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spex-xray / spex-help

These are the help and manual pages for the SPEX X-ray spectral fitting package.
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Trafo : What should be the new bin boundary value to enter manually (how to consider the value ?) #13

Closed snborah closed 3 years ago

snborah commented 3 years ago

Learning to use SPEX. I was using "trafo' to convert spectra in OGIP formate to SPEX formate. On entering the name of the response matrix file, I got the message like this,

"Enter filename response matrix to be read: M1_rmf.rmf Reading response matrix ... Lower model bin boundary for bin 1 must be positive; current values: 0.000000E+00 5.000000E-03 Enter new bin boundary values manually:"

What minimum value should be entered. I got that it must be positive. I tried with 1 , 0.1. But no result was found after waiting for time. Please give me some idea.

jdeplaa commented 3 years ago

Any number that is smaller than 5.0E-3 and larger than 0 is fine. Usually, I put 3E-5 there.

For some instruments (e.g. EPIC MOS on XMM), the lowest energy bin boundary is 0, which is actually unphysical, because photons with 0 energy do not exist. Hence, SPEX wants to correct this. Since this first bin is usually ignored in a spectral analysis, it does not matter a lot what is being filled out here, as long as it is smaller than the upper bin boundary and not 0.

snborah commented 3 years ago

Thanks for valuable suggestion. I am using your value, it is taking time (for reading response matrix) after I put 3E-5. Regards, SN Borah.

On Mon, 31 May 2021, 12:37 Jelle de Plaa, @.***> wrote:

Any number that is smaller than 5.0E-3 and larger than 0 is fine. Usually, I put 3E-5 there.

For some instruments (e.g. EPIC MOS on XMM), the lowest energy bin boundary is 0, which is actually unphysical, because photons with 0 energy do not exist. Hence, SPEX wants to correct this. Since this first bin is usually ignored in a spectral analysis, it does not matter a lot what is being filled out here, as long as it is smaller than the upper bin boundary and not 0.

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