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Koji Mori, H. Tsunemi, E. Miyata, C.J. Baluta (Osaka University), Tsunemi Laboratory Team
The Chandra mirrors, the HRMA, have the best angular resolution that any X-ray telescope has yet achieved. This results in images with a resolution of about 0.5 arc-second PSF (FWHM). In spite of this value, the pixel size of the CCD(0.492arc-second) is not small enough for the full imaging capability of Chandra to be realized by using the ACIS.
Since the primary charge cloud generated by an X-ray photon has a finite size , the charge distribution of the X-ray event will give us more precise position information than that determined by the pixel size. In particular, the location of ASCA-grade 6 events, corner pixel events, can be localized to about one tenth of the pixel size as confirmed by employing the identical ACIS CCD  and by the mesh technique . Therefore, we can expect an improvement of the position resolution by collecting corner pixel events.
We are applying this technique to all the available data in the public archive, from stars to AGNs. In the meeting, we will report the validity of this technique and discuss the results from the astrophysical point of view.
 J. Hiraga, H. Tsunemi, K. Yoshita, E. Miyata, and M. Ohtani, ``How big are charge clouds inside the charge-coupled device produced by X-ray photons ?'' Jpn. J. Appl. Phys., Vol. 37, 4627, 1998.
 M. Pivovaroff, S. Jones, M. Bautz, S. Kissel, G. Prigozhin, G. Ricker, H. Tsunemi, and E. Miyata, ``Measurement of the Sub-pixel Structure of AXAF CCDs,'' IEEE Trans. Nucl. Sci., Vol. 45, 164, 1998.
 H. Tsunemi, S. Kitamoto, and K. Yoshita, ``New Technique of the X-Ray Efficiency Measurement of a Charge-Coupled Device with a Subpixel Resolution.'' Jpn. J. Appl. Phys., Vol. 36, 2906, 1998.