-
H. Yoshii,
T. Baba,
T. Kaneko,
K. Suga,
F. Kakimoto,
S. Ogio,
Y. Shirasaki,
N. Gironda,
M. Teshima,
Y. Toyoda, [......],
N. Tajima,
S. Shimoda,
H. Nakatani,
Y. Yamada,
E. Gotoh,
A. Veralde,
L. Siles, P. Miranda,
W. Velasquez,
and I. Poma
[show abstract]
[hide abstract]
ABSTRACT: Searches for gamma rays above 100 TeV from SN 1987A and above 50 TeV from Cen X-3 were carried out with an air shower array at Mount Chacaltaya over a period of 3 years. The array, which consists of 13 4 m2 and 28 1 m2 scintillation detectors, was located on a slope of about 30° facing southward to effectively observe air showers coming from the directions of these sources. In the analysis, a selection by shower age parameter was applied to reduce the background due to showers initiated by protons or nuclei.No significant excess of gamma rays (and/or neutral particles) from these sources was found; our upper limits on the flux of gamma rays above 100 TeV from SN 1987A and above 50 TeV from Cen X-3 are 2.2×10–13 and 3.5×10–13 photons cm–2 s–1 (95% confirdence level), respectively.
The Astrophysical Journal 01/2009; 472(2):800. · 6.02 Impact Factor
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K. Watanabe,
Y. Muraki,
Y. Matsubara,
K. Murakami,
T. Sako,
H. Tsuchiya,
S. Masuda,
M. Yoshimori,
N. Ohmori, P. Miranda,
N. Martinic,
R. Ticona,
A. Velarde,
F. Kakimoto,
S. Ogio,
Y. Tsunesada,
H. Tokuno,
and Y. Shirasaki
[show abstract]
[hide abstract]
ABSTRACT: Solar neutrons have been detected using the neutron monitor located at Mount Chacaltaya, Bolivia, in association with a large solar flare on 2000 November 24. This is the first detection of solar neutrons by a neutron monitor that has been reported so far in solar cycle 23. The statistical significance of the detection is 5.5 σ. In this flare, the intense emission of hard X-rays and γ-rays has been observed by the Yohkoh Hard X-ray Telescope (HXT) and Gamma Ray Spectrometer (GRS), respectively. The production time of solar neutrons is better correlated with those of hard X-rays and γ-rays than with the production time of soft X-rays. The observations of the solar neutrons on the ground have been limited to solar flares with soft X-ray class greater than X8 in former solar cycles. In this cycle, however, neutrons were detected associated with an X2.3 solar flare on 2000 November 24. This is the first report of the detection of solar neutrons on the ground associated with a solar flare with an X-ray class smaller than X8.
The Astrophysical Journal 12/2008; 592(1):590. · 6.02 Impact Factor
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T. Sako,
K. Watanabe,
Y. Muraki,
Y. Matsubara,
H. Tsujihara,
M. Yamashita,
T. Sakai,
S. Shibata,
J. F. Valdés-Galicia,
L. X. González, [......],
F. Kakimoto,
S. Ogio,
Y. Tsunesada,
H. Tokuno,
Y. T. Tanaka,
I. Yoshikawa,
T. Terasawa,
Y. Saito,
T. Mukai,
and M. Gros
[show abstract]
[hide abstract]
ABSTRACT: Strong signals of neutral emissions were detected in association with a solar flare that occurred on 2005 September 7. They were produced by both relativistic ions and electrons. In particular, relativistic neutrons were observed with the solar neutron telescopes (SNTs) located at Mount Chacaltaya in Bolivia and Mount Sierra Negra in Mexico and with neutron monitors (NMs) at Chacaltaya and Mexico City with high statistical significances. At the same time, hard X-rays and γ-rays, which were predominantly emitted by high-energy electrons, were detected by the Geotail and the INTEGRAL satellites. We found that a model of the impulsive neutron emission at the time of the X-ray/γ-ray peak can explain the main peaks of all the detected neutron signals, but failed to explain the long tailed decaying phase. An alternative model, in which the neutron emission follows the X-ray/γ-ray profile, also failed to explain the long tail. These results indicate that the acceleration of ions began at the same time as the electrons but that ions were continuously accelerated or trapped longer than the electrons in the emission site. We also demonstrate that the neutron data observed by multienergy channels of SNTs put constraints on the neutron spectrum.
