11 research outputs found
CANGAROO-III Search for Gamma Rays from SN 1987A and the Surrounding Field
Optical images of SN 1987A show a triple ring structure. The inner (dust)
ring has recently increased in brightness and in the number of hot spots
suggesting that the supernova shock wave has collided with the dense
pre-existing circumstellar medium, a scenario supported by radio and X-ray
observations. Such a shocked environment is widely expected to result in the
acceleration of charged particles, and the accompanying emission of very high
energy gamma-rays. Here, we report the results of observations made in 2004 and
2006 which yield upper limits on the TeV gamma-ray flux, which are compared
with a theoretical prediction. In addition, we set upper limits on the TeV flux
for four high energy objects which are located within the same field of view of
the observation: the super-bubble 30 Dor C, the Crab-like pulsar PSR
B054069, the X-ray binary LMC X-1, and the supernova remnant N157B.Comment: 5 pages, 5 figures, Accepted for publication in Ap
Observation of Very High Energy Gamma Rays from HESS J1804-216 with CANGAROO-III Telescopes
We observed the unidentified TeV gamma-ray source HESS J1804-216 with the
CANGAROO-III atmospheric Cerenkov telescopes from May to July in 2006. We
detected very high energy gamma rays above 600 GeV at the 10 sigma level in an
effective exposure of 76 hr. We obtained a differential flux of
(5.0+/-1.5_{stat}+/-1.6_{sys})\times 10^{-12}(E/1 TeV)^{-\alpha}
cm^{-2}s^{-1}TeV^{-1} with a photon index \alpha of 2.69 +/- 0.30_{stat} +/-
0.34_{sys}, which is consistent with that of the H.E.S.S. observation in 2004.
We also confirm the extended morphology of the source. By combining our result
with multi-wavelength observations, we discuss the possible counterparts of
HESS J1804-216 and the radiation mechanism based on leptonic and hadronic
processes for a supernova remnant and a pulsar wind nebula.Comment: 11 pages, 12 figures, Accepted in Ap
Observation of an extended VHE gamma-ray emission from MSH 15-52 with CANGAROO-III
We have observed the supernova remnant MSH 15-52 (G320.4-1.2), which contains
the gamma-ray pulsar PSR B1509-58, using the CANGAROO-III imaging atmospheric
Cherenkov telescope array from April to June in 2006. We detected gamma rays
above 810 GeV at the 7 sigma level during a total effective exposure of 48.4
hours. We obtained a differential gamma-ray flux at 2.35 TeV of
(7.9+/-1.5_{stat}+/-1.7_{sys}) \times 10^{-13} cm^{-2}s^{-1}TeV^{-1} with a
photon index of 2.21+/-0.39_{stat}+/-0.40_{sys}, which is compatible with that
of the H.E.S.S. observation in 2004. The morphology shows extended emission
compared to our Point Spread Function. We consider the plausible origin of the
high energy emission based on a multi-wavelength spectral analysis and
energetics arguments.Comment: 9 pages, 9 figures, Accepted in Ap
CANGAROO-III search for TeV Gamma-rays from two clusters of galaxies
Because accretion and merger shocks in clusters of galaxies may accelerate
particles to high energies, clusters are candidate sites for the origin of
ultra-high-energy (UHE) cosmic-rays. A prediction was presented for gamma-ray
emission from a cluster of galaxies at a detectable level with the current
generation of imaging atmospheric Cherenkov telescopes. The gamma-ray emission
was produced via inverse Compton upscattering of cosmic microwave background
(CMB) photons by electron-positron pairs generated by collisions of UHE cosmic
rays in the cluster. We observed two clusters of galaxies, Abell 3667 and Abell
4038, searching for very-high-energy gamma-ray emission with the CANGAROO-III
atmospheric Cherenkov telescope system in 2006. The analysis showed no
significant excess around these clusters, yielding upper limits on the
gamma-ray emission. From a comparison of the upper limit for the north-west
radio relic region of Abell 3667 with a model prediction, we derive a lower
limit for the magnetic field of the region of ~0.1 micro G. This shows the
potential of gamma-ray observations in studies of the cluster environment. We
also discuss the flux upper limit from cluster center regions using a model of
gamma-ray emission from neutral pions produced in hadronic collisions of
cosmic-ray protons with the intra-cluster medium (ICM). The derived upper limit
