-
M. Amenomori,
X. J. Bi,
D. Chen,
S. W. Cui,
Danzengluobu,
L. K. Ding,
X. H. Ding,
C. Fan,
C. F. Feng,
Zhaoyang Feng, [......],
T. Yuda,
H. M. Zhang, J. L. Zhang,
N. J. Zhang,
X. Y. Zhang,
Y. Zhang,
Yi Zhang,
Ying Zhang,
Zhaxisangzhu,
X. X. Zhou
[show abstract]
[hide abstract]
ABSTRACT: Using the Tibet-III air shower array, we search for steady TeV
γ-rays from 18 pulsars in the Fermi Large Area Telescope pulsar
catalog. Among them, we observe 8 sources including the Crab instead of
the expected 0.41 sources at a significance of 2 σ or more excess.
Under the assumption of Poisson distribution, the chance probability is
estimated to be 1.4×10-8. When the Crab is excluded, it
becomes 1.8×10-7. These low chance probabilities
clearly show that the Fermi pulsars have a statistically significant
correlations with TeV γ-ray excesses.
Astrophysics and Space Sciences Transactions 05/2011; 7:211-215.
-
M. Amenomori,
X. J. Bi,
D. Chen,
S. W. Cui,
Danzengluobu,
L. K. Ding,
X. H. Ding,
C. Fan,
C. F. Feng,
Zhaoyang Feng, [......],
T. Yuda,
H. M. Zhang, J. L. Zhang,
N. J. Zhang,
X. Y. Zhang,
Y. Zhang,
Yi Zhang,
Ying Zhang,
Zhaxisangzhu,
X. X. Zhou
[show abstract]
[hide abstract]
ABSTRACT: The energy spectrum of cosmic rays around the knee measured by Tibet
air-shower experiment is summarized and its characteristic features are
discussed under two possible scenarios. The result of Tibet experiment
measured over wide range of 1014-1017 eV with high
statistics provided details of the knee at the energy around
4×1015 eV. The study of the chemical composition based
on measurements of proton and helium spectra obtained from air-shower
core detection indicates the dominance of heavy nuclei around the knee.
Such feature can be explained either by contribution of nearby sources
with source composition dominated by heavy nuclei or by nonlinear effect
in diffusive shock acceleration mechanism.
Astrophysics and Space Sciences Transactions 12/2010; 7:15-20.
-
M. Amenomori,
X. J. Bi,
D Chen,
S. W. Cui,
Danzengluobu,
L. K. Ding,
X. H. Ding,
C Fan,
C. F. Feng,
Zhaoyang Feng, [......],
T Yuda,
H M Zhang, J L Zhang,
N. J. Zhang,
X Y Zhang,
Y Zhang,
Yi Zhang,
Ying Zhang,
Zhaxisangzhu,
X. X. Zhou
[show abstract]
[hide abstract]
ABSTRACT: We analyze the large-scale two-dimensional sidereal anisotropy of multi-TeV cosmic rays by Tibet Air Shower Array, with the data taken from 1999 November to 2008 December. To explore temporal variations of the anisotropy, the data set is divided into nine intervals, each in a time span of about one year. The sidereal anisotropy of magnitude about 0.1% appears fairly stable from year to year over the entire observation period of nine years. This indicates that the anisotropy of TeV Galactic cosmic rays remains insensitive to solar activities since the observation period covers more than a half of the 23rd solar cycle. Comment: 18 pages, 2 figures, accepted by The Astrophysical Journal
01/2010;
-
M. Amenomori,
X. J. Bi,
D Chen,
S. W. Cui,
Danzengluobu,
L. K. Ding,
X. H. Ding,
C Fan,
C. F. Feng,
Zhaoyang Feng, [......],
T Yuda,
H M Zhang, J L Zhang,
N. J. Zhang,
X Y Zhang,
Y Zhang,
Yi Zhang,
Ying Zhang,
Zhaxisangzhu,
X. X. Zhou
[show abstract]
[hide abstract]
ABSTRACT: Using the Tibet-III air shower array, we search for TeV gamma-rays from 27 potential Galactic sources in the early list of bright sources obtained by the Fermi Large Area Telescope at energies above 100 MeV. Among them, we observe 7 sources instead of the expected 0.61 sources at a significance of 2 sigma or more excess. The chance probability from Poisson statistics would be estimated to be 3.8 x 10^-6. If the excess distribution observed by the Tibet-III array has a density gradient toward the Galactic plane, the expected number of sources may be enhanced in chance association. Then, the chance probability rises slightly, to 1.2 x 10^-5, based on a simple Monte Carlo simulation. These low chance