Broken power law, two break energies. XSPEC model.
A three-segment broken power law (i.e. with two break energies).
A(E)= KE^(-PhoIndx1) for E < BreakE1
A(E)= KBreakE1^(PhoIndx2-PhoIndx1) * (E/1keV)^-PhoIndx2 for BreakE1 <= E <= BreakE2
A(E)= KBreakE1^(PhoIndx2-PhoIndx1)*BreakE2^(PhoIndx3-PhoIndx2)*(E/1keV)^-PhoIndx3 for BreakE2 <= E
If POW_EMIN and POW_EMAX have been defined by the set_xsxset command, then the norm becomes the flux in units of 10^-12 ergs/cm2/s over the energy range (POW_EMIN, POW_EMAX) keV, unless POW_EMIN = POW_EMAX, in which case the norm becomes the flux density in micro-Jansky at POW_EMIN keV. In these cases it is important that POW_EMIN and POW_EMAX lie within the energy range on which the model is being evaluated.
This is an additive model component.
|1||PhoIndx1||power law photon index for E < E_break,1|
|2||BreakE1||first break point for the energy, keV|
|3||PhoIndx2||power law photon index for E_break,1 < E < E_break,2|
|4||BreakE2||second break point for the energy, keV|
|5||PhoIndx3||power law photon index for E > E_break,2|
|6||norm||K; photons/keV/cm^2/s at 1 keV|
This information is taken from the XSPEC User's Guide. Version 12.9.1n of the XSPEC models is supplied with CIAO 4.10.
For a list of known bugs and issues with the XSPEC models, please visit the XSPEC bugs page.
To check the X-Spec version used by Sherpa, use the get_xsversion routine from the xspec module:
sherpa> from sherpa.astro.xspec import get_xsversion sherpa> get_xsversion() '12.9.1n'
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