Sources Of High-energy Neutrinos Research Articles

Are starburst galaxies a common source of high energy neutrinos and cosmic rays?

A recent analysis of cosmic ray air showers observed at the Pierre Auger Observatory indicates that nearby starburst galaxies (SBGs) might be the cause of ∼10% of the Ultra-High-Energy Cosmic Ray flux at energies E > 39 EeV . Since high energy neutrinos are a direct product of cosmic ray interactions, we investigate SBGs as a possible source of some of the ∼ 10−2–1 PeV neutrinos observed at IceCube. A statistical analysis is performed to establish the degree of positional correlation between the observed neutrinos and a set of 45 nearby radio- and infrared-bright SBGs. Our results are consistent with no causal correlation. However, a scenario where ∼ 10% of the High Energy Starting Events (HESE) in the detector are coming from the candidate SBGs is not excluded. The same conclusion is reached for different data subsets, as well as two different subsets of SBGs motivated by the Pierre Auger Observatory analysis.

The presence of interstellar scintillation in the 15 GHz interday variability of 1158 OVRO-monitored blazars

ABSTRACTWe have conducted the first systematic search for interday variability in a large sample of extragalactic radio sources at 15 GHz. From the sample of 1158 radio-selected blazars monitored over an ∼10 yr span by the Owens Valley Radio Observatory 40-m telescope, we identified 20 sources exhibiting significant flux density variations on 4-d time-scales. The sky distribution of the variable sources is strongly dependent on the line-of-sight Galactic H α intensities from the Wisconsin H α Mapper Survey, demonstrating the contribution of interstellar scintillation (ISS) to their interday variability. 21 per cent of sources observed through sightlines with H α intensities larger than 10 rayleighs exhibit significant ISS persistent over the ∼10 yr period. The fraction of scintillators is potentially larger when considering less significant variables missed by our selection criteria, due to ISS intermittency. This study demonstrates that ISS is still important at 15 GHz, particularly through strongly scattered sightlines of the Galaxy. Of the 20 most significant variables, 11 are observed through the Orion–Eridanus superbubble, photoionized by hot stars of the Orion OB1 association. The high-energy neutrino source TXS 0506+056 is observed through this region, so ISS must be considered in any interpretation of its short-term radio variability. J0616−1041 appears to exhibit large ∼20 per cent interday flux density variations, comparable in magnitude to that of the very rare class of extreme, intrahour scintillators that includes PKS0405−385, J1819+3845, and PKS1257−326; this needs to be confirmed by higher cadence follow-up observations.

Astronomical data fusion: recent progress and future prospects — a survey

Over the past year, the discovery of the first electromagnetic counterparts to sources of gravitational waves and high-energy neutrinos has brought us to the new era of ”multi-messenger” astrophysics (MMA). These new events provide deep insights into astrophysics, meanwhile, lead to the development of astronomical data fusion techniques. Each messenger carries information from different observation process and fusing all messengers can therefore provide the best understanding of the celestial objects’ attributes and expose various astrophysical phenomena. Over the decades, for the full exploitation of multi-band astronomical data, advanced unified platforms and data fusion techniques have been developed and become a research topic of interest for the astronomical community. In this paper, we present a systematic review of the popular and state-of-the-art fusion methods and platforms in different formats of astronomical data, aiming to give a comprehensive introduction to the current progress in this field; at the same time, we put forward insightful prospects for future study of multi-messenger data fusion, hoping to provide new thoughts for researchers in MMA era.

Baikal-GVD - the Next Generation Neutrino Telescope in Lake Baikal

The Baikal collaboration is building the next generation Gigaton-scale deep underwater neutrino telescope in Lake Baikal. Its goal is to discover and observe high-energy (E > 100 GeV) neutrino sources in the Universe. Since April 2018 the telescope is operating in a configuration of three subarrays of optical modules (OMs) with 864 OMs on 24 vertical strings in total. We present the status of the experiment and first results obtained from data taken 2015 - 2017.