probabilities clearly show that the Fermi bright Galactic sources have statistically significant correlations with TeV gamma-ray excesses. We also find that all 7 sources are associated with pulsars, and 6 of them are coincident with sources detected by the Milagro experiment at a significance of 3 sigma or more at the representative energy of 35 TeV. The significance maps observed by the Tibet-III air shower array around the Fermi sources, which are coincident with the Milagro >=3sigma sources, are consistent with the Milagro observations. This is the first result of the northern sky survey of the Fermi bright Galactic sources in the TeV region. Comment: 17 pages, 2 figures, 1 table, Accepted for publication in ApJ Letters
12/2009;
-
M. Amenomori,
X. J. Bi,
D Chen,
S. W. Cui,
Danzengluobu,
L. K. Ding,
X. H. Ding,
C Fan,
C. F. Feng,
Zhaoyang Feng, [......],
H M Zhang, J L Zhang,
N. J. Zhang,
X Y Zhang,
Y Zhang,
Yi Zhang,
Ying Zhang,
Zhaxisangzhu,
X. X. Zhou,
J. Kota
[show abstract]
[hide abstract]
ABSTRACT: We develop a model anisotropy best-fitting to the two-dimensional sky-map of multi-TeV galactic cosmic ray (GCR) intensity observed with the Tibet III air shower (AS) array. By incorporating a pair of intensity excesses in the hydrogen deflection plane (HDP) suggested by Gurnett et al., together with the uni-directional and bi-directional flows for reproducing the observed global feature, this model successfully reproduces the observed sky-map including the "skewed" feature of the excess intensity from the heliotail direction, whose physical origin has long remained unknown. These additional excesses are modeled by a pair of the northern and southern Gaussian distributions, each placed ~50 degree away from the heliotail direction. The amplitude of the southern excess is as large as ~0.2 %, more than twice the amplitude of the northern excess. This implies that the Tibet AS experiment discovered for the first time a clear evidence of the significant modulation of GCR intensity in the heliotail and the asymmetric heliosphere. Comment: 4 pages, 1 figure, 31st International Cosmic Ray Conference (Lodz, Poland), 2009
09/2009;
-
M Amenomori,
X J Bi,
D Chen,
S W Cui,
Danzengluobu,
L K Ding,
X H Ding,
C Fan,
C F Feng,
Z Feng, [......],
G C Yu,
A F Yuan,
T Yuda,
H M Zhang, J L Zhang,
N J Zhang,
X Y Zhang,
Y Zhang,
Zhaxisangzhu,
X X Zhou
[show abstract]
[hide abstract]
ABSTRACT: The Tibet air shower array, which has an effective area of 36,900 m2, has been in operation at Yangbajing in Tibet, China at an altitude of 4,300 m above sea level. In this paper, we will briefly introduce the recent gamma-ray observation with the present Tibet air shower array and our future plan which is called the Tibet muon detector (MD) project.
Journal of Physics Conference Series 07/2008; 120(6):062024.
-
Y Wang,
X. J. Bi,
S. W. Cui,
L. K. Ding,
Danzengluobu,
X. H. Ding,
C Fan,
C. F. Feng,
Zhaoyang Feng,
Z. Y. Feng, [......],
A. F. Yuan,
H M Zhang, J L Zhang,
N. J. Zhang,
X Y Zhang,
Y Zhang,
Yi Zhang,
Zhaxisangzhu,
X. X. Zhou,
Q Yuan
[show abstract]
[hide abstract]
ABSTRACT: Using the data taken from Tibet II High Density (HD) Array (1997 February-1999 September) and Tibet-III array (1999 November-2005 November), our previous northern sky survey for TeV $\gamma-$ray point sources has now been updated by a factor of 2.8 improved statistics. From $0.0^{\circ}$ to $60.0^{\circ}$ in declination (Dec) range, no new TeV $\gamma-$ray point sources with sufficiently high significance were identified while the well-known Crab Nebula and Mrk421 remain to be the brightest TeV $\gamma-$ray sources within the field of view of the Tibet air shower array. Based on the currently available data and at the 90% confidence level (C.L.), the flux upper limits for different power law index assumption are re-derived, which are approximately improved by 1.7 times as compared with our previous reported limits.
