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Suzaku Guest Observer Facility

XRT Calibration Updates


The 2008-07-09 release of Suzaku CALDB contains an updated calibration of the XRTs and the corresponding updates to the XIS quantum efficiency files. The latter are files are new and correct the problems in the 2008-06-02 release, while the XRT files

Applying the new calibration

IMPORTANT: two tools that use the Suzaku raytracing library, xissim and xissimarfgen, must be updated to Suzaku FTOOLS release version 8 or later (see notes on the latest Suzaku FTOOLS) to use the new XRT calibration files. Older versions of these tools do not work with the new calibration files, while the new version of the raytracing library is backward compatible with the older calibration files.

The new calibration can be applied without reprocessing the event data. The only requirement is to re-generate the response files using xisrmfgen and xissimarfgen, most conveniently done by re-extracting the spectra in xselect while specifying resp=yes. (There is one change in the teldef files that affects the OPTIC keywords in the event files, when reprocessed with xiscoord. However, it is safe to feed spectral files with incorrect OPTIC keywords to response generators.)

PSF/EEF and Vignetting

The vignetting calibration has been updated. For full details, see Suzaku memo 2008-05.

The imaging calibration has been updated. The geometry parameters for each quadrant of each XRT have now been individually adjusted. As a result, the calibration of the point-spread function (PSF)/encircled energy function (EEF) has improved, particularly beyond 2 arcmin from the image center. The simulated EEF now coincides with the observed values within 4% from 1 to 6 arcmin radius. For full details, see Suzaku memo 2008-04.

Effective Area

The combination of the XRT and XIS calibration changes is such that, for observations at XIS nominal position analyzed using a large (e.g., 250 pixel radius) extraction region, changes are relatively small.

NOTE, however, that the relative normalization for the PIN data is now 1.16 and 1.18 for the Crab nebula observed at the XIS and HXD nominal positions, respectively (with estimated errors of 0.015).

For full details, see Suzaku memo 2008-06.

Note also that the changes in EEF and vignetting calibration affects effective area calibration as a function of source location and extraction region radius. Be advised that effective area calibration may have changed significantly for some extraction regions.


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This file was last modified on Thursday, 31-Jul-2008 19:44:52 EDT

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