Cosmic ray transport and radiative processes in nuclei of starburst galaxies

AbstractThe high rate of star formation and supernova explosions of starburst galaxies make them interesting sources of high-energy radiation. Depending on the level of turbulence present in their interstellar medium, the bulk of cosmic rays produced inside starburst galaxies may lose most of their energy before escaping, thereby making these sources behave as calorimeters, at least up to some maximum energy. Contrary to previous studies, here we investigate in detail the conditions under which cosmic ray confinement may be effective for electrons and nuclei and we study the implications of cosmic ray confinement in terms of multifrequency emission from starburst nuclei and production of high-energy neutrinos. The general predictions are then specialized to three cases of active starbursts, namely, M82, NGC 253, and Arp220. Both primary and secondary electrons, as well as electron–positron pairs produced by gamma-ray absorption inside starburst galaxies are taken into account. Electrons and positrons produced as secondary products of hadronic interactions are found to be responsible for most of the emission of leptonic origin. In particular, synchrotron emission of very high energy secondary electrons produces an extended emission of hard X-rays that represents a very interesting signature of hadronic process in starburst galaxies, potentially accessible to current and future observations in the X-ray band. A careful understanding of both the production and absorption of gamma-rays in starburst galaxies is instrumental to the assessment of the role of these astrophysical sources as sources of high-energy astrophysical neutrinos.

High-energy Emission from Interacting Supernovae: New Constraints on Cosmic-Ray Acceleration in Dense Circumstellar Environments

Abstract Supernovae (SNe) with strong interactions with circumstellar material (CSM) are promising candidate sources of high-energy neutrinos and gamma-rays and have been suggested as an important contributor to Galactic cosmic rays (CRs) beyond 1015 eV. Taking into account the shock dissipation by a fast velocity component of SN ejecta, we present comprehensive calculations of the nonthermal emission from SNe powered by shock interactions with a dense wind or CSM. Remarkably, we consider electromagnetic cascades in the radiation zone and subsequent attenuation in the pre-shock CSM. A new time-dependent phenomenological prescription provided by this work enables us to calculate gamma-ray, hard X-ray, radio, and neutrino signals, which originate from CRs accelerated by the diffusive shock acceleration (DSA) mechanism. We apply our results to Type IIn SN 2010jl and Type Ib/IIn SN 2014C, for which the model parameters can be determined from the multiwavelength data. For SN 2010jl, the more promising case, by using the the latest Fermi Large Area Telescope Pass 8 data release, we derive new constraints on the CR energy fraction, ϵ p ≲ 0.05–0.1. We also find that the late-time radio data of these interacting SNe are consistent with our model. Further multimessenger and multiwavelength observations of nearby interacting SNe should give us new insights into the DSA in dense environments, as well as pre-SN mass-loss mechanisms.

The role of magnetic fields in the formation and propagation of hadronic microquasars jets

In the present work, we examine the role of the magnetic field (MF), which causes a rather pronounced confinement of the jets at microquasars. Due to radial Lorentz forces acting on the jet’s matter towards the jet’s axis, the outgoing flux is collimated along the same axis and vertically to the compact object. Alternatively, a rotating central object may drag the surrounding MF into collimation around the produced jet. In such objects, jet emerges from each side of the accretion disc.These jets operate as cosmic engines, capable of accelerating particles on very high energies (~10^2 TeV) and consist sources of high energy neutrinos and gamma rays. We also examine the role of the MF, which causes to a rather pronounced jet confinement. Our aim is to investigate and model its role on various physical observables of the jet, by simulating the jet’s flow and derive 2D and 3D visualizations and furthermore examine its effect on the neutrino emissivity.

