Long gamma-ray bursts (GRBs) are at present well confirmed sites of acceleration of particles to relativistic energies due to observations of gamma-ray emission in the GeV-TeV energy range. We ...consider a scenario in which the mechanism accelerating electrons is also responsible for acceleration of hadrons in the GRB jets to multi-PeV energies. Since progenitors of long GRBs are massive stars still immersed in dense stellar clusters, these hadrons can efficiently interact with the matter after escaping from the jet. We calculate the spectra of neutrinos from the interaction of those hadrons with the matter of a huge cloud surrounding GRB. Those neutrinos form an afterglow on a time scale determined by their diffusion time scale in the cloud. Due to this long delay, their identification with any specific GRB is not possible. We estimate contribution of neutrinos from such afterglows to the extragalactic neutrino background recently reported by the IceCube Observatory.
ABSTRACT
We discuss a scenario in which TeV neutrinos are produced during explosions of novae. It is argued that hadrons are accelerated to very high energies in the inner part of a nova wind, as a ...result of reconnection of the strong magnetic field of a white dwarf. Hadrons are expected to interact efficiently with a dense matter of the wind, either already during the acceleration process or during their advection with the equatorial wind. We calculate the neutrino spectra and estimate the muon neutrino event rates in the IceCube telescope, in the case of a few novae. In general, those event rates are unlikely to be detected with the present neutrino detectors. However, for a favourable location of the observer, some neutrino events might be detected not only from the class of novae recently detected in the GeV γ-rays by the Fermi-LAT (Large Area Telescope), but also from novae not detected in γ-rays. The GeV γ-ray emission observed from novae cannot originate in terms of the model discussed here, since protons are accelerated within a few stellar radii of the white dwarf, i.e. in the region in which GeV γ-rays are expected to be severely absorbed in the interactions with the radiation field and the matter of the wind.
Long gamma-ray bursts (GRBs) are at present well confirmed sites of acceleration of particles to relativistic energies due to observations of gamma-ray emission in the GeV-TeV energy range. We ...consider a scenario in which the mechanism accelerating electrons is also responsible for acceleration of hadrons in the GRB jets to multi-PeV energies. Since progenitors of long GRBs are massive stars still immersed in dense stellar clusters, these hadrons can efficiently interact with the matter after escaping from the jet. We calculate the spectra of neutrinos from the interaction of those hadrons with the matter of a huge cloud surrounding GRB. Those neutrinos form an afterglow on a time scale determined by their diffusion time scale in the cloud. Due to this long delay, their identification with any specific GRB is not possible. We estimate contribution of neutrinos from such afterglows to the extragalactic neutrino background recently reported by the IceCube Observatory.
We discuss a scenario in which TeV neutrinos are produced during explosions of Novae. It is argued that hadrons are accelerated to very high energies in the inner part of a Nova wind, as a result of ...reconnection of the strong magnetic field of a White Dwarf. Hadrons are expected to interact efficiently with a dense matter of the wind, either already during the acceleration process or during their advection with the equatorial wind. We calculate the neutrino spectra, and estimate the muon neutrino event rates in the IceCube telescope, in the case of a few Novae. In general, those event rates are unlikely to be detected with the present neutrino detectors. However, for favourable location of the observer, some neutrino events might be detected not only from the class of Novae recently detected in the GeV \(\gamma\)-rays by the {\it Fermi}-LAT telescope but also from novae not detected in \(\gamma\)-rays. The GeV \(\gamma\)-ray emission observed from Novae cannot originate in terms of the model discussed here, since protons are accelerated within a few stellar radii of the White dwarf, i.e. in the region in which GeV \(\gamma\)-rays are expected to be severely absorbed in the interactions with the radiation field and the matter of the wind.
Cosmic rays are atomic nuclei arriving from outer space that reach the highest energies observed in nature. Clues to their origin come from studying the distribution of their arrival directions. ...Using 3 × 10
cosmic rays with energies above 8 × 10
electron volts, recorded with the Pierre Auger Observatory from a total exposure of 76,800 km
sr year, we determined the existence of anisotropy in arrival directions. The anisotropy, detected at more than a 5.2σ level of significance, can be described by a dipole with an amplitude of Formula: see text percent toward right ascension α
= 100 ± 10 degrees and declination δ
= Formula: see text degrees
That direction indicates an extragalactic origin for these ultrahigh-energy particles.
It is planned to operate the Pierre Auger Observatory until at least the end of 2024. An upgrade of the experiment has been proposed in order to provide additional measurements to allow one to ...elucidate the mass composition and the origin of the flux suppression at the highest energies, to search for a flux contribution of protons up to the highest energies and to reach a sensitivity to a contribution as small as 10% in the flux suppression region, to study extensive air showers and hadronic multi-particle production. With operation planned until 2024, event statistics will more than double compared with the existing Auger data set, with the critical added advantage that every event will now have mass information. Obtaining additional composition-sensitive information will not only help to better reconstruct the properties of the primary particles at the highest energies, but also improve the measurements in the energy range just above the ankle. Furthermore, measurements with the new detectors will help to reduce systematic uncertainties related to the modelling hadronic showers and to limitations in the reconstruction algorithms. A description of the principal proposed Auger upgrade will be presented. The Auger upgrade promises high-quality future data, and real scope for new physics.
The Pierre Auger Observatory, in Argentina, is the present flagship experiment studying ultrahigh-energy cosmic rays (UHECRs). Facing the challenge due to low cosmic-ray flux at the highest energies, ...the Observatory has been taking data for more than a decade, reaching an exposure of over 50 000 km2 sr yr. The combination of a large surface detector array and fluorescence telescopes provides a substantial improvement in energy calibration and extensive air shower measurements, resulting in data of unprecedented quality. Moreover, the installation of a denser subarray has allowed extending the sensitivity to lower energies. Altogether, this contributes to provide important information on key questions in the UHECR field in the energy range from 0.1 EeV up to 100 EeV. A review of main results from the Pierre Auger Observatory is presented with a particular focus on the energy spectrum measurements, the mass composition studies, the arrival directions analyses, the search for neutral cosmic messengers, and the investigation of high-energy hadronic interactions. Despite this large amount of valuable results, the understanding of the nature of UHECRs and of their origin remains an open science case that the Auger collaboration is planning to address with the AugerPrime project to upgrade the Observatory.
We present a combined fit of a simple astrophysical model of UHECR sources to both the energy spectrum and mass composition data measured by the Pierre Auger Observatory. The fit has been performed ...for energies above 5 EeV, i.e. the region of the all-particle spectrum above the so-called “ankle”’ feature. The astrophysical model we adopted consists of identical sources uniformly distributed in a comoving volume, where nuclei are accelerated with a rigidity-dependent mechanism. The fit results suggest sources characterized by relatively low maximum injection energies and hard spectral indices. The impact of various systematic uncertainties on the above result is discussed.
PDF
