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Strangeon star atmosphere model.

This model is now in the Xspec release and this page is superceded by the Xspec manual

The strangeon star atmosphere (ssa) model describes the radiation from interstellar medium accreted plasma atmosphere on a strangeon star surface and its spectrum. The ssa could simply be regarded as the upper layer of a normal neutron star because the radiation from strangeon matter can be neglected (Wang et al. 2017, 1705.03763). The atmosphere is in radiative, thermal equilibrium and two-temperature. The ssa spectrum is based on bremsstrahlung from an extremely thin hydrogen plasma. More details of the ssa model are described in Wang et al. (2017, ApJ, 837, 81).

The model parameters are the following:

par1 = Te, the electron temperature (keV).

par2 = y, = ni02 Ti / R, where ni0 is the ion number density on the stellar surface (cm-3), Ti is the ion temperature (keV), and R is the stellar radius (km).
y is in units of 1042 keV/km/cm6.

norm = (R/d)2, where d is the distance to the star in units of 10 kpc.

To install as an XSPEC local model download the source code and model description file.