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Over the past eight years, observations of BL Lacertae type objects have been an important part of the observing program at the Whipple Observatory 10 m γ-ray telescope. During this time, TeV emission was detected from five such objects: Markarian 421, Markarian 501, 1ES2344+514, H1426+428 and 1ES1959+650. Upper limits were placed on the TeV emission from 29 other BL Lacertae objects. Among these objects are two unconfirmed TeV sources, 3C66A and BL Lacertae. An overview of the results of these observations of BL Lacertae objects, between 1995 and 2000, at the Whipple Observatory is presented here. [Copyright &y& Elsevier]

Abstract: We describe a dedicated cosmic-ray telescope that explores a new method for detecting Cherenkov radiation from high-energy primary cosmic rays and the large particle air shower they induce upon entering the atmosphere. Using a camera comprising 16 multi-anode photomultiplier tubes for a total of 256 pixels, the Track Imaging Cherenkov Experiment (TrICE) resolves substructures in particle air showers with 0.086° resolution. Cherenkov radiation is imaged using a novel two-part optical system in which a Fresnel lens provides a wide-field optical trigger and a mirror system collects delayed light with four times the magnification. TrICE records well-resolved cosmic-ray air showers at rates ranging between 0.01Hz and 0.1Hz. [Copyright &y& Elsevier]

Abstract: The short gamma-ray front air-cherenkov experiment (SGARFACE) uses the Whipple 10m telescope to search for bursts of γ-rays. SGARFACE is sensitive to bursts with duration from a few ns to ∼20μs and with γ-ray energy above 100MeV. SGARFACE began operating in March 2003 and has collected 2.2 million events during an exposure time of 2267h. A search for bursts of γ-rays from explosions of primordial black holes (PBH) was carried out. A Hagedorn-type PBH explosion is predicted to be visible within 60pc of Earth. Background events were caused by cosmic rays and by atmospheric phenomena and their rejection was accomplished to a large extent using the time-resolved images. No unambiguous detection of bursts of γ-rays could be made as the remaining background events mimic the expected shape and time-development of bursts. Upper limits on the PBH explosion rate were derived from the SGARFACE data and are compared to previous and future experiments. We note that a future array of large wide-field air-Cherenkov telescopes equipped with a SGARFACE-like trigger would be able to operate background-free with a 20–30 times higher sensitivity for PBH explosions. [Copyright &y& Elsevier]