hatm: Nonmagnetic hydrogen atmosphere of a neutron star

This model provides the spectra emitted from a nonmagnetic hydrogen atmosphere of a neutron star. The model spectra in a 0 - 20 keV range of (unredshifted) photon energy are computed on a grid of surface gravity accelerations log(g)=13.7 - 14.9 (in cgs units) and effective temperatures T = 0.5 - 10 MK. For a given set of the fitting parameters, the surface gravity g and the gravitational redshift z are derived from the mass M and radius R of the star. The trial spectra are computed using a linear interpolation between the nearest model spectra on the T-log(g) grid, and the boundaries of the energy bins and the number of photons in each bin are divided by (1+z). The details of the model can be found in Suleimanov et al. (2017) and Klochkov et al. (2015).

The directory used for the files required by this model can be changed by using the xset command to set HATM.

The parameters are:

par1	Effective temperature T (MK)
par2	Neutron star mass M (M$_{\rm sol}$)
par3	Neutron star radius R (km)
par4	Normalization K = A/(d$_{10}$kpc)$^2$ where d$_{10}$kpc is the distance to the source in units of 10 kpc and A characterizes the fraction of the surface emitting the radiation (A=1 corresponds to the case when the radiation is emitted from the entire surface).

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Last modified: Wednesday, 12-Mar-2025 17:05:24 EDT