NS Non-Magnetic Atmosphere Model
NOTE: This model is now in the Xspec release and this page is superceded by the Xspec manual
NOTE: The nsx model has been included as part of the Xspec distribution since version 12.8.2, and should no longer be built as a local model.
20200918: added spectral data for Hydrogen
This model was updated on 4/3/14 to make a small correction to the fitted normalization.
The NSX model interpolates from a grid of neutron star (NS) atmosphere spectra to produce a final spectrum that depends on the parameters listed below. Atmosphere spectra are obtained using opacity tables computed by The Opacity Project and are for non-magnetic atmospheres (note that NSX is fully compatible with the magnetic atmosphere spectral tables of NSMAXG, and both NSX and NSMAXG spectral tables can easily be made compatible with other XSPEC NS fitting models). Atmosphere models are constructed by solving the radiative transfer equation, and the atmosphere is assumed to be in radiative and hydrostatic equilibrium. Atmosphere models depend on the surface effective temperature Teff and surface gravity g=(1+zg)GM/R2, where 1+zg=(1-2GM/R)-1/2 is the gravitational redshift and M and R are the NS mass and radius, respectively. See here for a list of models and model ranges of Teff, g, and energy.
The model parameters are :
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