17 research outputs found
Estimate of the correlation signal between cosmic rays and BL Lacs in future data
The existing correlation between BL Lacertae objects (BL Lacs) and cosmic-ray
events observed by HiRes experiment provide sufficient information to formulate
quantitatively the hypothesis about the flux of neutral cosmic-ray particles
originated from BL Lacs. We determine the potential of future cosmic ray
experiments to test this hypothesis by predicting the number of coincidences
between arrival directions of cosmic rays and positions of BL Lacs on the
celestial sphere, which should be observed in the future datasets. We find that
the early Pierre Auger data will not have enough events to address this
question. On the contrary, the final Pierre Auger data and the early Telescope
Array data will be sufficient to fully test this hypothesis. If confirmed, it
would imply the existence of highest-energy neutral particles coming from
cosmological distances.Comment: 5 page
Testing the correlations between ultra-high-energy cosmic rays and BL Lac type objects with HiRes stereoscopic data
Previously suggested correlations of BL Lac type objects with the arrival
directions of the ultra-high-energy cosmic ray primaries are tested by making
use of the HiRes stereoscopic data. The results of the study support the
conclusion that BL Lacs may be the cosmic ray sources and suggest the presence
of a small (a few percent) fraction of neutral primaries at E>10^{19} eV.Comment: 4 pages, 3 figure
Identification of extragalactic sources of the highest energy EGRET photons by correlation analysis
We found significant correlations between the arrival directions of the
highest energy photons (E>10 GeV) observed by EGRET and positions of the BL Lac
type objects (BL Lacs). The observed correlations imply that not less than
three per cent of extragalactic photons at these energies originate from BL
Lacs. Some of the correlating BL Lacs have no counterparts in the EGRET source
catalog, i.e. do not coincide with strong emitters of gamma-rays at lower
energy. The study of correlating BL Lacs suggests that they may form a subset
which is statistically different from the total BL Lac catalog; we argue that
they are prominent candidates for TeV gamma-ray sources. Our results
demonstrate that the analysis of positional correlations is a powerful approach
indispensable in cases when low statistics limits or even prohibits the
standard case-by-case identification.Comment: 5 pages, MNRAS styl
Comment on "Correlation of the Highest-Energy Cosmic Rays with Nearby Extragalactic Objects"
We argue that the data published by the Pierre Auger Collaboration
(arXiv:0711.2256) disfavor at 99% confidence level their hypothesis that most
of the highest-energy cosmic rays are protons from nearby astrophysical
sources, either Active Galactic Nuclei or other objects with a similar spatial
distribution.Comment: 1000 words, 2 figures, scicite.st
Evidence for a connection between the gamma-ray and the highest energy cosmic-ray emissions by BL Lacertae objects
A set of potentially gamma-ray--loud BL Lac objects is selected by
intersecting the EGRET and BL Lac catalogs. Of the resulting 14 objects, eight
are found to correlate with arrival directions of ultra--high-energy cosmic
rays (UHECRs), with significance of the order of 5 sigma. This suggests that
gamma-ray emission can be used as a distinctive feature of those BL Lac objects
that are capable of producing UHECR.Comment: 11 pages, 1 figure, version published in APJ Letter
Photon-axion mixing and ultra-high-energy cosmic rays from BL Lac type objects -- Shining light through the Universe
Photons may convert into axion like particles and back in the magnetic field
of various astrophysical objects, including active galaxies, clusters of
galaxies, intergalactic space and the Milky Way. This is a potential
explanation for the candidate neutral ultra-high-energy (E>10^18 eV) particles
from distant BL Lac type objects which have been observed by the High
Resolution Fly's Eye experiment. Axions of the same mass and coupling may
explain also TeV photons detected from distant blazars.Comment: Revtex 10 pages, 6 figures. V.2: QED dispersion effects taken into
account; principal results unchanged. V3: misprints and sqrt(4*pi) factors in
Gauss to eV conversion corrected; conclusions unchange
Light Nuclei solving Auger puzzles. The Cen-A imprint
Ultra High Energy Cosmic Rays (UHECR) map at 60 EeV have been found recently
by AUGER group spreading anisotropy signatures in the sky. The result have been
interpreted as a manifestation of AGN sources ejecting protons at GZK edges
mostly from Super-galactic Plane. The result is surprising due to the absence
of much nearer Virgo cluster. Moreover, early GZK cut off in the spectra may be
better reconcile with light nuclei (than with protons). In addition a large
group (nearly a dozen) of events cluster suspiciously along Cen-A. Finally,
proton UHECR composition nature is in sharp disagreement with earlier AUGER
claim of a heavy nuclei dominance at 40 EeV. Therefore we interpret here the
signals as mostly UHECR light nuclei (He, Be, B, C, O), very possibly mostly
the lightest (He,Be) ones, ejected from nearest AGN Cen-A, UHECR smeared by
galactic magnetic fields, whose random vertical bending is overlapping with
super-galactic arm. The eventual AUGER misunderstanding took place because of
such a rare coincidence between the Super Galactic Plane (arm) and the smeared
(randomized) signals from Cen-A, bent orthogonally to the Galactic fields. Our
derivation verify the consistence of the random smearing angles for He, Be and
B, C, O, in reasonable agreement with the AUGER main group events around Cen-A.