05/2008;
-
Tibet Asγ Collaboration,
S. Ayabe,
X. J. Bi,
D. Chen,
S. W. Cui,
Danzengluobu,
L. K. Ding,
X. H. Ding,
C. F. Feng,
Zhaoyang Feng, [......],
A. F. Yuan,
T. Yuda,
H. M. Zhang, J. L. Zhang,
N. J. Zhang,
X. Y. Zhang,
Y. Zhang,
Yi Zhang,
Zhaxisangzhu,
X. X. Zhou
[show abstract]
[hide abstract]
ABSTRACT: We report on the spectral index of cosmic rays around 10 TeV energy
region obtained by observation of the Compton-Getting anisotropy due to
the terrestrial orbital motion around the Sun with the Tibet III air
shower array during the period from 1999 to 2005. The spectral index has
turned out to be 2.99±0.54, which is consistent with 2.74 by the
direct energy spectrum measurement. This method is a new approach to
measure the spectral index and is complementary to the conventional
energy spectrum measurement.
Nuclear Physics B - Proceedings Supplements 12/2007; 175:427-430. · 0.88 Impact Factor
-
M. Amenomori,
X. J. Bi,
D Chen,
S. W. Cui,
Danzengluobu,
L. K. Ding,
X. H. Ding,
C Fan,
C. F. Feng,
Zhaoyang Feng, [......],
A. F. Yuan,
T Yuda,
H M Zhang, J L Zhang,
N. J. Zhang,
X Y Zhang,
Y Zhang,
Yi Zhang,
Zhaxisangzhu,
X. X. Zhou
[show abstract]
[hide abstract]
ABSTRACT: The Tibet air shower array, which has an effective area of 37,000 square meters and is located at 4300 m in altitude, has been observing air showers induced by cosmic rays with energies above a few TeV. We have a plan to add a large muon detector array to it for the purpose of increasing its sensitivity to cosmic gamma rays in the 100 TeV energy region by discriminating them from cosmic-ray hadrons. We have deduced the attainable sensitivity of the muon detector array using our Monte Carlo simulation. We report here on the detailed procedure of our Monte Carlo simulation.
11/2007;
-
M. Amenomori,
X. J. Bi,
D Chen,
S. W. Cui,
Danzengluobu,
L. K. Ding,
X. H. Ding,
C Fan,
C. F. Feng,
Zhaoyang Feng, [......],
A. F. Yuan,
T Yuda,
H M Zhang, J L Zhang,
N. J. Zhang,
X Y Zhang,
Y Zhang,
Yi Zhang,
Zhaxisangzhu,
X. X. Zhou
[show abstract]
[hide abstract]
ABSTRACT: The Tibet air shower array, which has an effective area of 37,000 square meters and is located at 4300 m in altitude, has been observing air showers induced by cosmic rays with energies above a few TeV. We are planning to add a large muon detector array to it for the purpose of increasing its sensitivity to cosmic gamma rays in the 100 TeV (10 - 1000 TeV) energy region by discriminating them from cosmic-ray hadrons. We report on the possibility of detection of gamma rays in the 100 TeV energy region in our field of view, based on the improved sensitivity of our air shower array deduced from the full Monte Carlo simulation.
