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New GIS RMFs available from the GIS team

Dear ASCA PIs and Archival Researchers:

[The following message can also be viewed on the ASCA GOF WWW homepage,
the URL of which is http://heasarc.gsfc.nasa.gov/docs/asca/ascagof.html.
Please look under "GIS News".]

Two new GIS response matrices (RMFs) are available via anonymous FTP in
the directory:


The files are called:


and supersede the response matrices released on 1994 April 20
(gis2v3_1.rmf and gis3v3_1.rmf).

In these previous versions, the low-energy tail of the pulse-height
distribution was underestimated, causing an artificial soft-excess to
appear in spectra with high absorption and low-energy photons. In the
new RMFs, the low-energy response has been modified by taking account of
ground calibration results and new theoretical calculations. The 
artificial soft-excesses disappear with the new RMFs.

However, the response at energies above 4 keV has not been changed. This
means that the high energy response problems noted in the "Calibration
Uncertainties" (systematic residuals around 6 keV and above 8 keV)
remain unsolved. But note that these residuals are about 5 per cent, and
are dominated by statistical errors for sources of several counts per
second or less.

For the new RMFs, in common with previous versions:

  o The GIS RMF converts energy (keV) to output channel (PI: Pulse
    Invariant, i.e., gain-corrected PHA).

  o RTI-based background rejection is assumed.

  o The efficiency of the RMFs is normalized to unity: they should be
    used in conjunction with an ARF file which contains the XRT/GIS

  o The GIS2 and GIS3 RMFs are the same except for identifying keywords
    in the headers.

Charles Day & Ken Ebisawa (ASCA GOF)
Makoto Tashiro (GIS Team, University of Tokyo)

Please send comments and questions to ascahelp@athena.gsfc.nasa.gov