183 research outputs found
The sidereal anisotropy of cosmic rays around 3 x 10 (15) eV observed at a middle north latitude
The sidereal time variation of cosmic rays (median primary energy : 3 10 to the 15th power eV) is investigated with air shower observations at Akeno, Japan (900 m a.s.l.) which started in September 1981. Air showers are detected by a coincidence requirement on several muon detectors. The result obtained for three years is suggestive of a big semi-diurnal variation (0.37 % in amplitude). On the other hand, the diurnal variation is rather small than the semi-diurnal one. The feature of the sidereal anisotropy supposed from the present result looks quite different from that below 10 to the 14th power eV
A simulation of high energy cosmic ray propagation 1
High energy cosmic ray propagation of the energy region 10 to the 14.5 power - 10 to the 18th power eV is simulated in the inter steller circumstances. In conclusion, the diffusion process by turbulent magnetic fields is classified into several regions by ratio of the gyro-radius and the scale of turbulence. When the ratio becomes larger then 10 to the minus 0.5 power, the analysis with the assumption of point scattering can be applied with the mean free path E sup 2. However, when the ratio is smaller than 10 to the minus 0.5 power, we need a more complicated analysis or simulation. Assuming the turbulence scale of magnetic fields of the Galaxy is 10-30pc and the mean magnetic field strength is 3 micro gauss, the energy of cosmic ray with that gyro-radius is about 10 to the 16.5 power eV
Gamma rays of energy or = 10(15) eV from Cyg X-3
The experimental data of extensive air showers observed at Akeno have been analyzed to detect the gamma ray signal from Cyg X-3. After muon poor air showers are selected, the correlation of data acquisition time with 4.8 hours X-ray period is studied, giving the data concentration near the phase 0.6, the time of X-ray maximum. The probability that uniform backgrounds create the distribution is 0.2%. The time averaged integral gamma ray flux is estimated as (1.1 + or - 0.4)x 10 to the -14th power cm(-2) sec(-1) for Eo 10 to the 15th power eV and (8.8 + or - 5.0)x 10 to the 14th power cm(-2) sec(-1) for Eo 6 x 10 to the 14th power eV
EAS development curve at energy of 10(16) - 10(18) eV measured by optical Cerenkov light
The data of optical Cerenkov light from extensive air shower observed at the core distance more than 1 Km at Akeno are reexamined. Applying the new simulated results, the shower development curves for the individual events were constructed. For the showers of 10 to 17th power eV the average depth at the shower maximum is determined to be 660 + or - 40 gcm/2. The shower curve of average development is found to be well described by a Gaisser-Hillas shower development function with above shower maximum depth
Design Study of CANGAROO-III, Stereoscopic Imaging Atmospheric Cherenkov Telescopes for sub-TeV Gamma-ray
CANGAROO-III is an Imaging Atmospheric Cherenkov Telescope (IACT) array of
four 10 m telescopes for very high energy (sub-TeV) gamma-ray astronomy. A
design study of the CANGAROO-III telescope system was carried out using the
Monte Carlo technique in order to optimize the pixel size and the telescope
spacing. Studies were also made of observations at low elevation angles.Comment: 17pages, 13 figures, elsart, to appear in Astro. Part. Phy
Evidence for TeV gamma-ray emission from the shell type SNR RXJ1713.7-3946
We report the results of TeV gamma-ray observations of the shell type SNR
RXJ1713.7-3946 (G347.3-0.5). The discovery of strong non-thermal X-ray emission
from the northwest part of the remnant strongly suggests the existence of
electrons with energies up to 100 TeV in the remnant, making the SNR a good
candidate TeV gamma-ray source. We observed RXJ1713.7-3946 from May to August
1998 with the CANGAROO 3.8m atmospheric imaging Cerenkov telescope and obtained
evidence for TeV gamma-ray emission from the NW rim of the remnant with the
significance of 5.6 sigma. The observed TeV gamma-ray flux from the NW rim
region was estimated to be (5.3 +/- 0.9[statistical] +/- 1.6[systematic]) *
10^{-12} photons cm^{-2} s^{-1} at energies >= 1.8 +/- 0.9 TeV. The data
indicate that the emitting region is much broader than the point spread
function of our telescope. The extent of the emission is consistent with that
of hard X-rays observed by ASCA. This TeV gamma-ray emission can be attributed
to the Inverse Compton scattering of the Cosmic Microwave Background Radiation
by shock accelerated ultra-relativistic electrons. Under this assumption, a
rather low magnetic field of 11 micro gauss is deduced for the remnant from our
observation.Comment: Accepted for publication by Astronomy and Astrophysics (5 pages, 2
figures
Observations of the supernova remnant W28 at TeV energies
The atmospheric Cerenkov imaging technique has been used to search for
point-like and diffuse TeV gamma-ray emission from the southern supernova
remnant, W28, and surrounding region. The search, made with the CANGAROO 3.8m
telescope, encompasses a number of interesting features, the supernova remnant
itself, the EGRET source 3EG J1800-2338, the pulsar PSR J1801-23, strong 1720
MHz OH masers and molecular clouds on the north and east boundaries of the
remnant. An analysis tailored to extended and off-axis point sources was used,
and no evidence for TeV gamma-ray emission from any of the features described
above was found in data taken over the 1994 and 1995 seasons. Our upper limit
(E>1.5 TeV) for a diffuse source of radius 0.25deg encompassing both molecular
clouds was calculated at 6.64e-12 photons cm^-2 s^-1 (from 1994 data), and
interpreted within the framework of a model predicting TeV gamma-rays from
shocked-accelerated hadrons. Our upper limit suggests the need for some cutoff
in the parent spectrum of accelerated hadrons and/or slightly steeper parent
spectra than that used here (-2.1). As to the nature of 3EG J1800-2338, it
possibly does not result entirely from pi-zero decay, a conclusion also
consistent with its location in relation to W28.Comment: 11 pages, 5 figures. Accepted for publication in Astronomy and
Astrophysic
TeV observations of Centaurus A
We have searched for TeV gamma-rays from Centaurus A and surrounding region
out to +/- 1.0 deg using the CANGAROO 3.8m telescope. No evidence for TeV
gamma-ray emission was observed from the search region, which includes a number
of interesting features located away from the tracking centre of our data. The
3 sigma upper limit to the flux of gamma-rays above 1.5 TeV from an extended
source of radius 14' centred on Centaurus A is 1.28e-11 photons cm^-2 s^-1.Comment: 4 pages. Astroparticle Physics, accepted for publication. Some upper
limits overestimated by factor 2-4 in original version astro-ph/9901316. Now
correcte
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