Re: define_counts question

From: David P. Huenemoerder <dph_at_email.domain.hidden>
Date: Thu, 10 Jul 2008 13:41:40 -0400
    rgibson> 1) load an arf and rmf, assign them to an empty data set

    rgibson> 2) define a model and evaluate that model on the arf/rmf
    rgibson> grid to get a counts spectrum

    rgibson> 3) use x=get_model_counts and then define_counts(x) to
    rgibson> generate a counts spectrum that exactly corresponds to
    rgibson> the model

Instead of 2 and 3, why not use fakeit() to generate the simulated
counts spectrum?  If you want a low-noise simulation, use
set_arf_exposure to some very large exposure time.

    rgibson> 4) use flux_corr to convert the new counts spectrum into
    rgibson> a flux spectrum

    rgibson> But when I compare the plot_data_flux spectrum to that of
    rgibson> my model, they don't quite match.  They match up in the


This is an approximation to the flux. The response isn't precisely
diagonal, so for a very steep spectrum, you might get some difference
between the model and the flux-corrected version.  See the isis manual
for the definition of flux correction.



-- Dave

David Huenemoerder  617-253-4283 (o); -253-8084 (f); http://space.mit.edu/home/dph
MIT Kavli Institute for Astrophysics and Space Research
70 Vassar St., NE80-6065,
Cambridge, MA  02139
[Admin. Asst.: Elaine Tirrell, 617-253-7480, egt_at_email.domain.hidden
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Received on Thu Jul 10 2008 - 13:41:43 EDT

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