Active galactic nuclei and the origin of IceCube's diffuse neutrino flux

The excess of neutrino candidate events detected by IceCube from the direction of TXS 0506+056 has generated a great deal of interest in blazars as sources of high-energy neutrinos. In this study, we analyze the publicly available portion of the IceCube dataset, performing searches for neutrino point sources in spatial coincidence with the blazars and other active galactic nuclei contained in the Fermi 3LAC and the Roma BZCAT catalogs, as well as in spatial and temporal coincidence with flaring sources identified in the Fermi Collaboration's All-Sky Variability Analysis (FAVA). We find no evidence that blazars generate a significant flux of high-energy neutrinos, and conclude that no more than 5–15% of the diffuse flux measured by IceCube can originate from this class of objects. While we cannot rule out the possibility that TXS 0506+056 has at times generated significant neutrino emission, we find that such behavior cannot be common among blazars, requiring TXS 0506+056 to be a rather extreme outlier and not representative of the overall blazar population. The bulk of the diffuse high-energy neutrino flux must instead be generated by a significantly larger population of less-luminous sources, such as non-blazar active galactic nuclei.

IceCube flavor ratios with identified astrophysical sources: towards improving new physics testability

Motivated by the discovery of the first high-energy astrophysical neutrino source, the blazar TXS 0506+056, we revisit the IceCube flavor ratio analysis. Assuming large statistics from identified blazars, collected in the forthcoming years by the IceCube detector and its successor IceCube-Gen2, we demonstrate that the constraints on several new physics scenarios in which the baseline dependent terms in neutrino oscillation probabilities are not averaged, can be improved. As a representative case, we consider pseudo-Dirac neutrinos while neutrino decay is also discussed.

Search for Multimessenger Sources of Gravitational Waves and High-energy Neutrinos with Advanced LIGO during Its First Observing Run, ANTARES, and IceCube

Abstract Astrophysical sources of gravitational waves, such as binary neutron star and black hole mergers or core-collapse supernovae, can drive relativistic outflows, giving rise to non-thermal high-energy emission. High-energy neutrinos are signatures of such outflows. The detection of gravitational waves and high-energy neutrinos from common sources could help establish the connection between the dynamics of the progenitor and the properties of the outflow. We searched for associated emission of gravitational waves and high-energy neutrinos from astrophysical transients with minimal assumptions using data from Advanced LIGO from its first observing run O1, and data from the Antares and IceCube neutrino observatories from the same time period. We focused on candidate events whose astrophysical origins could not be determined from a single messenger. We found no significant coincident candidate, which we used to constrain the rate density of astrophysical sources dependent on their gravitational-wave and neutrino emission processes.

Gravitational waves and neutrinos joint searches in the Mediterranean Sea

The recent detection of gravitational waves (GW) have launched effectively the field of multimessenger astronomy. High energy neutrinos (HEN) have been detected as a diffuse flux and show indications of transient point sources. They can bring crucial informations on cataclysmic cosmic events by identifying hadrons acceleration to high energies and pointing back to the source at the degree level which is an asset for follow-up of GW events with photonic telescopes. We will review the current searches for joint sources of gravitational waves and high energy neutrinos performed with the ANTARES telescope and the perspectives offered by its successor KM3NeT.

Machine Learning in KM3NeT

The KM3NeT Collaboration is building a network of underwater Cherenkov telescopes at two sites in the Mediterranean Sea, with the main goals of investigating astrophysical sources of high-energy neutrinos (ARCA) and of determining the neutrino mass hierarchy (ORCA). Various Machine Learning techniques, such as Random Forests, BDTs, Shallow and Deep Networks are being used for diverse tasks, such as event-type and particle identification, energy/direction estimation, source identification, signal/background discrimination and data analysis, with sound results as well as promising research paths. The main focus of this work is the application of Convolutional Neural Network models to the tasks of neutrino interaction classification, as well as the estimation of energy and direction of the propagating particles. The performances are also compared to those of the standard reconstruction algorithms used in the Collaboration.

Searching for Optical Counterparts to High-Energy Neutrino Sources with the Zwicky Transient Facility

The IceCube neutrino observatory has discovered a flux of extragalactic neutrinos. However, the origin of these neutrinos is still unknown. Among the possible candidates are Gamma-Ray Bursts (GRBs), Core-Collapse Supernovae (SNe), Active Galactic Nuclei (AGN) and Tidal Disruption Events (TDEs) - all are accompanied by a characteristic optical counterpart. The goal of this study is thus to identify the neutrino sources by detecting their optical counterparts with the Zwicky Transient Facility (ZTF). ZTF features a high cadence northern-sky survey enabling realtime correlation of optical transients with high-energy neutrino candidates. In this talk I will highlight the multimessenger potential of ZTF for an online neutrino correlation study with Ice- Cube.