of the cosmic-ray energy density within this framework is an order of magnitude
higher than that of our Galaxy.Comment: 7 pages, 6 figures, Accepted in Ap
CANGAROO-III Search for Gamma Rays from Centaurus A and the Centauri Region
We have observed the giant radio galaxy Centaurus A and the globular cluster
Centauri in the TeV energy region using the CANGAROO-III stereoscopic
system. The system has been in operation since 2004 withan array of four
Imaging Atmospheric Cherenkov Telescopes (IACT) with 100-m spacings. The
observations were carried out in March and April 2004. In total, approximately
10 hours data were obtained for each target.No statistically significant
gamma-ray signal has been found above 420 GeV over a wide angular region (a
one-degree radius from thepointing center) and we derive flux upper limits
using all of the field of view.Implications for the total energy of cosmic rays
and the density of the cold dark matter are considered.Comment: 7 pages, 6 figures, to appear in ApJ, emulateapj.cl
CANGAROO-III Observations of the supernova remnant RX J0852.04622
Sub-TeV gamma-ray emission from the North-West rim of the supernova remnant
RX J0852.04622 was detected with the CANGAROO-II telescope and recently
confirmed by the H.E.S.S. group. In addition, the H.E.S.S. data revealed a very
wide (up to two degrees in diameter), shell-like profile of the gamma-ray
emission. We have carried out CANGAROO-III observations in January and February
2005 with three telescopes and show here the results of three-fold coincidence
data. We confirm the H.E.S.S. results about the morphology and the energy
spectrum, and find the energy spectrum in the NW-rim is consistent with that of
the whole remnant.Comment: 9 pages, 13 figures, to appear in Ap
CANGAROO-III Search for Gamma Rays from Kepler's Supernova Remnant
Kepler's supernova, discovered in October 1604, produced a remnant that has
been well studied observationally in the radio, infrared, optical, and X-ray
bands, and theoretically. Some models have predicted a TeV gamma-ray flux that
is detectable with current Imaging Cherenkov Atmospheric Telescopes. We report
on observations carried out in 2005 April with the CANGAROO-III telescope. No
statistically significant excess was observed, and limitations on the allowed
parameter range in the model are discussed.Comment: 6 pages 6 figures, to appear in ApJ, August 20, 2008, v683n
� ¢  � © ,  H. £ KUBO
Abstract: More than forty gamma-ray sources have been detected by atmospheric Cherenkov telescopes at TeV energies. Although there are many theoretical predictions on the possible gamma-ray fluxes from these gigantic objects assuming various emission mechanisms, no cluster of galaxies have been proven t
Cangaroo-III observations of the 2006 outburst of PKS 2155-304
Copyright © 2008. The American Astronomical Society. All rights reserved. Printed in U.S.A.We have used the CANGAROO-III imaging atmospheric Cerenkov telescopes to observe the high-frequency-peaked BL Lacertae (HBL) object PKS 2155-304 between 2006 July 28 (MJD 53,944) and August 2, triggered by the H.E.S.S. report that the source was in a high state of TeV gamma-ray emission. A signal was detected at the 4.8 σ level in an effective live time of 25.1 hr during the outburst period. The flux of very high energy gamma rays from the CANGAROO-III observations shows variability on the timescale of less than a few hours. The averaged integral flux above 660 GeV is (1.6 ± 0.3stat ± 0.5syst) × 10-11 cm-2 s -1, which corresponds to ∼45% of the flux observed from the Crab Nebula. Follow-up observations between August 17 (MJD 53,964) and 25 indicate that the source activity had decreased. © 2008. The American Astronomical Society. All rights reserved.Y. Sakamoto, K. Nishijima, T. Mizukami, E. Yamazaki, J. Kushida, R. Enomoto, M. Ohishi, G. V. Bicknell, R. W. Clay, P. G. Edwards, S. Gunji, S. Hara, T. Hattori, S. Hayashi, Y. Higashi, Y. Hirai, K. Inoue, C. Itoh, S. Kabuki, F. Kajino, H. Katagiri, A. Kawachi, T. Kifune, R. Kiuchi, H. Kubo, R. Mizuniwa, M. Mori, H. Muraishi, T. Naito, T. Nakamori, S. Nakano, D. Nishida, A. Seki, V. Stamatescu, T. Suzuki, D. L. Swaby, T. Tanimori, G. Thornton, F. Tokanai, K. Tsuchiya, S. Watanabe, Y. Yamada, S. Yanagita, T. Yoshida, T. Yoshikoshi, and Y. Yukaw