of jets of relativistic particles produced by accretion onto a spinning black hole. Microquasars are near enough to allow detailed imaging of spatial features across the multiwavelength spectrum.…

The detection of high energy neutrinos ($10^{15}-10^{20}$ eV or $1-10^{5}$ PeV) is an important step toward understanding the most energetic cosmic accelerators and would enable tests of fundamental physics at energy scales that cannot…

Instrumentation and Methods for Astrophysics · Physics 2016-05-12 A. G. Vieregg , K. Bechtol , A. Romero-Wolf

We explore the radio properties of powerful (rest-frame luminosity $\gtrsim10^{28}$ W Hz$^{-1}$ at 500 MHz) high-redshift (z > 3.5) quasars. The aim of this study is to gain a better understanding of radio-loud sources at the epoch when…

Astrophysics of Galaxies · Physics 2024-07-02 Alessandro Capetti , Barbara Balmaverde

An updated analysis of a targeted search for high-energy neutrinos from Markarian 421 and Markarian 501 is reported. They are two of the closest and brightest extragalactic sources in the TeV band. In contrast to other types of active…

High Energy Astrophysical Phenomena · Physics 2019-11-13 Mukharbek Organokov , Thierry Pradier

Transrelativistic supernovae (SNe), which are likely driven by central engines via jets or winds, have been among candidate sources of ultrahigh-energy cosmic rays (UHECRs). We investigate acceleration and survival of UHECR nuclei in the…

High Energy Astrophysical Phenomena · Physics 2019-11-13 B. Theodore Zhang , Kohta Murase

We use 3 years of data from the Swift/BAT survey to select a complete sample of X-ray blazars above 15 keV. This sample comprises 26 Flat-Spectrum Radio Quasars (FSRQs) and 12 BL Lac objects detected over a redshift range of 0.03<z<4.0. We…

Cosmology and Nongalactic Astrophysics · Physics 2010-02-04 M. Ajello , L. Costamante , R. M. Sambruna , N. Gehrels , J. Chiang , A. Rau , A. Escala , J. Greiner , J. Tueller , J. V. Wall , R. F. Mushotzky

The diffuse flux of cosmic neutrinos has been measured by the IceCube Observatory from TeV to PeV energies. We show that an improved characterization of this flux at the lower energies, TeV and sub-TeV, reveals important information on the…

High Energy Astrophysical Phenomena · Physics 2022-07-20 Ke Fang , John S. Gallagher , Francis Halzen

The cumulative emission resulting from hadronic cosmic-ray interactions in star-forming galaxies (SFGs) has been proposed as the dominant contribution to the astrophysical neutrino flux at TeV to PeV energies reported by IceCube. The same…

High Energy Astrophysical Phenomena · Physics 2017-04-25 Keith Bechtol , Markus Ahlers , Mattia Di Mauro , Marco Ajello , Justin Vandenbroucke

Cosmic rays accelerated to ultra-high energies (E>4x10^19 eV) in electric fields in accretion discs around supermassive black holes are discussed. Particle injection spectra are assumed to be harder than those formed in acceleration on…

High Energy Astrophysical Phenomena · Physics 2020-01-08 A. Uryson

We estimate the high energy neutrino flux from the giant flare of SGR 1806-20 on December 27, 2004, which irradiated Earth with a gamma-ray flux ~10^4 times larger than the most luminous gamma-ray bursts (GRBs) ever detected. The Antarctic…

Astrophysics · Physics 2009-11-10 Kunihito Ioka , Soebur Razzaque , Shiho Kobayashi , Peter Meszaros

The main goal of the construction of large volume, high energy neutrino telescopes is the detection of extra-Galactic neutrino sources. The existence of such sources is implied by observations of ultra-high energy, >10^{19} eV, cosmic-rays…

Astrophysics · Physics 2009-11-10 Eli Waxman

IceCube discovered a flux of cosmic neutrinos originating in extragalactic sources with an energy density close to that in gamma rays and cosmic rays. A multimessenger campaign triggered by the coincident observation of a gamma-ray flare…

High Energy Astrophysical Phenomena · Physics 2019-09-23 Francis Halzen

We performed observations with the Effelsberg 100-m radio telescope to measure flux densities and polarised emission of sources selected from the "Deep X-ray Radio Blazar Survey" (DXRBS) to better define their spectral index behaviour in…

Cosmology and Nongalactic Astrophysics · Physics 2011-07-28 Franco Mantovani , Marco Bondi , Karl-Heinz Mack

In recent years, blazar surveys at radio and X-ray energies have greatly increased our understanding of this type of active galaxy. The combination of multi-wavelength data has shown that blazars follow a well defined sequence in terms of…

Astrophysics · Physics 2007-05-23 I. de la Calle Perez

More than a decade ago, the IceCube Neutrino Observatory discovered a diffuse flux of 10 TeV-10 PeV neutrinos from our Universe. This flux of unknown origin most likely emanates from an extragalactic population of neutrino sources, which…

High Energy Astrophysical Phenomena · Physics 2025-06-03 Kathrine Mørch Groth , Markus Ahlers

We present the results from the Suzaku X-ray observations of five flat-spectrum radio quasars (FSRQs), namely PKS0208-512, Q0827+243, PKS1127-145, PKS1510-089 and 3C 454.3. All these sources were additionally monitored simultaneously or…

High Energy Astrophysical Phenomena · Physics 2015-05-18 LAT Collaboration , A. A. Abdo , F. Tavecchio , M. Sikora , P. Schady , P. Roming , M. M. Chester , L. Maraschi