M. Ohnishi
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View article: A Simulation Study on the Cosmic-Ray Energy Spectra of Elemental Mass Groups using the Tibet Air-Shower and Muon Detector Arrays through the Bayesian Unfolding Method
A Simulation Study on the Cosmic-Ray Energy Spectra of Elemental Mass Groups using the Tibet Air-Shower and Muon Detector Arrays through the Bayesian Unfolding Method Open
We study the analysis method to determine the cosmic-ray energy spectra of different mass groups assuming the use of the Tibet AS$\gamma$ experiment, which consists of the high-density Tibet air-shower array and the underground muon detect…
View article: Are Kronberger 80 and/or Kronberger 82 regions PeVatron candidates for LHAASO J2108+5157?
Are Kronberger 80 and/or Kronberger 82 regions PeVatron candidates for LHAASO J2108+5157? Open
High-energy gamma-rays have been detected in the region of LHAASO J2108+5157 by the Fermi–LAT, HAWC and LHAASO-KM2A observatories. Cygnus OB2 in Cygnus-X has been confirmed as the first strong stellar cluster PeVatron in our Galaxy. Thus, …
View article: ALPACA project to observe sub-PeV gamma-ray sky in the southern hemisphere
ALPACA project to observe sub-PeV gamma-ray sky in the southern hemisphere Open
Though the maximum energy of the charged cosmic ray observations exceeds 100 EeV, the energy frontier of the gamma-ray observations is PeV. In the past years, Tibet AS𝛾, HAWC and LHAASO opened a new window of astronomy in the sub-PeV to Pe…
View article: $$\gamma $$/hadron discrimination by analysis of the muon lateral distribution and the ALPAQUITA array
$$\gamma $$/hadron discrimination by analysis of the muon lateral distribution and the ALPAQUITA array Open
A new method using the muon lateral distribution and an underground muon detector to achieve high discrimination power against hadrons is presented. The method is designed to be applied in the Andes Large-area PArticle detector for Cosmic-…
View article: Intermediate Fluence Downward Terrestrial Gamma Ray Flashes as Observed by the Telescope Array Surface Detector
Intermediate Fluence Downward Terrestrial Gamma Ray Flashes as Observed by the Telescope Array Surface Detector Open
On 11 September 2021, two small thunderstorms developed over the Telescope Array Surface Detector (TASD) that produced an unprecedented number of six downward terrestrial gamma ray flashes (TGFs) within one‐hour timeframe. The TGFs occurre…
View article: Quantitative Constraint on the Contribution of Resolved Gamma-Ray Sources to the Sub-PeV Galactic Diffuse Gamma-Ray Flux Measured by the Tibet ASγ Experiment
Quantitative Constraint on the Contribution of Resolved Gamma-Ray Sources to the Sub-PeV Galactic Diffuse Gamma-Ray Flux Measured by the Tibet ASγ Experiment Open
Motivated by the difference between the fluxes of sub-PeV Galactic diffuse gamma-ray emission (GDE) measured by the Tibet AS γ experiment and the LHAASO collaboration, our study constrains the contribution to the GDE flux measured by Tibet…
View article: Neural networks for separation of cosmic gamma rays and hadronic cosmic rays in air shower observation with a large area surface detector array
Neural networks for separation of cosmic gamma rays and hadronic cosmic rays in air shower observation with a large area surface detector array Open
The Tibet AS γ experiment has been observing cosmic gamma rays and cosmic rays in the energy range from teraelectron volts to several tens of petaelectron volts with a surface detector array since 1990. The derivation of cosmic gamma-ray f…
View article: Modeling of TeV Galactic Cosmic-ray Anisotropy based on Intensity Mapping in an MHD Model Heliosphere
Modeling of TeV Galactic Cosmic-ray Anisotropy based on Intensity Mapping in an MHD Model Heliosphere Open
Cosmic rays do not arrive at the Earth uniformly. Recent experiments have consistently observed small anisotropies with amplitudes of ∼0.2% in the arrival directions of cosmic rays at TeV energies. We perform the modeling of the cosmic-ray…
View article: On the source contribution to the Galactic diffuse gamma rays above 398 TeV detected by the Tibet ASγ experiment
On the source contribution to the Galactic diffuse gamma rays above 398 TeV detected by the Tibet ASγ experiment Open
Potential contribution from gamma-ray sources to the Galactic diffuse gamma rays observed above 100 TeV (sub-PeV energy range) by the Tibet ASγ experiment is an important key to interpreting recent multi-messenger observations. This paper …