Recent Results from the Antares Neutrino Telescope

Antares, the first undersea neutrino telescope, has been continuously operating since 2007 in the Mediterranean Sea. The transparency of the water allows for a very good angular resolution in the reconstruction of neutrino events of all flavors. This results in an unmatched sensitivity for neutrino source searches, in a large fraction of the Southern Sky, at TeV energies. As a consequence, Antares provides valuable constraints on the origin of the cosmic neutrino flux discovered by the IceCube Collaboration. Based on an all-flavor dataset spanning nine years of operation of the detector, the latest results of Antares searches for neutrino point sources, and for diffuse neutrino emission from the entire sky as well as from several interesting regions such as the Galactic Plane, are presented. Several results have been obtained through a joint analysis with the IceCube Collaboration. Concerning the multi-messenger program, the focus is made on the follow-up searches of IceCube alerts, in particular the one related to the TXS 0506+056 blazar, thought to be the first extragalactic high-energy neutrino source identified so far.

Constraining high-energy neutrinos from choked-jet supernovae with IceCube high-energy starting events

Different types of core-collapse supernovae (SNe) have been considered as candidate sources of high-energy cosmic neutrinos. Stripped-envelope SNe, including energetic events like hypernovae and super-luminous SNe, are of particular interest. They may harbor relativistic jets, which are capable of explaining the diversity among gamma-ray bursts (GRBs), low-luminosity GRBs, ultra-long GRBs, and broadline Type Ib/c SNe. Using the six-year IceCube data on high-energy starting events (HESEs), we perform an unbinned maximum likelihood analysis to search for spatial and temporal coincidences with 222 samples of SNe Ib/c. We find that the present data are consistent with the background only hypothesis, by which we place new upper constraints on the isotropic-equivalent energy of cosmic rays, ℰcr≲1052 erg, in the limit that all SNe are accompanied by on-axis jets. Our results demonstrate that not only upgoing muon neutrinos but also HESE data enable us to constrain the potential contribution of these SNe to the diffuse neutrino flux observed in IceCube. We also discuss implications for the next-generation neutrino detectors such as IceCube-Gen2 and KM3Net.

A Multimessenger Picture of the Flaring Blazar TXS 0506+056: Implications for High-energy Neutrino Emission and Cosmic-Ray Acceleration

Abstract Detection of the IceCube-170922A neutrino coincident with the flaring blazar TXS 0506+056, the first and only ∼3σ high-energy neutrino source association to date, offers a potential breakthrough in our understanding of high-energy cosmic particles and blazar physics. We present a comprehensive analysis of TXS 0506+056 during its flaring state, using newly collected Swift, NuSTAR, and X-shooter data with Fermi observations and numerical models to constrain the blazar’s particle acceleration processes and multimessenger (electromagnetic (EM) and high-energy neutrino) emissions. Accounting properly for EM cascades in the emission region, we find a physically consistent picture only within a hybrid leptonic scenario, with γ-rays produced by external inverse-Compton processes and high-energy neutrinos via a radiatively subdominant hadronic component. We derive robust constraints on the blazar’s neutrino and cosmic-ray emissions and demonstrate that, because of cascade effects, the 0.1–100 keV emissions of TXS 0506+056 serve as a better probe of its hadronic acceleration and high-energy neutrino production processes than its GeV–TeV emissions. If the IceCube neutrino association holds, physical conditions in the TXS 0506+056 jet must be close to optimal for high-energy neutrino production, and are not favorable for ultrahigh-energy cosmic-ray acceleration. Alternatively, the challenges we identify in generating a significant rate of IceCube neutrino detections from TXS 0506+056 may disfavor single-zone models, in which γ-rays and high-energy neutrinos are produced in a single emission region. In concert with continued operations of the high-energy neutrino observatories, we advocate regular X-ray monitoring of TXS 0506+056 and other blazars in order to test single-zone blazar emission models, clarify the nature and extent of their hadronic acceleration processes, and carry out the most sensitive possible search for additional multimessenger sources.

