Invariance Violation Extends the Cosmic Ray Horizon ?

We postulate in the present paper that the energy-momentum relation is modified for very high energy particles to violate Lorentz invariance and the speed of photon is changed from the light velocity c. The violation effect is amplified, in a sensitive way to detection, through the modified kinematical constraints on the conservation of energy and momentum, in the absorption process of gamma-rays colliding against photons of longer wavelengths and converting into an electron-positron pair. For gamma-rays of energies higher than 10 TeV, the minimum energy of the soft photons for the reaction and then the absorption mean free path of gamma-rays are altered by orders of magnitude from the ones conventionally estimated. Consideration is similarly applied to high energy cosmic ray protons. The consequences may require the standard assumptions on the maximum distance that very high energy radiation can travel from to be revised.Comment: 14 pages, 1 figure, to be published in Ap J Letter

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

Detection of Gamma-rays around 1TeV from RX J0852.0-4622 by CANGAROO-II

We have detected gamma-ray emission at the 6sigma level at energies greater than 500GeV from the supernova remnant RX J0852.0-4622 (G266.2-1.2) using the CANGAROO-II Imaging Atmospheric Cherenkov Telescope (IACT). The flux was 0.12 times of that of Crab at 1TeV. The signal centroid is consistent with the peak of the X-ray emission in the north-west rim of the remnant.Comment: 12pages, 4figures, to be published in ApJ

A Search for TeV Gamma-ray Emission from the PSR B1259-63/SS2883 Binary System with the CANGAROO-II 10-m Telescope

Observations of the PSR B1259-63/SS2883 binary system using the CANGAROO-II Cherenkov telescope are reported. This nearby binary consists of a 48msec radio pulsar in a highly eccentric orbit around a Be star, and offers a unique laboratory to investigate the interactions between the outflows of the pulsar and Be star at various distances. It has been pointed out that the relativistic pulsar wind and the dense mass outflow of the Be star may result in the emission of gamma rays up to TeV energies. We have observed the binary in 2000 and 2001, 47 and 157 days after the October 2000 periastron. Upper limits at the 0.13--0.54 Crab level are obtained. A new model calculation for high-energy gamma-ray emission from the Be star outflow is introduced and the estimated gamma-ray flux considering Bremsstrahlung, inverse Compton scattering, and the decay of neutral pions produced in proton-proton interactions, is found to be comparable to the upper limits of these observations. Comparing our results with these model calculations, the mass-outflow parameters of the Be star are constrained.Comment: 29 pages, 10 figures, accepted by Ap

Development of an atmospheric Cherenkov imaging camera for the CANGAROO-III experiment

A Cherenkov imaging camera for the CANGAROO-III experiment has been developed for observations of gamma-ray induced air-showers at energies from 10$^{11}$ to 10$^{14}$ eV. The camera consists of 427 pixels, arranged in a hexagonal shape at 0.17$^\circ$ intervals, each of which is a 3/4-inch diameter photomultiplier module with a Winston-cone--shaped light guide. The camera was designed to have a large dynamic range of signal linearity, a wider field of view, and an improvement in photon collection efficiency compared with the CANGAROO-II camera. The camera, and a number of the calibration experiments made to test its performance, are described in detail in this paper.Comment: 25 pages, 29 figures, elsart.cls, to appear in NIM-

The New Cangaroo Telescope And The Prospect Of Vhe Gamma Ray Observation At Woomera

A summary of the observations of very high energy gamma rays at Woomera, South Australia is presented to discuss the current status and prospect of gamma ray astronomy. Emission of gamma rays are due to copious production of electron and positron, in contrast to apparently "silent protons". Electrons radiate into multi-wavelengths from radio to gamma rays, linking the gamma ray data to the other bands. A new telescope for VHE gamma ray astronomy is to commence operation at Woomera in 1999. The telescope of light-collecting area of 7m diameter has a threshold energy of detecting gamma rays near 100 GeV. Also discussed is the next step we plan to take, in which a system of four telescopes of 10m size will be constructed. With the telescopes in the next generation, more number of Galactic sources will become detectable as well as extragalactic ones at larger distances. We expect that there will appear new types of gamma ray sources, shedding a new light on the long-standing puzzle of the ..

CANGAROO PROJECT AND VERY HIGH ENERGY GAMMA RAY ASTRONOMY

The CANGAROO Project and the results are discussed as well as about the present status of TeV-ray astronomy. The observation through the shortest wavelength of electromagnetic radiation is so far considerably in uenced by the results from other bands. A fair, unbiased outline of the non-thermal, high energy Universe seen at TeV-rays remains to be seeked for.

All Sky Monitor for Energetic-rays

Abstract. Survey over all the sky by energetic-rays would uncover new, mysterious aspects of the Universe that are otherwise hard to see � violently time variable, hidden sources, extended emission, and exotic mechanism for high energy radiations. Imaging air Cerenkov telescope of a large solid angle is available by using Fresnel lens refractor. Such telescope accepts air scintillation lights with detection area 100 km 2, and provides deeper survey at higher energies, pushing forward the high energy frontier of-ray astronomy