View article: On the Source Contribution to the Galactic Diffuse Gamma Rays above 398 TeV Detected by the Tibet ASγ Experiment
On the Source Contribution to the Galactic Diffuse Gamma Rays above 398 TeV Detected by the Tibet ASγ Experiment Open
Potential contribution from gamma-ray sources to the Galactic diffuse gamma rays observed above 100 TeV (sub-PeV energy range) by the Tibet AS γ experiment is an important key to interpreting recent multimessenger observations. This paper …
View article: Nobeyama Cygnus-X Survey: Physical Properties of C$^{18}$O clumps in DR-6(W), DR-9 and DR-13S regions
Nobeyama Cygnus-X Survey: Physical Properties of C$^{18}$O clumps in DR-6(W), DR-9 and DR-13S regions Open
Cygnus-X is considered a region of interest for high-energy astrophysics, since the Cygnus OB2 association has been confirmed as a PeVatron in the Cygnus cocoon. In this research note, we present new high-resolution (16'') $^{12,13}$CO(J=1…
View article: Quantitative constraint on the source contribution to the Galactic diffuse gamma rays detected by the Tibet air shower array
Quantitative constraint on the source contribution to the Galactic diffuse gamma rays detected by the Tibet air shower array Open
The fraction of the contribution from yet-unresolved gamma-ray sources in the Galactic diffuse gamma rays observed by the Tibet air shower array is an important key to interpreting recent multi-messenger observations. This paper shows a su…
View article: Observation of Gamma Rays up to 320 TeV from the Middle-aged TeV Pulsar Wind Nebula HESS J1849−000
Observation of Gamma Rays up to 320 TeV from the Middle-aged TeV Pulsar Wind Nebula HESS J1849−000 Open
Gamma rays from HESS J1849−000, a middle-aged TeV pulsar wind nebula (PWN), are observed by the Tibet air shower array and the muon detector array. The detection significance of gamma rays reaches 4.0 σ and 4.4 σ levels above 25 TeV and 10…
View article: Nobeyama Cygnus-X Survey: Physical Properties of C$^{18}$O clumps in DR-6W, DR-9 and DR-13S regions
Nobeyama Cygnus-X Survey: Physical Properties of C$^{18}$O clumps in DR-6W, DR-9 and DR-13S regions Open
Cygnus-X is considered a region of interest for high-energy astrophysics, since the Cygnus OB2 association has been confirmed as a PeVatron in the Cygnus cocoon. In this research note, we present new high-resolution (16'') $^{12,13}$CO(J=1…
View article: Observation of gamma rays from the northern celestial sky up to the sub-PeV range with the Tibet air shower array and its underground muon detector array
Observation of gamma rays from the northern celestial sky up to the sub-PeV range with the Tibet air shower array and its underground muon detector array Open
Gamma-ray observation in the sub-PeV range helps us search for Galactic PeV cosmic-ray accelerators, PeVatrons. Measurement of the energy spectrum of gamma rays from astrophysical sources is especially crucial to discuss their hadronic or …
View article: Versatile Trigger Time Recording System for Air Shower Array
Versatile Trigger Time Recording System for Air Shower Array Open
In the energy region above TeV, many experimental groups use surface air shower arrays to observe cosmic gamma rays. These experiments require accurate trigger time measurement systems to observe abrupt cosmic phenomena. Therefore, we have…
View article: Study of water Cherenkov detector designs to determine air shower arrival direction with accuracy
Study of water Cherenkov detector designs to determine air shower arrival direction with accuracy Open
In recent years, a few groups have reported detections of gamma rays in the 100 TeV region from astronomical objects in the Galaxy using extensive air shower arrays. These observations have certainly taken a newstep in researching cosmic-r…
View article: First High‐Speed Video Camera Observations of a Lightning Flash Associated With a Downward Terrestrial Gamma‐Ray Flash
First High‐Speed Video Camera Observations of a Lightning Flash Associated With a Downward Terrestrial Gamma‐Ray Flash Open
In this paper, we present the first high‐speed video observation of a cloud‐to‐ground lightning flash and its associated downward‐directed Terrestrial Gamma‐ray Flash (TGF). The optical emission of the event was observed by a high‐speed vi…
View article: Evidence for a gamma-ray molecular target in the enigmatic PeVatron candidate LHAASO J2108+5157
Evidence for a gamma-ray molecular target in the enigmatic PeVatron candidate LHAASO J2108+5157 Open
