The INTEGRAL / IBIS Scientific Data Analysis ?

The gamma-ray astronomical observatory INTEGRAL, succesfully launched on 17 th October 2002, carries two large gamma-ray telescopes. One of them is the coded-mask imaging gamma-ray telescope onboard the INTEGRAL satellite (IBIS) which provides high-resolution (≈ 12 ′) sky images of 29 • × 29 • in the energy range from 15 keV to 10 MeV with typical on-axis sensitivity of ≈ 1 mCrab at 100 keV (3σ, 10 6 s exposure). We report here the general description of the IBIS coded-mask imaging system and of the standard IBIS science data analysis procedures. These procedures reconstruct, clean and combine IBIS sky images providing at the same time detection, identification and preliminary analysis of point-like sources present in the field. Spectral extraction has also been implemented and is based on simultaneous fitting of source and background shadowgram models to detector images. The procedures are illustrated using some of the IBIS data collected during the inflight calibrations and present performance is discussed. The analysis programs described here have been integrated as instrument specific software in the Integral Science Data Center (ISDC) analysis software packages currently used for the Quick Look, Standard and Off-line Scientific Analysis. 1. The IBIS coded aperture imaging system The IBIS telescope (Imager on Board of the INTEGRAL Satellite) (Ubertini et al. 2003), launched onboard the ESA gamma-ray space mission INTEGRAL (Winkler et al. 2003) on October 2002, is a hard-X ray/soft γ-ray telescope based on a coded aperture imaging system (Goldwurm et al. 2001).) the source radiation is spatially modulated by a mask of opaque and transparent elements before being recorded by a position sensitive detector, allowing simultaneous measurement of source plus background (detector area corresponding to the mask holes) and background fluxes (detector corresponding to the opaque elements). Mask patterns are designed to allow each source in the field of view (FOV) to cast a unique shadowgram on the detector, in order to avoid ambiguities Send offprint requests to: A. Goldwurm : [email protected] ⋆ Based on observations with INTEGRAL, an ESA project with instruments and science data centre funded by ESA member states (especially the Poland, and with the participation of Russia and the USA. in the reconstruction of the sky image. This reconstruction (deconvolution) is generally based on a correlation procedure between the recorded image and a decoding array derived from the mask pattern. Assuming a perfect position sensitive detector plane (infinite spatial resolution), the angular resolution …