new asca response matrices available in Caldb

[zellar@timaeus.gsfc.nasa.gov (Ron Zellar)]

Two new response matrices are available on legacy.gsfc.nasa.gov under
/caldb/data/asca/gis/cpf/95mar06.  The files are named

        gis2v4_0.rmf
        gis3v4_0.rmf

and they supercede the response matrices released on April 20, 1994
(gis2v3_1.rmf and gis3v3_1.rmf).

The files were created by the GIS team and delivered to the Calibration
Database by Ken Ebisawa of the ASCA GOF.  Further information about these
files is appended below.

Ron
HEASARC Calibration Database

------------------------------------------------------------------------------

##################################################
#                                                #
# Release note of the new GIS response function  #
#                                                #
##################################################

March 7, 1995
written by Ken Ebisawa (ASCA GOF) based on the memo
by M. Tashiro (GIS team) written in Japanese.

New GIS response files (RMF) are released from the
GIS team.  They are named gis2v4_0.rmf and gis3v4_0.rmf.
Actually, these files are identical except the keywords
which tell the instrument identification (GIS2 or 3).
These new RMFs supercede the previous ones (gis2v3_1.rmf,
gis3v3_1.rmf).

As it has been,  GIS RMF describes the gis response in
terms of 2-dimentional matrix of input energy (keV) and
output channel (PI -- pulse invariance).  The efficiency
is normalized to one, and GIS/XRT efficiency is taken
into account in ARFs.  In GIS spectral fitting, both RMF
and ARF are necessary.

In the old version (gis2/3v3_1.rmf), low energy tails of the
pulse-height distribution were underestimated, and artificial 'soft-excess'
had appeared for spectra with high absorption and low energy
photons (e.g., Crab°¢EXO2030+375,GRS1915+105).
In the new RMFs, low energy response was modified taking
account of ground calibration results and new theoretical calculations, and
consequently, these soft-excess disappeared..

In the new RMFs, however, energy range above 4 keV has been untouched.
Hence, the proclaimed high energy response problems (systematic residual
at around 6 keV and above 8 keV for GIS), are not solved yet.  These residuals
are about 5 %, and not significant for sources with several counts/s, being
dominated by statistical errors.