Re: Normalization issue

From: Michael Nowak <mnowak_at_email.domain.hidden>
Date: Mon, 7 Dec 2009 16:42:16 -0500
On Dec 7, 2009, at 4:32 PM, Herbert Pablo wrote:

> and while it works fine with a flux corrected spectrum. The same  
> spectrum just in counts there is an issue with the diskbb  
> normalization parameter. when I do eval_counts() I get something  
> 10^-31 when it should be on the order of about 3000. I have done a  
> similar fitting on both flux and count spectra for this object  
> before with no issues so I'm not sure where they are coming from  
> here. If anyone has any ideas, they would be greatly appreciated.


Multiple datasets fit simultaneously?

This looks like the kind of thing where you have a data channel with  
zero counts in it, and you have allowed the ISIS statistical errors to  
go very small (as opposed to the usual ISIS default of 1).  In which  
case, the fit is pegging itself to that one zero channel with  
amazingly small error bar.  (This kind of thing might get more easily  
hidden when flux correcting the data.  But since I never fit flux  
data, I could be wrong about that.)

If you do:

	Minimum_Stat_Err = 1;

and that fixes the problem, then that was it.

-Mike


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Received on Mon Dec 07 2009 - 16:42:22 EST

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