Background-sensitive event selection in the search for gamma-ray sources
Abstract
Poor angular resolution of present day gamma ray telescopes (1° at 100 MEV) together with the complicated gamma ray sky structures at compareable angular extents and poor statistics available necessitate the selection of those gammas which will increase the observable signal from a suspected source. A method for such a selection using the pre-known time signature of the source as its signal, has been developed (Özel and Mayer-Haβelwander, 1983). In an iterative procedure based on the improvement of source signal, generalized zones around the source are defined, from which gamma rays should be accepted to construct the optimum light curve of the source. These zones depend on the energy of the probed gamma rays, on the spatial structure and intensity of the background around the source, on the (estimated and/or tentative) intetnsity of the source and finally on the observing instrument's angular and energy response functions. The method, when applied to simulated and observed COS-B data demonstrated its feasibility and merits over the previonsly used circular event-acceptance cones method which was the basis of searches for gamma ray emission from radio pulsars (see for example Kniffen et al., 1974; Ögelman, et al. 1976; Kanbach, et al., 1977; and references therein). Present method does not introduce ``trials'' which usually reduce the significance of the results obtained, fully accounts the available knowledge on the topography of gamma ray sky, makes use of all the information about the sky, source and the instrument and therefore is the proper way of handling gamma ray data in pulsar-type searches.
Presently, method is applied in the analyses of COS-B data in the context of searches for gamma ray emitting X-ray and radio pulsars. Results will be published elsewhere.- Publication:
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Advances in Space Research
- Pub Date:
- 1984
- DOI:
- 10.1016/0273-1177(84)90070-X
- Bibcode:
- 1984AdSpR...3j..95O
- Keywords:
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- gamma ray radiation;
- gamma ray sources;
- data analysis