The Astrophysical Journal 12/2008; 651(1):L69. · 6.02 Impact Factor
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S. Ogio,
F. Kakimoto,
Y. Kurashina,
O. Burgoa,
D. Harada,
H. Tokuno,
H. Yoshii,
A. Morizawa,
E. Gotoh,
H. Nakatani, [......],
Y. Yamada,
T. Kaneko,
K. Murakami,
Y. Toyoda,
Y. Matsubara,
Y. Mizumoto,
Y. Shirasaki,
Y. Tsunesada, P. Miranda,
and A. Velarde
[show abstract]
[hide abstract]
ABSTRACT: We have measured extensive air showers with primary energies above 6 TeV at Mount Chacaltaya in Bolivia. The data were collected by an air shower array called the Minimum Air Shower (MAS) array starting in 2000 March. We applied an equi-intensity analysis method to the extensive air showers extended over the region of their maximum development. We varied the mixture of protons and iron in our simulations and compared these to the data to determine the mixing ratio of protons as a function of the primary energy. Using this, we derived the primary energy spectrum from 1014 to 5 × 1016 eV. Consequently, we conclude that the power-law index of the spectrum changes gradually around 1015.5 eV and that the obtained proton ratio decreases with increasing energy. We directly measured the longitudinal development of air showers generated by primaries with energies around the knee. We found that the average mass number of primary cosmic rays shows a steady increase with energy above 1014.5 eV and that the dominant component around the knee is not protons.
The Astrophysical Journal 12/2008; 612(1):268. · 6.02 Impact Factor
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K. Watanabe,
Y. Muraki,
Y. Matsubara,
K. Murakami,
T. Sako,
H. Tsuchiya,
S. Masuda,
M. Yoshimori,
N. Ohmori, P. Miranda,
N. Martinic,
R. Ticona,
A. Velarde,
F. Kakimoto,
S. Ogio,
Y. Tsunesada,
H. Tokuno,
Y. Shirasaki
[show abstract]
[hide abstract]
ABSTRACT: Solar neutrons have been detected using the neutron monitor located at
Mt. Chacaltaya, Bolivia, in association with a large solar flare on
August 25, 2001. The statistical significance of the detection is 4.7
σ . In this flare, intense emission of hard X-rays and γ
-rays was observed by the Yohkoh Hard X-ray telescope (HXT) and Gamma
Ray spectrometer (GRS), respectively. The time of solar neutron
production is better correlated with that of hard X-rays and γ
-rays than with the production time of soft X-rays.
06/2003; 6:3179.
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H. Tokuno,
F. Kakimoto,
S. Ogio,
D. Harada,
Y. Kurashina,
Y. Tsunesada,
N. Tajima, P. Miranda,
A. Morizawa,
Y. Matsubara,
H. Yoshii,
A. Velarde,
BASJE Collaboration
[show abstract]
[hide abstract]
ABSTRACT: For a study of the chemical composition at the Knee region, we have
measured lateral distributions both of air Cherenkov photons and of
charged particles simultaneously at Mt. Chacaltaya in Bolivia since
August 2001. The measured lateral distributions of air Cherenkov photons
were fitted with an empirical function which includes a parameter
reflecting mass numbers of primary cosmic rays. The observed
distributions of this parameter were compared with those simulated using
the CORSIKA code with the QGSJET hadronic interaction model for three
species of primary cosmic rays: proton, C, Fe. As a result, the mean
logarithmic mass number of primary cosmic rays ln A in the energy range
from 1014 to 1016 eV was determined. The result shows that ln A
decreases in the range from 1014.1 to 1014.7 eV and increases from
1014.7 to 1015.8 eV.