Context. Peta-eV (PeV) astronomy emerged in 2021 with the discovery of ultra-high-energy gamma-ray sources associated with powerful natural particle accelerators known as PeVatrons. In order to determine the nature of their emission, namel…
View article: Evidence for a gamma-ray molecular target in the enigmatic PeVatron candidate LHAASO J2108+5157
Evidence for a gamma-ray molecular target in the enigmatic PeVatron candidate LHAASO J2108+5157 Open
To determine the nature of the PeVatron's emission (hadronic or leptonic), it is essential to characterize the physical parameters of the environment from where it originates. We unambiguously confirm the association of molecular gas with …
View article: Detection of a new molecular cloud in the LHAASO J2108+5157 region supporting a hadronic PeVatron scenario
Detection of a new molecular cloud in the LHAASO J2108+5157 region supporting a hadronic PeVatron scenario Open
PeVatrons are the most powerful naturally occurring particle accelerators in the Universe. The identification of counterparts associated to astrophysical objects such as dying massive stars, molecular gas, star-forming regions, and star cl…
View article: Detection of a new molecular cloud in the LHAASO J2108+5157 region supporting a hadronic PeVatron scenario
Detection of a new molecular cloud in the LHAASO J2108+5157 region supporting a hadronic PeVatron scenario Open
PeVatrons are the most powerful naturally occurring particle accelerators in the Universe. The identification of counterparts associated to astrophysical objects such as dying massive stars, molecular gas, star-forming regions, and star cl…
View article: ALPACA experiment: A new air shower array to explore the sub-PeV gamma-ray sky in the southern hemisphere
ALPACA experiment: A new air shower array to explore the sub-PeV gamma-ray sky in the southern hemisphere Open
In the last few years, gamma-ray astronomy opens a new window in the sub-PeV to PeV range inaugurated by the Tibet AS𝛾 collaboration followed by the HAWC and LHAASO collaborations. The successful three experiments are located in the northe…
View article: Sensitivity of the large muon detector with the Tibet air-shower array to measure the primary proton spectrum between 40 and 630 TeV
Sensitivity of the large muon detector with the Tibet air-shower array to measure the primary proton spectrum between 40 and 630 TeV Open
The Tibet ASγ group has been continuously observing cosmic rays and cosmic gamma rays above several TeV using the muon detector array (MD) and high-density Tibet air-shower array (Tibet-III) installed on the Tibet plateau at an altitude of…
View article: Hadronic Interaction Model Dependence in Cosmic Gamma-ray Flux Estimation Using an Extensive Air Shower Array with a Muon Detector
Hadronic Interaction Model Dependence in Cosmic Gamma-ray Flux Estimation Using an Extensive Air Shower Array with a Muon Detector Open
Observation techniques of high-energy gamma rays using air showers have remarkably progressed via the Tibet AS$\gamma$, HAWC, and LHAASO experiments. These observations have significantly contributed to gamma-ray astronomy in the northern …
View article: Measurement of the Gamma-Ray Energy Spectrum beyond 100 TeV from the HESS J1843–033 Region
Measurement of the Gamma-Ray Energy Spectrum beyond 100 TeV from the HESS J1843–033 Region Open
HESS J1843–033 is a very high energy gamma-ray source whose origin remains unidentified. This work presents, for the first time, the energy spectrum of gamma rays beyond 100 TeV from the HESS J1843–033 region using the data recorded by the…
View article: First High-speed Video Camera Observations of a Lightning Flash Associated with a Downward Terrestrial Gamma-ray Flash
First High-speed Video Camera Observations of a Lightning Flash Associated with a Downward Terrestrial Gamma-ray Flash Open
In this paper, we present the first high-speed video observation of a cloud-to-ground lightning flash and its associated downward-directed Terrestrial Gamma-ray Flash (TGF). The optical emission of the event was observed by a high-speed vi…
View article: Observation of variations in cosmic ray single count rates during thunderstorms and implications for large-scale electric field changes
Observation of variations in cosmic ray single count rates during thunderstorms and implications for large-scale electric field changes Open
We present the first observation by the Telescope Array Surface Detector (TASD) of the effect of thunderstorms on the development of cosmic ray single count rate intensity over a 700 km2 area. Observations of variations in the secondary lo…