1,092 research outputs found
The implications from CANGAROO-III observations of TeV blazar PKS 2155-304
We have observed the high-frequency-peaked BL Lacertae object PKS2155-304 in
2004, 2005 and 2006 with the CANGAROO-III imaging atmospheric Cherenkov
telescope, and have detected a signal above 660 GeV at the 4.8/sigma level
during the 2006 outburst period. Intranight flux variability on time scale of
half an hour is observed. From this variability time scale, the size of the TeV
gamma-ray emission region is restricted to 5x10^13\delta cm, and the super
massive black hole mass is estimated to be less than 1.9x10^8\delta M_{Solar},
where \delta is the beaming factor. The differential energy spectrum is
obtained, and an upper limit of the extragalactic infrared background light
(EBL) flux is derived under some assumption. We also fit a synchrotron self
Compton (SSC) model to the spectral energy distribution (SED) and derive the
beaming factor and magnetic field strength.Comment: 4 pages, 5 figures, proceedings of the "4th Heidelberg International
Symposium on High Energy Gamma-Ray Astronomy" July 7-11, 2008, Heidelberg,
German
Reanalysis of Data Taken by the CANGAROO 3.8 Meter Imaging Atmospheric Cherenkov Telescope: PSR B1706-44, SN 1006, and Vela
We have reanalyzed data from observations of PSR B1706-44, SN 1006, and the
Vela pulsar region made with the CANGAROO 3.8 m imaging atmospheric Cherenkov
telescope between 1993 and 1998 in response to the results reported for these
sources by the H.E.S.S. collaboration. In our reanalysis, in which gamma-ray
selection criteria have been determined exclusively using gamma-ray simulations
and OFF-source data as background samples, no significant TeV gamma-ray signals
have been detected from compact regions around PSR B1706-44 or within the
northeast rim of SN 1006. We discuss reasons why the original analyses gave the
source detections. The reanalysis did result in a TeV gamma-ray signal from the
Vela pulsar region at the 4.5 sigma level using 1993, 1994, and 1995 data. The
excess was located at the same position, 0.13 deg. to the southeast of the Vela
pulsar, as that reported in the original analysis. We have investigated the
effect of the acceptance distribution in the field of view of the 3.8 m
telescope, which rapidly decreases toward the edge of the field of the camera,
on the detected gamma-ray morphology. The expected excess distribution for the
3.8 m telescope has been obtained by reweighting the distribution of HESS
J0835-455 measured by H.E.S.S. with the acceptance of the 3.8 m telescope. The
result is morphologically comparable to the CANGAROO excess distribution,
although the profile of the acceptance-reweighted H.E.S.S. distribution is more
diffuse than that of CANGAROO. The integral gamma-ray flux from HESS J0835-455
has been estimated for the same region as defined by H.E.S.S. from the
1993-1995 data of CANGAROO to be F(> 4.0 +/- 1.6 TeV) = (3.28 +/- 0.92) x
10^{-12} photons cm^{-2} s^{-1}, which is statistically consistent with the
integral flux obtained by H.E.S.S.Comment: Published in ApJ, minor improvement
CANGAROO-III Observation of TeV Gamma Rays from the vicinity of PSR B1 706-44
Observation by the CANGAROO-III stereoscopic system of the Imaging Cherenkov
Telescope has detected extended emission of TeV gamma rays in the vicinity of
the pulsar PSR B170644. The strength of the signal observed as
gamma-ray-like events varies when we apply different ways of emulating
background events. The reason for such uncertainties is argued in relevance to
gamma-rays embedded in the "off-source data", that is, unknown sources and
diffuse emission in the Galactic plane, namely, the existence of a complex
structure of TeV gamma-ray emission around PSR B170644.Comment: 10 pages, 13 figures, to be published in Ap
Simulating Cherenkov Telescope Array observation of RX J1713.7-3946
We perform simulations of Cherenkov Telescope Array (CTA) observations of a
young supernova remnant RX J1713.7-3946. This target is not only one of the
brightest sources ever discovered in very high-energy gamma rays but also well
observed in other wavebands. In X-rays, the emission is dominated by
synchrotron radiation, which links directly to the existence of high-energy
electrons. Radio observations of CO and HI gas have revealed a highly
inhomogeneous medium surrounding the SNR, such as clumpy molecular clouds.
Therefore gamma rays from hadronic interactions are naturally expected.
However, the spectrum in GeV energy range measured by Fermi/LAT indicates more
typical of leptonic emission from accelerated electrons. Despite lots of
multi-wavelength information, the competing interpretations have led to much
uncertainty in the quest of unraveling the true origin of the gamma-ray
emission from RX~J1713.7--3946. CTA will achieve highest performance ever in
sensitivity, angular resolution, and energy resolution. We estimate CTA
capability to examine the emission mechanisms of the gamma rays through
simulated spatial distribution, spectra, and their time variation.Comment: 8 pages, 3 figures. In Proceedings of the 34th International Cosmic
Ray Conference (ICRC2015), The Hague, The Netherlands. All CTA contributions
at arXiv:1508.0589
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