Search

The Short GAmma Ray Front Air-Cherenkov Experiment (SGARFACE) uses the Whipple 10 m telescope to search for bursts of gamma rays. Bursts can be detected on time scales from a few ns to 20 !s and with gamma-ray energy above 100 MeV. SGARFACE began operating in March 2003 and has acquired 2.2 million events since. A search for explosions of primordial black holes (PBH) was carried out using the recorded time-resolved images. No unambiguous burst detection could be made due to background events produced by cosmic rays. Upper limits on the PBH explosion rare are presented and compared to other experiments. [ABSTRACT FROM AUTHOR]

Next generation ground based γ-ray observatories such as AGIS1 and CTA2 are expected to cover a 1 km2 area with 50–100 imaging atmospheric Cherenkov telescopes. The stereoscopic view ol air showers using multiple view points raises the possibility to use a topological array trigger that adds substantial flexibility, new background suppression capabilities and a reduced energy threshold. In this paper we report on the concept and technical implementation of a fast topological trigger system, that makes use of real time image processing of individual camera patterns and their combination in a stereoscopic array analysis. A prototype system is currently under construction and we discuss the design and hardware of this topological array trigger system. [ABSTRACT FROM AUTHOR]

The Very Energetic Radiation Imaging Telescope Array System (VERI-TAS) is a wide energy range (50 GeV–50 TeV) atmospheric Cherenkov detector and will start operation in 2004. The design is driven by a major scientific interest in jets of active galactic nuclei, probing the intergalactic IR fields with TeV γ-ray beams, measuring the high energy spectrum of γ-ray bursts and galactic sources of cosmic rays. Also γ-rays signatures of quantum gravity, neutralinos and primordial black holes constitute the exotic scientific motivations to built a highly versatile detector that can be operated in various modes. The technical concept and design of the seven-telescope array system is described. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The Advanced Gamma-ray Imaging System (AGIS), a future gamma-ray telescope consisting of an array of ∼50 atmospheric Cherenkov telescopes distributed over an area of ∼1 km2, will provide a powerful new tool for exploring the high-energy universe. The order-of-magnitude increase in sensitivity and improved angular resolution could provide the first detailed images of γ-ray emission from other nearby galaxies or galaxy clusters. The large effective area will provide unprecedented sensitivity to short transients (such as flares from AGNs and GRBs) probing both intrinsic spectral variability (revealing the details of the acceleration mechanism and geometry) as well as constraining the high-energy dispersion in the velocity of light (probing the structure of spacetime and Lorentz invariance). A wide field of view (∼4 times that of current instruments) and excellent angular resolution (several times better than current instruments) will allow for an unprecedented survey of the Galactic plane, providing a deep unobscured survey of SNRs, X-ray binaries, pulsar-wind nebulae, molecular cloud complexes and other sources. The differential flux sensitivity of ∼10-13 erg cm-2 sec-1 will rival the most sensitive X-ray instruments for these extended Galactic sources. The excellent capabilities of AGIS at energies below 100 GeV will provide sensitivity to AGN and GRBs out to cosmological redshifts, increasing the number of AGNs detected at high energies from about 20 to more than 100, permitting population studies that will provide valuable insights into both a unified model for AGN and a detailed measurement of the effects of intergalactic absorption from the diffuse extragalactic background light. A new instrument with fast-slewing wide-field telescopes could provide detections of a number of long-duration GRBs providing important physical constraints from this new spectral component. The new array will also have excellent background rejection and very large effective area, providing the very high sensitivity needed to detect emission from dark matter annihilation in Galactic substructure or nearby Dwarf spheroidal galaxies. [ABSTRACT FROM AUTHOR]

We report on a periodicity analysis of γ-ray observations of very high energy (VHE, E>250 GeV) γ-rays from Markarian 501 (Mrk 501) taken with the Whipple telescope between March and July of 1997. The data correspond to a period of bright flaring of the source, quasi-periodic signals were detected by the Telescope Array Project (TAP) and HEGRA collaboration. Periodic analysis of these data is complicated because the source observations are not continuous and the reported period (approx. 24 days) is very close to the sampling period. We use the Lomb method, a technique for extracting spectral information from unevenly sampled data, in an attempt to overcome this difficulty. Similar results are shown to exist in data from the strongly correlated X-ray band sampled by the RXTE ASM instrument. No periodicity in the data could be identified with a source frequency. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The Whipple Collaboration has been carrying out an upgrade program, GRANITE III, on the 10m telescope atop Mt. Hopkins. The 3 year program, 1996 through 1999, has involved a large field-of-view camera, a hardware pattern recognition trigger, and finally a small pixel camera. Results of the first and second stage of the program indicate that a large field-of-view yield an increased collection area for cosmic-ray triggers and the hardware pattern trigger reduces the energy threshold of the telescope by greatly suppressing night sky accidental triggers over a simple multiplicity coincidence trigger. The final phase of the program, being completed during the summer and fall of 1999, will be the installation of a small pixel camera. The pixel size of ∼0°.12 will yield the lowest threshold energy at which the 10 m Whipple telescope has ever operated. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

An overview of the current status and scientific goals of VERITAS, a proposed hexagonal array of seven 10 m aperture imaging Cherenkov telescopes, is provided. The selected site is close to Mt. Hopkins, the site of the Whipple Observatory, in Arizona. Each telescope, of 12 m focal length, will be equipped with a 499 element photomultiplier camera covering a 3.5 degree field of view. A central station will initiate the readout of 500 MHz FADCs upon receipt of multiple telescope triggers. The minimum detectable flux sensitivity will be 0.5% of the Crab Nebula flux at 200 GeV. VERITAS will operate primarily as a γ-ray observatory in the 50 GeV to 50 TeV range for the study of active galaxies, supernova remnants, pulsars and gamma-ray bursts. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]