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Astron. Astrophys. 354, L57-L61 (2000)

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2. Instrument and observation

The CANGAROO 3.8m imaging TeV gamma-ray telescope is located near Woomera, South Australia (136o47'E, 31o06'S) (Hara et al. 1993). A high resolution camera of 256 photomultiplier tubes (Hamamatsu R2248) is installed in the focal plane. The field of view of each tube is about 0o.12 [FORMULA] 0o.12, and the total field of view (FOV) of the camera is about 3o. The pointing accuracy of the telescope is [FORMULA], determined from a study of the trajectories of stars of magnitude 5 to 6 in the FOV. RX J1713.7-3946 was observed in May, June and August in 1998. During on-source observations, the center of the FOV tracked the NW rim (right ascension [FORMULA], declination [FORMULA] (J2000)), which is the brightest point in the remnant in hard X-rays (Koyama et al. 1997). An off-source region having the same declination as the on-source but a different right ascension was observed before or after the on-source observation for equal amounts of time each night under moonless and usually clear sky conditions. The total observation time was 66 hours for on-source data and 64 hours for off-source data. After rejecting data affected by clouds, a total of 47.1305 hours for on-source data and 45.8778 hours for off-source data remained for this analysis.

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© European Southern Observatory (ESO) 2000

Online publication: January 31, 2000