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Suzaku Guest Observer Facility

XIS Calibration around the Si K edge

Updated 2012 June 8

There is currently a 10%-level calibration problem around the Si K edge in the XIS data. Here we provide a summary of this issue.

In Version 1.x processed data, there was a relatively narrow (+/-50 eV), large (almost a factor of 2) artefact around the Si K edge at 1.8 keV. This was due to imperfect calibration of the gain discontiunity at the K edge. The gain calibration in this region was updated in Version 2.x processing, and users should not see this artefact in any data that are currently available.

The current problem peaks at about 1.7 keV, and may be due to an imperfect calibration of the instrumental Si K fluorescence line. This is shown in the figure below; the data are for the Tycho supernova remnant, fitted with a power law plus Gaussian Si K line model, where the line center energy was allowed to vary. The fitted line energy indicates a slight shift between the front-illuminated and back-illuminated chips.

Si Cal

Note added in 2012 June: The XIS team has recently updated the quantum efficiency calibration file around 2 keV, in an effort to solve this issue. See this page for more.

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This file was last modified on Friday, 08-Jun-2012 11:18:39 EDT

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