The origin of the high-energy neutrinos (0.1$-$1 PeV range) detected by IceCube remains a mystery. In this work we explore the possibility that efficient neutrino production can occur in structured jets of BL Lac objects, characterized by a fast inner spine surrounded by a slower layer. This scenario has been widely discussed in the framework of the high-energy emission models for BL Lacs and radiogalaxies. One of the relevant consequences of a velocity structure is the enhancement of the inverse Compton emission caused by the radiative coupling of the two zones. We show that a similar boosting could occur for the neutrino output of the spine through the photo-meson reaction of high-energy protons scattering off the amplified soft target photon field of the layer. Assuming the local density and the cosmological evolution of $γ$-ray BL Lac derived from {\it Fermi}-LAT data, we calculate the expected diffuse neutrino intensity, that can match the IceCube data for a reasonable choice of the parameters.
We analyze the energy distributions of final (stable) products - gamma rays, neutrinos, and electrons - produced in inelastic proton-proton collisions in the PeV energy regime. We also calculate the energy spectrum of synchrotron radiation from secondary electrons, assuming that these are promptly cooled in the surrounding magnetic field. We show that the synchrotron radiation has an energy distribution much shallower than that of primary protons, and hence we suggest to take advantage of such a feature in the spectral analysis of the highest energy (cut-off) emission region from particle acce…
The identification of major contributors to the locally observed fluxes of Cosmic Rays (CRs) is a prime objective towards the resolution of the long-standing enigma of CRs. We report on a compelling similarity of the energy and radial distributions of multi-TeV CRs extracted from observations of very high energy (VHE) $γ$-rays towards the Galactic Center (GC) and two prominent clusters of young massive stars, Cyg~OB2 and Westerlund~1. This resemblance we interpret as a hint that CRs responsible for the diffuse VHE $γ$-ray emission from the GC are accelerated by the ultracompact stellar cluster…
The recent discovery of a new population of ultra-high-energy gamma-ray sources with spectra extending beyond 100 TeV revealed the presence of Galactic PeVatrons - cosmic-ray factories accelerating particles to PeV energies. These sources, except for the one associated with the Crab Nebula, are not yet identified. With an extension of 1 degree or more, most of them contain several potential counterparts, including Supernova Remnants, young stellar clusters and Pulsar Wind Nebulae (PWNe), which can perform as PeVatrons and thus power the surrounding diffuse ultra-high energy gamma-ray structure…
The unidentified PeV source LHAASO J2108+5157: A microquasar remnant?
Universidad de Jaén（哈恩大学）；Instituto Argentino de Radioastronomía (CCT La Plata, CONICET（阿根廷射电天文研究所）；CICPBA（拉普拉塔国立大学天文与地球科学学院）；UNLP)（巴塞罗那大学）；Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata；Universitat de Barcelona
Blazars are potential candidates of cosmic-ray acceleration up to ultrahigh energies ($E\gtrsim10^{18}$ eV). For an efficient cosmic-ray injection from blazars, $pγ$ collisions with the extragalactic background light (EBL) and cosmic microwave background (CMB) can produce neutrino spectrum peaks near PeV and EeV energies, respectively. We analyze the contribution of these neutrinos to the diffuse background measured by the IceCube neutrino observatory. The fraction of neutrino luminosity originating from individual redshift ranges is calculated using the distribution of BL Lacs and FSRQs provi…
Starburst galaxies (SBGs) and more in general starforming galaxies represent a class of galaxies with a high star formation rate (up to 100 solar masses/year). Despite their low luminosity, they can 19 be considered as guaranteed "factories" of high energy neutrinos, being "reservoirs" of accelerated 20 cosmic rays and hosting a high density target gas in the central region. In this contribution 21 we present a novel multimessenger study of these sources and the possibility of observing their 22 neutrino signals with the KM3NeT/ARCA telescope. The differential sensitivity for different SBG 23 …
Since the report of the PeV-TeV neutrinos by the IceCube Collaboration, various particle physics models have been proposed to explain the neutrino spectrum by dark matter particles decaying into neutrinos and other Standard Model particles.In such scenarios, simultaneous $γ$-ray emission is commonly expected. Therefore, multi-messenger connections are generally important for the indirect searches of dark matters. The recent development of $γ$-ray astronomy puts stringent constraints on the properties of dark matter, especially by observations with the Fermi $γ$-ray satellite in the last severa…
We examine the potential multi-messenger role of BL Lac objects emitting at high energy (so-called HBL) focusing on the limits on the energy density of soft radiation in the jet frame, a critical parameter which regulates the proton cooling and the fragmentation of ultra-high energy cosmic ray (UHECR) nuclei possibly accelerated in the jet. We show that (under the assumption that the high-energy emission bump is dominated by inverse Compton emission) the energy density of any external soft radiation field (e.g. produced by a layer surrounding the jet or in the accretion flow) cannot be larger …
Cosmic rays, gamma rays and neutrinos from discrete black hole X-ray binary ejecta
Institute of Astronomy, University of Cambridge（剑桥大学天文研究所）；Astrophysics sub-Department, Department of Physics, University of Oxford（牛津大学物理系天体物理子部门）；Laboratoire d’Annecy-le-Vieux de Physique Théorique (LAPTh), USMB, CNRS（阿讷西勒维尤理论物理实验室，萨瓦大学，法国国家科学研究中心）；Center for Astrophysics and Space Science (CASS), New York University Abu Dhabi（阿布扎比纽约大学天体物理学与空间科学中心）；Department of Astronomy, University of Cape Town（开普敦大学天文学系）
A Unified Framework for 10 TeV to EeV Diffuse Neutrino Sky and KM3-230213A
Department of Physics and Astronomy, University of Utah（犹他大学物理与天文学系）；Key Laboratory of Particle Astrophysics and Experimental Physics Division and Computing Center, IHEP, CAS（中国科学院高能物理研究所粒子天体物理重点实验室及实验物理部计算中心）；TIANFU Cosmic Ray Research Center, Chengdu, Sichuan, China（中国四川成都天府宇宙线研究中心）
The detection of a high energy muon neutrino on 22 September 2017 by IceCube neutrino detector coincides with the multiwavelength flaring from the BL Lac object TXS 0506+056, most likely confirming AGN as a source of high energy cosmic rays and neutrinos. Using the photohadronic model, we have explained the very high energy $γ$-rays observed by MAGIC telescopes few days after the neutrino event and extend the model to calculate the neutrino flux at different windows consistent with the flaring period of TXS 0506+056 and compared with the IceCube and MAGIC estimates. We also use this model to e…
The origin of Petaelectronvolt (PeV) astrophysical neutrinos is fundamental to our understanding of the high-energy Universe. Apart from the technical challenges of operating detectors deep below ice, oceans, and lakes, the phenomenological challenges are even greater than those of gravitational waves; the sources are unknown, hard to predict, and we lack clear signatures. Neutrino astronomy therefore represents the greatest challenge faced by the astronomy and physics communities thus far. The possible neutrino sources range from accretion disks and tidal disruption events, to relativistic je…
The Antarctic Impulsive Transient Antenna (ANITA) experiment has observed two air shower events with energy $\sim 500~{\rm PeV}$ emerging from the Earth with exit angles $\sim 30^\circ$ above the horizon. As was immediately noted by the ANITA Collaboration, these events (in principle) could originate in the atmospheric decay of an upgoing $τ$-lepton produced through a charged current interaction of a $ν_τ$ inside the Earth. However, the relatively steep arrival angles of these perplexing events create tension with the standard model (SM) neutrino-nucleon interaction cross section. Deepening th…