11/2007;
-
M. Amenomori,
X. J. Bi,
D Chen,
S. W. Cui,
Danzengluobu,
L. K. Ding,
X. H. Ding,
C Fan,
C. F. Feng,
Zhaoyang Feng, [......],
T Yuda,
H M Zhang, J L Zhang,
N. J. Zhang,
X Y Zhang,
Y Zhang,
Yi Zhang,
Zhaxisangzhu,
X. X. Zhou,
for The Tibet ASgamma Collaboration
[show abstract]
[hide abstract]
ABSTRACT: The amplitude of the Compton-Getting (CG) anisotropy contains the power-law index of the cosmic-ray energy spectrum. Based on this relation and using the Tibet air-shower array data, we measure the cosmic-ray spectral index to be $-3.03 \pm 0.55_{stat} \pm < 0.62_{syst}$ between 6 TeV and 40 TeV, consistent with $-$2.7 from direct energy spectrum measurements. Potentially, this CG anisotropy analysis can be utilized to confirm the astrophysical origin of the ``knee'' against models for non-standard hadronic interactions in the atmosphere. Comment: accepted to ApJL
11/2007;
-
M Amenomori,
S Ayabe,
X J Bi,
D Chen,
S W Cui,
Danzengluobu,
L K Ding,
X H Ding,
C F Feng,
Zhaoyang Feng, [......],
A F Yuan,
T Yuda,
H M Zhang, J L Zhang,
N J Zhang,
X Y Zhang,
Y Zhang,
Yi Zhang,
Zhaxisangzhu,
X X Zhou
[show abstract]
[hide abstract]
ABSTRACT: The intensity of Galactic cosmic rays is nearly isotropic because of the influence of magnetic fields in the Milky Way. Here, we present two-dimensional high-precision anisotropy measurement for energies from a few to several hundred teraelectronvolts (TeV), using the large data sample of the Tibet Air Shower Arrays. Besides revealing finer details of the known anisotropies, a new component of Galactic cosmic ray anisotropy in sidereal time is uncovered around the Cygnus region direction. For cosmic-ray energies up to a few hundred TeV, all components of anisotropies fade away, showing a corotation of Galactic cosmic rays with the local Galactic magnetic environment. These results have broad implications for a comprehensive understanding of cosmic rays, supernovae, magnetic fields, and heliospheric and Galactic dynamic environments.
Science 11/2006; 314(5798):439-43. · 31.20 Impact Factor
-
M Amenomori,
S Ayabe,
S W Cui,
Danzengluobu,
L K Ding,
X H Ding,
C F Feng,
Z Y Feng,
X Y Gao,
Q X Geng, [......],
G C Yu,
A F Yuan,
T Yuda,
H M Zhang, J L Zhang,
N J Zhang,
X Y Zhang,
Y Zhang,
Zhaxisangzhu,
X X Zhou
[show abstract]
[hide abstract]
ABSTRACT: We report on the solar diurnal variation of the galactic cosmic-ray intensity observed by the Tibet III air shower array during the period from 1999 to 2003. In the higher-energy event samples (12 and 6.2 TeV), the variations are fairly consistent with the Compton-Getting anisotropy due to the terrestrial orbital motion around the Sun, while the variation in the lower-energy event sample (4.0 TeV) is inconsistent with this anisotropy. This suggests an additional anisotropy superposed at the multi-TeV energies, e.g., the solar modulation effect. This is the highest-precision measurement of the Compton-Getting anisotropy ever made.
Physical Review Letters 09/2004; 93(6):061101. · 7.37 Impact Factor
-
M. Amenomori,
S. Ayabe,
S. W. Cui,
Danzengluobu,
L. K. Ding,
X. H. Ding,
C. F. Feng,
Z. Y. Feng,
X. Y. Gao,
Q. X. Geng, [......],
G. C. Yu,
A. F. Yuan,
T. Yuda,
H. M. Zhang, J. L. Zhang,
N. J. Zhang,
X. Y. Zhang,
Y. Zhang,
Zhaxisangzhu,
X. X. Zhou
[show abstract]
[hide abstract]
ABSTRACT: We have been observing multi-TeV cosmic rays by the Tibet I I I air
shower array since November 1999. This continuous observation enables us
a detailed analysis of the sidereal and solar daily variations of the
galactic cosmic-ray intensity. The observed solar daily variation is
compared with the expected variation that includes the Compton-Getting
effect due to the revolution motion of the earth around the sun. The
variation in the higher-energy event samples (log mean energy 6.7 TeV)
is consistent with the expected anisotropy, while the variation in the
lower-energy event samples (log mean energy 3.8 TeV) suggests an
additional diurnal anisotropy superp osed, probably due to the solar
modulation. This is the highest-precision measurement of the
Compton-Getting anisotropy ever made.
06/2003; 7:3917.
