Re: Compatibility issues

On Sat, Feb 02, 2013 at 00:05 +0000, Carlo Ferrigno wrote:
> Dear All,
> 
> the ASTRO-H collaboration has released some time ago the
> spectral responses and ARFs based on the expectations they have
> for the instrument performances. Being part of the science
> working group of the mission (but not of the instrument or s/w
> teams), I have tried to simulate some spectra. 
> 
> I wanted to use Isis to simulate narrow emission lines, but the
> provided files are compatible with Xspec (at least the ones for
> the calorimeter) but not with Isis. After a quick
> investigation, I have not yet found the reason. As you are
> unfortunately quite used to these problems, it might be that
> finding the reason will take only a few minutes for you, so I
> have decided to write this message. The rsp and arf files are
> in:

I think the problem is that the grid in the ARF does not
exactly match the corresponding grid in the RMF.

In the ARF, I see:
#       ENERG_LO        ENERG_HI        SPECRESP
#            keV             keV           cm**2
   0.0000000E+00   1.0000000E-03   0.0000000E+00
   1.0000000E-03   2.0000001E-03   0.0000000E+00

and in the MATRIX extension of the RMF, I see:
#       ENERG_LO        ENERG_HI       N_GRP      F_CHAN 
#            keV             keV                         
   9.9999997E-05   1.0000000E-03           1           0 ...
   1.0000000E-03   2.0000001E-03           1           0 ...

The ARF has ENERG_LO=0 keV, while the RMF has ENERG_LO=1.e-4 keV.

Isis is strict about checking grids for compatibility. In this
case, maybe it's being too strict.

One simple solution is to set the isis global variable
Rmf_Grid_Tol to a large value.  In this case, I think setting
Rmf_Grid_Tol=1.0 will solve the problem.

The other solution is to change either the ARF grid or the RMF
grid so that they match more precisely.

Thanks,
-John


> 
> http://dl.dropbox.com/u/82756855/rsp_files.tgz
> 
> while the output of the screen is
> 
> ****
> isis> require("xspec");
>  Solar Abundance Vector set to angr:  Anders E. & Grevesse N. Geochimica et Cosmochimica Acta 53, 197 (1989)
>  Cross Section Table set to bcmc:  Balucinska-Church and McCammon, 1998
> isis> sxs_a = load_arf("sxt-s_100208_ts02um_intallpxl.arf.gz");
> Keyword not set: EXPOSURE
> isis> sxs_r = load_rmf("ah_sxs_5ev_basefilt_20100712.rmf.gz");
> isis>
> isis> assign_arf(sxs_a,1);  % Dataset 1 = HEG-1
> isis>
> isis> assign_rmf(sxs_r,1);  % Dataset 1 = HEG-1
> Error: 16384 RMF bins vs 16384 ARF bins
> Largest fractional errors:  1.19202e-07 (low edge)  0.995 (high edge)
> Failed: assigning RMF 1 to data set 1
> ***
> 
> Many thanks for your support and apologies for the disturbance
> 
> Regards,
> 
> Carlo
> 
> 
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