In chandra-users, you wrote:
>Hmm, this gets me started. I'll try your suggestions for Sherpa. But in the
>meantime I have a couple of further questions regarding what you said about
>pile-up:
>
>[...]
>> Pile-up model in Sherpa is only available for 1D analysis. The
>> modification of PSF by pile-up needs to be folded into your psf image.
>
>I'm a bit lost here: how do you propose I modify my PSF file for pile-up?
>Also it seems to me that doing things this way would force one into assuming
>that all sources have exactly the same fraction of piled-up pohtons. This
>isn't the case in my data: there are four sources affected by pile-up, with
>fluxes (and presumably piled-up fractions) that vary by about a factor 4.
>
I think the only way you could do this is to do spectral modeling of
each source independently with the pileup model to determine the
unpiled number of counts. This doesn't give you the piled psf,
though. For that, you might have to perform some forward-folding
iteration to determine the unpiled count density vs radial distance to
then estimate a pileup fraction vs radius for the model, then perturb
the model psf accordingly.
As Aneta said, we don't have any spatial pileup models.
Hope this helps.
>Thanks,
>
>Eric
>
>--
>Eric S. Perlman E-mail: perlman@jca.umbc.edu
>Joint Ctr. for Astrophysics, Physics Dept. Phone: +1 410 455 1982
>University of Maryland, Baltimore County Fax: +1 410 455 1072
>1000 Hilltop Circle WWW: www.jca.umbc.edu/~perlman
>Baltimore, MD 21250
>
>
-- Dave David Huenemoerder (617-253-4283; fax: 253-8084) MIT Center for Space Research/Chandra X-ray Center 70 Vassar St., NE80-6023, Cambridge, MA 02139 [Admin. Asst.: Deborah Gage 617-253-0228, dgage@space.mit.edu]
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