Only few other rare events are spread elsewhere. The most collimated from Cen-A
are the lightest. The most spread the heavier. Consequently Cen-A is the best
candidate UHE neutrino tau observable by HEAT and AMIGA as enhanced AUGER array
at tens-hundred PeV energy. This model maybe soon tested by new events
clustering around the Cen-A and by composition imprint study.Comment: 4 pages, 5 figures
Ultra-High Energy Cosmic Ray production in the polar cap regions of black hole magnetospheres
We develop a model of ultra-high energy cosmic ray (UHECR) production via
acceleration in a rotation-induced electric field in vacuum gaps in the
magnetospheres of supermassive black holes (BH). We show that if the poloidal
magnetic field near the BH horizon is misaligned with the BH rotation axis,
charged particles, which initially spiral into the BH hole along the equatorial
plane, penetrate into the regions above the BH "polar caps" and are ejected
with high energies to infinity. We show that in such a model acceleration of
protons near a BH of typical mass 3e8 solar masses is possible only if the
magnetic field is almost aligned with the BH rotation axis. We find that the
power of anisotropic electromagnetic emission from an UHECR source near a
supermassive BH should be at least 10-100 times larger then UHECR power of the
source. This implies that if the number of UHECR sources within the 100 Mpc
sphere is ~100, the power of electromagnetic emission which accompanies proton
acceleration in each source, erg/s, is comparable to the typical
luminosities of active galactic nuclei (AGN) in the local Universe. We also
explore the acceleration of heavy nuclei, for which the constraints on the
electromagnetic luminosity and on the alignment of magnetic field in the gap
are relaxed
Search for Anisotropy of Ultra-High Energy Cosmic Rays with the Telescope Array Experiment
We study the anisotropy of Ultra-High Energy Cosmic Ray (UHECR) events
collected by the Telescope Array (TA) detector in the first 40 months of
operation. Following earlier studies, we examine event sets with energy
thresholds of 10 EeV, 40 EeV, and 57 EeV. We find that the distributions of the
events in right ascension and declination are compatible with an isotropic
distribution in all three sets. We then compare with previously reported
clustering of the UHECR events at small angular scales. No significant
clustering is found in the TA data. We then check the events with E>57 EeV for
correlations with nearby active galactic nuclei. No significant correlation is
found. Finally, we examine all three sets for correlations with the large-scale
structure of the Universe. We find that the two higher-energy sets are
compatible with both an isotropic distribution and the hypothesis that UHECR
sources follow the matter distribution of the Universe (the LSS hypothesis),
while the event set with E>10 EeV is compatible with isotropy and is not
compatible with the LSS hypothesis at 95% CL unless large deflection angles are
also assumed. We show that accounting for UHECR deflections in a realistic
model of the Galactic magnetic field can make this set compatible with the LSS
hypothesis.Comment: 10 pages, 9 figure
Upper limit on the flux of photons with energies above 10(19) eV using the Telescope Array surface detector
We search for ultra-high energy photons by analyzing geometrical properties of shower fronts of events registered by the Telescope Array surface detector. By making use of an event-by-event statistical method, we derive upper limits on the absolute flux of primary photons with energies above 1019, 1019.5, and 1020 eV based on the first three years of data takenopen4