Multimessenger observations of a flaring blazar coincident with high-energy neutrino IceCube-170922A.

Previous detections of individual astrophysical sources of neutrinos are limited to the Sun and the supernova 1987A, whereas the origins of the diffuse flux of high-energy cosmic neutrinos remain unidentified. On 22 September 2017, we detected a high-energy neutrino, IceCube-170922A, with an energy of ~290 tera-electron volts. Its arrival direction was consistent with the location of a known γ-ray blazar, TXS 0506+056, observed to be in a flaring state. An extensive multiwavelength campaign followed, ranging from radio frequencies to γ-rays. These observations characterize the variability and energetics of the blazar and include the detection of TXS 0506+056 in very-high-energy γ-rays. This observation of a neutrino in spatial coincidence with a γ-ray-emitting blazar during an active phase suggests that blazars may be a source of high-energy neutrinos.

First results of the KM3NeT/ARCA detector

The KM3NeT collaboration started to build a multi-km3neutrino telescope in the Mediterranean Sea. The telescope is composed of two parts: the ARCA detector, optimised for searches for high energy neutrino sources in the Universe, and ORCA, for the determination of the mass hierarchy of neutrinos. ARCA is under construction at the Capo Passero site, Italy, 80 km offshore at a depth of 3500 m while ORCA is located in the Toulon area, France, 40 km offshore at a depth of 2500 m. The basic detection element of the KM3NeT detector is the Digital Optical Module. The module is a pressure resistant glass sphere, containing 31 photo-multiplier tubes. Eighteen modules are arranged in the detection unit, a vertical structure anchored on the sea floor. The detection units are deployed on the sea bed to form a three-dimensional array of optical modules to detect Cherenkov light produced by neutrino-induced muons. In these proceedings preliminary results obtained with the first two detection units of ARCA are presented. The capability to select and reconstruct atmospheric muons is discussed. The dependence of the muon flux with the sea depth is derived, showing that the detector is well calibrated and the systematics are kept under control.

Neutrino and γ-ray Emission from the Core of NGC1275 by Magnetic Reconnection: GRMHD Simulations and Radiative Transfer/Particle Calculations

AbstractVery high energy (VHE) emission has been detected from the radio galaxy NGC1275, establishing it as a potential cosmic-ray (CR) accelerator and a high energy neutrino source. We here study neutrino and γ-ray emission from the core of NGC1275 simulating the interactions of CRs assumed to be accelerated by magnetic reconnection, with the accreting plasma environment. To do this, we combine (i) numerical general relativistic (GR) magneto-hydrodynamics (MHD), (ii) Monte Carlo GR leptonic radiative transfer and, (iii) Monte Carlo interaction of CRs. A leptonic emission model that reproduces the SED in the [103-1010.5] eV energy range is used as the background target for photo-pion interactions+electromagnetic cascading. CRs injected with the power-law index κ=1.3 produce an emission profile that matches the VHE tail of NGC1275. The associated neutrino flux, below the IceCube limits, peaks at ∼PeV energies. However, coming from a single source, this neutrino flux may be an over-estimation.

On the High-Energy Neutrino Emission from Active Galactic Nuclei

We review observational aspects of the active galactic nuclei and their jets in connection with the detection of high-energy neutrinos by the Antarctic IceCube Neutrino Observatory. We propose that a reoriented jet generated by the spin-flipping supermassive black hole in a binary merger is likely the source of such high-energy neutrinos. Hence they encode important information on the afterlife of coalescing supermassive black hole binaries. As the gravitational radiation emanating from them will be monitored by the future LISA space mission, high-energy neutrino detections could be considered a contributor to multi-messenger astronomy.