Hello,
I think your problem is not really related to xsmekal model, but rather
to the range of the parameters you trying to vary. The first statistic value
output in Powell is calculated at the boundary of the allowed parameter values.
These can be far away from your minimum giving you NaN. You may change the
default range of min/max for the temperature and see whether this helps.
Note that the temperature for Raymond-Smith model has lower upper values.
Since you are far away from your solution this may take awhile for Powell to
find a minimum, so hanging may be a side effect of that. You can change the
verbose in method to 5 to get more information on the screen during the
fitting run.
Please let me know if this change anything.
Thanks,
Aneta
> Hi,
>
> I've been unable to get the xsmekal model to fit data within Sherpa. A
> NAN is produced that halts (freezes) the process.
>
> I'm using CIAO 2.01, Linux i686.
>
> For example, the sherpa script:
> data L.pi
> ignore energy :0.5, 9:
> subtract
> # The emission model.
> xsmekal[p1]
> p1.kT = 10.0
> p1.nH = 1e-5
> p1.Abund = 0.2
> p1.Redshift = 0.05
> p1.Switch = 0
> p1.norm = 1e-3
> thaw p1.kT
> thaw p1.norm
> freeze p1.nH
> freeze p1.Abund
> freeze p1.Redshift
> freeze p1.Switch
> # The source model.
> source = p1
> statistic chi gehrels
> method powell
> fit
>
> Produces the output:
>
> The inferred file type is PHA. If this is not what you want, please
> specify the type explicitly in the data command.
> Background data are being input from:
> L_bg.pi
> RMF is being input from:
> L.rmf
> ARF is being input from:
> L.arf
> powll: v1.2
> powll: initial function value = NAN
>
> Which hangs (^C interupts)
>
> While the same thing, but using a Raymond-Smith model, manages to fit
> the data. As is shown
> by the following script and output:
>
> data L.pi
> ignore energy :0.5, 9:
> subtract
> # The emission model. Raymond-Smith
> xsraymond[p1]
> p1.Abundanc = 0.2
> p1.Redshift = 0.05
> thaw p1.kT
> thaw p1. norm
> freeze p1.Abundanc
> freeze p1.Redshift
> # The source model.
> source = p1
> statistic chi gehrels
> method powell
> fit
>
> Output:
>
> The inferred file type is PHA. If this is not what you want, please
> specify the type explicitly in the data command.
> Background data are being input from:
> L_bg.pi
> RMF is being input from:
> L.rmf
> ARF is being input from:
> L.arf
> powll: v1.2
> powll: initial function value = 6.16132E+03
> powll: converged to minimum = 3.88723E+02 at iteration = 5
> powll: final function value = 3.88723E+02
> p1.kT 12.3582 keV
> p1.norm 0.00467887 10**-14 / (4 pi D**2) Int n_e n_H dV
>
>
> Any ideas as to what I'm doing wrong?
>
> --
> Dr. Eric Tittley Post Doctoral Research Associate
> Joint Center for Astrophysics UMBC
>
-- __________________________________________________________________________ Aneta Siemiginowska Chandra X-Ray Center (CXC) asiemiginowska@cfa.harvard.edu Harvard-Smithsonian Center for Astrophysics Phone:(617)-495-7243 60 Garden St. MS-4 FAX: (617)-495-7356 Cambridge, MA 02138 __________________________________________________________________________
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