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The Telescope Array (TA) is an experiment to observe Ultra-High Energy Cosmic Rays (UHECRs). TA's recent results, the energy spectrum and anisotropy based on the 6-year surface array data, and the primary composition obtained from the…
Very high-energy gamma-ray measurements of distant blazars can be well explained by secondary gamma rays emitted by cascades induced by ultra-high-energy cosmic rays. The secondary gamma rays will enable one to detect a large number of…
We compare two observations of gamma-rays before, during, and after lightning flashes initiated by upward leaders from a tower during low-altitude winter thunderstorms on the western coast of Honshu, Japan. While the two leaders appear…
We present a systematic search for short-duration gamma-ray bursts (GRBs) in the local Universe based on 14 years of observations with the Neil Gehrels Swift Observatory. We cross-correlate the GRB positions with the GLADE catalogue of…
Gamma-ray bursts have been detected at photon energies up to tens of GeV. We review some recent developments in the X-ray to GeV photon phenomenology in the light of Swift and Fermi observations, and some of the theoretical models developed…
The Large Area Telescope on board the Fermi satellite observed a gamma-ray flare in the Crab nebula lasting for approximately nine days in April of 2011. The source, which at optical wavelengths has a size of ~11 ly across, doubled its…
Tau Air-showers are the best trace of rarest Ultra High Energy neutrinos UHE $\nu_{\tau}$, $\bar\nu_{\tau}$ and $\bar{\nu}_e$ at PeV and higher energy. $\tau$ Air-showers may generate billion times amplified signals by their secondaries .…
Gamma-ray bursts of short duration may harbor vital clues to the range of phenomena producing bursts. However, recent progress from the observation of optical counterparts has not benefitted the study of short bursts. We have searched for…
The multi-messenger observation of gamma-ray burst (GRB)\,170817A from the nearby binary neutron-star merger GW170817 demonstrated that low-energy $\gamma$-ray emission can be observed at relatively large angles from GRB jet axes. If such…
A search for gamma-ray bursts (GRBs) above 20 TeV within the field of view (1 sr) of the HEGRA AIROBICC Cherenkov array (29N, 18W, 2200 m a.s.l.) has been performed using data taken between March 1992 and March 1993. The search is based on…
Over the past decade, our knowledge of the \gamma-ray sky has been revolutionized by ground- and space-based observatories by detecting photons up to several hundreds of tera-electron volt (TeV) energies. A major population of the…
After seven years of science operation, the Fermi mission has brought great advances in the study of Gamma-ray Bursts (GRBs). Over 1600 GRBs have been detected by the Gamma-ray Burst Monitor, and more than 100 of these are also detected by…
Two scenarios have been proposed to account for sustained $\ge 30$\,MeV gamma-ray emission in solar flares: (1) prolonged particle acceleration/trapping involving large-scale magnetic loops at the flare site, and (2) precipitation of…
Gamma-ray Bursts (GRB) were discovered by satellite-based detectors as powerful sources of transient $\gamma$-ray emission. The Fermi satellite detected an increasing number of these events with its dedicated Gamma-ray Burst Monitor (GBM),…
Gamma-Flash is an Italian project funded by the Italian Space Agency (ASI) and led by the National Institute for Astrophysics (INAF), devoted to the observation and study of high-energy phenomena, such as terrestrial gamma-ray flashes and…
Ultra high energy neutrinos UHE neutrino Tau, anti-neutrino Tau, anti-neutrino electron at PeVs, and higher energy may induce tau air-showers whose detectability is million to billion times amplified by their secondaries. We considered UHE…
Some gamma-ray bursts (GRBs) have an afterglow in the tera-electronvolt (TeV) band, but the early onset of this afterglow has not been observed. We report observations with the Large High Altitude Air Shower Observatory of the bright GRB…
The Milagrito water Cherenkov telescope operated for over a year. The most probable gamma-ray energy was ~1 TeV and the trigger rate was as high as 400 Hz. We have developed an efficient technique for searching the entire sky for short…
Gamma ray bursts (GRBs) are astronomical phenomena detected at highest energies. The gamma ray photons carry energies on the order of mega-electronovolts and arrive to us from the point-like sources that are uniformly distributed on the…
Gamma-ray bursts (GRBs) divide into two classes: "long", which typically have initial durations of T90>2s, and "short", with durations of T90<2s (where T90 is the time to detect 90% of the observed fluence). Long bursts, which on average…