On Thursday 23 May 2002 08:23 pm, wqd@gcs.astro.umass.edu wrote:
> Hi,
>
> This is about the creation of a spectrally-weighted instrument map in an
> energy band. I was trying to understand the weights produced by a member of
> our group for various chips, using Sherpa. The weights are drastically
> different from one chip to another, which does not make sense to me. Then I
> was reading the online thread
> (http://asc.harvard.edu/ciao/threads/spectral_weights/), which is
> complicated and seems to problematic. However, I do understand the help on
> the routine mkinstmap (ahelp mkinstmap) and the quoted article by John
> Houck. Let me explain my problems in the following:
Daniel,
If you're having trouble with the threads, the best place for help is the CXC
helpdesk (http://cxc.harvard.edu/helpdesk/ - which is linked to from the
bottom of each page).
> The thread requires the use of both RMF and ARF files, in addition to a
> spectral data file. I am not exactly sure how these files are incorporated
> in the calculation of the weights, since I don't use Sherpa. It seems to me
> that none of these files should be needed to calculate the weights, if they
> are instrument-independent. However, the files might be required in order
> to get the model spectrum, although the results don't depend on the files
> at all. If this is the case, the thread should be designed in a much
> simpler way and should explain clearly that the results are independent of
> the input files.
The thread is designed for the case of a user fitting a model to a spectrum
so as to determine what parameters to use. The spectrum.sl script used to
calculate the weights file used by mkinstmap is just a list of energies (kev)
and fluxes (photon/cm^2/s) [ie is independent of chip as you said], so if you
already know the model parameters you want to use you can create this
directly in sherpa (or whatever fitting package you use).
Doug
--------------------------------------------------------------
Doug Burke | Email: dburke@cfa.harvard.edu
Harvard-Smithsonian | Phone: (617) 496 7853
Center for Astrophysics | Fax: (617) 495 7356
60 Garden Street MS-83 | Office: P-138
Cambridge, MA 02138 |
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