Galactic sites of acceleration of cosmic rays to energies of order 10^15 eV and higher, dubbed PeVatrons, reveal themselves by recently discovered gamma radiation of energies above 100 TeV. However, ...joint gamma-ray and neutrino production, which marks unambiguously cosmic-ray interactions with ambient matter and radiation, was not observed until now. In November 2020, the IceCube neutrino observatory reported an ~150 TeV neutrino event from the direction of one of the most promising Galactic PeVatrons, the Cygnus Cocoon. Here we report on the observation of a 3.1-sigma (post trial) excess of atmospheric air showers from the same direction, observed by the Carpet-2 experiment and consistent with a few-months flare in photons above 300 TeV, in temporal coincidence with the neutrino event. The fluence of the gamma-ray flare is of the same order as that expected from the neutrino observation, assuming the standard mechanism of neutrino production. This is the first evidence for the joint production of high-energy neutrinos and gamma rays in a Galactic source.
Blazars may accelerate protons and/or nuclei as well as electrons. The
hadronic component of accelerated particles in blazars may constitute the bulk
of their high-energy budget; nevertheless, this ...component is elusive due to a
high value of the energy threshold of proton interaction with photon fields
inside the source. However, broad line regions (BLRs) of some flat spectrum
radio quasars (FSRQs) may contain a sufficient amount of matter to render
primary protons "visible" in $\gamma$ rays via hadronuclear interactions. In
the present paper we study the persistent $\gamma$-ray emission of the FSRQ PKS
1510-089 in its low state utilizing the publicly-available Fermi-LAT data, as
well as using the spectrum measured with the MAGIC imaging atmospheric
Cherenkov telescopes. We find an indication for an excess of $\gamma$ rays at
the energy range $\gtrsim 20$ GeV with respect to a simple baseline
log-parabolic intrinsic spectral model. This excess could be explained in a
scenario invoking hadronuclear interactions of primary protons on the BLR
material with the subsequent development of electromagnetic cascades in photon
fields. We present a Monte Carlo calculation of the spectrum of this cascade
component, taking as input the BLR photon field spectrum calculated with the
Cloudy code. To our knowledge, this is the first calculation of electromagnetic
cascade spectrum inside a blazar based on a direct calculation of the photon
field spectrum with a spectral synthesis code.
We review extragalactic $\gamma$-ray propagation models with emphasis on the
electromagnetic (EM) cascade process in the magnetized expanding Universe. We
consider cascades initiated by primary ...protons of ultra-high energy accelerated
by blazars and show that the observable spectrum is similar to the universal
spectrum of a purely EM cascade. We also present a detailed calculation of the
observable angular distribution for the case of EM cascades developing from
relatively nearby (<20 Mpc) sources. Finally, we calculate the point-like
source differential sensitivity of a novel liquid Argon time projection chamber
$\gamma$-ray telescope and show that its sensitivity is several times better
than the Fermi LAT sensitivity in the 100 MeV -- 100 GeV energy range.
Blazars may accelerate protons and/or nuclei as well as electrons. The hadronic component of accelerated particles in blazars may constitute the bulk of their high-energy budget; nevertheless, this ...component is elusive due to a high value of the energy threshold of proton interaction with photon fields inside the source. However, broad line regions (BLRs) of some flat spectrum radio quasars (FSRQs) may contain a sufficient amount of matter to render primary protons "visible" in \(\gamma\) rays via hadronuclear interactions. In the present paper we study the persistent \(\gamma\)-ray emission of the FSRQ PKS 1510-089 in its low state utilizing the publicly-available Fermi-LAT data, as well as using the spectrum measured with the MAGIC imaging atmospheric Cherenkov telescopes. We find an indication for an excess of \(\gamma\) rays at the energy range \(\gtrsim 20\) GeV with respect to a simple baseline log-parabolic intrinsic spectral model. This excess could be explained in a scenario invoking hadronuclear interactions of primary protons on the BLR material with the subsequent development of electromagnetic cascades in photon fields. We present a Monte Carlo calculation of the spectrum of this cascade component, taking as input the BLR photon field spectrum calculated with the Cloudy code. To our knowledge, this is the first calculation of electromagnetic cascade spectrum inside a blazar based on a direct calculation of the photon field spectrum with a spectral synthesis code.
We review extragalactic \(\gamma\)-ray propagation models with emphasis on the electromagnetic (EM) cascade process in the magnetized expanding Universe. We consider cascades initiated by primary ...protons of ultra-high energy accelerated by blazars and show that the observable spectrum is similar to the universal spectrum of a purely EM cascade. We also present a detailed calculation of the observable angular distribution for the case of EM cascades developing from relatively nearby (<20 Mpc) sources. Finally, we calculate the point-like source differential sensitivity of a novel liquid Argon time projection chamber \(\gamma\)-ray telescope and show that its sensitivity is several times better than the Fermi LAT sensitivity in the 100 MeV -- 100 GeV energy range.
