16 research outputs found
TeV neutrinos from microquasars in compact massive binaries
We consider a compact binary system in which a Wolf-Rayet star supplies
matter onto a stellar mass black hole or a neutron star. This matter forms an
accretion disk which ejects a jet as observed in Galactic microquasars. A part
of the jet kinetic energy, typically 10%, can be transfered to relativistic
nuclei. These nuclei lose nucleons as a result of photo-disintegration process
in collisions with thermal photons from the accretion disk and the massive
star. Due to the head on photon-nucleus collisions most of neutrons released
from nuclei move towards the surface of the accretion disk and/or the massive
star producing neutrinos in collisions with the matter. We calculate the
spectra of muon neutrinos and expected neutrino event rates in a 1 km^2
neutrino detector of the IceCube type from a microquasar inside our Galaxy
applying, as an example, the parameters of the Cyg X-3 binary system, provided
that nuclei are accelerated to the Lorentz factors above 10^6 with the power
law spectrum with an index close to 2.Comment: 13 pages, 2 figures, ApJ, accepte
TeV neutrinos from accreting X-ray pulsars
Pulsars inside binary systems can accrete matter that arrives up to the
pulsar surface provided that its period is long enough. During the accretion
process, matter has to be accelerated to the rotational velocity of the pulsar
magnetosphere at the distance where the balance between the pressure of matter
and the magnetic field is achieved. At this distance, a very turbulent and
magnetized region is formed in which hadrons can be accelerated to relativistic
energies. These hadrons can interact with the very strong radiation field
coming from the hot polar cap on the neutron star surface created by the
in-falling matter. We calculate the neutrino event rates produced in an km
detector that can be expected from accreting millisecond and classical X-ray
pulsars at a typical distance within our own Galaxy.Comment: 5 pages, accepted to Physical Review
The impact of clouds on image parameters in IACT at very high energies
The effective observation time with the Cherenkov telescopes arrays is limited to clear sky conditions due to considerable absorption of Cherenkov light by the possible presence of clouds. However below the cloud altitude the primary particles with high energies can still produce enough Cherenkov photons to allow the detection by the large telescopes. In this paper, using the standard CORSIKA code, we investigate the changes of image parameters due to the absorption of Cherenkov radiation by the cloud (for γ-ray and proton showers with various energies – from 2 TeV to 100 TeV and from 10 TeV to 200 TeV, respectively). We consider the clouds with different transmissions located at various altitudes above the ground level (between 8 km and 3 km). We show that, for both simulated primary particles at fixed energy, the WIDTH and the DIST distributions are shifted towards larger values in the presence of clouds in comparison to the clear sky simulations. This shift decreases with the cloud altitude. The LENGTH distributions are shifted towards smaller values for images of primary γ-rays, while for primary protons this shift is not observed. We conclude that the large Cherenkov telescopes with large camera FOV could be used for observation of γ-ray showers with high energies in the presence of clouds
The impact of clouds on image parameters in IACT at very high energies
The effective observation time with the Cherenkov telescopes arrays is limited to clear sky conditions due to considerable absorption of Cherenkov light by the possible presence of clouds. However below the cloud altitude the primary particles with high energies can still produce enough Cherenkov photons to allow the detection by the large telescopes. In this paper, using the standard CORSIKA code, we investigate the changes of image parameters due to the absorption of Cherenkov radiation by the cloud (for γ-ray and proton showers with various energies – from 2 TeV to 100 TeV and from 10 TeV to 200 TeV, respectively). We consider the clouds with different transmissions located at various altitudes above the ground level (between 8 km and 3 km). We show that, for both simulated primary particles at fixed energy, the WIDTH and the DIST distributions are shifted towards larger values in the presence of clouds in comparison to the clear sky simulations. This shift decreases with the cloud altitude. The LENGTH distributions are shifted towards smaller values for images of primary γ-rays, while for primary protons this shift is not observed. We conclude that the large Cherenkov telescopes with large camera FOV could be used for observation of γ-ray showers with high energies in the presence of clouds
Gamma-Ray Variability Induced by Microlensing on Intermediate Size Structures in Lensed Blazars
Changes of the magnification ratio of images in a lensed blazar, caused by microlensing on individual stars, have been proposed as a probe of the size and velocity of the emission region in the lensed source. We study whether similar changes in the magnification ratio can be caused by the microlensing on the intermediate size structures in the lensing galaxy, namely stellar clusters and giant molecular clouds. Our numerical simulations show that changes in the magnification ratio of two images with similar time scales (as seen in QSO B0218+357) can be obtained for relativistically-moving emission regions with sizes up to 0.01 pc in the case of microlensing on clumps in giant molecular clouds