Research Note

A new determination of the INTEGRAL/IBIS point source location accuracy

¹ Department of Astrophysics, IMAPP, Radboud University Nijmegen, PO Box 9010, 6500 GL Nijmegen, The Netherlands e-mail: S.Scaringi@astro.ru.nl
² School of Physics and Astronomy, University of Southampton, Southampton, SO17 1BJ, UK
³ Laboratoire d'Astrophysique de Grenoble, UMR 5571 CNRS, BP 53, 38041 Grenoble, France
⁴ INAF-IASF Roma, via Fosso del Cavaliere 100, 00133, Roma, Italy
⁵ INAF-IASF Bologna, via P. Gobetti 101, 40129, Bologna, Italy

Received: 5 February 2010
Accepted: 23 February 2010

Abstract

Aims. We determine the point source location accuracy (PSLA) of the INTEGRAL/IBIS telescope based on analysis of archival in-flight data.

Methods. Over 40 000 individual pointings (science windows) of INTEGRAL/IBIS data were analysed using the latest Off-line Science Analysis software (version 7.0). Reconstructed source positions were then compared with the most accurate positions available, determined using focusing X-ray telescopes. Since the PSLA is a strong function of source detection significance, histograms of the offsets from true position were compiled to determine the 90% confidence limits for both sources in the fully coded field of view (FCFOV) and partially coded field of view (PCFOV).

Results. The PSLA is found to have improved significantly since measurements were first made for early mission data and software for both FCFOV and PCFOV.

Conclusions. This result has implications for observers executing follow-up programs on IBIS sources since the sky area to be searched is reduced by more than 50% in some cases.