06/2003; 1:159.
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K Watanabe,
Y. Muraki,
Y Matsubara,
K Murakami,
T Sako,
H Tsuchiya,
S Masuda,
M. Yoshimori,
N Ohmori, P. Miranda,
N. Martinic,
R. Ticona,
A. Velarde,
F. Kakimoto,
S. Ogio,
Y. Tsunesada,
H Tokuno,
Y. Shirasaki
[show abstract]
[hide abstract]
ABSTRACT: Solar neutrons have been detected using the neutron monitor located at Mt. Chacaltaya, Bolivia, in association with a large solar flare on November 24, 2000. This is the first detection of solar neutrons by the neutron monitor that have been reported so far in solar cycle 23. The statistical significance of the detection is 5.5 sigma. In this flare, the intense emission of hard X-rays and gamma-rays has been observed by the Yohkoh Hard X-ray Telescope (HXT) and Gamma Ray Spectrometer (GRS), respectively. The production time of solar neutrons is better correlated with those of hard X-rays and gamma-rays than with the production time of soft X-rays. The observations of the solar neutrons on the ground have been limited to solar flares with soft X-ray class greater than X8 in former solar cycles. In this cycle, however, neutrons were detected associated with an X2.3 solar flare on November 24, 2000. This is the first report of the detection of solar neutrons on the ground associated with a solar flare with its X-ray class smaller than X8. Comment: 20 pages, 12 figures. accepted for publication in the Astronomical Journal
04/2003;
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H. Tsuchiya,
Y. Matsubara,
Y. Muraki,
K. Murakami,
T. Sako,
F. Kakimoto,
S. Ogio,
Y. Tsunesada,
H. Tokuno,
H. Yoshii,
N. Tajima,
N. Martinic, P. Miranda,
R. Ticona,
A. Velarde
[show abstract]
[hide abstract]
ABSTRACT: Solar neutrons were detected by the Mt. Chacaltaya neutron detector in
Bolivia (S E, 5250 m above sea
level) in association with solar flares on 1997 November 6th. A clear
signal was observed in association with a C4.7 solar flare which
occurred at about 10 minutes before the X9.4 large solar flare.
Previously, there have been no observation of solar neutrons in
association with C class solar flares. Moreover, the signal was detected
at early in the morning(7:41 Local Time). Therefore, solar neutrons
which arrive at the earth must travel through a thick atmosphere to
reach the detector because of large incident angle
(?) to the atmosphere. In the thick
atmosphere, it has been believed that solar neutrons could not arrive at
the detector if we applied the usual attenuation model. However,
calculations based on a new attenuation model for solar neutrons in the
atmosphere, which takes account of multiple and/or large scattering,
gives us a new possibility for us detecting solar neutrons under extreme
conditions.
07/2001; 8:3040.
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N Inoue,
T Kaneko,
H Yoshii,
K Hagiwara,
F Kakimoto,
Y Miyazaki,
T Enoki,
K Suga,
K Nishi,
N Martinic, P Miranda,
L Siles
[show abstract]
[hide abstract]
ABSTRACT: The longitudinal development of electrons in extensive air showers before the maximum has been studied by measuring the arrival time distributions of atmospheric Cerenkov light from air showers, with primary energies in the range 6*1015 to 2*1017 eV, in the Chacaltaya air-shower array. The Cerenkov light apparatus was the same as that operated at the Akeno air-shower array. These arrival time distributions are consistent with those calculated using a model of particle interactions which contains Feynman scaling in the fragmentation region, an E1/2 multiplicity law in the pionisation region and a rising cross section for primary protons. Such a model also reproduces the arrival time distributions of Cerenkov light measured in the Akeno air-shower array which implies a very fast development before the maximum and a slow development after the maximum. The multiplicity in this model is much higher than that given by an extrapolation of empirical formulae for multiplicities measured with accelerators up to s1/2 of 540 GeV and therefore the present result suggests a commencement of particle interactions with copious production of pi +or- and pi 0 or gamma rays above 1016 eV.
