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INTEGRAL's sharper view of the hard X-ray sky

INTEGRAL's sharper view of the hard X-ray sky

Date: 19 May 2010
Satellite: INTEGRAL
Copyright: Roland Walter/ISDC

The recent 9th release of the INTEGRAL Offline Scientific Analysis package (OSA 9) provides improved software for the soft gamma-ray imager IBIS/ISGRI. This picture highlights the improvement in image quality for a field centred on the black-hole candidate Cygnus X-1 (left panel), by comparing an enhanced background image generated with OSA 8 (middle panel) and OSA 9 (right panel).

The circular structures in the OSA 8 enhanced background image are artefacts related to the absorption of hard X-ray photons by the glue used to mount the instrument coded mask on its supporting structure. The intensity of these artefacts for OSA 8 is of the order of 0.2% of that of the brightest source in the field of view.

Thanks to an extensive in-flight calibration effort this glue could be modelled much better, reducing the artefacts by a factor of 10 for OSA 9 (right panel). In this image, new faint hard X-ray sources could now be detected for the first time. The source in the green circle, for example, is two thousand times fainter than Cygnus X-1.

The OSA 9 software package is available at the INTEGRAL Science Data Centre (

Last Update: 1 September 2019
11-Jul-2020 04:50 UT

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