アイテム詳細

要旨

Locating TeV sources with H.E.S.S. with sub-arcminute precision Gamma-ray experiments using the imaging atmospheric Cherenkov technique have a relatively modest angular resolution of typically 0.05 to 0.1 per event. The centroid of a point-source emitter, however, can be determined with much higher precision, down to a few arcseconds for strong sources. For H.E.S.S. it is therefore desirable to lower the systematic pointing error to the same level. It is not necessary to actively control the telescope pointing to the same accuracy, as one can correct the pointing o ine. In this thesis it is demonstrated that one can achieve the desired arcsecondlevel pointing precision by a two step procedure: a mechanical pointing model is used to predict pointing deviations, and a ne correction is derived using stars observed in a guide telescope equipped with a CCD camera. Before applying the pointing corrections adequate systematic errors are determined. For the data of 2003 the achieved accuracy is in the range of 10" to 20". Finally positions of three sources are investigated: A.) The AGN PKS 2155-304 serves as an ultimate pointing check as it is a point source with a precisely known position. B.) The Crab nebula position is compared to the expectations from X-ray data. C.) The TeV signal from the galactic centre region is shown to originate more likely from Sgr A* than from Sgr A East.