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Gamma-ray Burst (GRB) observations at Very High Energies (VHE, E > 100 GeV) can impose tight constraints on some GRB emission models. Many GRB after-glow models predict a VHE component similar to that seen in blazars and supernova remnants, in which the GRB spectral energy distribution has a double-peaked shape extending into the VHE regime. Consistent with this afterglow scenario, EGRET detected delayed high energy emission from all five bright BATSE GRBs that occurred within its field of view. GRB observations have had high priority in the observing program at the Whipple 10m Telescope and will continue to be high priority targets when the next generation observatory VERITAS comes online. Upper limits on the VHE emission from ten GRBs observed with the Whipple Telescope are reported here. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

The Advanced Gamma-Ray Imaging System (AGIS) is a concept for the next generation observatory in ground-based very high energy gamma-ray astronomy. Design goals are ten times better sensitivity, higher angular resolution, and a lower energy threshold than existing Cherenkov telescopes. Simulations show that a substantial improvement in angular resolution may be achieved if the pixel diameter is reduced to the order of 0.05 deg, i.e. two to three times smaller than the pixel diameter of current Cherenkov telescope cameras. At these dimensions, photon detectors with smaller physical dimensions can be attractive alternatives to the classical photomultiplier tube (PMT). Furthermore, the operation of an experiment with the size of AGIS requires photon detectors that are among other things more reliable, more durable, and possibly higher efficiency photon detectors. Alternative photon detectors we are considering for AGIS include both silicon photomultipliers (SiPMs) and multi-anode photomultipliers (MAPMTs). Here we present results from laboratory testing of MAPMTs and SiPMs along with results from the first incorporation of these devices into cameras on test bed Cherenkov telescopes. [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]