-
M. Amenomori,
S. Ayabe,
S. W. Cui,
Danzengluobu,
L. K. Ding,
X. H. Ding,
C. F. Feng,
Z. Y. Feng,
X. Y. Gao,
Q. X. Geng, [......],
G. C. Yu,
A. F. Yuan,
T. Yuda,
H. M. Zhang, J. L. Zhang,
N. J. Zhang,
X. Y. Zhang,
Y. Zhang,
Zhaxisangzhu,
X. X. Zhou
[show abstract]
[hide abstract]
ABSTRACT: The Tibet air shower array has been in operation since 1999 as TibetI I
I (22, 050 m2 ) with energy threshold of a few TeV. As primary cosmic
rays are shielded by the moon having the finite size of 0.5o in
diameter, we observe a deficit in cosmic rays called the moon's shadow
with statistical significance of 32σ . The center of the moon's
shadow shifts westwardly due to the geomagnetic field. By analyzing this
energy-dep endent westward displacement carefully, we set an upper limit
of 11% at 90% confidence level on the cosmic-ray antiproton/proton ratio
at multi-TeV energies. 2. Introduction Cosmic antiprotons are mainly
produced by collisions of cosmic-ray protons with interstellar hydrogen
gas: p+ p-→ p+ p+ p+ p. Accelerator experiments measured the
antiproton/proton ratio (R(p/p)) to be about 10-3 ˜
10-4 in this process. The energy spectrum of the parent cosmic-ray
protons has a power-law index ˜ -2.7 above 10 GeV and the
power-law index of pshould also be ˜ -2.7. According to a
pure secondary production model during the propagation of cosmic rays in
the galaxy, R(p/p) decreases as E -0.6 above 10 GeV. Various
experimental
06/2003; 3:1651.
-
M. Amenomori,
S. Ayabe,
S. W. Cui,
L. K. Ding,
X. Y. Ding,
C. F. Feng,
Z. Y. Feng,
Y. Fu,
X. Y. Gao,
Q. X. Geng, [......],
Z. H. Ye,
G. C. Yu,
A. F. Yuan,
T. Yuda,
H. M. Zhang, J. L. Zhang,
N. J. Zhang,
X. Y. Zhang,
Zhaxiciren,
Zhaxisangzhu
[show abstract]
[hide abstract]
ABSTRACT: Using a high density air-shower array (Tibet-HD array), we succeeded in
detecting multi-TeV γ-ray signals from the Crab Nebula in 1999. In
the late fall of 1999, the HD array was enlarged from 5175 m2 up to
22000 m2 (TibetIII array). Using the 316 live-day data taken between
1999 November and 2001 May with this enlarged new array, we studied the
emission of TeV γ-rays from the Crab Nebula. A preliminary
analysis gives the excess γ-ray signal at the statistical
significance of 4.8 σ. The energy spectrum of γrays observed
is consistent with the previous observation. We report the result on the
study of the Crab flux.
07/2001; 6:2395.
-
M. Amenomori,
S. Ayabe,
S. W. Cui,
L. K. Ding,
X. Y. Ding,
C. F. Feng,
Z. Y. Feng,
Y. Fu,
X. Y. Gao,
Q. X. Geng, [......],
Z. H. Ye,
G. C. Yu,
A. F. Yuan,
T. Yuda,
H. M. Zhang, J. L. Zhang,
N. J. Zhang,
X. Y. Zhang,
Zhaxiciren,
Zhaxisangzhu
[show abstract]
[hide abstract]
ABSTRACT: Several strong TeV gamma-ray bursts were detected from Markarian 421
(Mrk 421) in the years 2000 and 2001 by the Tibet-III air-shower array
at the statistical significance of 6.9 σ level. Mrk 421 was
unprecedentedly active at X-ray and TeV gamma-ray energies during this
period. The observed differential energy spectral index of the
gamma-rays from Mrk 421 is 3.65±0.50 0.55 at energies from 2.6
TeV to 39 TeV, assuming a power law spectrum.
07/2001; 7:2661.
