3 research outputs found
Search for VHE gamma rays from SS433/W50 with the CANGAROO-II telescope
SS433, located at the center of the supernova remnant W50, is a close
proximity binary system consisting of a compact star and a normal star. Jets of
material are directed outwards from the vicinity of the compact star
symmetrically to the east and west. Non-thermal hard X-ray emission is detected
from lobes lying on both sides. Shock accelerated electrons are expected to
generate sub-TeV gamma rays through the inverse-Compton process in the lobes.
Observations of the western X-ray lobe region of SS433/W50 system have been
performed to detect sub-TeV gamma-rays using the 10m CANGAROO-II telescope in
August and September, 2001, and July and September, 2002. The total observation
times are 85.2 hours for ON source, and 80.8 hours for OFF source data. No
significant excess of sub-TeV gamma rays has been found at 3 regions of the
western X-ray lobe of SS433/W50 system. We have derived 99% confidence level
upper limits to the fluxes of gamma rays and have set constraints on the
strengths of the magnetic fields assuming the synchrotron/inverse-Compton model
for the wide energy range of photon spectrum from radio to TeV. The derived
lower limits are 4.3 microgauss for the center of the brightest X-ray emission
region and 6.3 microgauss for the far end from SS433 in the western X-ray lobe.
In addition, we suggest that the spot-like X-ray emission may provide a major
contribution to the hardest X-ray spectrum in the lobe.Comment: 7 pages, 8 figures, to be published in Astroparticle Physic
Searches for very high energy gamma rays from blazars with CANGAROO-III telescope in 2005-2009
We have searched for very high energy (VHE) gamma rays from four blazars
using the CANGAROO-III imaging atmospheric Cherenkov telescope. We report the
results of the observations of H 2356-309, PKS 2155-304, PKS 0537-441, and 3C
279, performed from 2005 to 2009, applying a new analysis to suppress the
effects of the position dependence of Cherenkov images in the field of view. No
significant VHE gamma ray emission was detected from any of the four blazars.
The GeV gamma-ray spectra of these objects were obtained by analyzing Fermi/LAT
archival data. Non-simultaneous wide range (radio to VHE gamma-ray bands)
spectral energy distributions (SEDs) including CANGAROO-III upper limits, GeV
gamma-ray spectra, and archival data are discussed using a one-zone synchrotron
self-Compton (SSC) model in combination with a external Compton (EC) radiation.
The HBLs (H 2356-309 and PKS 2155-304) can be explained by a simple SSC model,
and PKS 0537-441 and 3C 279 are well modeled by a combination of SSC and EC
model. We find a consistency with the blazar sequence in terms of strength of
magnetic field and component size.Comment: 11 pages, 8 figures, Accepted for publication in Astroparticle
Physic