AAS 201st Meeting, January, 2003
Session 55. Instrumental Calibration and Data Analysis Techniques
Poster, Tuesday, January 7, 2003, 9:20am-6:30pm, Exhibit Hall AB

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[55.04] Further Tests of Subpixel Event Repositioning for Chandra/ACIS Imaging Data

J. Li, J.H. Kastner (Chester F. Carlson Center for Imaging Science, Rochester Institute of Technology), N.S. Schulz, H.L. Marshall, G.Y. Prigozhin (Center for Space Research, Massachusetts Institute of Technology)

We are investigating the effectiveness of subpixel event repositioning (SER) techniques for Chandra X-ray CCD imaging observations. SER techniques are based on the premise that the sizes of charge clouds generated by photons incident on the Advanced CCD Imaging Spectrometer (ACIS) are quite small compared to an ACIS pixel, such that the landing positions for split events should be near the pixel boundaries instead of the pixel centers. Therefore SER algorithms designed to reposition split event landing positions, if suitably constrained by ACIS CCD models, should improve the spatial resolution of Chandra/ACIS observations. However, the resolution improvement may be different for frontside-illuminated (FI) and backside-illuminated (BI) CCDs. Using BI/FI archival Chandra/ACIS data obtained for Orion Nebula Cluster (ONC) and ACIS CCD models to determine the detailed relationship between landing positions and split event geometries, we evaluated a modified SER algorithm based on that proposed by Tsunemi et al. (2001, ApJ, 554, 496). By applying this SER technique to ONC point like sources, we establish the degree of image improvement achieved by SER for both BI and FI devices as a function of off-axis angle, split event percentage, and total source counts. We also apply the SER technique to various extended sources, and present the resulting improvements in image quality.

J.H.K. and J.L. acknowledge support for this research provided by NASA/CXO grants GO0--1067X and G02--3009X to RIT. N.S.S and H.L.M acknowledge support from Smithsonian Astrophysical Observatory (SAO) contract SVI-61010 for the Chandra X-Ray Center (CXC).

The author(s) of this abstract have provided an email address for comments about the abstract: jxl7626@cis.rit.edu

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