-
K. Munakata,
Y. Takayanagi,
H. Washimi,
T. Tanaka,
S. Yasue,
C. Kato,
S. Mori,
M. Amenomori,
S. Ayabe,
S. W. Cui, [......],
Z. H. Ye,
G. C. Yu,
A. F. Yuan,
T. Yuda,
H. M. Zhang, J. L. Zhang,
N. J. Zhang,
X. Y. Zhang,
Zhaxiciren,
Zhaxisangzhu
[show abstract]
[hide abstract]
ABSTRACT: We analyze the sidereal daily variation (SDV) of galactic cosmic-ray
intensity observed by the Tibet II airshower array during 29 months
between October 1995 and August 1999. The high-count observations help
us analyze the SDV with a great significance. We found that the
magnitude of the observed SDV shows a significant seasonal change (1
cycle/year) with an amplitude exceeding 50% of the average SDV. This
seasonal change in magnitude produces spurious solar (365 cycle/year)
and extended sidereal (367 cycle/year) daily variations at sideband
frequencies of the SDV (366 cycle/year). The observed solar daily
variation corrected for this effect is consistent with the variation
expected from the ComptonGetting anisotropy due to the earth's
revolution around the sun. The extended sidereal daily variation
observed is also consistent with the variation expected from the
seasonal change of the SDV. The phase of maximum (minimum) SDV in March
(September) suggests the influence of the large-scale solar magnetic
field on the propagation of charged particles in the heliosphere. We
discuss on such effect by comparing the observed SDV with that
reproduced from the calculation of cosmic-ray orbits in a model
heliosphere.
07/2001; 10:3919.
-
M. Amenomori,
S. Ayabe,
S. W. Cui,
L. K. Ding,
X. Y. Ding,
C. F. Feng,
Z. Y. Feng,
Y. Fu,
X. Y. Gao,
Q. X. Geng, [......],
Z. H. Ye,
G. C. Yu,
A. F. Yuan,
T. Yuda,
H. M. Zhang, J. L. Zhang,
N. J. Zhang,
X. Y. Zhang,
Zhaxiciren,
Zhaxisangzhu
[show abstract]
[hide abstract]
ABSTRACT: Our study is made for a search for TeV counterparts to GRBs observed by
BATSE using the Tibet II/HD air-shower data set. Analysed Tibet data are
taken during the period October 1995 through September 1999. BATSE
detected 67 GRBs within the field of view of Tibet array during this
period. Six kinds of time durations, 5, 10, 20, 30, 40 and 50 sec just
after BATSE trig-ger, are employed for the examination. GRB971115a is
found to be the most prominent GRB having Power value of 6.05. The
probability that Power value is greater than 6.05 is occurred by the
statistical uctuation is estimated by Monte Carlo simulation, and was
found to be 2 × 10-1 . Therefore, such Power value can be
understood as consistent with statistical uctuation. So, no clearly
significant TeV gamma-ray bursts of employed time durations were
detected from our analysis of Tibet II data set.
07/2001; 7:2753.
-
M. Amenomori,
S. Ayabe,
S. W. Cui,
L. K. Ding,
X. Y. Ding,
C. F. Feng,
Z. Y. Feng,
Y. Fu,
X. Y. Gao,
Q. X. Geng, [......],
Z. H. Ye,
G. C. Yu,
A. F. Yuan,
T. Yuda,
H. M. Zhang, J. L. Zhang,
N. J. Zhang,
X. Y. Zhang,
Zhaxiciren,
Zhaxisangzhu
[show abstract]
[hide abstract]
ABSTRACT: Signals of diffuse gamma rays from the galactic plane are searched using
both the Tibet-II array and high density (HD) array data with mode
energy 10 TeV and 3 TeV, respectively. No significant signal is found
both from inner Galaxy (IG) for 20° ≤ l ≤ 55° near the
galactic center and outer Galaxy (OG) 140° ≤ l ≤ 225°
around the anti-galactic center both with |b| ≤ 5° . Then the
flux upper limits with 90% c.l. are obtained as 1.30×10-10
cm-2 s-1 sr-1 from IG and 4.05×10-11
cm-2 s-1 sr-1 from OG at 10 TeV, and also
2.34×10-9 cm-2 s-1 sr-1 from IG and
2.24×10-10 cm-2 s-1 sr-1 from OG at 3 TeV,
respectively. The present data seem to exclude the inverse Compton model
in an extreme case of assumed flat spectrum of power index 2.0 of
injected local electrons. Correspondence to: Yamamoto
(yamamoto@hep.konan-u.ac.jp)
07/2001; 6:2344.
