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> GSO ARF
ARF file for GSO analysis
Release of the GSO ARF file
2007.04.24 by the HXD team
Dear Suzaku users,
As shown in the in-orbit performance paper of HXD (Kokubun et al. 2007),
there are about 20% residual in Crab spectra observed by the GSO
when fitted with the single power-law model. Through the clarification
of the current response (ae_hxd_gso[hx,xi]nom_20080129.rsp),
the HXD team realized that the GSO discrepancy is mainly caused
by the diagonal elements of the response matrix, which is connected
with difficulties in data handling around lower threshold, and so on.
Since these problems cannot be resolved easily and it is difficult
to construct a new response matrix promptly, we first release an
correction "arf" file
for each aim point, to reduce the discrepancy.
The correction factor C(E) is obtained as to reproduce the 70-300 keV
Crab spectra smoothly with the single power-law model of which the
parameters were determined by the 12-70 keV PIN spectra.
Then, the factor becomes,
C(E) = 1.36 * (E/100)^0.65 * exp(-E/230) @ XIS nominal
1.18 * (E/100)^0.55 * exp(-E/320) @ HXD nominal ,
where E is the energy in the unit of keV.
The correction arf files can be simply used with the current
response files in XSPEC as follows (in case of xis nominal dataset):
data 1 gso_cl.pha
backgrnd 1 gso_bgd.pha
response 1 ae_hxd_gsoxinom_20080129.rsp
arf 1 ae_hxd_gsoxinom_crab_20070502.arf
Please be careful that
1) the correction factor was obtained only in the 70-300 keV energy band, and
2) there might still remain calibration uncertainties with the level of about 10%.
An example without/with the arf file is shown below.
With utilizing the correction arf,
the 12-300 keV Crab spectrum at the XIS nominal position
(2005 September 15 observation) is well represented
with the single power-law model
(photon index = 2.10 +/- 0.01, normalization @ 1 keV = 11.5 +/- 0.2).
The best-fit parameters obtained at the HXD nominal position
are almost the same
(photon index = 2.09 +/- 0.01, normalization @ 1 keV = 10.8 +/- 0.3).
ISAS/JAXA Department of High Energy Astrophysics
Last Modified: Wednesday, 12-Nov-2008 19:28:08 JST