The CALorimetric Electron Telescope (CALET) cosmic ray detector on the International Space Station (ISS) has been in operation since its launch in 2015. The main instrument, the CALorimeter (CAL), is optimized to observe high-energy electrons up to TeV energies, but its three-storied, composite and thick detector enable us to discriminate gamma rays from overwhelming background of charged cosmic rays. Thus, it is monitoring the gamma ray sky from 1 GeV up to 10 TeV with a field of view of about 2 sr, but the exposure is somewhat non-uniform because of the limitation imposed by the inclination angle (51.6 degree) of the ISS orbit. In this paper we report results from gamma ray observations obtained during its mission for more than seven years with increased statistics compared with previous reports. They include properties of the Galactic diffuse gamma rays, spectra of bright Galactic point sources, and light curves of extragalactic active galactic nuclei, which show good consistencies with Fermi-LAT observations of which energy range overlaps with CALET.

Calorimeter (particle physics)

International Space Station

Spitzer Space Telescope

10.22323/1.444.0708

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Citations (4)

Observation of thundercloud-related gamma rays and neutrons in Tibet

Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D, Particles, fields, gravitation, and cosmology (2012)

H. Tsuchiya K. Hibino K. Kawata N. Hotta N. Tateyama

During the 2010 rainy season in Yangbajing (4300 m above sea level) in Tibet, China, a long-duration count enhancement associated with thunderclouds was detected by a solar neutron telescope and neutron monitors installed at the Yangbajing Comic Ray Observatory. The event, lasting for $\sim$40 min, was observed on July 22, 2010. The solar neutron telescope detected significant $\gamma$-ray signals with energies $>$40 MeV in the event. Such a prolonged high-energy event has never been observed in association with thunderclouds, clearly suggesting that electron acceleration lasts for 40 min in thunderclouds. In addition, Monte Carlo simulations showed that $>$10-MeV $\gamma$ rays largely contribute to the neutron monitor signals, while $>$1-keV neutrons produced via a photonuclear reaction contribute relatively less to the signals. This result suggests that enhancements of neutron monitors during thunderstorms are not necessarily a clear evidence for neutron production, as previously thought.

Neutron monitor

10.1103/physrevd.85.092006

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Citations (83)

Large-scale sidereal anisotropy of multi-TeV galactic cosmic rays and the heliosphere

arXiv (Cornell University) (2009)

M. Amenomori Xiao-Jun Bi D. Chen S. W. Cui Danzengluobu Danzengluobu

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.

Sidereal time

Heliosphere

10.48550/arxiv.0909.1026

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Citations (4)

Joint analysis of the energy spectrum of ultra-high-energy cosmic rays as measured at the Pierre Auger Observatory and the Telescope Array

Proceedings of 36th International Cosmic Ray Conference — PoS(ICRC2019) (2021)

Y. Tsunesada Rasha Abbasi T. Abu‐Zayyad Monica Allen Yuto Arai

The measurement of the energy spectrum of ultra-high-energy cosmic rays (UHECRs) is of crucial importance to clarify their origin and acceleration mechanisms. The Pierre Auger Observatory in Argentina and the Telescope Array (TA) in the US have reported their measurements of UHECR energy spectra observed in the southern and northern hemisphere, respectively. The region of the sky accessible to both Observatories ($[-15,+24]$ degrees in declination) can be used to cross-calibrate the two spectra. The Auger-TA energy spectrum working group was organized in 2012 and has been working to understand the uncertainties in energy scale in both experiments, their systematic differences, and differences in the shape of the spectra. In previous works, we reported that there was an overall agreement of the energy spectra measured by the two observatories below 10 EeV while at higher energies, a remaining significant difference was observed in the common declination band. We revisit this issue to understand its origin by examining the systematic uncertainties, statistical effects, and other possibilities. We will also discuss the differences in the spectra in different declination bands and a new feature in the spectrum recently reported by the Auger Collaboration.

Pierre Auger Observatory

Right ascension

10.22323/1.395.0337

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Citations (27)

Search for TeV transient gamma-ray sources of the northern sky using the Tibet- III air shower array

M. Sakata M. Amenomori S. Ayabe D. Chen S. W. Cui

Air shower

Shower

Transient (computer programming)

Source

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Galactic Anisotropy of ~ 10TeV Cosmic-Ray Intensity Observed by the Tibet Air Shower Array

International Cosmic Ray Conference (2003)

K. Munakata Y. Tsuchida S. Yasue C. Kato S. Mori

Air shower

Shower

Intensity

Source

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Erratum: Charge-Sign Dependent Cosmic-Ray Modulation Observed with the Calorimetric Electron Telescope on the International Space Station [Phys. Rev. Lett. 130 , 211001 (2023)]

Physical Review Letters (2023)

O. Adriani Yosui Akaike Katsuaki Asano Y. Asaoka E. Berti

Received 21 August 2023DOI:https://doi.org/10.1103/PhysRevLett.131.109902Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasCosmic ray composition & spectraCosmic ray propagationCosmic ray sourcesCosmic rays & astroparticlesGravitation, Cosmology & Astrophysics

10.1103/physrevlett.131.109902

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Study of Performance of an AS Array at Mt. Norikura for Search for Gamma-Ray Point Sources

International Cosmic Ray Conference (1990)

M. Amenomori H. Nanjo I. Ohta N. Hotta K. Mizutani

Source

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ПОИСК НЕЙТРИНО УЛЬТРАВЫСОКИХ ЭНЕРГИЙ ПО ДАННЫМ НАЗЕМНОЙ РЕШЕТКИ ЭКСПЕРИМЕНТА TELESCOPE ARRAY

Журнал Экспериментальной и Теоретической Физики (2020)

Rasha Abbasi M. Abe T. Abu‐Zayyad M. Allen R. Azuma

10.31857/s0044451020080052

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Citations (3)

Search for point sources of ultra-high-energy photons with the Telescope Array surface detector

Monthly Notices of the Royal Astronomical Society (2019)

Rasha Abbasi Mitsuru Abe T. Abu‐Zayyad M. Allen R. Azuma

The surface detector (SD) of the Telescope Array (TA) experiment allows one to indirectly detect photons with energies of order $10^{18}$ eV and higher and to separate photons from the cosmic-ray background. In this paper we present the results of a blind search for point sources of ultra-high energy (UHE) photons in the Northern sky using the TA SD data. The photon-induced extensive air showers (EAS) are separated from the hadron-induced EAS background by means of a multivariate classifier based upon 16 parameters that characterize the air shower events. No significant evidence for the photon point sources is found. The upper limits are set on the flux of photons from each particular direction in the sky within the TA field of view, according to the experiment's angular resolution for photons. Average 95% C.L. upper limits for the point-source flux of photons with energies greater than $10^{18}$, $10^{18.5}$, $10^{19}$, $10^{19.5}$ and $10^{20}$ eV are $0.094$, $0.029$, $0.010$, $0.0073$ and $0.0058$ km$^{-2}$yr$^{-1}$ respectively. For the energies higher than $10^{18.5}$ eV, the photon point-source limits are set for the first time. Numerical results for each given direction in each energy range are provided as a supplement to this paper.

Air shower

Point source

10.1093/mnras/stz3618

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Citations (9)