3,620 research outputs found
Study of 23 day periodicity of Blazar Mkn501 in 1997
We confirm a 23 day periodicity during a large flare in 1997 for X-ray data
of X-ray satellite RXTE all sky monitor(ASM), 2 TeV gamma ray data from Utah
Seven Telescope and HEGRA, with a Fourier analysis. We found the three results
to be the same with a newly estimated error. We confirm the presence of a
frequency dependent power (1/f noise) in a frequency-power diagram. Further, we
calculated a chance probability of the occurrence of the 23 day periodicity by
considering the 1/f noise and obtained a chance probability 4.88*10^-3 for the
HEGRA data: this is more significant than previous result by an order. We also
obtained an identical peridoicity with another kind of timing analysis-epoch
folding method for the ASM data and HEGRA data. We strongly suggest an
existence of the periodicity. We divided the HEGRA data into two data sets,
analyzed them with a Fourier method, and found an unstableness of the
periodicity with a 3.4 sigma significance. We also analyzed an energy spectra
of the X-ray data of a RXTE proportional counter array and we found that a
combination of three parameters-a magnetic field, a Lorentz factor, and a
beaming factor-is related to the periodicity.Comment: 25 page, 27 figures, acceptted by astroparticle physic
Unmasking the tail of the cosmic ray spectrum
A re-examination of the energy cosmic ray spectrum above eV is
presented. The overall data-base provides evidence, albeit still statistically
limited, that non-nucleon primaries could be present at the end of the
spectrum. In particular, the possible appearance of superheavy nuclei (seldom
discussed in the literature) is analysed in detail.Comment: To appear in Phys. Lett. B with the title ``Possible explanation for
the tail of the cosmic ray spectrum'
A new method to search for a cosmic ray dipole anisotropy
We propose a new method to determine the dipole (and quadrupole) component of
a distribution of cosmic ray arrival directions, which can be applied when
there is partial sky coverage and/or inhomogeneous exposure. In its simplest
version it requires that the exposure only depends on the declination, but it
can be easily extended to the case of a small amplitude modulation in right
ascension. The method essentially combines a minimization of the
distribution in declination to obtain the multipolar components along the
North-South axis and a harmonic Rayleigh analysis for the components involving
the right ascension direction
Implications of a Possible Clustering of Highest Energy Cosmic Rays
Very recently, a possible clustering of a subset of observed ultrahigh energy
cosmic rays above about 40EeV (4x10^19eV) in pairs near the supergalactic plane
was reported. We show that a confirmation of this effect would provide
information on origin and nature of these events and, in case of charged
primaries, imply interesting constraints on the extragalactic magnetic field.
The observed time correlation would most likely rule out an association of
these events with cosmological gamma ray bursts. If no prominent astrophysical
source candidates such as powerful radiogalaxies can be found, the existence of
a mechanism involving new fundamental physics would be favored.Comment: 10 latex pages, 1 postscript figure, uses aaspp4.sty, submitted to
Astrophysical Journal Letter
Development of Atmospheric Monitoring System at Akeno Observatory for the Telescope Array Project
We have developed an atmospheric monitoring system for the Telescope Array
experiment at Akeno Observatory. It consists of a Nd:YAG laser with an
alt-azimuth shooting system and a small light receiver. This system is
installed inside an air conditioned weather-proof dome. All parts, including
the dome, laser, shooter, receiver, and optical devices are fully controlled by
a personal computer utilizing the Linux operating system.
It is now operated as a back-scattering LIDAR System. For the Telescope Array
experiment, to estimate energy reliably and to obtain the correct shower
development profile, the light transmittance in the atmosphere needs to be
calibrated with high accuracy.
Based on observational results using this monitoring system, we consider this
LIDAR to be a very powerful technique for Telescope Array experiments. The
details of this system and its atmospheric monitoring technique will be
discussed.Comment: 24 pages, 13 figures(plus 3 gif files), Published in NIM-A Vol.488,
August 200
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