Journal of Physics G Nuclear Physics 12/1998; 11(5):669.
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[show abstract]
[hide abstract]
ABSTRACT: Energetic delayed hadrons in air showers with electron sizes in the range 10 to the 6th power to 10 to the 9th power were studied by observing the delayed bursts produced in the shield of nine square meter scintillation detectors in the Chacaltaya air-shower array. The frequency of such delayed burst is presented as a function of electron size, core distance and sec theta.
09/1985;
-
[show abstract]
[hide abstract]
ABSTRACT: Arrival directions of air showers with primary energies in the range 10 to the 16.5 power eV to 10 to the 18th power eV show the first harmonic in right ascension (RA) with amplitude of 2.7 + or - 1.0% and phase of 13-16h. However, the second harmonic in RA slightly seen for showers in the range 10 to the 18th power eV to 10 to the 19th power eV disappeared by accumulation of observed showers. The distribution of arrival directions of low-mu air showers with primary energies around 10 to the 15th power eV observed at Chacaltaya from 1962 to 1967 is referred to, relating to the above-mentioned first harmonic. Also presented in this paper are arrival directions of old-age low-mu air showers observed at Chacaltaya from 1962 to 1967, for recent interest in gamma-ray air showers.
09/1985;
-
N. Inoue,
T. Enoki,
Y. Miyazaki,
F. Kakimoto,
K. Suga,
T. Kaneko,
H. Yoshii,
K. Hagiwara,
K. Nishi,
H. Nakatani,
E. Gotoh,
N. Martinic,
M. Arellano,
J. A. Zelaya, P. Miranda,
L. Siles,
D. Veramendi
07/1983; 11:398.
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T. Kaneko,
N. Inoue,
F. Kakimoto,
K. Suga,
N. Martinic,
J. A. Zelaya, P. Miranda,
L. Siles,
D. Veramendi,
H. Yoshii,
K. Hagiwara
07/1983; 11:428.
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Y. Shirasaki,
F. Kakimoto,
S. Ogio,
N. Gironda,
M. Takeda,
T. Kaneko,
H. Yoshii,
T. Baba,
S. Sano,
K. Nishi, [......],
S. Shimoda,
H. Nakatani,
E. Gotoh,
K. Murakami,
Y. Toyoda,
Y. Matsubara,
Y. Mizumoto,
W. Velasquez,
A. Velarde, P. Miranda
[show abstract]
[hide abstract]
ABSTRACT: The chemical composition of primary cosmic rays with energies from 1015 to 1016.5 eV, so called “knee” region, is examined. We have observed the time structures of air Čerenkov light associated with air showers at Mt. Chacaltaya, Bolivia, since 1995. The distribution of a parameter that characterizes the observed time structures is compared with that calculated with a Monte Carlo technique for various chemical compositions. Then the energy dependence of the average logarithmic mass numbers
〈ln A〉 of the primary cosmic rays is determined. The present result at 1015.3 eV is almost consistent with the result of JACEE (A≃12) and shows gradual increase in
〈ln A〉 as a function of the primary energy (A≃24 at 1016 eV). Form the comparison of the observational results with several theoretical models, we conclude that the supernova explosion of massive stars is a plausible candidate for the origin of cosmic rays around the “knee” region.
Astroparticle Physics.
