Search for γ rays above 1014 eV from Cygnus X-3 during the June and July 1989 radio outbursts

Journal ArticleWe have looked for γ-ray emission above 100 TeV from the binary x-ray source Cygnus X-3 during a period of intense radio emission in the summer of 1989. We find no evidence for excess air showers from the direction of the source and the muon content of air showers from this direction is the same as that of ordinary cosmic rays. The flux of γ rays from Cygnus X-3 with energies exceeding 2.1x10^14 eV is < 5.5x10^-13 cm-1 sec-1 (90% C.L.)

Search for > 200 TeV photons from Cygnus X-3 in 1988 and 1989

Journal ArticleOver a period of 16 months from April 1988 to August 1989, we have monitored the flux of cosmic-ray showers with energies above 2X 101 4 eV. We used a two-level array of scintillators covering an area of 3 X 104 m2. Counters on the surface measure the size and direction of each shower while counters buried 3 m beneath the surface sample the muons

Science capabilities of the VERITAS array of 10m imaging atmospheric Cherenkov gamma-ray detectors

Journal ArticleThe Very Energetic Radiation Imaging Telescope Array System (VERITAS) is an array of seven 10m aperture telescopes used for gamma-ray astronomy in the 50 GeV to 50 TeV (1 TeV= 101 2 electron Volt) energy range. The gamma rays are detected by measuring the optical Cherenkov light emitted by the cascade of electromagnetic particles that is generated by interactions of the high energy gamma-ray with the Earth's Atmosphere. This paper describes the science goals of the VERITAS array, a description of the array, and expected performance of the instrument

Evidence for correlated changes in the spectrum and composition of cosmic rays at extremely high energies

Journal ArticleThe Utah Fly's Eye detector has revealed a change in the cosmic ray composition which is correlated with structure in the all-particle energy spectrum. The data can be fitted by a simple model of a steep power law spectrum of heavy nuclei which is overtaken at high energies by a flatter spectrum of protons. The transition occurs near 10^18.5 eV. Anisotropy is not detected, so the high-rigidity particles above the transition energy do not originate in the disk of the Galaxy. An outstanding event of 3x10^20 eV implies that the highest energy particles originate in the contemporary era of the Universe

Search for compact sources of cosmic photons above 200 TeV

Journal ArticleFrom April 1988 to February 1990 we used a two-level array of scintillators to search in the cosmic radiation for compact sources of y rays above 200 TeV. Counters on the surface measured the size and direction of extensive air showers while counters buried 3 m below ground measured their muon content. Showers induced by y rays are expected to have many fewer muons than those initiated by hadrons so the selection of muon-poor showers should greatly reduce the background of hadronic showers

Prototype 9.7 m Schwarzschild-Couder telescope for the Cherenkov Telescope Array: status of the optical system

The Cherenkov Telescope Array (CTA) is an international project for a next-generation ground-based gamma ray observatory, aiming to improve on the sensitivity of current-generation experiments by an order of magnitude and provide energy coverage from 30 GeV to more than 300 TeV. The 9.7m Schwarzschild-Couder (SC) candidate medium-size telescope for CTA exploits a novel aplanatic two-mirror optical design that provides a large field of view of 8 degrees and substantially improves the off-axis performance giving better angular resolution across all of the field of view with respect to single-mirror telescopes. The realization of the SC optical design implies the challenging production of large aspherical mirrors accompanied by a submillimeter-precision custom alignment system. In this contribution we report on the status of the implementation of the optical system on a prototype 9.7 m SC telescope located at the Fred Lawrence Whipple Observatory in southern Arizona.Comment: Proceedings of the 35th International Cosmic Ray Conference (ICRC 2017), Busan, Korea. All CTA contributions at arXiv:1709.0348