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Suzaku Guest Observer Facility

Updated XIS Calibration around 2 keV

Updated 2013 March 5

In the Suzaku/XIS spectra of bright sources, residuals are often seen around 2 keV, with those in XIS1 (with the back-illuminated chip) being in the opposite sense to those in the other XIS units with front-illuminated chips.

1. Calibration File Update (2012 June)

The XIS team has released a set of new quantum efficiency files, dated 20120428.

  • This update modifies XAFS structures around the Si K edge and Al K edge by adopting new absorption coefficients.
  • The quantum efficiency of the BI CCD changes little (left) while those of FI CCDs change significantly (middle) to solve the "Si edge" problem.
  • X-ray transmission of the optical blocking filter around the Al K edge has also been updated (right).

Changes in QE Cal at 2 keV

The quantum efficiency files, ae_xiN_quanteff_20120428.fits (or later), are used by the RMF generator, xisrmfgen. To use the new calibration, install/use the latest calibration database and re-run xisrmfgen; there is no need to reprocess the event files or re-generate the ARF files.

2. Software Update (2012 December)

Although the above update applies in principle to the BI chip as well as to the FI chips, the differences are small for XIS1 and did not solve its calibration problem around 2 keV.

Suzaku FTOOLS Version 20 was released in 2012 December as part of HEAsoft version 6.13: xisrmfgen in this release has two new hidden parameters, bi_si_edge_mode and fi_si_edge_mode. The former is set to 1 by default, which instructs xisrmfgen to use a new and improved response model around Si K edge for XIS1; setting it to 0 will reproduce the old response. fi_si_edge_mode is reserved for future use, is set to 0, and should not be changed from the default for the time being.

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This file was last modified on Tuesday, 05-Mar-2013 17:10:56 EST

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