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          Institute: MPI für extraterrestrische Physik     Collection: High Energy Astrophysics at MPE     Display Documents

ID: 10136.0, MPI für extraterrestrische Physik / High Energy Astrophysics at MPE
Point spread function and centroiding accuracy measurements with the JET-X mirror and MOS CCD detector of the Swift gamma ray burst explorer's X-ray telescope
Authors:Ambrosi, R. M.; Abbey, A. F.; Hutchinson, I. B.; Willingale, R.; Wells, A.; Short, A. D. T.; Campana, S.; Citterio, O.; Tagliaferri, G.; Burkert, W.; Bräuninger, H.
Date of Publication (YYYY-MM-DD):2002
Title of Journal:Nuclear Instruments & Methods in Physics Research Section A
Journal Abbrev.:Nucl. Instrum. Methods Phys. Res. Sect. A
Issue / Number:3
Start Page:543
End Page:554
Review Status:Peer-review
Audience:Experts Only
Abstract / Description:The optical components of the Swift X-ray telescope (XRT) are already developed items. They are the flight spare X-ray mirror from the JET-X/Spectrum-X program and an MOS CCD (CCD22) of the type currently operating in orbit as part of the EPIC focal plane camera on XMM-Newton (SPIE 4140 (2000) 64). The JET-X mirrors were first calibrated at the Max Plank Institute for Extraterrestrial Physics' (MPE) Panter facility, Garching, Germany in 1996 (SPIE 2805 (1996) 56; SPIE 3114 (1997) 392). Half-energy widths of 16 arcsec at 1.5 keV were confirmed for the two flight mirrors and the flight spare. The calibration of the flight spare was repeated at Panter in July 2000 in order to establish whether any changes had occurred during the 4yr that the mirror had been in storage at the OAB, Milan, Italy. The results reported in this paper confirm that the resolution of the JET-X mirrors has remained stable over this storage period. In an extension of this test program, the flight spare EPIC camera was installed at the focus of the JET-X mirror to simulate the optical system of the Swift XRT. Tolerances in the mirror focal length, the on-axis and off-axis point spread functions were measured and calibration data sets were used to obtain centroid positions of X-ray point sources. The results confirmed Swift's ability to determine the centroid positions of sources at 100 mCrab brightness to better than 1 arcsec and provided a calibration of the centroiding process as a function of source flux and off-axis angle. The presence of background events in the image frame introduced errors in the centroiding process and this was accounted for by reducing the sampling area used for the centroiding algorithm. 2002 Elsevier Science B.V. All rights reserved.
Free Keywords:centroid; half-energy width; focus; point response function; X- ray; gamma ray burst
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für extraterrestrische Physik
External Affiliations:Univ Leicester, Dept Phys & Astron, Ctr Space Res, Univ Rd,; Leicester LE1 7RH, Leics, England; Univ Leicester, Dept Phys & Astron, Ctr Space Res, Leicester LE1 7RH, Leics, England; Osserv Astron Brera, Milan, Italy; Max Planck Inst Extraterr Phys, D-8046 Garching, Germany
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