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K. Watanabe,
R.P. Lin,
S. Krucker,
R.J. Murphy,
G.H. Share,
M.J. Harris,
M. Gros,
Y. Muraki,
T. Sako,
Y. Matsubara, [......],
A. Hurtado,
O. Musalem, P. Miranda,
N. Martinic,
R. Ticona,
A. Velarde,
F. Kakimoto,
Y. Tsunesada,
H. Tokuno,
S. Ogio
[show abstract]
[hide abstract]
ABSTRACT: Relativistic neutrons were observed by the neutron monitors at Mt. Chacaltaya and Mexico City and by the solar neutron telescopes at Chacaltaya and Mt. Sierra Negra in association with an X17.0 flare on 2005 September 7. The neutron signal continued for more than 20 min with high statistical significance. Intense emissions of γ-rays were also registered by INTEGRAL, and during the decay phase by RHESSI. We analyzed these data using the solar-flare magnetic-loop transport and interaction model of Hua et al. [Hua, X.-M., Kozlovsky, B., Lingenfelter, R.E. et al. Angular and energy-dependent neutron emission from solar flare magnetic loops, Astrophys. J. Suppl. Ser. 140, 563–579, 2002], and found that the model could successfully fit the data with intermediate values of loop magnetic convergence and pitch-angle scattering parameters. These results indicate that solar neutrons were produced at the same time as the γ-ray line emission and that ions were continuously accelerated at the emission site.
Advances in Space Research 44(7):789-793. · 1.18 Impact Factor
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T. Kaneko,
H. Yoshii,
F. Kakimoto,
M. Teshima,
T. Umezawa,
Y. Toyoda,
K. Murakami,
M. Matsuoka,
K. Nishi,
N. Tajima,
S. Shimoda,
H. Nakatani,
Y. Yamada,
E. Gotoh,
L. Siles, P. Miranda,
W. Velasquez,
I. Poma,
I. Villca,
O. M. Villegas
2:205.
-
[show abstract]
[hide abstract]
ABSTRACT: Cosmic rays physics is currently study with rather sophisticated detectors running in a variety of either experimental conditions or atmospheric depths in the world. In this paper we present some cosmic ray physics investigations at Chacaltaya Laboratory, (Bolivia, 5220 m a.s.l.) and we describe the main properties of the observed features of high-energy nuclear interaction phenomena of cosmic rays, with particular emphasis on some experimental observations by using the emulsion chamber technique. A discussion on the past and present achievements as well as the future prospects of the high altitude mountain laboratories for cosmic ray physics as Chacaltaya is presented. .
-
-
K Watanabe,
R. P. Lin,
S. Krucker,
R. J. Murphy,
G. H. Share,
M. J. Harris,
M. Gros,
Y. Muraki,
T Sako,
Y Matsubara, [......],
A. Hurtado,
O. Musalem, P. Miranda,
N. Martinic,
R. Ticona,
A. Velarde,
F. Kakimoto,
Y. Tsunesada,
H Tokuno,
S. Ogio
Advances in Space Research, v.44, 789-793 (2009).
-
H. Tokuno,
F. Kakimoto,
S. Ogio,
D. Harada,
Y. Kurashina,
Y. Tsunesada,
N. Tajima,
Y. Matsubara,
A. Morizawa,
O. Burgoa, [......],
K. Murakami,
H. Nakatani,
K. Nishi,
S. Shimoda,
Y. Shirasaki,
Y. Toyoda,
A. Velarde,
K. Yamada,
Y. Yamada,
H. Yoshii
[show abstract]
[hide abstract]
ABSTRACT: We have measured the lateral distributions of atmospheric C˘erenkov photons associated with extensive air showers to study the chemical composition of the primary cosmic rays in the energy range from 1014.5 to 1016 eV, so called knee region. The atmospheric C˘erenkov photon detectors were installed in the EAS array at Mt. Chacaltaya. The measured lateral distributions were fitted with an empirical formula with a parameter which is sensitive to mass numbers of primary cosmic rays. A three species model (proton, carbon, and iron nuclei) is used for the chemical composition study of the present experiment. To determine the mixing ratio of the three species, the distributions of the parameter for the observed events were examined to reproduce those for the simulated ones calculated with the CORSIKA code using the QGSJET hadronic interaction model. From the obtained mixing ratio of the three species, we determined the mean logarithmic mass numbers of primary cosmic rays, 〈ln A〉, in the knee region. The present result shows that the values of 〈ln A〉 are higher than the logarithmic mass number for carbon and the proton component is no more dominant at the knee.
Astroparticle Physics.
