Leipzig 2002 – wissenschaftliches Programm

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T: Teilchenphysik

T 301: Kosmische Strahlung III

T 301.2: Vortrag

Dienstag, 19. März 2002, 14:45–15:00, HS 19

Very high-energy γ-ray observations of the Crab nebula and other sources with the GRAAL experiment — •Maria Diaz Trigo¹, F. Arqueros², J. Ballestrin³, D. M. Borque², R. Enriquez², H.-J. Gebauer¹, and R. Plaga¹ — ¹Max Planck Institut fuer Physik, D-80805 Muenchen, Germany — ²Facultad de Ciencias Fisicas, Universidad Complutense, E-28040, Madrid, Spain — ³CIEMAT- Departamento de Energias Renovables, Plataforma Solar de Almeria, E-04080, Almeria, Spain

The “Gamma Ray Astronomy at ALmería” (GRAAL) experiment uses 63 heliostat-mirrors with a total mirror area of ≈ 2500 m² from the CESA-1 field to collect Cherenkov light from airshowers. The detector is located in a central solar tower and detects photon-induced showers with an energy threshold of 250 ± 110 GeV and an asymptotic effective detection area of about 15000 m².

Data sets taken in the period September 1999-March 2001 in the direction of the Crab pulsar and other candidates for γ-ray sources were analysed for high-energy γ-ray emission. Evidence for γ-ray flux from the Crab pulsar with a significance of 4.5 σ in a total (usable) observing time of 7 hours and 10 minutes on source was found.

The effect of field-of-view restricted to the central part of a detected airshower on the lateral distribution and timing properties of Cherenkov light and their effect on an efficient γ-hadron separation are discussed.